Exhaust Matters

Editorial Staff

Wednesday, February 23, 2022 at 01:48 AM ET

Verified

Key Takeaways:

Aircraft exhaust systems, particularly mufflers, are susceptible to various failures including leaks, cracks, internal component damage, and weld failures.
Many of these defects can be difficult to detect visually, requiring specific tests (e.g., pressure tests) or presenting through operational symptoms like carbon monoxide warnings or engine roughness.
Failures can occur across a wide range of operating hours, sometimes at very low part total times, emphasizing the critical importance of thorough and regular inspections.

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Cessna 172M Skyhawk

Leaking Tailpipe

While carrying out the pressure test in AD CF90-03-R2, large leaks were found in the area surrounding the muffler tailpipe area under the heat muff shroud support structure. No defects in this area were visible. Without the pressure test, this defect would not have been found. It is assumed the muffler is original to the airplane.

Part total time: Unknown

Cessna 172S Skyhawk SP

Failed Support Flange Welds

During flight, the carbon monoxide warning illuminated. Pilot returned to land. Maintenance discovered two spot welds on the shroud support flange of the muffler had failed, resulting in open holes in the muffler can. Muffler was replaced.

Part total time: 212.0 hours

Cessna 182B Skylane

Cracked Inlet Flange

While conducting the inspection required by AD CF-90-03 R2, found exhaust cracked at right hand inlet flange radius. Exhaust muffler, left-hand and right-hand exhaust header pipes were removed and sent to manufacturer for inspection and repair.

Part total time: 50.0 hours

Piper PA-280180 Cherokee 180

Baffling Blockage

When a flashlight was shined in the exhaust portion of the forward muffler, a restriction was observed resulting from baffling failure. The degree of restriction was estimated at 50 percent. A similar condition was found in the aft muffler, estimated at 90 percent. The front muffler’s time in service could not be determined; the aft muffler’s was 1359 hours. During the last annual inspection, the recommended muffler inspection was not performed.

Part total time: 1359.0 hours

Piper PA-44-180 Seminole

Broken Internals

During inspection of the left engine for roughness, a visual inspection was carried out on the right engine. When the exhaust tailpipe was inspected, it was found to be blocked. The aft muffler was removed for #3 and #4 cylinders on the right engine. The internal pipe was found to be broken from the end pieces. About four inches of it were lodged in the tailpipe. A large amount of the internal pipe appeared to be missing.

Part total time: 880.0 hours