Bondline - User contributions [en]

Structural Repair

2008-05-17T09:22:25Z

Jbowman90: Somehow the link to the major structural repair was removed. Added it back.

== Introduction ==

The maintenance manual has an extensive collection of structural repair details. Many cover "Grumman only" procedures like splicing the firewall and cabin floor with a factory repair section, or replacing the entire tailcone from the honeycomb aft.

There are also numerous factory repairs for mistakes made on the factory floor. These can be very helpful in the field to repair worn and damaged components.

The factory also published Service Kit 125A instructions which are the basis for repair of any debonded joint on the plane. The original need was because of the problems with debonding early-on from the "purple glue", but there are other debonding and repair issues that can be addressed with the factory supplied data.

Because of the relatively unique construction of the Grummans, most shops are not familiar with repairs to honeycomb and bonded structures. A considerable amount of material has been added to [http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAdvisoryCircular.nsf/0/99C827DB9BAAC81B86256B4500596C4E?OpenDocument AC 43.13-1B Change 1], that deals with bonded and honeycomb repairs.

== Common Structural Repairs ==

* [[Repair of Debonding]]
* [[Lower Cowling Split]]

== Major Structural Repairs ==

* [[An_Example_Repair|An Example Repair - Cheetah Horizontal stab]]

== Other ==

* [[Tail Tiedown Repair]]

Maintenance

2008-05-16T23:53:11Z

Jbowman90: added bullet for tail tiedown repair

We've organized this section to mirror the headings in the factory maintenance manual. Note that the section headings are "clickable" and take you to summary pages for that section. Links are repeated on those summary pages.

== [[Maintenance: General|General]] ==

* Required Information and Documentation
* Logbooks and Recording

== [[Servicing]] ==

* Inspections
* Oil Changes

== [[Airframe]] ==

* Disassembly
* Headliner
* Interior_Trim|Interior
* Window_Replacement|Windows
* Replacement Parts

== [[Landing Gear]] ==

* Brake System
* Nose Strut
* Wheels
* Main Landing Gear Attach Bolts

== [[Control Systems]] ==

* Rigging
* Stall Warning System

== [[Powerplant]] ==

* Engine Baffles
* Cylinders
* Oil and Filter
* Overhaul and field service
* TBO considerations
* Valve Wobble Testing
* Vacuum Pump

== [[Propeller]] ==

* Back Plate

== [[Fuel System]] ==

* Fuel Tank Leaks
* Auxiliary Fuel Tank

== [[Instrumentation]] ==

* Installing Mitchell Gauges

== [[Structural Repair]] ==

* An Example Repair
* Lower Cowling Split
* Repair of Debonding
* Tail Tiedown Repair

== [[Preparations for Painting|Painting]] ==

* Preparations for Painting

== [[Electrical Systems]] ==

* Charging Systems
* Panel Switches

Towing

2008-05-16T23:52:17Z

Jbowman90: added link to tail tiedown repair page

== Hanger Winch ==

[[Image:winch-pully.JPG|thumb|200 px|Overview of the winching system]]
[[Image:winch-attach.JPG|thumb|200 px|Rings welded to tow bar with snap hooks attached]]
[[Image:winch-overall.JPG|thumb|200 px|Yellow poly rope is attached to winch cable (easier to handle). Pully rides on rope to even the pull to both sides of the nose wheel while steering.]]

I use a winch to pull my tiger into the hanger. I do NOT attach the winch to the tail or the steps. See the [[Tail_Tiedown_Repair|tail tiedown repair]] page for an example of possible damage from a winch. I have rings welded to the towbar where it attaches to the nose wheel. A snap hook connects a 6 ft rope from one side of the nose wheel to the other side. Riding on the rope is a pully to which is attached the winch cable. The pulling load is kept centered by the pully while I steer. This works great and puts the winching force where you normally would manually with the towbar.

Brad Keleher

Tail Tiedown Repair

2008-05-16T23:43:51Z

Jbowman90: added link to towing page, fixed some grammar

[[Image:DSC00738_bondline.JPG|thumb|200 px|Repair Viewed from the Inside]]
[[Image:DSC00741_bondline.JPG|thumb|200 px|Tiedown Ring Before Removal]]
[[Image:DSC00746_bondline.JPG|thumb|200 px|Tiedown ring removed showing radial cracks]]
[[Image:DSC00752_bondline.JPG|thumb|200 px|Large-area washer deformed by unknown loading condition]]
[[Image:DSC00753_bondline.JPG|thumb|200 px|The deformation is asymmetric suggesting an off-axis load on the ring]]
[[Image:DSC00754_bondline.JPG|thumb|200 px|Ground down rivets and debonded skin and aft bulkhead]]

== Introduction ==

The tail tiedown can become damaged two different ways. First, a hard landing with the nose high can cause the tail tiedown to strike the runway. Second, a common method to pull an airplane back into a hangar involves using a winch connected to the tiedown ring. See the [[towing]] page for an idea on how to safely winch a Grumman. In both cases, loads are being placed on the tiedown ring that it was not designed to handle. The ring and its supporting structure are designed to take a mostly downward, axial load (it's good not to exceed 45 degrees from the vertical) from a tiedown rope. A hard landing may shove the ring up in the fuselage, or it may bend it to either side or front to back twisting the attached structure. Put enough force on the tiedown with a winch, and the ring will start to pull aft twisting the attached structure.

== Tiedown Structure ==

The attached structure mentioned in the introduction is the aft fuselage bulkhead, which is '''primary''' structure. The aft spar of the horizontal stabilizer, which takes most of the stabilizer and elevator loads, attaches to this bulkhead. The bulkhead is bent on the sides and bottom to form a lip that fits tightly over the fuselage skin, and the two are bonded with rivets in a few spots for good measure. Someone else will have to confirm or fix this, but it appears the factory installation of the ring is through the bottom lip into a nut plate on the interior. The aft bulkhead is not very thick, and the lip is not that wide. Any non-vertical load on the ring has the potential to very easily start deforming the lip and debond the bulkhead from the fuselage skin.

== Suspected Winch Damage ==

... And how not to repair it.

The images to the right illustrate a repair to the tiedown ring and surrounding structure and what it looks like from the outside. Notice that the channel section does not appear to lie flat against the fuselage bottom. You can possibly see that the washer is deformed. Right now, it is hard because of the oil and dirt.

After removing the tiedown ring and the existing repair, there was obvious damage. The middle third of the bondline along the bottom is gone, and the aft bulkhead has started cracking towards the radius that separates the bottom from the back face of the bulkhead. The lateral cracks towards the old nut plate rivet holes are not nearly as concerning. But to install the channel section, the mechanic ground down the rivets on either side of the lower lip.

One of two things happened at this point. First, whoever installed the tiedown ring after the repair torqued it down so tight that it severely deformed the large area washer, the lower aft bulkhead, and initiated cracks. Another possibility is that someone winched the airplane into their hangar using the tiedown ring. The way the structure and washer was deformed is consistent with an off-axis load on the tiedown ring from a winch.

Tail Tiedown Repair

2008-05-16T23:36:46Z

Jbowman90: Updated lay out and size of images for a better fit

[[Image:DSC00738_bondline.JPG|thumb|200 px|Repair Viewed from the Inside]]
[[Image:DSC00741_bondline.JPG|thumb|200 px|Tiedown Ring Before Removal]]
[[Image:DSC00746_bondline.JPG|thumb|200 px|Tiedown ring removed showing radial cracks]]
[[Image:DSC00752_bondline.JPG|thumb|200 px|Large-area washer deformed by unknown loading condition]]
[[Image:DSC00753_bondline.JPG|thumb|200 px|The deformation is asymmetric suggesting an off-axis load on the ring]]
[[Image:DSC00754_bondline.JPG|thumb|200 px|Ground down rivets and debonded skin and aft bulkhead]]

== Introduction ==

The tail tiedown can become damaged two different ways. First, a hard landing with the nose high can cause the tail tiedown to strike the runway. Second, a common method to pull an airplane back into a hangar involves using a winch connected to the tiedown ring. In both cases, loads are being placed on the tiedown ring that it was not designed to handle. The ring and its supporting structure is designed to take a mostly downward load (it's good not to exceed 45 degrees from the vertical) from a tiedown rope. A hard landing may shove the ring up in the fuselage, or it may bend it to either side or front to back twisting the attached structure. Put enough force on the tiedown with a winch, and the ring will start to pull aft twisting the attached structure.

== Tiedown Structure ==

The attached structure mentioned in the introduction is the aft fuselage bulkhead, which is '''primary''' structure. The aft spar of the horizontal stabilizer, which takes most of the stabilizer and elevator loads, attaches to this bulkhead. The bulkhead is bent on the sides and bottom to form a lip that fits tightly over the fuselage skin, and the two are bonded with rivets in a few spots for good measure. Someone else will have to confirm or fix this, but it appears the factory installation of the ring is through the bottom lip into a nut plate on the interior. The aft bulkhead is not very thick, and the lip is not that wide. Any non-vertical load on the ring has the potential to very easily start deforming the lip and debond the bulkhead from the fuselage skin.

== Suspected Winch Damage ==

... And how not to repair it.

The images to the right illustrate a repair to the tiedown ring and surrounding structure and what it looks like from the outside. Notice that the channel section does not appear to lie flat against the fuselage bottom. You can possibly see that the washer is deformed. Right now, it is hard because of the oil and dirt.

After removing the tiedown ring and the existing repair, there was obvious damage. The middle third of the bondline along the bottom is gone, and the aft bulkhead has started cracking towards the radius that separates the bottom from the back face of the bulkhead. The lateral cracks towards the old nut plate rivet holes are not nearly as concerning. But to install the channel section, the mechanic ground down the rivets on either side of the lower lip.

One of two things happened at this point. First, whoever installed the tiedown ring after the repair torqued it down so tight that it severely deformed the large area washer, the lower aft bulkhead, and initiated cracks. Another possibility is that someone winched the airplane into their hangar using the tiedown ring. The way the structure and washer was deformed is consistent with an off-axis load on the tiedown ring from a winch.

File:DSC00754 bondline.JPG

2008-05-16T23:33:17Z

Jbowman90: Ground down rivets and debonded skin and aft bulkhead

Ground down rivets and debonded skin and aft bulkhead

File:DSC00753 bondline.JPG

2008-05-16T23:32:48Z

Jbowman90: The deformation is asymmetric suggesting an off-axis load on the ring

The deformation is asymmetric suggesting an off-axis load on the ring

File:DSC00752 bondline.JPG

2008-05-16T23:32:22Z

Jbowman90: Large-area washer deformed by unknown loading condition

Large-area washer deformed by unknown loading condition

File:DSC00746 bondline.JPG

2008-05-16T23:31:49Z

Jbowman90: Tiedown ring removed showing radial cracks

Tiedown ring removed showing radial cracks

File:DSC00741 bondline.JPG

2008-05-16T23:30:57Z

Jbowman90: Tiedown Ring Before Removal

Tiedown Ring Before Removal

File:DSC00738 bondline.JPG

2008-05-16T23:30:14Z

Jbowman90: Tail tiedown repair Viewed from the inside

Tail tiedown repair Viewed from the inside

Tail Tiedown Repair

2008-05-16T23:28:58Z

Jbowman90: Updated damage section

== Introduction ==

The tail tiedown can become damaged two different ways. First, a hard landing with the nose high can cause the tail tiedown to strike the runway. Second, a common method to pull an airplane back into a hangar involves using a winch connected to the tiedown ring. In both cases, loads are being placed on the tiedown ring that it was not designed to handle. The ring and its supporting structure is designed to take a mostly downward load (it's good not to exceed 45 degrees from the vertical) from a tiedown rope. A hard landing may shove the ring up in the fuselage, or it may bend it to either side or front to back twisting the attached structure. Put enough force on the tiedown with a winch, and the ring will start to pull aft twisting the attached structure.

== Tiedown Structure ==

The attached structure mentioned in the introduction is the aft fuselage bulkhead, which is '''primary''' structure. The aft spar of the horizontal stabilizer, which takes most of the stabilizer and elevator loads, attaches to this bulkhead. The bulkhead is bent on the sides and bottom to form a lip that fits tightly over the fuselage skin, and the two are bonded with rivets in a few spots for good measure. Someone else will have to confirm or fix this, but it appears the factory installation of the ring is through the bottom lip into a nut plate on the interior. The aft bulkhead is not very thick, and the lip is not that wide. Any non-vertical load on the ring has the potential to very easily start deforming the lip and debond the bulkhead from the fuselage skin.

== Suspected Winch Damage ==

... And how not to repair it.

[[Image:DSC00738_bondline.JPG|thumb|300 px|Repair Viewed from the Inside]]
[[Image:DSC00741 _bondline.JPG|thumb|300 px|Tiedown Ring Before Removal]]

The images to the right illustrate a repair to the tiedown ring and surrounding structure and what it looks like from the outside. Notice that the channel section does not appear to lie flat against the fuselage bottom. You can possibly see that the washer is deformed. Right now, it is hard because of the oil and dirt.

After removing the tiedown ring and the existing repair, there was obvious damage. The middle third of the bondline along the bottom is gone, and the aft bulkhead has started cracking towards the radius that separates the bottom from the back face of the bulkhead. The lateral cracks towards the old nut plate rivet holes are not nearly as concerning. But to install the channel section, the mechanic ground down the rivets on either side of the lower lip.

[[Image:DSC00746_bondline.JPG|thumb|300 px|Tiedown ring removed showing radial cracks]]
[[Image:DSC00752_bondline.JPG|thumb|300 px|Large-area washer deformed by unknown loading condition]]
[[Image:DSC00753_bondline.JPG|thumb|300 px|The deformation is asymmetric suggesting an off-axis load on the ring]]
[[Image:DSC00754_bondline.JPG|thumb|300 px|Ground down rivets and debonded skin and aft bulkhead]]

One of two things happened at this point. First, whoever installed the tiedown ring after the repair torqued it down so tight that it severely deformed the large area washer, the lower aft bulkhead, and initiated cracks. Another possibility is that someone winched the airplane into their hangar using the tiedown ring. The way the structure and washer was deformed is consistent with an off-axis load on the tiedown ring from a winch.

Tail Tiedown Repair

2008-05-16T20:25:42Z

Jbowman90: Created page. Will complete winch damage section soon. Final repair will have to wait.

Structural Repair

2008-05-16T20:03:48Z

Jbowman90: Added link to tail tiedown repair page

== Introduction ==

The maintenance manual has an extensive collection of structural repair details. Many cover "Grumman only" procedures like splicing the firewall and cabin floor with a factory repair section, or replacing the entire tailcone from the honeycomb aft.

There are also numerous factory repairs for mistakes made on the factory floor. These can be very helpful in the field to repair worn and damaged components.

The factory also published Service Kit 125A instructions which are the basis for repair of any debonded joint on the plane. The original need was because of the problems with debonding early-on from the "purple glue", but there are other debonding and repair issues that can be addressed with the factory supplied data.

Because of the relatively unique construction of the Grummans, most shops are not familiar with repairs to honeycomb and bonded structures. A considerable amount of material has been added to [http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAdvisoryCircular.nsf/0/99C827DB9BAAC81B86256B4500596C4E?OpenDocument AC 43.13-1B Change 1], that deals with bonded and honeycomb repairs.

== Common Structural Repairs ==

* [[Repair of Debonding]]
* [[Lower Cowling Split]]

== Major Structural Repairs ==

* [[An Example Repair]]

== Other ==

* [[Tail Tiedown Repair]]

Towing

2008-05-16T19:56:19Z

Jbowman90: Adjusted captions to go with correct picture

== Hanger Winch ==

[[Image:winch-pully.JPG|thumb|200 px|Overview of the winching system]]
[[Image:winch-attach.JPG|thumb|200 px|Rings welded to tow bar with snap hooks attached]]
[[Image:winch-overall.JPG|thumb|200 px|Yellow poly rope is attached to winch cable (easier to handle). Pully rides on rope to even the pull to both sides of the nose wheel while steering.]]

I use a winch to pull my tiger into the hanger. I do NOT attach the winch to the tail or the steps. I have rings welded to the towbar where it attaches to the nose wheel. A snap hook connects a 6 ft rope from one side of the nose wheel to the other side. Riding on the rope is a pully to which is attached the winch cable. The pulling load is kept centered by the pully while I steer. This works great and puts the winching force where you normally would manually with the towbar.

Brad Keleher

Towing

2008-05-16T19:48:27Z

Jbowman90: Adjusted layout slightly so that text and pictures line up, minor spelling fix

== Hanger Winch ==

[[Image:winch-overall.JPG|thumb|200 px|Overview of the winching system]]
[[Image:winch-attach.JPG|thumb|200 px|Rings welded to tow bar with snap hooks attached]]
[[Image:winch-pully.JPG|thumb|200 px|Yellow poly rope is attached to winch cable (easier to handle). Pully rides on rope to even the pull to both sides of the nose wheel while steering.]]

