Category: navion, vernier, control
Applicability: All aircraft using Shakespeare vernier , models 3A-42 and 3A-81 (many Beech and Navions)
Supersedes: n/a
Compliance: No later than April 1, 1950
Procedure: A serious
accident recently occurred on an aircraft employing a Vernier throttle
control of the above type due to unscrewing of the male thread adapter
which secures the outer casing of the flexible control to the body tube,
at the instrument panel end. This resulted in the pilot's being unable
to control the throttle. The means employed in these controls to secure
this connection is the machining of some imperfect threads on the brass
adapter.
This method of locking is not considered satisfactory,
as assembly and disassembly of these components can result in rendering
this
locking means ineffective. The control manufacturer has
advised that a staking operation to positively secure this connection is
now being incorporated on all their Vernier type flexible controls during
manufacturer, To prevent the possibility of the adapter becoming separated
from the body tube on aircraft in service equipped with the subject Vernier
control, all such controls must be inspected to ascertain whether these
components are positively secured by staking, drilling and lock- wiring,
or equivalent means. If the adapter is not found to be so secured in the
body tube, it should be locked by one of the foregoing locking means.
Notes: Beech Engineering
Service Bulletins Nos. 35-16 and A35-7, dated November 23, 1949, cover
this subject as it applies to their Models 35
and A-35 airplanes.
AD-50-05-02