Engine Exhaust System, Muffler Cracking

1 FAA Aviation Safety SPECIAL AIRWORTHINESS INFORMATION BULLETIN SUBJ: Engine Exhaust System, Muffler Cracking SAIB: CE-17-18 Date: 06/20/2017 This is information only. Recommendations aren’t mandatory.

Introduction This Special Airworthiness Information Bulletin (SAIB) alerts owners and operators of an airworthiness concern on Aviat Aircraft Inc. Models A-1, A-1A, A-1B, and A-1C-180 airplanes, specifically the possibility of low flight hour muffler cracking. 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 Aviation Regulations (14 CFR) part 39. Background In February, the Federal Aviation Administration (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. Recommendation 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.

For Further Information Contact Richard Thomas (Aerospace Safety Engineer); Denver Aircraft Certification Office, East 68th Avenue, Room 214, Denver, Colorado 80249; phone 303-342-1085; fax 303-342-1088; e-mail [email protected].

2 For Related Service Information Contact Aviat Aircraft Inc., P.O. Box 1240, Afton, WY 83110; phone (307) 885–3151; fax: (307) 885–9674; email: [email protected]; Internet: http://aviataircraft.com.