I use a winch to pull my tiger into the hanger. I do NOT attach the winch to the tail or the steps. I have rings welded to the towbar where it attaches to the nose wheel. A snap hook connects a 6 ft rope from one side of the nose wheel to the other side. Riding on the rope is a pully to which is attached the winch cable. The pulling load is kept centered by the pully while I steer. This works great and puts the winching force where you normally would manually with the towbar.

Brad Keleher

Structural Repair

2008-03-05T22:07:39Z

Jbowman90: Lost the "An Example Repair" link when fixing the main maintenance page. Added it here.

Maintenance

2008-03-03T17:24:58Z

Jbowman90: Completed Bob S removal of links from list items

We've organized this section to mirror the headings in the factory maintenance manual. Note that the section headings are "clickable" and take you to summary pages for that section. Links are repeated on those summary pages.

== [[Maintenance: General|General]] ==

* Required Information and Documentation
* Logbooks and Recording

== [[Servicing]] ==

* Inspections
* Oil Changes

== [[Airframe]] ==

* Disassembly
* Headliner
* Interior_Trim|Interior
* Window_Replacement|Windows
* Replacement Parts

== [[Landing Gear]] ==

* Brake System
* Nose Strut
* Wheels
* Main Landing Gear Attach Bolts

== [[Control Systems]] ==

* Rigging
* Stall Warning System

== [[Powerplant]] ==

* Engine Baffles
* Cylinders
* Oil and Filter
* Overhaul and field service
* TBO considerations
* Valve Wobble Testing
* Vacuum Pump

== [[Propeller]] ==

* Back Plate

== [[Fuel System]] ==

* Fuel Tank Leaks
* Auxiliary Fuel Tank

== [[Instrumentation]] ==

* Installing Mitchell Gauges

== [[Structural Repair]] ==

* An Example Repair
* Lower Cowling Split
* Repair of Debonding

== [[Preparations for Painting|Painting]] ==

* Preparations for Painting

== [[Electrical Systems]] ==

* Charging Systems
* Panel Switches

Rigging Checks and adjustments

2008-03-03T17:21:31Z

Jbowman90: Replaced manual markup with standard wiki markup, spelling fixes

== Introduction ==

'''Mechanical Difficulty:''' [[image:wrench.jpg]]

'''This is a job which an owner/pilot can do without any additional supervision or sign off, because you are only CHECKING the control travel, not making adjustments to the primary flight controls.'''

Checking the rigging on a Grumman is a very simple job if you have the factory templates shown in the Maintenance Manual. They are available for rent from [http://www.fletchair.com/catalog/section12.pdf FletchAir] on a weekly basis.

Many rigging checks can be made without the factory templates, with slightly more effort. Each year at the [http://www.aya.org/aya.aspx?pgID=1070 AYA Convention], the rigging templates and the Rigging Check volunteers are available to help owners check for discrepancies in their rigging of their planes.

The goal of rigging checks (and adjustments as needed) is to bring the plane into compliance with its Type Certificate Data Sheet specs, and to improve the handling and performance of the plane. In the hundreds of planes checked at the AYA conventions since 1998-- the first Cody Convention when I spearheaded the effort to start the rigging checks, I have yet to see ONE PLANE that had correct rigging on all surfaces. All that I have personally checked had at least 2 measurements out of spec. Too little or too much control displacement, but always at least 2 out of spec!

Significant performance changes can be obtained by removing the errors and getting the plane correctly rigged. At conventions its been sort of a tradition to help correct the plane that "wins" the worst rigged plane award. There have been elevators without enough UP travel that caused the pilot to always have to land at 90 mph in order to be able to flare, planes with bent outboard aileron bearing brackets that had made it impossible to fly "hands off" since the plane was purchased by its current owner, and an amazing array of other rigging errors that induced all sorts of strange handling characteristics that the owners just put up with. Then there were those rigged so poorly that they had significant performance deficits. Some people have spent many thousands of dollars for "speed mods", and found more performance in FREE rigging adjustments than in all their combined speed mod improvements.

== Rigging Adjustments ==

'''Mechanical Difficulty:''' [[image:wrench2.jpg]]

'''Any adjustments to the flight controls requires appropriate certificates and a log book sign off. You will need an Airframe mechanic to supervise and sign off the following work. '''

After rigging checks determine that there are control travels outside the specified limits, the next step is to attempt to correct the errors. An experienced A&P should be able to use the factory templates, the maintenance manual, and perhaps this page of instructions to correctly rig any Grumman.

=== Elevator and Rudder ===

The adjustments are under the plastic tail cone. They consist of 4 stop bolts with jam nuts on them to prevent unwanted movement of the stops. Loosen the jam nut on the stop in question (7/16" offset box end wrench is the best tool I've found), and then turn the stop bolt IN for more travel and OUT for less. Re-check with template or protractor to confirm the adjustment, and when correct, re-snug the jam nut. Most of the Type Certificate Data Sheet specs give a range of travel that is acceptable. Adjusting to the maximum travel will give the most control authority, and may provide the last bit of control that you need some day.

'''Tip:''' The lower rudder bearing is frequently worn or extruded from cold flow as a result of the constant tension of the rudder cables. To test for this, slowly push the rudder to the stop, such that the control horn JUST touches the stop. Now look closely at the lower bearing and support bracket, and gently push the rudder more firmly against the stop. You will almost certainly see some movement of the rudder torque tube in the bearing. If so, then the rudder will move beyond the initial limits set by the stop as the pivot point moves and changes the geometry of the hinge and stop. A new bearing insert will tighten the clearance up significantly.

=== Elevator Trim ===

The trim tab can not be "adjusted" for total travel, but it can be adjusted to center the travel such that the UP and DN limits are correct. The most common cause of elevator trim miss-rigging is lack of maintenance. The trim wheel in the console between the front seats drives the indicator, and it also drives a pair of bevel gears that convert the motion of the wheel into rotation of the trim drive, a long aluminum tube just above the floor in the tail cone. Failure to clean the old dried grease and grit from the gears, from the bearings that support the trim drive tube, and from the threads and actuator nut in the plastic tail cone can lead to excess torque required to move the trim. This can cause the bevel gears to slip, and cause the trim position indicator to no longer be sync'd with the actual position of the trim. The fix is to clean all the trim drive parts and re-lubricate them, and then set the indicator to match the elevator trim by disengaging the bevel gears and re-meshing them. Its also important to check the backlash in the gears and adjust the depth of their engagement, so that the trim won't easily return to its mis-adjusted state.

=== Flaps ===

The first step is to inspect for the correct AMOUNT of total travel. If the flap motor and drive assembly is moving the flaps too much or too little travel, then its probably a limit switch problem, either adjustment or failure. If the correct amount of travel in total degrees of movement is correct, then the flap drive mechanism can be adjusted via the Heim joints on each side to place the flap in the correct position at the UP stop. The [http://www.aircraftspruce.com/catalog/thumbnails/heim.jpg Heim joints], one pair for each side, are located below and just outboard of the back seat cushion. The seat bottom must be flipped over and the canvas cover removed to be able to see the adjustments. Begin by loosening the jam nut on the threaded area between the joints. Then remove the bolt in the top or bottom Heim joint and allow the joint to disconnect from the flap arms. Rotate the Heim joints relative to one another. Closer together raises the flaps and further apart extends them. Insert the bolt to hold the joint to the flap drive arm and check position of the flap. Repeat until the flap is positioned correctly per the template or protractor. Secure the joint by installing the nut removed earlier and properly snug the jam nut on the threads between the joints. Repeat for the opposite side.

'''Tip''' Many planes have excessive play in the flaps. This seems especially prevalent on the AA-5 series, which have a more complex flap drive and more places to allow wear and increase the play. This would also be a good time to verify that the aileron torque tube is accurately centered within the flap torque tube. This keeps the pins on the special flap drive bolts from possibly wearing a groove in the aileron torque tube.

=== Ailerons ===

Rigging the ailerons are subject to several possible faults. The cables can be incorrectly tensioned, the adjustment of the front cables to the control yoke can be mis-adjusted relative to the aft "turn around" cable that connects the 2 cables from the yokes, the aileron outboard bracket can be bent or damaged, and the outboard aileron bracket can be positioned incorrectly on the aft spar. Any of these can cause large errors in the angular position of the ailerons, and also synchronization problems side to side.

Cable tensioning requires a [http://www.aircraftspruce.com/catalog/topages/cablemeter.php cable tensiometer], which ought to have its calibration checked, if you are unsure of its testing and certification status. The basic operation is to clamp the tensiometer onto the cable in question and read the tension on the scale appropriate for the diameter of the cable. Adjustments are made by removing the safety wire or locking clip that holds the turnbuckle such that it can not let the cables unscrew from its ends. The first thing one needs to know about turnbuckles is that they have RH threads on one end, and LH threads on the other, such that if one holds the cable ends, and rotate the turnbuckle, you will either loosen or tighten the cable tension. It is important that you not turn one cable to change the tension.

The [http://www.aircraftspruce.com/catalog/appages/cliplocking.php safety clips] or the [http://www.aircraftspruce.com/catalog/appages/safetywire.php safety wire] are NOT to be reused, so be sure to have some on hand before you start. Additionally you will need to be familiar with the [[correct way to safety wire a turnbuckle]], you might be surprised at the number of A&Ps that can't do it right without looking at the book. The advantage of the [http://www.wicksaircraft.com/catalog/product_cat.php/subid=3606/index.html MS21256] style safety clips is that they are quick and easy to install correctly. (Note that both the -1 and the longer -2 size clips are needed on Grummans, depending on which cable system is being worked on.} They clips can be installed one-handed in a tight spot where trying to wrap safety wire would be very difficult. I've seen a mix of turnbuckles installed on the fleet. Some have the groove in the threads for the safety clips, and some don't, so safety wire may be the only option in some cases.

== Repairs When Adjustments Won't Correct the Rigging ==

[[Image:Wrench3.jpg]]'''-''' [[Image:Wrench4.jpg]]

Sometimes there is damage to the plane, or in rarer cases, planes that left the factory without the means to achieve the correct control travel. In these cases, more extreme measures are needed. The good news is that the approved data to make these repairs has already been published in most every case.

'''Tip'''

Because these procedures involve work that is very Grumman specific, and in most all cases new holes being drilled, these may be jobs that should involve one of the more experienced Grumman mechanics and some scheduling and travel, rather than giving the local Cessna dealer the job.

=== Drooping Aileron Counterweight ===

Incorrect drilling by the factory, or in the case of a new aileron being installed in the field, incorrect drilling by the installer. Unique to the AA-5x series. Grumman published a factory repair.
You can tell that your plane has this problem if you hold each aileron centered by putting your thumb and finger on the trailing edge of the wing tip and holding the aileron such that it has equal thickness above and below the wing tip, and then reaching under the wing tip to feel if the aileron counterweight is 1/4"-3/8" inside the wing tip. If its flush with the lower surface, then its a little out of position, and if its actually below the lower surface, then its far enough out of position that its affecting the up and down limits of travel, and should be re-drilled per the factory instructions.

=== Aileron throw incorrect ===

See Drooping aileron counterweight as one possible cause. Another is a bent or mis-positioned outboard aileron bearing bracket. The proper repair for a bent aileron outboard bearing bracket is a NEW BRACKET from [http://www.fletchair.com FletchAir]. To determine if the bracket is bent, remove it and check on a flat surface to see if the center line of the bearing hole is the same, no matter which side you view it from. Check the bracket with a square to see that it does not lean to either side. To detect a mis-positioned outboard bearing bracket, measure the centerline of the bearing bracket from both surfaces of the wing (after confirming the bracket is straight, per the above instructions), and if not, examine the aft spar and the mounting holes for evidence that the bracket was drilled off center top to bottom. To repair a mis-positioned outboard bearing bracket, a doubler of at least the thickness of the aft spar is fabricated to fill the space on the front side of the aft spar (note proper radius to match the stamped curve in the rib), and it is double-flush riveted, such that the new holes to be drilled in the aft spar will not interfere with the rivets. The bearing bracket is clamped into place and the new holes are drilled through the spar and the doubler. Slightly longer AN3 bolts will be needed to account for the spar doubler.

=== Split Elevator ===

When each half of the elevator is at a different angle. Check for this by aligning one elevator tip with the horizontal stabilizer, and then measuring the opposite tip to see if its mis-aligned with the stabilizer. Even slight differences in the zero position of the two tips can induce a rolling moment that must be corrected by adjusting the aileron trim tabs. This causes drag from the elevators and from the ailerons, and can add up to several knots of speed lost on the top end. The factory designed repair is the align the tips and ream the bolt hole(s) with a "G" letter reamer and install an NAS 6604 "X" oversize bolt to fill the larger hole. This mates the elevator half to the control horn and can cause fit up issues should the elevator ever need to be replaced. Because the oversize bolt is only ~0.015" oversize, there is only a small amount of adjustment in elevator alignment available. It is suggested that one side be re-drilled, moving the elevator halves as close to aligned as the bolt diameter increase will allow, and then, if needed, the other side be drilled to center it to the first side, thus doubling the total error that can be corrected. After reaming the holes it will be necessary check and adjust the elevator stops for proper travel.

=== Excess Play in Flaps ===

There are a number of causes, all wear related. The difficulty is in locating the real cause.

It can be the bearings on the flap drive tubes, the bracket that holds the flap drive tube on the inside of the honeycomb, the flap motor bracket cracking under the motor where it can not be seen unless the motor is removed, the bearings at the ends of the jack shaft that transfers the movement to the other side, or in the links that connect the jack shaft to the arms on the flap drive tubes. A little play in 3 or 4 locations can be several degrees by the time its all added up at the flap trailing edge. If your flaps have play, its probably a good plan to start on the list above and check/repair each item until you have eliminated the play.

=== Split Flaps ===

Although probably not showing up as a rigging problem right now, ANY history of split flap extension requires careful investigation, because the problem did not "heal" itself, and lies dormant waiting for a bad moment to re-appear. The flaps are driven by an aluminum arm that clamps the flap drive tube and is pinned by a pair of special bolts. The tip of the bolt has the threads removed, such that a round pin is created, and this pin fits into a hole in the flap drive tube. Improper assembly causes the flap drive tube to not be properly aligned when the pinning bolts are tightened, and this causes the bolt to deform the tube rather than to lock it in place. This leaves only the friction of the clamp to hold the flap in alignment, and sets the stage for split flaps. The repair is to remove the flap drive tube and either do some blacksmithing to raise the dimpled metal and restore the holes to flush with the rest of the tube, or to swap sides with the tubes and use the other set of factory drilled holes to install the pinning bolts correctly.

Brake Master and Slave Cylinders

2008-03-01T22:59:28Z

Jbowman90: Replace manual formatting with standard wiki markup and layout

__TOC__

== Introduction ==

Properly maintaining the brake system on Grumman American aircraft is extremely important because the brakes are the only way to steer the plane on the ground at low speeds where the rudder is ineffective.

The hydraulic brakes use a [http://www.aircraftspruce.com/catalog/lgpages/aeroshell_bflu.php Mil Spec fluid MIL-H-5606G], commonly referred to as "5606". This is a red petroleum-based fluid, as opposed to the Glycol based automotive fluids, and the system is not compatible with any other fluid.

If hydraulic fluid leaks have been found at the brake caliper on either main wheel, the likely causes are worn o-ring, pitted wheel cylinder or cracked wheel cylinder casting at the inlet or bleeder fitting.

The [http://www.parker.com//literature/Literature%20Files/ag/Aerospace%20Literature/maincov.pdf Cleveland Wheel and Brake Maintenance Manual] is available on-line. The [http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=794f31fd6027b03033374ec96690b9fe&rgn=div8&view=text&node=14:1.0.1.3.20.0.363.10&idno=14 FARs require] the use of the manufacturer's current maintenance instructions, and the Grumman maintenance manual gives very little detail about the wheel and brake system.

== The Wheel Slave Cylinder ==

'''Mechanical Difficulty:''' [[Image:Wrench2.jpg]]

To remove the caliper the 1/4" bolts that hold the outer brake pad retaining plate in place must be removed. The inlet line should then be removed by untorquing the [http://www.aircraftspruce.com/catalog/hapages/an818.php AN 818-4D] line nut. The line nut should require no more than 1/8 turn with a wrench before being free enough to spin off with your fingers. If the threads require a wrench to loosen them further, careful inspection of the line nut and inlet fitting threads is in order.

As soon as the line nut is loosened, 5606 fluid will begin leaking out. A small catch pan is a good idea to prevent a spill and an unsafe condition with a slippery floor. A well prepared mechanic will have an [http://www.performanceplumbing.com/AN_Adapters_2.html AN 806-4D] plug ready to seal the line and prevent losing all the fluid in that side of the brake system!

With the brake line removed the caliper can be pulled inboard and removed from the mounting bracket. Exploded views of the caliper can be found in the [http://www.parker.com/ag/wbd/cleveland/pdf/Wbcov.pdf Cleveland Wheel and Brake Parts Catalog] for easy reference to part numbers and assembly details.

