AD-128 Page 1 of
3
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Airworthiness Directive: 128
Date:
June
26,
2002
Subject:
Aileron push pull tubes / Rear lift struts with adjustable lower end
Compliance: Mandatory
Models Effected:
Aileron push pull tubes:
All S-6 Models, S-7, all S-12 models, S-14, S-17,
S-18, (assembled or under construction)
Rear lift struts with adjustable lower end:
All airplanes with rod ends for adjustment at the lower end of the rear lift
struts (assembled or under construction)
Aileron push-pull tubes:
An S-12 experienced a disconnection at one aileron push pull tube. The male rod end was pulled out of
the threaded push pull tube end fitting. This caused loss of control over one aileron in flight. The pilot was
able to land the airplane safely.
An inspection revealed, that the male rod end was only engaged about 3 threads due to error in
assembly. The manual calls for minimum engagement of at least 6 full threads.
The disconnection occurred at the wing bell crank.
Before next flight or during final assembly of unfinished airplanes:
1. Visually inspect all rod end connections in the control system for proper assembly (thread
engagement of at least 10 full threads), for presence and security of stop nuts as per assembly
and parts manual for your airplane. Also, feel the connection for existence of play.
If you find loose connections or insufficient thread engagement, disconnect and visual inspect
condition of threads. Replace worn parts with new parts.
2.
Re-adjust the long aileron push pull tubes (from fuselage bell crank to wing bell crank’s) and the
short aileron push pull tube’s (from wing bell crank to aileron), so the rod ends connected to the
wing bell crank’s are turned all the way in and tightened against the push pull tube end fitting.
Reference Figure 1 on next page.
NOTE: The S-7 does only use the short push pull tube.
IMPORTANT: Retain position of bell cranks and ailerons according to rigging
instructions for your airplane (refer to assembly manual).
