Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
AIR-21-20
December 16, 2021
This is information only. Recommendations
aren’t mandatory.
Introduction
This special airworthiness information bulletin (SAIB) alerts owners,
operators, maintenance technicians, and inspectors of an airworthiness
concern on Textron Aviation Inc. (formerly Cessna Aircraft Company)
Model 310, 310A, 310B, 310C, 310D, 310F, 310G, 310H, 310I, 310J,
310J-1, 310K, 310L, 310N, 310P, 310Q, 310R, 320, 320-1, 320A, 320B,
320C, 320D, 320E, 320F, 335, 340, 340A, 401, 401A, 401B, 402, 402A,
402B, 402C, 411, 411A, 414, 414A, 421, 421A, 421B, 421C, and 425
airplanes. The intent is to emphasize the importance of ensuring
control cable tensions are set correctly during airplane maintenance,
particularly when similar cables require different tensioning.
At this time, the airworthiness concern is not an unsafe condition that
would warrant airworthiness directive (AD) action under Title 14 of the
Code of Federal Regulations (14 CFR) part 39.
Background
The FAA received a report of an event that occurred on November 26,
2019, where the flap extend cable failed during approach. The pilot
felt a sudden right roll and right yaw, which they corrected with near
full left aileron and left rudder. When the flaps were retracted, the
airplane became controllable again. A no-flap landing was conducted,
and the aircraft rolled out and stopped without further incident. A
search of the FAA’s service difficulty report (SDR) system revealed 24
similar events of flap extend cable failure over the last 35 years, all
without a serious outcome.
The FAA suspects improper tensioning as a contributing factor in the
flap extend cable failures. The flap extend cable has a specified
tension significantly lower than the retract cable. In general,
improper tensioning of the flight control cables may result in cable
failure or interference with airplane structure.
Textron has revised their manuals for the airplane models listed above
to emphasize the differences between extension and retraction rigging
tensions.
Recommendations
The FAA recommends using the latest revision of the applicable service
manual to ensure control cable extension and retraction rigging
tensions are set correctly during airplane maintenance.