With the caliper off the mounting bracket, slide the inner brake pad and backing plate off the mounting pins and remove the piston. A common method is to wrap the caliper assembly in a rag and apply air pressure to the inlet fitting to drive the piston out of the bore. There is a small amount of fluid that remains in the caliper and eye protection is suggested to prevent a chemical irritation should the remaining fluid spray in the direction of your face.

After the piston is removed, a thorough cleaning of the caliper housing and piston is next. A solvent rinse (mineral spirits or an automotive style "brake cleaner") to degrease, followed by soap and water with a mild abrasive like Scotch-Brite to remove stubborn dirt and oxidation, completed by a fresh water rinse and air drying should be sufficient to allow a good inspection.

Evidence of pitting in the caliper bore is quite common on older components, especially those that have been operated in a corrosive environment. If the pitting is very light, and only at the outer edges of the bore, it may not cause a leak under normal circumstances. The o-ring that seals the piston to the caliper bore is set back from the edge of the piston, so the actual seal takes place deeper in the bore. However as the brake pads and the rotor wear, the piston can move further out and reach a point where the o-ring may leak.

The minimum thickness of the rotor and the minimum thickness of the brake pads are designed such that the piston will not travel too far out of the bore when the minimum thicknesses are reached, and the o-ring will still seal if the bore is in good shape. Allowing the brakes to deteriorate past the point of the recommended minimum thickness can cause the piston to move far enough that the o-ring pops out of the caliper bore, and all brake effectiveness is lost without warning.

After cleaning and inspecting the caliper and piston, I suggest an acid etch and alodine, just like the pre-treatment of structural aluminum in preparation for painting. A coat of zinc chromate or an epoxy primer on the external surfaces, followed by a color coat to protect against future corrosion would be a good idea. The caliper has a data plate on it that identifies the manufacturer (Cleveland), the model and other info like the date of production (month and year) in most cases. If the data plate is missing or unreadable, then the part is technically unairworthy. The good news is, that if you contact Cleveland support at the number in the on line manuals, and you ask '''nicely''' for replacement data plates, they will send them to you AT NO CHARGE. The current production data plates are laser printed on a plastic based label, and just peel off and attach to a clean, smooth surface.

After all the surface prep, primer and paint, the caliper is ready to assemble. Install a new O-ring. Its important to use the correct part number that is made of the right material, and not just some "hardware store" o-ring. The early planes use a 1.5" piston and the later models use a 2" piston. The Mil-Spec is an MS28775 in either [http://www.wicksaircraft.com/catalog/product_detail.php/pid=6320~subid=1689/index.html?PHPSESSID=544f063ebd63b7bfa3ced8221afb67b4 -222] or [http://www.wicksaircraft.com/catalog/product_detail.php/pid=6321~subid=1689/index.html -224]. It is important that the o-ring not be twisted in its groove. Lube it and the bore of the caliper with a generous amount of 5606 fluid, and insert the piston with a rotating motion. Once lined up correctly, it will slide into place with a quick motion and be ready to wipe off the excess fluid and install the assembly on the plane.

Refer to the section on [http://www.bondline.org/index.php/%3D%3D_Fixing_soft_brakes_caused_by_fluid_leaks_and_air_in_the_system_%3D%3D bleeding the brakes] for instructions on how to purge the air from the system.

== The Master Cylinders ==

'''Mechanical Difficulty:''' [[Image:wrench3.jpg]]

On most Grummans there are 4 Master Cylinders, a pair for each pilot. They are plumbed such that the pilot's side master cylinder output in hooked to the co-pilot's side master cylinder inlet, and the co-pilot's side master cylinder output is connected to the brake caliper by flex and hard lines.

This means that low fluid in the pilot's side master cylinder can cause a loss of brake effectiveness and a soft pedal, and the co-pilot's side brakes can continue to work.

Removing the brake master cylinders requires disconnecting the flex line from the output, and on the co-pilot's side, also disconnecting the flex line to the input. The master cylinder must be disconnected from its bracket on the floor, and from the brake pedal. The installation hardware can vary from year model to year model, with some having Clevis Pins, some Clevis Bolts, and some AN3 bolts. In all cases the greatest difficulty is in reaching the hardware. The master cylinders are on the firewall side of the rudder pedals, so its awkward to reach the hardware.

Some [http://www.performanceplumbing.com/AN_Adapters_2.html AN806-4D] flare plugs are handy to seal the flex lines as they are disconnected. Unless the fluid has all been drained from the brake system, several ounces of 5606 fluid will leak out when the lines are disconnected.

<TO BE CONTINUED>

Bondline

2008-03-01T09:11:22Z

Jbowman90: Added a break with a "clear: both" style to force the webring stuff to be the last info on the page. Most viewers won't see a difference.

[[Image:P9130251.JPG|thumb|300 px|Orange Airplane]]

Bondline is a place for [http://en.wikipedia.org/wiki/Grumman Grumman] owners and pilots to share their knowledge.

== Important Grumman Resources ==

* [http://www.aya.org/ Join AYA, the International Type Club for Grummans ''Now'']!
* Subscribe to the [http://www.ayaforum.org/ AYA Forum].
* Subscribe to the [http://www.grumman.net/ Grumman-Gang] email list. Note that many topics have been covered previously on the Grumman-Gang and can be found in the Grumman-Gang archives, available to subscribers.
* [http://www.fletchair.com FletchAir] The first source for PMA Grumman parts

== Technical Information ==

* [[General]]
* [[Maintenance]]
* [[Operations]]
* [[337s]]

<br style="clear:both;"/>
----
'''This site is a member of the Grumman Enthusiast's WebRing.'''

[http://p.webring.com/hub?ring=grumman;sid=33;id=33;hub Visit other Grumman Enthusiast's sites]

Performance

2008-03-01T09:08:00Z

Jbowman90: Removed superfluous introductory heading, removed blank lines between bullets

* [[Basic Engine and Propeller Performance]]
* [[Takeoff]]
* [[Climb]]

Preflight

2008-03-01T09:07:15Z

Jbowman90: Removed reference to AA-1 weight and balance page. This info was moved to the new Weight and Balance page

* [[Creating a Grumman-specific fuel tank dip stick]]
* [[Protecting the Fuel Tank Vents]]
* [[Stall Warning System]]
* [[Weight & Balance]]

Creating a Grumman-specific fuel tank dip stick

2008-03-01T09:05:53Z

Jbowman90: Added wiki markup to force some page structure. Someone may need to check for sanity.

== Introduction ==

The measurements for the Traveler and the Cheetah standard 19 gal/side tanks are different than the Tiger and long range Cheetah 26 gal/side tanks. The 19 gallon tank measurement is listed first, and the 26 gallon tank measurement is listed last. Note that the 19 gallon tank is NOT measuring inches, but rather the marks on the FuelHawk tube that is sold as a universal model not calibrated to any particular model of plane. The 26 gallon chart is actual inch measurements that can be transfered to any other suitable dipstick such as a wooden paint stirring stick. Sorry for the mismatch of measurement systems, but this is the way 2 different owners provided the information.

Gil Alexander has also turned these tables into calibration charts for those who prefer pictures. Just print the picture and laminate it. Three versions, just pick the applicable one.

== Fuel Hawk Calibrations ==

[[Image:Fuel-hawk-calibrated-small.jpg|thumb|200px|Universal Fuel Hawk For Small Grumman AA-5x Tanks]]
[[Image:Fuel-hawk-calibrated.jpg|thumb|200px|Universal Fuel Hawk For Large Grumman AA-5x Tanks]]

'''19 Gallon Tank'''
{| border="1" style="text-align:center"
! Gallons !! FuelHawk#
|-
|4 || Bottom of tank (0#)
|-
|4.4||1#
|-
|6.1||2#
|-
|7.7||3#
|-
|9.4||4#
|-
|11||5#
|-
|12.7||6#
|-
|14.3||7#
|-
|15.9||8#
|-
|17.3||9#
|-
|18.3||10#
|}

<br style="clear:both;"/>

== Calibration by Stick ==

[[Image:Fuel-inches-large-tank.jpg|thumb|200px|Generic Calibration for a Wooden Ruler For Large Grumman Tanks]]

Bondline contributor [http://www.bondline.org/index.php/User:GregAmy Greg Amy] gives his experience using a [http://www.aircraftspruce.com/catalog/pspages/fuelhawkfuelgauge.php "Fuelhawk C-152"] from J-Air, available at any FBO, with his 26 gallon tanks on a Tiger. It doesn't matter whether you use this, a paint stick, or your favorite pen, as long as the length of it is sufficient so you don't drop it into the tank (that would suck). What counts is the height of the fuel from the bottom of the tank, immediately below the cap opening. Sporty's makes a [http://www.sportys.com/acb/showdetl.cfm?&Product_ID=1286&DID=19 "Universal Fuel Gauge", P/N 5304A]. I used a permanent marker for the marks, and it's lasted a few year's worth of fuel dips so far.

The first number is the gallons useable remaining, the second is the distance from the bottom of the stick (tank). Experience with many fillups has shown this to be a very handy ''GUIDELINE''; I'd entertain any others' experiences to adjust this.

And a generic calibration for a wooden ruler and large Grumman tanks... perhaps the easiest method of all...

'''26 Gallon Tank'''
{| border="1" style="text-align:center"
! Gallons !! Distance inches
|-
|7 || Bottom of tank (0")
|-
|8||1/4"
|-
|9||7/16"
|-
|10||11/16"
|-
|11||13/16"
|-
|12||1"
|-
|13||1-1/4"
|-
|14||1-1/2"
|-
|15||1-13/16"
|-
|16||2-1/16"
|-
|17||2-3/8"
|-
|18||2-5/8"
|-
|19||3"
|-
|20||3-1/4"
|-
|21||3-5/8"
|-
|22||4-1/16"
|-
|23||4-1/2"
|-
|24||4-15/16"
|-
|25||5-1/2"
|}

Sample Binder

2008-03-01T08:50:48Z

Jbowman90: Removed superfluous introductory heading, changed binder picture to thumbnail, cleaned up markup for link to checklist

[[Image:Checklist_binder.jpg|thumb|200px]]

One option for checklists for those of us who don't like looking at the microscopic print on some of the commercial ones is to make our own on a PC. The best format for this is a surplus Air Force Crew Checklist binder - usually obtainable at aviation surplus places, e-bay and major fly-ins (I got mine at the Copperstate fly-in). These binders come with clear plastic page covers that will take a slightly trimmed down 8.5 x 11 paper folded in two. They are tough, easy to open up and fold over so you are only looking at a half page at one time. With the slide in sheets, they are easy to change if you want to customise a checklist to your requirements - You could add a "Check cell phone OFF" line as an example.
You can also leave a few slide in pages empty at the end and use them for the FAA kneeboard size PDF taxi diagrams of the towered airports you visit.

To help you get started, here are my checklists made as a MSword document. Check out the readability of the larger size fonts!

They cover Normal Operation, Emergencies and Preflight in 12 sheets, with clear section titles. I printed the Emergency pages on colored paper to make them easy to find. ''Gil Alexander''

[http://www.home.earthlink.net/~gilalex/Tiger/check-list-N12GA.doc Sample AA-5B knots Check List]

Bondline

2008-03-01T08:47:41Z

Jbowman90: Added blank line above web ring break for better visual appearance

[[Image:P9130251.JPG|thumb|300 px|Orange Airplane]]

Bondline is a place for [http://en.wikipedia.org/wiki/Grumman Grumman] owners and pilots to share their knowledge.

== Important Grumman Resources ==

* [http://www.aya.org/ Join AYA, the International Type Club for Grummans ''Now'']!
* Subscribe to the [http://www.ayaforum.org/ AYA Forum].
* Subscribe to the [http://www.grumman.net/ Grumman-Gang] email list. Note that many topics have been covered previously on the Grumman-Gang and can be found in the Grumman-Gang archives, available to subscribers.
* [http://www.fletchair.com FletchAir] The first source for PMA Grumman parts

== Technical Information ==

* [[General]]
* [[Maintenance]]
* [[Operations]]
* [[337s]]

----
'''This site is a member of the Grumman Enthusiast's WebRing.'''

[http://p.webring.com/hub?ring=grumman;sid=33;id=33;hub Visit other Grumman Enthusiast's sites]

Bondline

2008-03-01T08:46:25Z

Jbowman90: Removed extra blank line

[[Image:P9130251.JPG|thumb|300 px|Orange Airplane]]

Bondline is a place for [http://en.wikipedia.org/wiki/Grumman Grumman] owners and pilots to share their knowledge.

== Important Grumman Resources ==

* [http://www.aya.org/ Join AYA, the International Type Club for Grummans ''Now'']!
* Subscribe to the [http://www.ayaforum.org/ AYA Forum].
* Subscribe to the [http://www.grumman.net/ Grumman-Gang] email list. Note that many topics have been covered previously on the Grumman-Gang and can be found in the Grumman-Gang archives, available to subscribers.
* [http://www.fletchair.com FletchAir] The first source for PMA Grumman parts

== Technical Information ==

* [[General]]
* [[Maintenance]]
* [[Operations]]
* [[337s]]

----
'''This site is a member of the Grumman Enthusiast's WebRing.'''

[http://p.webring.com/hub?ring=grumman;sid=33;id=33;hub Visit other Grumman Enthusiast's sites]

Bondline

2008-03-01T08:45:19Z

Jbowman90: Change section headings from minor "===" to major "==", removed old statement about new subtopics, moved Orange airplane picture higher on the page

[[Image:P9130251.JPG|thumb|300 px|Orange Airplane]]

Bondline is a place for [http://en.wikipedia.org/wiki/Grumman Grumman] owners and pilots to share their knowledge.

== Important Grumman Resources ==

* [http://www.aya.org/ Join AYA, the International Type Club for Grummans ''Now'']!
* Subscribe to the [http://www.ayaforum.org/ AYA Forum].
* Subscribe to the [http://www.grumman.net/ Grumman-Gang] email list. Note that many topics have been covered previously on the Grumman-Gang and can be found in the Grumman-Gang archives, available to subscribers.
* [http://www.fletchair.com FletchAir] The first source for PMA Grumman parts

== Technical Information ==

* [[General]]
* [[Maintenance]]
* [[Operations]]
* [[337s]]

----
'''This site is a member of the Grumman Enthusiast's WebRing.'''

[http://p.webring.com/hub?ring=grumman;sid=33;id=33;hub Visit other Grumman Enthusiast's sites]

Operations

2008-03-01T08:37:26Z

Jbowman90: Removed orphaned "checklists" heading. This was accidentally left on the page after some recent edits.

* [[Sample Binder]]
* [[Preflight]]
* [[Normal Procedures]]
* [[Emergency]]
* [[Performance]]

Maintenance

2008-03-01T08:34:29Z

Jbowman90: Changed the page structure so that a Table of Contents could be generated. This should help simplify the page and help people find stuff better

We've organized this section to mirror the headings in the factory maintenance manual. Note that the section headings are "clickable" and take you to summary pages for that section. Links are repeated on those summary pages.

== [[Maintenance: General|General]] ==

* Required Information and Documentation
* Logbooks and Recording

== [[Servicing]] ==

* Inspections
* [[Oil and Filter|Oil Changes]]

== [[Airframe]] ==

* [[Disassembly]]
* [[Headliner]]
* [[Interior_Trim|Interior]]
* [[Window_Replacement|Windows]]
* [[Replacement Parts]]

== [[Landing Gear]] ==

* [[Brake System]]
* [[Nose Strut]]
* [[Wheels]]
* [[MLG Attach Bolts|Main Landing Gear Attach Bolts]]

== [[Control Systems]] ==

* [[Rigging_Checks_and_adjustments|Rigging]]
* [[Stall Warning System]]

== [[Powerplant]] ==

* [[Engine Baffles]]
* [[Cylinders]]
* [[Oil and Filter]]
* [[Overhaul and field service]]
* [[TBO considerations]]
* [[Valve Wobble Testing]]
* [[Vacuum Pump]]

== [[Propeller]] ==

* Back Plate

== [[Fuel System]] ==

[[Fuel System]]

* [[Fuel Tank Leaks]]
* [[Auxiliary Fuel Tank]]

== [[Instrumentation]] ==

* Installing Mitchell Gauges

== [[Structural Repair]] ==

* [[An Example Repair]]
* [[Lower Cowling Split]]
* [[Repair of Debonding]]

== [[Preparations for Painting|Painting]] ==

* [[Preparations for Painting]]

== [[Electrical Systems]] ==

* [[Charging Systems]]
* [[Panel Switches]]

Maintenance

2008-03-01T08:04:26Z

Jbowman90: Added direct link to oil and filter changes to Servicing although link appears on the Servicing page

We've organized this section to mirror the headings in the factory maintenance manual.

