TST Rudder lower hinge pin failure

[Guest TOSGcentral]

TST LOWER RUDDER HINGE FAILURE.

 

 

This only came in a couple of days prior to this Bulletin being produced – so data is still not complete and the photos are not crash hot either!

 

 

FAILURE.

 

 

The lower rudder hinge pin, normally welded to a bracket on the bottom of the fin stern post, has been found to have totally failed and is missing.

 

 

This failure DID NOT occur in flight but was found on the re-rig of a trailer transported TST.

 

 

SOME DATA. This pin is quite substantial (5 cm long) and is securely welded to the lower bracket on the fin. There is a secondary weld where it passes through a plate immediately below where the rudder normally seats. Totally losing this vital piece would be considered highly unlikely so it will not normally attract any detailed inspection.

 

 

CAUSES. Presently unknown. There is no surrounding damage and the pin is too sturdy for the rudder or ground shocks to break it.

 

 

What is known is that a modification has been done to this area of the fin. The normal clamp to stay the tailwheel spring has been discarded and the keel member drilled out to take a nut and bolt to secure the rear of the spring instead.

 

 

This work is immediately below the failure and extremely close to it.

 

 

INTERIM CONCLUSIONS. It is possible that the casual work done on this aircraft disturbed and weakened the hinge pin lower weld which eventually fatigue failed.

 

 

ACTION. It is advised that all affected types be inspected for cracking or other damage around the lower hinge pin. Use a strong torch so that you have good light and preferably slip the rudder off for a better look as well

 

 

AFFECTED TYPES. All of the following Thruster types have the same lower hinge pin assembly. TST, T100, T300, T500. Flying Fox, & Bilby.

 

 

Gemini X, Gemini A & B, Glasshouse A, B & C, and all the production single seaters (T83, T84, T85 (all models) Sprint, T85BG/Sprint hybrid & T85SG/T100 hybrid have different assemblies and are not affected.

 

Please note that TOSG is not an official airworthiness advice source and simply passes on information that may have significance to operators.