Tail Tiedown Repair

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 damage.

To be continued