*[[Maintenance: General|General]]
**Required Information and Documentation
**Logbooks and Recording
*[[Servicing]]
**Inspections
**[[Oil and Filter|Oil Changes]]
*[[Airframe]]
**Disassembly
**Headliner
**Interior
**Windows
**Replacement Parts
*[[Landing Gear]]
**Brakes
**Nose Strut
**Wheels
*[[Control Systems]]
**Rigging
**Stall Warning System
*[[Powerplant]]
**Engine Baffles
**Oil and Filter
**Overhaul and field service
**TBO considerations
**Valve Wobble Testing
**Vacuum Pump
*[[Propeller]]
**Back Plate
*[[Fuel System]]
**Fuel Leaks
**Auxiliary Fuel Tank
*[[Instrumentation]]
*[[Structural Repair]]
**[[An Example Repair]]
**[[Lower Cowling Split]]
**[[Repair of Debonding]]
* [[Preparations for Painting]]
*[[Electrical Systems]]
**Charging System

Charging Systems

2008-03-01T08:00:08Z

Jbowman90: Move "the usual scenario" to paragraph rather than stand alone

__TOC__

== The Basics ==

The battery stores power chemically, the alternator converts the engine's rotating motion into electrical energy, the Voltage Regulator (also known as the "Alternator Control Unit", or ACU) controls the alternator's output to keep the battery charged, but not over charged (which results in boiling out its acid).

For a more detailed explanation of charging system operation and theory, a quick Google search usually does the trick. Rather than rehash the theory here, [http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm Rowand.net] has a fairly good explanation of how generators and alternators work as well as the regulator.

To better understand some of the terminology below, the various terminals on the regulator are briefly discussed.

* "F" - Field terminal. Controls the current going to the electromagnets inside the alternator. When there is higher demand on the bus, the regulator increases the field strength to keep the bus voltage at the appropriate level, either 14V or 28V. How does it sense this ...
* "S" - Sense terminal. Measures the voltage in the electrical system downstream of the alternator. Why downstream? Ohmic losses will cause the alternator output voltage to be different than at the bus, for example. The regulator should be adjusting voltage to keep the battery properly charged.

== Troubleshooting ==

'''Mechanical Difficulty:'''[[Image:Wrench2.jpg]]

'''The usual scenario''' ... Your battery started discharging during your last flight. You shed loads by turning off unneeded equipment until you arrived at the airport and landed normally. Congrats on handling the in flight portion properly. Now how do you get it repaired?

You need to find out exactly which part failed. The usual FBO response is to replace the alternator AND the voltage regulator. They don't have to do much troubleshooting and they sell lots of expensive parts. A Field Rep for [http://www.kellyaerospace.com/index.html Kelly Aerospace], one of the largest OH shops for alternators, came to an FAA Safety meeting and told the attendees that 8 out of 10 alternators returned to them as cores for OH worked when tested before disassembly. He stated that A&P mechanics in the field were NOT doing their job properly, and that better troubleshooting techniques were needed, rather than replacing so many functional alternators.

If you have a Volt-Ohm meter, you can save lots of time and money. Inexpensive voltmeters are widely available from such vendors as [http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92020 Harbor Freight] and [http://www.radioshack.com/product/index.jsp?productId=2103534 Radio Shack], often for as little as $10.

To help you know what wire goes where, the maintenance manual has detailed schematics. Gary Vogt has re-drawn the [http://www.aucountry.com/ACA_Folder/Technical/Wire_Scan_76-77.jpg 76-77] and the [http://www.aucountry.com/ACA_Folder/Technical/Wire_Scan_78-79.jpg 78-79] Tiger/Cheetah schematics in a little less technical detail.

All the troubleshooting described below is done with the engine OFF and the keys in your pocket.

Open the cowl and locate the voltage regulator. On Grumman American singles its on the passenger side just inboard of the motor mount attach point, directly above the battery. On AA-5x you'll see a connector on the bottom with several wires. Look closely and you'll see that they are marked with letters on the regulator. On AA-1x there are only 2 wires and they are crimped to the airframe wiring harness without any quick disconnects.

Visually check all of the wires and their crimped fittings. Pull gently on the crimped fittings, none of them should be loose. After 30+ years in service all these wires warrant close examination. Generally inspect the wires for large cracks in the insulation, or, where appropriate, the shielding. Look for breaks in the shielding pigtails.

Turn on the Master switch.

=== AA-5x series 12V ===

Locate the "S" terminal on the AA-5x regulator. Using your VOM, measure the voltage between the S terminal on the regulator and a good ground such as the battery's negative terminal. The VOM should read close to 12.6 volts on a fully charged battery. In this example, however, your battery is not fully charged after the in-flight failure of the charging system, so a measurement equal to 10 volts or greater is acceptable. If an acceptable voltage is present, then your Master Switch, Master Relay, Alt Field Circuit Breaker and the associated wiring are all working well enough to charge the battery from the alternator. Continue to the next step.

Locate the "F" terminal and measure the voltage just as you did at the "S" terminal. As before, if the measured voltage is within a couple of volts of the nominal battery voltage, then the regulator is correctly trying to "excite" the alternator field so that the alternator can produce an output. Continue to the next step.

Reset the VOM to measure resistance instead of voltage. Remove the "F" wire from the regulator and measure between the wire and ground. You should measure less than 10 ohms of resistance, and usually about 5 ohms. If you have significantly higher resistance (say 20 ohms or more) then there are problems with the alternator field or brushes, or possibly the wiring going to the alternator is in bad condition. A reading of less than 5 ohms, would indicate a short in the Field wire or inside the alternator. Otherwise, since you have the appropriate resistance between the "F" wire and ground, you are through checking the easy stuff, and are ready to pull the nose bowl.

=== AA-1x series ===

Locate the "I" terminal wire on the AA-1x regulator. Using your VOM, measure the voltage between the I wire on the regulator and a good ground such as the battery's negative terminal. The VOM should read close to 12.6 volts on a fully charged battery. In this example, however, your battery is not fully charged after the in-flight failure of the charging system, so a measurement equal to 10 volts or greater is acceptable. If an acceptable voltage is present, then your Master Switch, Master Relay, Alt Field Circuit Breaker and the associated wiring are all working well enough to charge the battery from the alternator. Continue to the next step.

Locate the "F" wire and measure the voltage just as you did at the "I" wire. As before, if the measured voltage is within a couple of volts of the nominal battery voltage, then the regulator is correctly trying to "excite" the alternator field so that the alternator can produce an output. Continue to the next step.

Reset the VOM to measure resistance instead of voltage. Disconnect the "F" wire from the regulator and measure between the wire and ground. You should measure less than 10 ohms of resistance, and usually about 5 ohms. If you have significantly higher resistance (say 20 ohms or more) then there are problems with the alternator field or brushes, or possibly the wiring going to the alternator is in bad condition. A reading of less than 5 ohms, would indicate a short in the Field wire or inside the alternator. Otherwise, since you have the appropriate resistance between the "F" wire and ground, you are through checking the easy stuff, and are ready to pull the nose bowl.

=== Turn OFF the Master at this time ===

We are through with the powered portion of the testing, so turn off the Master switch.

Right about now you are wishing that you had installed the split nose bowl STC, because without it you have to remove the propeller to gain access to the alternator.

'''Mechanical Difficulty:''' [[Image:Wrench3.jpg]]

Up to this point, we were just CHECKING electrical measurements without any actual disassembly of the plane. If you do not have the split nose bowl STC, then this is the point at which you will require A&P supervision to complete the testing, removal and replacement of the alternator, prop, mounting bracket, etc. [http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgFAR.nsf/0/AC9BED30F1D032B9852566AB006BC89C?OpenDocument FAR 43 Appendix A paragraph (c)(19)] permits the owner/pilot to remove and install cowlings without A&P supervision, if the prop does not have to be removed, after demonstrating the ability to do it correctly.

On all 2 place and on Travelers before 75, you can check the wiring by removing the screws on the right-hand lower cowling and letting the cowl side tip out from the firewall and nose bowl just enough to enable you to reach under the front cylinder and touch the wires on the back of the alternator. On 75 Travelers with the "Cheetah nose" and on all Cheetahs and Tigers, you have to remove the nose bowl to continue troubleshooting. That's OK, because you have already narrowed the source of the problem to that area anyway.

With the nose bowl off, or at least the lower nose off if you have the split nose, now remove the alternator belt from the pulley. Our testing so far has not ruled out a worn, loose, or missing alternator belt, so make certain that the belt is in good condition and properly tensioned.

The required amount of tension on this belt is often underestimated. The amount of power required to turn the alternator increases as the SQUARE of its output (charging) current! Lycoming's service information was updated a couple years back, and they now suggest setting belt tension by checking to see if the belt will slip before reaching a specified torque. You can check this by putting a socket on the alternator drive pulley nut and setting a torque wrench to 540 in-lb (45 ft-lb), and then holding the prop and trying to turn the alternator (CCW when viewing it from the front) with the torque wrench. The wrench should indicate 540 in-lb BEFORE the pulley slips. The older method mentioned in the Maintenance Manual, no longer favored by Lycoming, was to press in the center of the belt span between the pulleys and measure the deflection. New belts were to have less deflection than those that were worn. Refer to the maintenance manual if you don't have a torque wrench handy.

If the belt itself is in good condition and is tensioned correctly, the next step is to remove the alternator for inspection. First release the tension on the belt. To do this, cut the safety wire on the bolt holding the alternator to the bracket, then loosen the bolt enough so that you are able to push the alternator up, thus relieving the belt tension.

In the next step, you remove the alternator, which is quite heavy. If you have a portable service table or stand, now would be a good time to position it under the alternator. Now remove the big bolt at the bottom of the alternator (the one that holds it to the engine mounting bracket). While supporting the alternator so the wiring is not stressed, remove the bolt that was safety wired. The alternator should slide off the engine mounting bracket and be attached only by the wiring on the back.

Carefully turn the alternator around, and lift the rubber boot that hides the connection of the big wire to the back of the alternator. This is a VERY common failure point on the aging fleet. The wire breaks off the ring lug that is bolted down, and the alternator output is prevented from flowing back to the battery by the broken connection. Look also at the small wire that is bolted to the same connection. This is the "A" or sense wire which tells the Voltage Regulator what the alternator is doing. The sense wire is also a common failure point, though not as often as the larger output wire. Look at the other small wire which attaches to a different post. This is the "F" or field wire. If the resistance checks were normal earlier, then this wire should be fine; nevertheless, after 30+ years in service all these wires warrant close examination. Inspect the wires for cracks in the insulation, or, where appropriate, the shielding. Make sure the shield grounds at both ends of the F and A wires are in good condition and still connected, and check the sheilding pigtails behind the alternator, they can rub on the baffling and get worn through.

If there are no obvious failures in the wiring, you need to mark them and remove them so that the alternator can be tested at a shop. Pep-Boys and AutoZone will check your alternator for free. If you have an AA-5x series, then tell them its from a 71 Ford Pickup with AC. That is the actual original application for the Ford DOFF-10300J alternator on your Traveler/Cheetah/Tiger. AA-1x use a Prestolite brand alternator, and they should have no trouble figuring out the connections.

After the alternator is spun up and bench tested, all but the rarest and intermittent failures will have been diagnosed, and you will be repairing JUST the wiring, or replacing the alternator or the voltage regulator, and NOT spending money on needless repairs.

Prior to installing the alternator, carefully inspect the U shaped mounting bracket for cracks. They are prone to crack across the middle of the U, often into one of the bolt holes. Replacement brackets are available from any Lycoming distributor or from FletchAir.

== Replacement Parts ==

If the alternator or regulator have failed, you may want to consider a modern replacement than have the old stuff overhauled. Honestly, for about the same price as an overhaul, you can have a new alternator. [http://www.plane-power.com/products.htm Plane Power] makes a PMA'd alternator that is about 1 lb lighter, and they claim that it makes power at lower RPM. They also make a PMA'd modern solid state voltage regular. Zeftronics is also a popular solid state regulator replacement. If either the alternator or regulator has failed, have the other tested. In some cases, a failure in one of these causes problems in the other.

Structural Repair

2008-03-01T07:57:38Z

Jbowman90: Removed superfluous introductory heading, deleted debonding and lower cowl information and referenced the new pages created for these

Repair of Debonding

2008-03-01T07:55:20Z

Jbowman90: Created page, move from Structural Repair page

Aside from problems with the infamous purple glue, used in late '74 through early '76 models, that resulted in [http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/15ABBB4154F287DA86256A38005E36C8?OpenDocument AD 76-17-03], there can be random debonding on the rest of the fleet. Often this is the result of corrosion.

[[Image:Corrosion_under_bonds.jpg]] [[Image:corrosion2.jpg]]

The staggered holes in the bonded area were drilled to allow the skin and ribs to be clecoed together in the same alignment that they were bonded, before the extent of the corrosion was determined. This created a "matched hole tooling" effect, much like [http://vansaircraft.com/public/kit-std.htm Van's RV series] uses on their airframes to reduce the amount of jigging that must be done to assemble the planes.

The factory provided data to be used in doing repairs of all types of debonding with the publication of Service Kit 125A. The short version is that nearly any debonding can be repaired with this data. That is good news for owners and mechanics as we attempt to preserve the aging fleet and repair various damage that is unrelated to the spontaneous debonding. The factory data doesn't speak to HOW or WHY the debonding occurred, so that means that if we intentionally debond the parts to replace a corroded or dented part, we are still allowed to use the SK-125A methods to install the replacement parts.

SK-125A calls out an "inhibited poly-sulfide sealant", which is the same Mil-Spec as high adhesion fuel tank sealant, and [http://www.pegasusautoracing.com/bigpicture.asp?RecId=3466 NAS1097] reduced head rivets to replace the original factory bond. Cleaning of the surfaces to be re-bonded is also explained, and care must be taken not to introduce contaminants that might initiate future corrosion.

Maintenance

2008-03-01T07:53:59Z

Jbowman90: Added link for Repair of Debonding

We've organized this section to mirror the headings in the factory maintenance manual.

*[[Maintenance: General|General]]
**Required Information and Documentation
**Logbooks and Recording
*[[Servicing]]
**Inspections
*[[Airframe]]
**Disassembly
**Headliner
**Interior
**Windows
**Replacement Parts
*[[Landing Gear]]
**Brakes
**Nose Strut
**Wheels
*[[Control Systems]]
**Rigging
**Stall Warning System
*[[Powerplant]]
**Engine Baffles
**Oil and Filter
**Overhaul and field service
**TBO considerations
**Valve Wobble Testing
**Vacuum Pump
*[[Propeller]]
**Back Plate
*[[Fuel System]]
**Fuel Leaks
**Auxiliary Fuel Tank
*[[Instrumentation]]
*[[Structural Repair]]
**[[An Example Repair]]
**[[Lower Cowling Split]]
**[[Repair of Debonding]]
* [[Preparations for Painting]]
*[[Electrical Systems]]
**Charging System

Lower Cowling Split

2008-03-01T07:51:51Z

Jbowman90: Created page, spelling fixes from old page, forced Table of Contents

__TOC__

== Introduction ==

Requests for information on splitting the lower cowl on Tigers and Cheetahs was made on the GG and I'll post some pictures and an explanation of the means I used to repair lower cowls that had failed the spot welds and had cracking doublers.

== Bob Stewart's Approach ==

Here is the Tiger lower cowl with failed spot welds and cracked doublers after removing the cowl from the plane and taking the doublers out. [[Image:Bottom_sm.jpg]]

This is a Cheetah LH lower cowl from the outside with larger ramp being drilled and clecoed in place. Paint is off because of the amount of metal work that was needed [http://www.tinmantech.com/html/powerhouse_wheeling_machines.php with an English Wheel] to smooth the ripples that had been filled with bondo during previous work by persons unknown (no log entry!).

[[Image:LH_Cowl.jpg]]

Here is the inside of that same Cheetah lower cowl half with the ramp in place and the new doubler mounted, ready to attach the other side with screws.

[[Image:Left_inside.jpg]]

== Gil Alexander's Approach ==

Gil Alexander took a slightly different approach for a Tiger repair, since he didn't want to harm a new paint job. Gil left the doubler in place and added a 0.032 strip of aluminum 1 7/8 wide on the inside. Here's what he did:

* Removed the nut plate at the front on the nose gear boot mount, and clamped the strip in place.
* Drilled #30 holes from the outside for the mounting screws, roughly located where rivets from a previous repair were removed. Clecos were inserted as the holes were drilled.
* Drilled matched #19 holes for #8 screws for the aft screw at the nose gear boot mount and for the central retaining screw into the nose bowl.
* Removed the strip.
* Drilled all holes in the cowling and new strip #19 for #8 screws and nutplates riveted to the new strip.

Only now, after the cowling is completely drilled, is the original joining strip cut down the middle with a [http://www.hobbypeople.net/gallery/516443.asp 2 inch cutting wheel on a Dremel tool]. Working from the inside, this avoids harming the (new) exterior paint.

