SAIB Notes Several Instances Of Problems On Low-Time Mufflers

The FAA has issued a Special Airworthiness Information Bulletin (SAIB) following several reports of cracked mufflers on Aviat Aircraft Inc. Models A-1, A-1A, A-1B, and A-1C-180 airplanes.

According to the SAIB, in February, the FAA was notified of several incidents where low flight hour mufflers had cracked where the muffler can is joined to the overboard tube beneath the heat shroud. One of the cracked mufflers that had 60.5 hours time-in-service (TIS) was discovered during an annual inspection. Another muffler that had 70 hours TIS was discovered during a 100 flight hour inspection. A third muffler that had 50 hours TIS was discovered after excessive play was found during a pre-flight inspection.

The FAA recommends that all owners and operators of the aircraft listed in the Introduction of this SAIB strictly adhere to the Instructions for Continued Airworthiness for the various models all of which require annual or not-to-exceed 100 flight hour inspection for cracks in the muffler can with the heat shroud removed. If cracks are found where the muffler can is joined to the overboard tube it is recommended the muffler be replaced rather than weld repaired.

It is also recommended that the fuselage exhaust pipe exit be examined each pre-flight for evidence of the exhaust pipe rubbing against the skin. If evidence of rubbing is found, it is suggested the 100 hour inspection for cracking be performed. If cracks are found, it is requested that this be reported to Aviat along with the muffler TIS and whether there are any marks on the muffler (typically on the overboard tube) indicating a manufacturing lot or manufacturing date. Under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the OMB has approved the information collection contained in this SAIB, and assigned OMB Control Number 2120-0731.

(Image from file)

FMI: SAIB