AD 2020-16-06 Requires Repetitive Inspections Of The Forward Horizontal Stabilizer Support Assembly...

The FAA is adopting a new airworthiness directive (AD) for all Aviat Aircraft Inc. Models A-1, A-1A, A-1B, A-1C-180, and A-1C-200 airplanes.

This AD requires repetitive inspections of the forward horizontal stabilizer support assembly and the rear horizontal stabilizer support tube and reporting information to the FAA. This AD was prompted by field reports of complete failure of both the forward support assembly and the rear support tube due to fatigue. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective September 1, 2020.

Supplementary Information: The FAA received three field reports from Aviat Aircraft Inc. of complete failure of the rear horizontal stabilizer inboard support tube. The first incident, discovered during a scheduled inspection, occurred in 2005, and the second incident, discovered while the airplane was being re-skinned, occurred in 2009. The third incident was discovered during a pre-flight inspection in 2012 and included a complete failure of the forward horizontal stabilizer inboard support assembly. Failure analysis of both parts from the 2012 incident concluded they failed due to fatigue. In addition to these complete failures of the rear support tube, the FAA received two field reports from Aviat Aircraft Inc. of cracks in the rear support tube, discovered during inspections, in 2005 and 2013.

Aviat Aircraft Inc. subsequently issued Service Bulletin No. 28, Revision A, dated April 2, 2015, which requires a one-time inspection of the rear stabilizer inboard support tube in response to the multiple reports of failures and cracks. In addition to the 2012 incident, which involved a failure of both supports, the FAA received two other field reports from Aviat Aircraft Inc. of complete failure of the forward horizontal stabilizer inboard support assembly, one in 2000 and one in 2019. In the first incident, the failure occurred during ground handling after flight. In the second incident the failure was discovered while the aircraft was being placed in a hanger.

Failure of either the forward or rear support transfers loads to the other support, increasing the likelihood that both could fail. This condition, if not addressed, could result in stabilizer departure and loss of airplane control.

FMI: www.regulations.gov