Only the forward 2 inches of the original joining strip need be removed. This ensures that the extra layer of the new joining strip does not create an extra layer at the center where the cowling is screwed to the nose bowl.

This technique ensures that the original alignment of the two halves of the cowling is precisely maintained, allowing accurate #19 holes (a slip fit for #8 screws) and fixed, not floating, nutplates to be used.

This photo shows the left side cowl and the center strip. Note that the center strip end that is shown at the bottom of the picture is actually the end that is attached to the nose bowl. The slight joggle in the strip can just be seen. This joggle keeps the same thicknesses of metal at the surfaces that are screwed to the nose bowl.

[[Image:Cowl-small-1.JPG]]

Maintenance

2008-03-01T07:49:15Z

Jbowman90: Added link for Lower Cowling Split. This will be a separate page.

We've organized this section to mirror the headings in the factory maintenance manual.

*[[Maintenance: General|General]]
**Required Information and Documentation
**Logbooks and Recording
*[[Servicing]]
**Inspections
*[[Airframe]]
**Disassembly
**Headliner
**Interior
**Windows
**Replacement Parts
*[[Landing Gear]]
**Brakes
**Nose Strut
**Wheels
*[[Control Systems]]
**Rigging
**Stall Warning System
*[[Powerplant]]
**Engine Baffles
**Oil and Filter
**Overhaul and field service
**TBO considerations
**Valve Wobble Testing
**Vacuum Pump
*[[Propeller]]
**Back Plate
*[[Fuel System]]
**Fuel Leaks
**Auxiliary Fuel Tank
*[[Instrumentation]]
*[[Structural Repair]]
**[[An Example Repair]]
**[[Lower Cowling Split]]
* [[Preparations for Painting]]
*[[Electrical Systems]]
**Charging System

Fuel Tank Leaks

2008-03-01T07:44:41Z

Jbowman90: Removed superfluous introductory heading, replaced manual formatting with standard wiki markup, edited layout for cleaner section headings

== Introduction ==

'''Mechanical Difficulty:''' [[Image:wrench2.jpg]] '''-''' [[Image:wrench4.jpg]]

On the AA-1x series there are only 4 possible leak points from the wing spar tanks. Each end of the spar tube has a machined aluminum plug with an O-ring in a groove around the outside of the plug. The outboard plug is secured in place with 4 AN3 bolts which have special washers known as [http://www.gen-aircraft-hardware.com/stat-o-seal.asp "Stat-o-seals"]. The inboard plug is secured in place with either 1 or 2 AN3 bolts, depending on the year model. The same Stat-o-seals are used on the bolts at the inboard end. Deterioration of the O-rings or the rubber covered Stat-o-seals can result in leaks. At the inboard end of the spar tank a block of aluminum is bonded on the bottom of the spar and a hole through the spar and the bonded block allow for draining the sump. A short section of 1/4" rubber hose leads from the bonded block to a cast fitting and the drain valve. This hose can fail and leak the entire contents of the tank.

On the AA-5x series there are 4 access panels on the bottom of each wing that are sealed with a special "low adhesion" sealant such as FlameMaster CS3300B or Desoto/PRC PR1428B. There has been an [http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/DCA089D17D5FBD8E862569AF00767BF2?OpenDocument AD on the sealant used by the factory], and it is normal to require periodic re-sealing of the access covers. The wing ribs have a hole that is slightly larger than the wing spar tube. This leaves a gap of 1/16"-3/32" between the rib and the spar tube that the factory filled with a fillet of sealant. After 30+ years that fillet of sealant may leak as the wing flexes and stretches the sealant. The perimeter of the tank along all the bonded joints has been known to leak in the event of an incomplete bonded section or in the case of the purple glue on the late 74 through early 76 models, at areas of debonding. The fuel level sender on the inboard rib of the tank has a rubber gasket that deteriorates with age and can leak. The tank vent tube comes out both ends of the tank and can leak at the inboard end where some models have a section of rubber hose that connects to the next length of aluminum tubing. The AA-5x series can have tank leaks at the access covers, around the inboard and outboard spar to rib joint, at the fuel level sender gasket, the fuel pickup fittings and at bonded joints that are incomplete or failing. It's no wonder that the AA-5x have many more fuel leak problems than the AA-1x.

== Find the source ==

The first step is to identify the true source of the leak(s). On AA-1x, this is straight forward, as there are fewer leak points, and they tend not to be confused with each other. Leaks at the outboard end of the tank are due to the large o-ring around the outer plug that also contains the filler neck, or around the Stat-o-seals. Leaks at the inboard end that drip at the center of the fuselage are from the large o-ring at the inboard plug, leaks inside the wing are either Stat-o-seal leaks or sump drain hose leaks.

[[Image:DCP_8269.jpg|right|thumbnail|Installing access panels in the orange airplane, a '71 AA1A, s/n AA1A-0031. FletchAir provided kits, complete with pre-drilled doublers and covers. More photos from sbw: http://urlizer.com/00/1903/]]

The inboard plug o-ring leaks require pulling the wing panel. All the others can be repaired with the wing on the plane. Late model AA-1B and all the AA-1C have access panels on the bottom of the wing in the area of the drain hose. These can be added to early models.

AA-5x wing tanks are more difficult to identify the true source of the leak(s). Many would be tank sealers have been fooled by the location of the leaks, and have diligently scraped and cleaned the old sealant out of the tank in the area they THOUGHT the leak was located in, and then re-sealed with the proper high adhesion sealant, only to find that the exact same leak reappeared upon filling the tank.

One method of locating the actual leak is to pressure test the tank. This is accomplished by removing all the fuel and then applying air pressure to the tank and spraying soapy water over the area where the leak is suspected to be. This will work around fuel level sender gaskets, fuel pick up bulkhead fittings, skin to rib bonded lap joints, and around the spar to rib joint.

Care must be taken to limit the pressure applied. The large surface area of the tank skin turns even very small pressures into TONS of load on the skin. '''It's possible to destroy a wing if air from a compressor is applied. The pressure applied for testing is measured in INCHES OF WATER COLUMN, not PSI!'''

Blowing into the tank vent with lung pressure is one convenient source of air that can not cause tank failures. Some gauges suitable for regulated propane or natural gas pressure, and a bicycle pump are another possibility. The idea is that you will not over pressurize the tank if you have the gauges attached and are manually pumping the air in with the bicycle pump. Hopefully you will get tired of pumping and look at the gauge long before you'd put too much pressure in the tank. Using a compressor air line or a tank of compressed air like you'd use for a tire can over inflate the wing very easily, and it can NOT be strongly enough stated that these are to be avoided.

== Fixing the leaks ==

=== AA-5x leaks at the fuel scupper drain ===

'''Mechanical Difficulty:''' [[Image:wrench.jpg]] '''-''' [[Image:wrench2.jpg]]

On 72-78 AA-5x the fuel cap has a "scupper" that catches spilled fuel, rain water, etc. and drains it. This depressed aluminum ring around the cap allows the cap to sit flush with the top wing skin for less drag. The scupper has a 1/4" aluminum tube welded to the bottom to act as a drain. The bottom of the fuel tank has an aluminum block with a matching 1/4" aluminum tube rising from it. This bottom tube creates a "standpipe" that prevents the loss of most of the fuel in the tank should the short section of rubber hose that connects the 2 tubes deteriorate.

A common problem on these planes is fuel leaking from the scupper drain, and water in the fuel tank sump. Both are symptoms of the rubber hose leaking.

It's possible to replace the hose through the filler neck without taking the fuel tank access cover off. A sharp utility knife and a pair of long needle nose pliers, [http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=68222&group_ID=761&store=snapon-store&dir=catalog AKA "Stork" pliers from Snap-On] or other tool companies, are all the tools required to do this job.

Fly the fuel off, below the 19 gallon tab on the LR tanks or below the level of the mounting block for the standpipe on the standard tanks, and then reach into the tank through the filler neck and grip the spring clamp at the bottom of the rubber tube and slide it to the bottom of the tank. Just let it sit there, it can't go anywhere, it's still on the aluminum standpipe. Now the top clamp is loosened and slid down, just the same.

Take the utility knife with a SHARP blade and slice the rubber tube lengthwise to that you can peel it off the aluminum tubes, top and bottom.

Remove the hose, cut a new piece the same length. I recommend a dab of Parker Fuel Lube on the inside of each end of the hose. Slide it down on the bottom tube all the way, and then bend the top over as needed to get it started on the top tube from the scupper and then slide it up about even with the bottom of the scupper.

Retrieve the 2 hose clamps and slide them up into place about 1/4" from each end of the rubber hose.

Collect up the tools, fill the tank and confirm the leak is gone.

I've seen a few planes that have had the spring clamps replaced with worm drive type clamps. They are harder to do, but the truly motivated can accomplish it through the filler neck. If yours are worm drive (tiny radiator hose clamps), then I'd suggest taking your new hose to the auto parts store and getting some spring clamps to re-install.

=== AA-5x leaks at the spar ===

'''Mechanical Difficult:''' [[Image:Wrench3.jpg]]

The most common tank sealant failure on the 4 place wings is at the spar tube to rib interface at the inboard and outboard ends of the wet portion of the wing. The rib has a hole in it that is slightly larger than the spar, allowing them to be slid into place and then attached with a bonded and riveted collar. The collars only cover the sides of the spar (not really any room above or below the spar), and that leaves a curved slot at the top and the bottom of the spar tube with only a fillet of sealant to prevent leaks. There is NO mechanical joint at this location and some relative movement occurs as the wings flex with flight loads. Over time the sealant loses its flexibility and begins to break loose or develop cracks that allow fuel to migrate out of the tank.

=== Leaks at the fuel pickup fitting ===

'''Mechanical Difficulty: '''[[Image:Wrench2.jpg]]

The 2 fuel pickup fittings on the AA-5x tanks are [http://www.aircraftspruce.com/catalog/hapages/an832.php AN832-8D] bulkhead fittings with an o-ring and a special washer under the nut, and a fuel strainer screen on the inside of the tank. The bulkhead fitting is inserted into the tank from the inboard side of the first fuel tank rib, then the o-ring, the washer and the nut are installed and tightened to seal the fitting, and finally the "finger screen" strainer is installed on the inner end. It's vitally important that the bulkhead fitting be held still while the fuel lines are installed and tightened. There isn't much room to work, but letting the fuel line turn, even a little, may cause your 30 year old o-ring to spring a leak! Even new o-rings can be tempermental about sealing, and proper torque and careful holding of the bulkhead fitting while servicing the connections may not keep you leak free!

The repair seems simple enough. Drain ALL the fuel out of the tank, take the inboard access cover(s) off as required to reach the forward or aft pickup, hold the bulkhead fitting on the outside of the tank, unscrew the finger screen, then unscrew the nut securing the bulkhead fitting, and remove the special washer and the old o-ring. Replace with new and re-assemble in the reverse order.

Hmmmm, sometimes this doesn't work, and the fitting weeps fuel. There isn't a good way to test for a leak before you've re-installed the access cover with new sealant and let it cure overnight before a pressure test.

I recommend a liberal coating of [http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php Parker Fuel Lube] on the tank side of the rib where the o-ring seats, on the o-ring, the inside of the special washer, and on the inboard side of the nut that slides on the washer and o-ring. This lets everything move smoothly without binding or scuffing the o-ring.

== A Grumman Owner's Story ==

Bluejay Adametz has constructed a [http://web.infoave.net/~bluejay/ web page] to tell the tale of his fuel tank leak and repair, and has graciously offered to share his experiences with Bondline.

Me? I'm Bluejay Adametz, and I've owned the subject Tiger since 1986 (with a little help from a bank). I've also been an A&P mechanic since 1992, which is real handy if you own an airplane. Someday I hope that the money I save by doing my own work will exceed the cost of the schooling, books, and tools.

During the 2002 annual of my 1979 Tiger, we discovered the telltale signs of a fuel leak in the area of the outboard tank rib in the left wing. Examination of the plumbing, bonding and the area around the spar led directly to that dreaded conclusion: my wet wing wasn't wet just on the inside anymore.

At first all the horror stories I heard about persistent leaks, thousands of dollars spent, etc... came to mind. Several people remarked that the leak wasn't really bad enough to worry about. I knew in my heart, however, that it wouldn't get any better, and if something is broke, I want to fix it. Besides just being good practice, it would probably get worse at the most inconvenient time.

I considered several possibilities. While I've been around Grummans for many years, maintaining my own Tiger and various Grummans belonging to friends, I don't consider myself to be an especially gifted mechanic. Then again, I am licensed to do this sort of thing, and the biggest risk would be the cost of my own labor if my repair didn't work out and I ended up sending the job to the experts.

If you're looking for more information or contemplating this repair yourself, the first thing you need is the maintenance manual. Aside from keeping the FAA folks happy, reviewing the relevant parts of the manual will give you a clearer idea of what you're getting into and allow you to proceed with confidence that you're doing it right.

You'll also need a licensed airframe mechanic. No way that I can read [ FAR 43 appendix A subparagraph c] lets me think that this job even might be preventive maintenance. However, being that this is a project that calls for a lot of raw labor, it is a good opportunity for the savvy owner to work with their mechanic and save some real dollars.

I strongly suggest you join the Grumman-Gang mailing list (go to http://grumman.net). Myself, and a number of very knowledgeable and helpful individuals hang out there.

The folks at Fletchair in Houston, TX were also invaluable as a source of parts, materials, and advice. Check them out at http://fletchair.com.

[http://web.infoave.net/~bluejay/before.html The Before pictures]

[http://web.infoave.net/~bluejay/day10.html After the First Day pictures]

[http://web.infoave.net/~bluejay/day20.html After the Second Day pictures]

[http://web.infoave.net/~bluejay/day30.html After the Third Day pictures] are we seeing a pattern yet?

[http://web.infoave.net/~bluejay/day40.html Yes, still scraping on Day Four!]

[http://web.infoave.net/~bluejay/day50.html Finally the sealant goes on!]

[http://web.infoave.net/~bluejay/day60.html The tools to do the job...]

[http://web.infoave.net/~bluejay/day70.html Day Seven... A new leak is found]<groan>

[http://web.infoave.net/~bluejay/day80.html Joy at last, it still flies!]

Bluejay reports that it's been over a year since the resealing, and it is not leaking, so he thinks he was successful in repairing his tank.

Valve Wobble Testing

2008-03-01T07:37:45Z

Jbowman90: Removed superfluous introductory heading

Everything you ever wanted to know about the dreaded [http://www.lycoming.textron.com/support/publications/maintenancePublications/serviceBulletins/SB388C.pdf Valve Wobble Test...] straight from [http://www.lycoming.textron.com Mother Lycoming].

The purpose of the Valve Wobble Test is to check for the proper clearance between the exhaust valve and the exhaust valve guide. Too little clearance, and the valve may stick in the guide and cause a loss of power or even a mechanical failure such as a broken valve or bent pushrod. Too much clearance leads to micro-fractures in the valve stem due to the valve seating off center on the tapered seat in the cylinder head, and wedging the head slightly crooked to match the seat taper. Repeated every combustion cycle at 1300-1400 degrees F, the valve stem eventually breaks and the head falls into the cylinder and is violently struck by the piston over and over. Tremendous damage results and the debris is often swept into other cylinders and causes more damage and power loss.

Needless to say, both possible failure modes, sticking valves from not enough clearance, or breaking valves from too much clearance are to be avoided.

The sticking valve is caused by a build up of deposits in the guide or on the valve stem. These are combustion deposits and cooked oil. Excessive CHT can encourage the oil that lubricates the guide to "coke" and turn to a baked on carbon layer. It is good practice to avoid CHTs over 400 degrees F. The stock baffling will do this if kept in good shape. After 30+ years, there is very little original baffle seal left in the fleet, and of that which has been replaced, it is quite common to see very poor installation, and often the wrong material used.

This is the Lycoming tool recommended by the SB-388C document...
[[Image:Lycoming-tool.JPG]]

A similar tool is available from Aircraft Spruce, but works slightly differently. The Lycoming tool depresses the exhaust valve spring when installed, the Aircraft Spruce one does not. The above tool is usually modified to use a dial indicator to get direct readings. As shown above, the small screw on the right is adjusted to be close to the valve stem extension and a feeler gauge is used to get readings.

TBO considerations

2008-03-01T07:36:39Z

Jbowman90: Removed superfluous introductory heading, simplified link to valve wobble test

All discussions about TBO should start by referring to [http://www.lycoming.textron.com/support/publications/maintenancePublications/serviceInstructions/SI1009AR.pdf Lycoming's SI 1009AR], the factory definitions and table of recommended TBO hours for each engine model.

As Lycoming is quick to point out, there is no guarantee that a particular engine will make it to TBO. These are just recommendations that they have made based on the extensive experience with the engines that come back for OH. Part 91 operators are not required to adhere to the TBO, unlike Part 121 Scheduled Airlines and Part 135 Air Taxi operators, that are required to pull engines from service at TBO unless special permission is granted by their FSDO.

