Nose Strut

Pulling the Nose Strut

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 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.

Torque Tube Box