This is good news for the private owners. We can take good care of our engines and try to extend the life past an arbitrary "average" that Lycoming has published. This doesn't come without some possible problems. The first one is that most of us don't fly enough to reach the TBO in hours in service before the Lycoming recommended TBO in calendar years.

The means to determine the condition of the engine, and whether it is time for an OH are usually based on maintenance checks like Compression Tests, or upon pilot experience with items like oil consumption or making rated static RPM during a run-up.

Lycoming says that the engine has a TBO of 2000 hours on the models we use on our Grummans, except the O-235 in the AA-1x, if it has been modified with a different part number piston, and if only genuine Lycoming parts are used. They also state that there is a CALENDAR limit of 12 years since new or the most recent Major OH.

Another important test of the engine's readiness to fly past the TBO is the [[Valve_Wobble_Testing|Valve Wobble Test]] as explained in SB388C. We know what causes stuck valves, and we know what causes valve breakage, so there is no point in ignoring the test that will tell you if either condition is occurring in the engine.

Oil and Filter

2008-03-01T07:33:29Z

Jbowman90: Added note about the old remote filter page so it didn't get orphaned without someone noticing. The admin features should have caught this, but you never know.

== Oil and Filter or Screen Service ==

Until more content is written, take a look at [http://www.lycoming.textron.com/support/aircraftRegistry/oilFilterProcedure.pdf what Lycoming says] about the proper way to inspect filters and screens at oil change.

== Change your Own Oil and Filter ==

'''Mechanical Difficulty: ''' [[Image:Wrench.jpg]]

Draining the oil from the sump, especially if there is a quick drain installed is an easy job for the owner/pilot. Removing, cleaning and re-installing the pressure screen is also something the owner/pilot can do, after demonstrating the ability to complete it correctly under supervision.

== Oil Change with Remote Filter and Quick Drain ==

''Note: This section incorporates the [[Oil Change with Remote Filter and Quick Drain]] page with edits. Bondline administrators should consider what to do with the orphaned page.''

After a few questions posted to the Grumman Gang I thought I would document my procedure for changing the oil in my '76 Cheetah. I keep refining it as I go, but I hope this provides some useful tips for those who wish to do your own oil changes.

First, as Norm would say, a note about shop safety: Always wear safely glasses and other appropriate protection. I believe this, like most owner maintenance, must be done with the supervision of an A&P the first time.

Here's how it went for me at my last oil change...took less than an hour from hangar door up to hangar door down (not including the short flight to warm up the oil). My Cheetah is equipped with an oil quick drain valve and an Airwolf remote mounted oil filter...I recommend both if you plan to regularly change your oil.

=== The Supplies ===

* One 5 gallon Kikkoman soy sauce bucket, empty, with tabs on lid cut so the lid can be removed (scavenged from a local Chinese restaurant).
* 2~3ft of surgical tubing (diameter to fit the oil quick drain valve).
* 8 qts appropriate oil
* Oil filter to fit remote mounted oil filter adapter.
* Wrench to remove oil filter (I use a socket wrench w/ pivoting head & socket).
* Safety wire & safety wire pliers (the cheap ones at Harbor Freight work just fine...and are worth it)
* Newspaper (oil filter is mounted upside down, still haven't figured out a good way to get it out without some oil spillage).

=== Why a Kikkoman Soy Sauce Bucket ===

Now I know you are asking why I specified this bucket...well...actually any bucket that has a lid that seals and contains one of those extendable pour spouts will do.
The advantages to the Kikkoman (or similar) bucket:

* Free from your favorite local Chinese restaurant.
* Convenient carrying handle.
* Can hold between 2~3 oil changes worth of oil depending on quantity at oil change time.
* Lid seals tight so spout can be used to pour oil out.
* Bucket with lid on and pour spout extended fits under cowl of the Cheetah
* Bucket fits well on most local oil collection tanks. Just open/extend the pour spout and set upside down over oil collection tank opening until bucket drains.
* Makes people wonder why you are taking a 5 gallon bucket of Kikkoman Soy Sauce into/out of the local Auto Zone, Napa, etc store. ;-)

=== The Hose ===

I've used a length of clear surgical tubing and have had no problems, but others have mentioned that the hose can slip off the quick drain. So, others have recommended using heater hose or using safety wire or some sort of clamp to hold the tube in place. Feel free to experiment as that will be far more fun than cleaning up 8 quarts of oil from inside your cowl and the surrounding floor. I'd also recommend not applying any forces to the hose while the oil drains.
Another tip I've received is that, if you use the surgical tubing or other soft walled tube, don't fold it but coil it up for storage. Otherwise the hose may remain kinked when unfolded.

=== The Process ===

[[Image:oil_bucket.JPG|thumb|200px]]
[[Image:oil_quick_drain.JPG|thumb|200px]]
[[Image:filter_quart.JPG|thumb|200px]]

# Run engine to heat oil so it flows easier...a great excuse to go flying.
# Open cowl so you can access filter and quick drain.
# Extend spout and remove cap on bucket, insert one end of hose into spout on bucket.
# Snake other end of hose through lower cowl opening and slide over quick drain.
# Open quick drain. Remove oil dipstick. Let the oil drain.
# Place a number of sheets of newspaper under the oil filter, shape so it will collect any oil. Consider how you plan on moving the oil filter when laying out the paper. Since the filter is mounted upside down (like a cup), there will be oil that will spill out when removed. I know some gang members have devised containers to catch oil from the filter area such as cutting apart an oil quart container or gallon milk jug...they don't fit well in my setup, but it may work for you.
# Remove safety wire and old filter. Set filter down so it doesn't spill oil (can use box it came in).
# Wipe mounting surface clean, inspect for any damage. Remove newspaper.
# Install new oil filter per instructions (gasket lube, tightening recommendations). Safety wire so it can not unscrew.
# Close quick drain and remove hose. Allow hose to drain into bucket. Use small amount of paper towel to seal ends of tube when done.
# Wipe off any drips from the quick drain (and cowling, but there shouldn't be any there). Confirm quick drain is closed.
# Put cap on spout of bucket, remove bucket lid and place upside down on floor.
# Pour any remaining oil from filter into bucket, then place filter with hole down on the upside down lid to finish draining (the last tablespoon or two of oil).
# Add 8 qts oil to engine. ''Tip:'' oil container quarts can actually screw into the oil filler neck - Don't force it, just give it a 1/2 twist or so and let it sit until empty (something I learned from my A&P the first time).
# Replace dipstick, remove all tools from engine area, and button everything back up.
# Start engine, verify oil pressure comes alive quickly, Run engine for several minutes, shut down.
# Open cowl, inspect for any leaks. Check quick drain, oil filter/screen area, etc. Close cowl.
# Get oil filter draining on bucket lid, wipe it off, and cut open for inspection (or put in box and take to your A&P and ask them to cut it open. Most around here will do it free of charge if you are a customer. It's what I actually do). Verify no metal in filter element.
# Put lid (with small amount of oil from the final draining of the filter), back on the bucket. Make sure lid seals.
# Note tach time. Add entry to engine log (the job ain't done until the paperwork is). ;-)
# You're done.

Well ... Ok, every 2 or 3 oil changes, go empty the bucket. I believe it is U.S. law that requires anyone that sells engine oil to collect used engine oil for recycling. I've also heard that some folks use heaters in their hangars that can burn used oil. I'm sure you'll find some legal and environmentally friendly means to dispose of the oil.

I hope you found this interesting. Please feel free to add to this if you have other tips and tricks. I'm always looking for a way to make it easier even though this process is far easier than changing the oil on any of my cars.

Happy Flying.
-Mike

Servicing

2008-03-01T07:30:03Z

Jbowman90: Added Oil and Filter link

* [[Pre-Purchase Inspections]]
* [[Inspection Horror Stories]]
* [[Oil and Filter]]

Oil and Filter

2008-03-01T07:29:01Z

Jbowman90: Combined page with Oil Change with Remote Filter page, spelling fixes, grammar fixes, picture layout changes, punctuation changes

== Oil and Filter or Screen Service ==

Until more content is written, take a look at [http://www.lycoming.textron.com/support/aircraftRegistry/oilFilterProcedure.pdf what Lycoming says] about the proper way to inspect filters and screens at oil change.

== Change your Own Oil and Filter ==

'''Mechanical Difficulty: ''' [[Image:Wrench.jpg]]

Draining the oil from the sump, especially if there is a quick drain installed is an easy job for the owner/pilot. Removing, cleaning and re-installing the pressure screen is also something the owner/pilot can do, after demonstrating the ability to complete it correctly under supervision.

== Oil Change with Remote Filter and Quick Drain ==

After a few questions posted to the Grumman Gang I thought I would document my procedure for changing the oil in my '76 Cheetah. I keep refining it as I go, but I hope this provides some useful tips for those who wish to do your own oil changes.

First, as Norm would say, a note about shop safety: Always wear safely glasses and other appropriate protection. I believe this, like most owner maintenance, must be done with the supervision of an A&P the first time.

Here's how it went for me at my last oil change...took less than an hour from hangar door up to hangar door down (not including the short flight to warm up the oil). My Cheetah is equipped with an oil quick drain valve and an Airwolf remote mounted oil filter...I recommend both if you plan to regularly change your oil.

=== The Supplies ===

* One 5 gallon Kikkoman soy sauce bucket, empty, with tabs on lid cut so the lid can be removed (scavenged from a local Chinese restaurant).
* 2~3ft of surgical tubing (diameter to fit the oil quick drain valve).
* 8 qts appropriate oil
* Oil filter to fit remote mounted oil filter adapter.
* Wrench to remove oil filter (I use a socket wrench w/ pivoting head & socket).
* Safety wire & safety wire pliers (the cheap ones at Harbor Freight work just fine...and are worth it)
* Newspaper (oil filter is mounted upside down, still haven't figured out a good way to get it out without some oil spillage).

=== Why a Kikkoman Soy Sauce Bucket ===

Now I know you are asking why I specified this bucket...well...actually any bucket that has a lid that seals and contains one of those extendable pour spouts will do.
The advantages to the Kikkoman (or similar) bucket:

* Free from your favorite local Chinese restaurant.
* Convenient carrying handle.
* Can hold between 2~3 oil changes worth of oil depending on quantity at oil change time.
* Lid seals tight so spout can be used to pour oil out.
* Bucket with lid on and pour spout extended fits under cowl of the Cheetah
* Bucket fits well on most local oil collection tanks. Just open/extend the pour spout and set upside down over oil collection tank opening until bucket drains.
* Makes people wonder why you are taking a 5 gallon bucket of Kikkoman Soy Sauce into/out of the local Auto Zone, Napa, etc store. ;-)

=== The Hose ===

I've used a length of clear surgical tubing and have had no problems, but others have mentioned that the hose can slip off the quick drain. So, others have recommended using heater hose or using safety wire or some sort of clamp to hold the tube in place. Feel free to experiment as that will be far more fun than cleaning up 8 quarts of oil from inside your cowl and the surrounding floor. I'd also recommend not applying any forces to the hose while the oil drains.
Another tip I've received is that, if you use the surgical tubing or other soft walled tube, don't fold it but coil it up for storage. Otherwise the hose may remain kinked when unfolded.

=== The Process ===

[[Image:oil_bucket.JPG|thumb|200px]]
[[Image:oil_quick_drain.JPG|thumb|200px]]
[[Image:filter_quart.JPG|thumb|200px]]

# Run engine to heat oil so it flows easier...a great excuse to go flying.
# Open cowl so you can access filter and quick drain.
# Extend spout and remove cap on bucket, insert one end of hose into spout on bucket.
# Snake other end of hose through lower cowl opening and slide over quick drain.
# Open quick drain. Remove oil dipstick. Let the oil drain.
# Place a number of sheets of newspaper under the oil filter, shape so it will collect any oil. Consider how you plan on moving the oil filter when laying out the paper. Since the filter is mounted upside down (like a cup), there will be oil that will spill out when removed. I know some gang members have devised containers to catch oil from the filter area such as cutting apart an oil quart container or gallon milk jug...they don't fit well in my setup, but it may work for you.
# Remove safety wire and old filter. Set filter down so it doesn't spill oil (can use box it came in).
# Wipe mounting surface clean, inspect for any damage. Remove newspaper.
# Install new oil filter per instructions (gasket lube, tightening recommendations). Safety wire so it can not unscrew.
# Close quick drain and remove hose. Allow hose to drain into bucket. Use small amount of paper towel to seal ends of tube when done.
# Wipe off any drips from the quick drain (and cowling, but there shouldn't be any there). Confirm quick drain is closed.
# Put cap on spout of bucket, remove bucket lid and place upside down on floor.
# Pour any remaining oil from filter into bucket, then place filter with hole down on the upside down lid to finish draining (the last tablespoon or two of oil).
# Add 8 qts oil to engine. ''Tip:'' oil container quarts can actually screw into the oil filler neck - Don't force it, just give it a 1/2 twist or so and let it sit until empty (something I learned from my A&P the first time).
# Replace dipstick, remove all tools from engine area, and button everything back up.
# Start engine, verify oil pressure comes alive quickly, Run engine for several minutes, shut down.
# Open cowl, inspect for any leaks. Check quick drain, oil filter/screen area, etc. Close cowl.
# Get oil filter draining on bucket lid, wipe it off, and cut open for inspection (or put in box and take to your A&P and ask them to cut it open. Most around here will do it free of charge if you are a customer. It's what I actually do). Verify no metal in filter element.
# Put lid (with small amount of oil from the final draining of the filter), back on the bucket. Make sure lid seals.
# Note tach time. Add entry to engine log (the job ain't done until the paperwork is). ;-)
# You're done.

Well ... Ok, every 2 or 3 oil changes, go empty the bucket. I believe it is U.S. law that requires anyone that sells engine oil to collect used engine oil for recycling. I've also heard that some folks use heaters in their hangars that can burn used oil. I'm sure you'll find some legal and environmentally friendly means to dispose of the oil.

I hope you found this interesting. Please feel free to add to this if you have other tips and tricks. I'm always looking for a way to make it easier even though this process is far easier than changing the oil on any of my cars.

Happy Flying.
-Mike

Oil and Filter

2008-03-01T07:20:37Z

Jbowman90: Capitalization fixes in section title

Oil and Filter

2008-03-01T07:16:31Z

Jbowman90: Replace manual formatting with standard wiki markup, Spelling fixes

Wheels

2008-03-01T07:07:14Z

Jbowman90: Replace manual formatting with standard wiki markup, Spelling fixes

== Introduction ==

The Cleveland wheels and brakes on the Grummans are divided into 2 groups with 2 different part numbers.

The early planes from 69-74 have the brake caliper with the smaller piston (30-55B) and a 40-86A Main wheel.

The later planes from 75 on have the brake caliper with the larger piston (30-56B) and a 40-88C Main wheel.

All the single engine Grummans use the part number nose wheel (40-77A).

A common problem on the 30+ year old wheels is CORROSION. The 70's production planes came with wheels that were painted silver on the outside, and had no paint or corrosion protection on the inside. Its not uncommon to take a wheel apart and find that under the excess grease slung into the inside is corrosion so severe as to render the part unusable.

Perhaps like THIS:

[[Image:Wheelcor.jpg|thumb|300px|This wheel is unserviceable and had to be replaced at a cost of several hundred dollars]]

This happens from a lack of proper maintenance in 2 ways.

# Too much grease is left on the wheel bearings when they are installed, and the excess is extruded into the hollow center of the wheel.
# The wrong grease is used, and the components of the grease that cause the lubricant to gel absorb moisture and when held against the bare metal inner surface of the wheel, cause corrosion to rapidly occur.

As a preventative measure, the wheels should be visually inspected at each annual for condition of the wheel and its data plate, the condition and proper torque of the hardware, and by looking through the axle hole with the bearing removed, the condition of the inside of the wheel. A strong light and some rags to wipe away any grease in the "corners" of the cast stiffeners will help identify areas of concern.

== Wheel Bearings, Dust Seals, and Proper Installation ==

[[User:GregAmy|Greg Amy]] writes:

There are two different sizes of washers on the main wheels of all the single engine Grummans. The two larger ones (153-0400) are used on the inside bearing, while a single smaller one (153-0300) is used on the outer. I had paid close attention to how it was all installed, and it just didn't look right. Even after reading the Cleveland parts book I was still confused. After talking it over with [http://www.bondline.org/index.php/User:Bob_Steward Bob Steward] I got it worked out.

[[Image:DSCN4153.JPG|thumb|300 px|A photo of a wheel to better describe the location, inside the outer wheel half.]]

I've had an ongoing discussion with my IA on some apparently-increasing damage on my wheels. There's a small lip on the inside of the outer wheel half, just above where the outer bearing race is; it's on this lip that the "C"-shaped felt seal retainer rides. Over the last couple of annuals we have been finding on my Tiger that this lip has been wearing significantly. Upon inspecting the order of installation of the parts it appeared that the outer washer/dust seal was wearing on that area. We inspected the washer and could not see how this wear could be avoided.

[[Image:DSCN4154.JPG|thumb|300px|The affected area, about halfway down to the bearing race, below where the retaining ring seats. Notice the "cut ridge" where the too-large washer "threaded" itself into the magnesium. It's possible that this wheel can be reused, as the C-channel seal retainer should seat properly.]]

This year I decided to get to the bottom of this. Per the [http://www.parker.com/literature/Literature%20Files/ag/Aerospace%20Literature/WBcov.pdf Cleveland parts book], there are two different sizes of washers; each wheel gets two of the larger ones on the inner side, and one smaller washer per wheel, which goes on the outside.

[[Image:Washers.jpg]]

Apparently, however, these washers have been installed incorrectly on my Tiger. Some time back someone had installed one of the larger washers on the outside bearing and we've been dutifully putting them back in that order since (hey it's how they came out!) Unfortunately, this causes two problems: first, the large washer, when placed on the outside, causes the OD of it to ride on the lip in the mag wheel where the seal should ride. Since the washer does not turn this causes significant wear on that lip, and thus the damage to the wheels. Second, using the smaller washer on the inside causes it to get pinched between the axle shaft and the inner bearing; I found wear evidence on the axle shaft on that radius where the bearing is supposed to seat, plus wear marks on the washer itself. Finally, using the larger washer (with a larger ID) on the outside bearing causes the wheel nut to not get a full contact when tightened, and the ID of then is slightly bent (and the bearing is not adequately tightened because of the drag on the washer-to-wheel contact). The larger washers are also further damagedby being "cupped" due to getting forced down to the bearing by the nut. It's really a screwed-up situation all around.

[[Image:DSCN4157.JPG|thumb|300px|Another view of the ridge cut by the too-large washer.]]

[[Image:DSCN4159.JPG|thumb|300px|Here's a situation where the top of the ridge was simply worn down to even with the top of the inner bearing race. In this case the C-channel seal retainer will sit too far in. This wheel half will probably need to be replaced.]]

I've used the current shop as long as I've owned my airplane (1995), and they assure me they pay close attention to the order of removal and installation, but they never questioned if it was correct; thus it appears that this situation has been this way since before I owned it.

I also suggest this is a common problem: [http://www.fletchair.com Fletchair] sent to me two good used wheels and all four outer wheel halves show evidence of the same problem.

The risk of this being installed incorrectly is not particularly dire; in addition to ruining perfectly good parts, the worst that that could happen is damaged bearings and/or a slightly loose wheel nut if the washer(s) were to frag themselves. It's probably not a safety-of-flight issue (a safety-of-taxiing issue?) but I believe it's something that needs to be brought to the attention of all folks working on these airplanes; most of the techs I talked to about it have indicated they were not even aware there were different size washers on these Cleveland brakes! Hey, if you don't pay attention and just pick up a washer at random from the pile, you've got roughly a 1/3 chance of getting the first one wrong, then a 50/50 chance of getting the second one wrong if you get the first one right! Those are not particularly good odds, which explains why there's probably a lot of incorrect airplanes out there.

So remember: the two larger washers go on the inside and the smaller one goes out. I'd be '''very''' interested to hear if others find theirs to be incorrect.

Nose Strut

2008-03-01T07:03:27Z

Jbowman90: Replace manual formatting with standard wiki markup

__TOC__

== Introduction ==

The factory recommended annual removal of the nose strut is probably one of the most disregarded maintenance tasks on the Grumman fleet. Frequent excuses about it being complex and time consuming are just not true, and probably spread by those that have never actually DONE it.

The intended purpose is not to run up the labor costs at annual, or to scare away Cessna mechanics from working on Grummans. Its to allow inspection of the nose strut on the inside and the outside. The strut is made of a high strength alloy steel. These type alloys are not particularly good at resisting corrosion, and the hollow nose strut is subjected to fairly high loading while just PARKED with the weight of the engine being supported.

The actual pulling of the strut can be somewhat anticlimactic. After the lower cowl is removed and the flexible rubber boot is removed (not installed on 77 up planes with the 2 small "shock absorbers" mounted to the strut), there are only 2 bolts that hold it in. They are special NAS shear bolts and are matched to the holes with a reamer. With the forward portion of the fuselage properly supported, such that the nose is raised several inches above the pavement, the 2 bolts are removed. Usually they will require a drift and a mallet to tap them out. At this point, if the plane has been properly maintained in the past, the nose strut can be grasped and rotated to shear the zinc chromate that was used to seal the strut to the socket. After rotating several degrees, pulling forward while rotating the strut side to side will slide it right out. If your nose strut has been inserted with "bear grease" as a few Grumman owners suggest, it may slide out by gravity after the bolts are removed. This isn't a good thing, as the freedom of the strut to move may create a "bolt cutter" effect by allowing the forces on the strut to try and shear the bolts. It is a stretch to think that this would happen, but its not what the manufacturer's instructions say to do, therefore it is improper. Also grease may not protect against moisture, since the grease is thickened with compounds that can absorb water.

== What if it's STUCK? ==

If the nose strut hasn't been taken out regularly and then properly re-installed with wet zinc chromate, then it may be harder to remove, due to corrosion in the socket and on the strut binding it.

The first step in removing a strut that resists rotation by hand, as described above, is to lube the strut and socket with a penetrant. Most any "bolt loosener" penetrant will work, but my personal favorite is [http://www.mousemilk.com/index.html Mouse Milk]. As with all penetrants, some patience is required in order to give the lubricant a chance to work. Take a lunch break and give it an hour or two.

If it still resists moving by hand after the penetrant has had a chance to work, a temporary tool can be constructed from a 4x4 piece of lumber and a couple 1/2" bolts. Having a 10 foot lever arm allows quite a bit of leverage to be applied. Even a small movement is a victory, since that will allow the penetrant to seep into areas previously unlubricated. Continue side to side movement and continue to add penetrant through the bolt holes. Direct the penetrant spray up the strut, so that it will run over the edge and find its way between the socket and the strut.

[[Image:Strut_tool.jpg]]

== Torque Tube Box ==

These instructions begin after airplane is properly on jacks, and the nose strut and nose wheel are removed. The upper and lower cowlings will be removed during the process, so taking them off before getting in the plane may be helpful.

Hopefully you are 5’2" tall, with the reach of someone 6’5", weigh about 100 lbs, and you are a dentist who is used to working upside down and backwards. Really it helps.

The service manual instructions were the basis for this article, but it lacked a few helpful techniques.

# '''Remove the front seats'''. The details on seat removal are slightly different for the 2 place and 4 place models.
## '''2 place models'''. The seat bottom may be lifted for access to the forward seat attach bolts at the spar. There is one AN3 bolt on each seat rail. Remove it and detach the springs, and the seat will slide forward and up out of the rear brackets on the floor.
## '''4 Place models'''. The seat is attached to brackets on the spar, and there are 2 clevis bolts (look like slotted screws when you are trying to find them) that are at the forward side. The seat latching mechanism can get in the way because the latching pawl pins fit into holes that are on either side of the clevis bolt heads. Remove the 2 clevis bolts with a straight blade screw driver. It may be more convenient to slide the seat to the position where the holes in the seat pan align with the locations of the clevis bolts, thus allowing SOME visual confirmation of the positioning of the screw driver. After the 2 clevis bots are removed, the seat will slide aft and out of the brackets.
# '''Remove the front console side panels''' also remove the left side fresh air box. It is right under the yoke. There are two Phillip head screws holding it on. You will need a long #2 Philips screwdriver to reach up through the bottom of the airbox. Look for 2 holes, possibly with snap in caps to seal them. You will also have to disconnect a drain tube coming up from the floor side panels.
# '''Remove the front side panels (kick panels near the floor) on both sides of the plane.''' Some of the screw holes may be hidden by upholstery and trim.
# '''Remove the lower cowling.''' As suggested at the beginning, before climbing into the plane.
# '''Remove the rudder return springs.''' Note, the manual says remove the eye bolts from the firewall etc. I didn’t and it wasn’t necessary. But now would be a good time to think about adding new springs if you have them. (I have spares in the plane.)
# '''Remove the co-pilot side right rudder bar attach bracket.''' It has two 3/8 nuts holding it to the floor. When you remove it the rudder bar can be moved up and aft to help remove the brake cylinders around without disconnecting them and allowing air into the system.
# '''Remove the brackets from the co-pilot and pilot side brake cylinders.''' Pay special attention not to bend them too sharply after you disconnect them. I disconnected the clevis pins right behind the top of each pedal so I could lay the pedals down and get a better shot at the other nuts holding all the cylinders down.
# '''Remove the clevis pins on the rudders''' (Been there done that, too!)
# '''Remove the parking brake connection to the pilot side master cylinder.''' ( I didn’t have a parking brake)
# '''Move the brake cylinders up and away''' and secure them out of the way so you have room to remove the torque tube later.
# '''Remove the throttle cable and clamp screws''' from the instrument panel brace. I didn’t I loosened the whole panel brace by removing the six 7/16 nuts.
# '''Remove the nut and bolt that holds the T-column to the floor.''' I didn’t when I moved the instrument panel brace the T-column moves with it. It has to move aft or you would not be able to get the torque tube assembly out on the pilot side. I did not touch any cables or pulleys to move the brace.
# '''Remove the six nuts that hold the center bracket for the torque tube assembly''' from the outside near the firewall. Someone else will have to remove the nuts as you hold the bolt inside with a 9/16 wrench. Work out the bolts and a small L bracket on each bolt completely.
# '''Remove the four snap plugs on the lower front of the fuselage.''' (I always wondered what was behind those things, now I know!) There are four bolts that have to be removed. Two on each side. Do the pilot side first. It is easier to get at. The forward nut is inside the cabin and is difficult to get a wrench on. Get a 9/16 socket wrench (a box end or open end one side and a socket on a 90 degree swivel on the other end.) Have your helper remove the bolt from the outside as you hold the nut from the inside to keep the nut from turning… have fun. Do both sides co-pilot side is very tight on the front bolt. Get creative with the way you hold the nut as the helper turns the bolt. Remember you are almost done.
# '''Remove the torque tube assembly from the pilot side.''' There may be a spacer for each side of the tube assembly next to the outside wall. Pull the yoke aft to help clear the space. It helps to get the center bracket clear first by pulling it up and aft, then you can pick up the pilot side higher and the tube will move. Be careful with the brake cables, don’t jerk anything around, it will come out, but pay attention to how everything is routed so you can put it back the same way it came out.

Read the service manual for reinstallation and torque values. Make sure you have everything inspected properly and clean up the goo on the floor under the pedals. Mine was loaded with small washers from (somewhere, sometime) and lots of sticky nasty dirt. A clean plane is a happy plane! Good luck, your experiences may vary on this project! I lost 5 lbs of sweat doing this job in about 7 hours removal time.

Fixing Soft Brakes

2008-03-01T06:53:45Z

Jbowman90: Spelling fixes, Added section headers and forced Table of Contents

__TOC__

== Introduction ==

Mechanical Difficulty: [[Image:Wrench2.jpg]]

Properly maintaining the brake system on Grumman American aircraft is extremely important because the brakes are the only way to steer the plane on the ground at low speeds where the rudder is ineffective.

Although the brake system on Grumman American singles is listed in the parts manual and sales brochures as having "optional" passenger side brakes, few seem to have been built with the "standard" brakes. Accordingly, I'll discuss the brake system as if they ALL have brake pedals on both sides.

Due to the way the pilot's side master cylinders plumb through the co-pilot's side master cylinders, if the fluid is too low in the reservoir(s), the pilot's side brake pedal(s) can be soft and ineffective, and the co-pilot's side can still operate normally -- but perhaps only for a few applications, depending on the size of the leak. This can be used to your advantage if the brakes are checked as part of a pre-landing checklist (step on the toe brakes in flight and see if either is soft) by giving you advance warning of the loss of brake effectiveness and allowing you to either change seats if solo, or to transfer braking responsibility to the co-pilot.

The hydraulic brakes use a [http://www.aircraftspruce.com/catalog/lgpages/aeroshell_bflu.php Mil Spec fluid MIL-H-5606G], commonly referred to as "5606". This is a red petroleum-based fluid, as opposed to the Glycol based automotive fluids, and the system is not compatible with any other fluid.

The pilot's side master cylinders each have built-in reservoirs that contain the surplus fluid needed as the brake pads wear and the wheel cylinder piston moves out to take up the missing pad thickness. The proper fill level is approximately 1/4" below the top of the reservoir, and can be measured with a pipe cleaner. Filling the system before the fluid level drops far enough to suck in air will prevent the loss of braking and subsequently, directional control on the ground.

== Bleeding the Brakes ==

When air enters the brake system, the brake pedals become mushy, soft, and ineffective. When this occurs, the air must be replaced with brake fluid by "bleeding" the brakes. The brakes are bled by pumping clean 5606 fluid into the bottom bleeder valve on the brake cylinder located on the inboard aft side of each main wheel. A 1/4" box end wrench is needed to loosen the bleeder. Note: Many people get confused about the direction to turn the bleeder screw, since it is upside down.

The best way to force fluid into the system is by using a pistol-grip style oil can with a short section of clear plastic line slipped over the tip. The vinyl line used on aquarium air systems works well, as does certain types of surgical rubber tube. Prepare for servicing the brakes by filling the oil can with several ounces of 5606 fluid and by attaching the flex hose to the end of the can. Finally, pump the flexible hose full of brake fluid to avoid pumping air bubbles INTO the system.

You're now ready to begin the bleeding procedure, which is greatly simplified by having a second person in the cockpit to monitor its progress.

Remove the filler plug from the master cylinder reservoir on the correct side of the brake system, and then put your 1/4" box end wrench on the bleeder fitting and crack it open. You'll know you've opened the fitting when a drop of fluid appears. While leaving the wrench on the bleeder hex-screw, slip the end of the preloaded flex hose over the end of the bleeder screw, loosen the bleeder screw an additional half-turn, and begin pumping enough to purge the air from the lines. My hand pump oil can usually takes 15-20 strokes to accomplish this.

Now, tighten the bleeder snugly--but leave the hose attached. Check the pedal on the pilot's side; if it's firm, then you can stop pumping. If not, open bleeder and continue pumping and checking until the pedal is firm.

After bleeding the brakes, check the fluid level with a pipe cleaner to make certain that it's within 1/4" of the top of the reservoir. If the fluid is lower, bring your pump inside and fill the reservoir. Re-install the filler plug when done.

== Other Source of Braking Problems ==

In addition to loss of brake fluid, there are many reasons why the brake pedal might become soft. A history of fluid loss requires a careful inspection of the brake masters, the flex lines in the cockpit, the hard lines in the cockpit, and especially the aluminum hard lines from the wing walk area to the wheel cylinders. Cracks in the flare of the aluminum tube where it enters the caliper are very common, especially on the older members of the fleet. The entire line can be replaced with a new part from FletchAir or one fabricated in the field from [http://www.aircraftspruce.com/catalog/mepages/alumtube_5052.php 5052-O aluminum tube (0.035" wall)] or many have been repaired with a [http://www.aircraftspruce.com/catalog/appages/aq666.php 6" section of teflon lined steel braided hose] and a [http://www.aircraftspruce.com/catalog/hapages/an815.php straight union AN fitting] to couple the re-flared line to the female flex hose.

Those planes with rubber covers over the main gear legs will need to split the aft edge of the rubber cover to access the aluminum brake line on the aft side of the main gear leg. The rubber comes in 2 halves and was glued together when installed. The glue can usually be separated with a dull butter knife. It will shear the glue without cutting the rubber cover. The trailing edge can be re-glued with [http://multimedia.mmm.com/mws/mediawebserver.dyn?ssssssa&kDGsMWtsFWtssTTddDvSSSSR- 3M Super Weatherstrip Adhesive], which is available in black or yellow.

Due to a change in the parking brake design on some '78 and all '79 and later 4-place, a rather baffling loss of fluid can occur. The fluid can disappear from one master cylinder reservoir, and over fill the other! The parking brakes are plumbed with a [http://www.aircraftspruce.com/catalog/lgpages/pbvalves.php valve] that can be closed to hold braking pressure after the pedals are released, and the o-rings in the valve are known to fail such that the pressure is leaked from one side of the system to the other side with no external leaking. The fix is to remove the parking brake valve from the firewall ahead of the co-pilot's rudder pedals and repair it with a new set of o-rings.

Windshields (2 & 4 place) and Canopy (2 place)

2008-03-01T06:49:41Z

Jbowman90: Replaced manual formatting with standard wiki markup

== Introduction ==

Windshield replacement in all models and Canopy replacement (2 place)

'''Mechanical Difficulty:''' [[Image:Wrench3.jpg]] '''-''' [[Image:Wrench4.jpg]]

'''Unlike side window replacement, windshields may NOT be signed off for return to service by the owner/pilot. You will have to have someone with an Airframe rating to supervise and make the log entry approving it for return to service.'''

Only the most intrepid (and some would say foolhardy) owners would attempt to install their own windshield or AA-1x canopy without the assistance of someone with experience doing Grumman bonded windshield replacement. No one step is particularly difficult, but the process does not allow for much error, and the cost of failure is high ($400-$500 in parts and shipping) for another windshield if you crack it drilling holes, or bond it in crooked such that the canopy won't seal tightly, etc.

Most of the steps for the windshield and canopy are very similar, especially the removal of the bow, the cleaning and then re-bonding to the new plexi. Only areas with significant differences will be shown under the "Canopy" heading. All the rest of the explanation can be applied to either part. It is not necessary to remove the windshield to work on the canopy or to remove the canopy to work on the windshield, however both tasks are explained below.

== Unbolting the windshield ==

There are 2 AN3 bolts on the lower end of each side of the windshield bow. To access them, remove the plastic trim and the screws holding the forward edge of the upholstery on the cabin sides. The plastic trim is held in by a several #4 sheet metal screws. On the AA-5x series the pilot's side has a rocker switch and a map light on a flexible stalk to be removed. Many AA-1x and most AA-5x have the compass located on the windshield bow. The wiring follows the forward edge of the windshield bow down the right side. The ground wire is attached with a screw to the honeycomb, and the power wire is crimped in the same connector as the panel light lead and must be cut off. A new connector can be installed later to allow the bow to be removed without cutting wires.

After accessing the AN3 bolts at the bottom of the bow, there are 7 screws around the lower edge of the windshield. 2 screws on each side of the fuselage, one at the bow and one a few inches forward, and 3 screws at the forward edge of the windshield. It may be easier to remove the 3 forward screws if the glareshield cover on top of the instruments is removed.

[[Image:LHbolts.jpg]] [[Image:Fscrews.jpg]]

The bolts on the right side are the same, but less wiring to deal with.

== Unbolting the Canopy ==

The canopy comes off the sliding rails with the removal of the bottom row of screws. A second person to help support and lift the canopy is strongly suggested.

After all the bottom row of screws is out, the canopy can be lifted straight up and off of the plane. This ought to be done by at least 2 people, and 3 would offer an additional level of safety. With a helper on the opposite wing root, lift the canopy straight up, taking care not to scratch the quarter windows with the sharp corners at the aft edge of the canopy. Once the canopy is above the turtledeck height, carefully hand it over to one person on the wing root. The other person then gets off the wing and comes to the trailing edge of the wing so that the person holding the canopy can hand it down.

== Removing the Windshield ==

At this point all the wiring is loose, all the screws are out, and all that is holding the windshield in place is the adhesion of the old sealant around the forward edge (which on some planes has incorrectly been replaced with RTV silicone by those that did not read the maintenance manual), and the spring tension of the aluminum bow. As needed, insert a thin bladed putty knife into the plexi-aluminum joint around the front of the windshield to pop the windshield loose. Push inward on the bow and attempt to slide the legs of the bow upward and aft to lift the windshield clear of the fuselage. Some more scraping with the putty knife may be needed as additional areas of adhesion are discovered. Lift the windshield and bow out of the plane and hand the complete assembly to a helper on the ground.

== Removing the Bow ==

Early models (69-73) have multiple holes drilled through the plexi and the aluminum bow, and screws to hold the assembly together. It is a simple matter to remove the screws and clean and residue of the gasket material from the bow.

Late models (74 on) have a bonded bow and plexi, with some later production planes having 2 screws, one on either side of the latch assembly to help resist the shearing force caused by the latch. On the bonded assemblies it is assumed that the windshield is not being reused, so cutting the bonding with a variety of methods is possible. A piece of safety wire wrapped around some wooden handles can be used to cut the RTV bonding. A putty knife can be used to slice the bonding. A single edged razor blade can be worked around the aft face of the bow to slice through the sealant about 1/2 way across the bow. In many cases the bonding may be failing and large sections of the bow may already be coming loose.

Tip: In the case where the RTV bonding is failing and the windshield or canopy is still in good shape, care to separate the remaining bond is needed to avoid damaging the plexi. The razor blade or putty knife methods have worked well for me in the past. Usually, once the RTV is starting to let go, it all comes apart pretty easy. Masking the inside if the windshield (or canopy), with some aluminum tape or a couple layers of duct tape from the bond line towards the part that you look through, would be a good idea. You may find that a sharp single edged razor blade held perpendicular to the inside of the plexi and used as a scraper can remove most all the old bonding material. I've followed this with a "DA" or random orbit sander and some 400 grit paper to remove scratch marks and the last of the RTV. The fogged apperance of the plexi will diminish sharply if the DOW 1205 primer is applied and the plastic allowed to soften slightly, as recommended for the original RTV bonding method.

== Removing the Canopy Skirt ==

At the aft edge of the plexi, there is an alumiunum skirt that completes the distance from the aft edge of the canopy to the turtle deck. A row of screws secures it to the plexi and the aft canopy bow. Removing the screws and taking the lock cylinder off the pilot's side will free the plexi and the aft bow from the skirt.

== Cleaning the Bow ==

Once the bow is released, the next step is to thoroughly clean the remaining bonding agent off the aluminum. Scraping with a putty knife works well. Sometimes small areas may need to be scraped with a single edge razor blade to remove particularly well attached bonding material. Sanding until smooth, followed by a solvent wipe to remove the oil from finger prints is a good final cleaning step.

== Checking the Bow ==

Now is a good time to check that the bow is straight. Its not uncommon for the windshield or forward canopy bow to not lay flat, and this must be addressed before any trimming or bonding takes place.

== Bonding the Bow to the Plexi ==

The OEM factory bonding and the instructions from LP Aero until recently were all based on a Silicone Rubber "RTV" bond. The instructions from LP Aero described the materials as Dow Corning 732 RTV and Dow Corning 1200 and 1205 primers. This method was used successfully for more than 30 years and resulted in excellent bonding, if the primers were used and care was taken to prevent contamination of the bond area. Because the smallest quantity the primers are sold in is 13 oz. and they require a Hazmat charge to ship them, it could cost $40 for the two primers and another $20 in Hazmat charges, and all that is needed is about 1 oz. of each primer. Because of these costs and inconveniences, another bonding process has begun to replace the RTV. Recently LP Aero changed its instructions, and a new poly-sulfide based bonding material was recommended. This material is "Pro-seal" fuel tank sealant and is compatible with MIL-S-8802. Its available in several brands, but its vitally important that you use the "Adhesion Promoter" AC-251 from Advanced Chemistry and Technology, or its equivalent in the brand of sealant you use.

== On the Plane or On the Bench? ==

The bow can be clamped in place with the plexi and bow jigged on the plane, or it can be "bench bonded" and then installed on the plane. Both methods have their advantages and also some drawbacks. In the on plane installation you will need at least 12-15 2-3" C-clamps to apply the pressure that keeps the plexi aligned with the bow during the cure of the adhesive. With the bench method, you'll need a table large enough for the entire bow to lay flat and some sort of surface that can be drilled and screws installed to provide the needed clamping action.

[[Image:Benchbond.jpg]] [[Image:RTVbond.jpg]]

The windshields are slightly oversize to accommodate production tolerances of the airframes. This means that the excess must be trimmed. The question is how much is excess and exactly WHERE it should be trimmed. Windshields that are bench bonded typically have the forward edge trimmed after the bonding is cured. Canopies that are bench bonded have the aft edge trimmed, and the bottom edges along the canopy rails also need to be trimmed. The problem begins with the lack of rigidity of the plexi. Trying to hold it in place at one location will cause it to spring loose on the opposite side. This is one of the reasons that first time installers have such a hard time doing a good job. They just can't get that big floppy piece of plexi to lay down so they can figure out where to trim and mark the locations.

To bench bond a canopy or windshield bow, one should start with the bow out of the plane and checked for flatness. Some metal work to make it lay down flat on the face of the angle that would be vertical when installed, may be needed. The exact distance between the mounting holes at the bottom of the bow is also needed, so that you can measure that distance out on your table. Marking the hole centers and then securing the bow to the table (#6x1" drywall screws are very handy for this) lets you measure the bow to find the center. A mark on the table is a good way to keep that location visible. You will be cleaning the bow and treating it with primer and covering it with bonding agent, so any mark made on the bow will be gone.

Measure the plexi and mark the center of the plexi with a china marker or with a permanent marker on the "spray lat" protective covering on the outside, because you will remove the inner covering when bonding, and your mark will be gone with it! Now you can position the plexi on the table over the bow and line up the center marks. The plexi should end at the same distance on both legs of the bow, as a quick check that you have accurate center marks. A mark on the table at each lower corner of the plexi will be helpful later in assuring that the plexi did not slide while clamping it.

The inner spray lat is removed, or at least the first few inches. The plexi is laid over the bow, and the edge of the bonding is masked with masking tape or duct tape. Make sure that you have burnished the edge down well, as the primer and bonding agent can wick under the tape edge and leave your bond line uneven.

Lightly sand the area to be bonded. 320-400 grit paper is a good choice. A wipe with Naptha on a clean cloth will remove the sanding dust and your finger prints along with the oils from your skin that would contaminate the bond. The bow is prepared with a solvent wipe (MEK is a strong degreaser that leaves no residue when it flashes off), and the primer is appied per the instructions that come with it. If using the 732 RTV and the 1200 and 1205 primer system, 1200 is used on the metal bow, and 1205 is used on the plexi. If using the Pro-Seal method, the AC-451 adhesion promoter is used on both the metal and the plexi.

The plexi is prepared with the primer, and the bonding material is applied to the bow and trowelled so an even thickness of about 1/8" thick. The plexi is placed over the bow and lined up with the center mark and the two end marks previously located. Because of the thickness of the sealant, the two end marks will not quite match the plexi, but the distance should be evenly split between them. It can help to have someone hold the plexi sides out just a bit (away from the cleaned and primed area) so that the plexi doesn't scrape off the bonding agent as it is being slid into position.

Secure the windshield by clamping the bonded area. The wood blocks and drywall screws shown in the picture work very well on a bench that can have screw holes placed in it. They are easy to make and very inexpensive.

Start in the middle and work out to both corners evenly. Watch that you have squeezed the excess sealant out of the bonded area, but don't press so hard as to force ALL the sealant out. You should stop clamping before you see the aluminum bow pressed against the inside of the plexi. Wipe the excess sealant off the inside of the bow/windshield joint. It is much easier to make a nice finished edge now and have the clean up work complete while the bonding agent is still soft.

Wait overnight, or longer if the temperature is not above 70 degrees F.

'''TIP: An electric blanket laid over the outside of the bond and draped up over the plexi can be a big help with the temperatures are low overnight.'''

Check the cure of the bond by testing an edge of the sealant in an area that you can't see after the plexi is installed. It should be firm and rubbery, and not at all sticky. If not cured enough keep it warm and wait another 6-12 hours. You really can not rush the curing, and releasing the clamps before the bonding is done will contribute to the bond coming apart.

== The On the Plane Method (Under Construction) ==

Canopy Side Windows

2008-03-01T06:45:54Z

Jbowman90: Replaced manual formatting with standard wiki markup

== Canopy Side Windows on the 4 Place ==

'''Mechanical Difficulty:''' [[Image:Wrench2.jpg]]'''-''' [[Image:Wrench3.jpg]]

'''Tip: Don't even THINK about doing this except in warm weather or unless you can move the canopy assembly to a heated room indoors. Its critical that the plexiglass temperature be at least a comfortable room temperature, and warm enough that you are sweating on it is even better.

=== Canopy Removal ===

The AA-5x canopy side windows slide in from the bottom, and that means that step one is to remove the canopy assembly from the plane. To do this remove the bottom row of screws on the canopy. There are 2 shims at the aft edge held on by the last 2 screws on each side, be sure to keep them for re-installation.

After all the bottom row of screws is out, the canopy can be lifted straight up and off of the plane. This ought to be done by at least 2 people, and 3 would offer an additional level of safety. With a helper on the opposite wing root, lift the canopy straight up, taking care not to scratch the quarter windows with the sharp corners at the aft edge of the canopy. Once the canopy is above the turtledeck height, carefully hand it over to one person on the wing root. The other person then gets off the wing and comes to the trailing edge of the wing so that the person holding the canopy can hand it down. The canopy should be placed upside down on a padded surface. A packing blanket or sleeping bag folded a few times is a good pad on the ground.

=== Taking the interior plastic trim out ===

The windows are clamped to the frame at the "bottom" by another row of screws that hold the bottom of the window frame in place. Remove the screws and the stiffener can be removed. The interior plastic is sandwiched between the stiffener and the outside canopy. The interior plastic can now be removed. There are screws and rivets along the front edge of the plastic under the canopy bow seal. Remove the seal. Its probably old and in need of replacement anyway. A stiff bladed putty knife can help shear the glue that holds the seal in place. Use [http://products3.3m.com/catalog/us/en001/auto_marine_aero/aerospace/node_GSSPN37QHGgs/root_GST1T4S9TCgv/vroot_GSNNJ6NQDKge/bgel_GSK7J6PZ1Jbl/gvel_GSYCNP8Q3Ggl/theme_us_aerospace_3_0/command_AbcPageHandler/output_html 3M General Purpose Adhesive Cleaner] to soften the glue and remove it from the bow. Under the glue the pull rivet heads and the screws can be found.

Remove the screws and carefully drill out the rivets. Best practice is to use a small punch to tap the rivet stem back out of the way and then drill the rivet using the mandrel hole as a pilot. Use a 1/8th inch drill bit to avoid drilling the holes over-size.

There are a series of rivets along the aft bow of the canopy as well. Remove them the same way as those of the front bow.

With all the rivets and screws at the 2 bows out of the way, remove the #4 screws that hold the cover on the canopy latch and the center panel of the headliner in place. Remove the #6 screws above each window and the interior trim should now be free to come out.

=== Removing each window ===

The windows slide in the tracks, hence the need for the plastic to be warm. With the curvature of the canopy, the window must bend to slide out or in.

There is not much spare room to maneuver the window in the tracks, so the best plan is to "walk" it out about 1" at a time, alternating front and back. This takes 2 people to hold the canopy frame and move the plexi. Grasp the window by putting a flat palm on the inside and outside and pulling one end of the window out of the track slightly. When it moves, no matter how small the movement, position your hands on the opposite end of the window and repeat the pulling until it moves again. Keep swapping ends and walking the window out of the frame. After a few inches it may be easier to pull on the exposed edge of the window along the "top" of the plexi. Once it is completely out, the canopy shell is going to be very wobbly. Be careful not to damage the aluminum shell while the windows are out.

[[Image:Can_shell.jpg]]

=== Preparing the new window ===

Because of manufacturing tolerances, the bonded tracks can vary in distance apart, and its occasionally necessary to trim as much as 1/8" off one side of the window to let it fit the tracks. Measure carefully the length of the old windows and compare to the new ones. Sand or file the new one(s) if they are longer than the old ones.

Sand the edge of the new window completely smooth with sand paper in a succession of grits ending at no less than 400 grit. The goal is to remove the tool marks on the edge to leave a stress free surface. Be sure to wrap some sandpaper on a wood block and chamfer the sharp edges of the plexi with a small radius. Plexiglass expands and contracts much more than aluminum when subjected to "normal" temperatures on the ramp and in flight. This continual changing in size causes any discontinuity in the edge to become a stress concentration, and leads to small cracks and crazing in the corners, long before the window should need to be replaced. Examine the old windows on most light planes and you'll see those cracks forming in the corners. If you are using the Fletchair foam tape, it is best applied with some stretch to it, especially as you go around the corners of the plexiglas. This will make the tape "sit" down flat on the corners. This tape has a high "stickiness", and cannot be re-positioned, so apply it carefully.

=== Installing the new window ===

With the practice gained by walking the window(s) out of the tracks, you have learned the basic skill needed to re-install the windows. Lube each track and the felt or foam tape with a generous coating of clear silicone spray. Insert the window into the the track and line up both ends so that they start together. Now carefully walk the window into the tracks. The goal is NOT to wedge it tight on either end, but just take the movement that will easily happen, stop and swap ends to move the other end a little.

You can NOT force the plexi! Any suggestions of "putting a block of wood on the edge and hitting it" should be considered an admission that you didn't properly prepare the plexi, or that you are using the wrong technique. At the second Cody Convention in 2002, a group had been working to do a canopy window installation as a demonstration, and after much struggling by various persons that should have been able to install it, I was called upon to assist. After removing the jammed window from the frame and inspecting for damage to the foam tape, the plexi and the canopy shell, I re-lubed the window and the track and installed the window in a smooth easy motion alternately applying pressure at each end as I felt the resistance building and was later told that it took 41 seconds to install the window. I freely admit it usually takes 2-3 minutes to walk one into place, but I have NEVER found the need to resort to excessive pressure or hitting the plexi to drive it in.