Mufflers And Exhausts

The following is derived from maintenance facility submissions to the FAA’s Service Difficulty Reports database.

Editorial Staff

Sunday, September 29, 2024 at 05:00 AM ET

Verified

Key Takeaways:

Aircraft exhaust systems, including mufflers, flanges, and ball joints, are prone to developing cracks and structural deterioration across various models and operating hours.
These failures commonly lead to exhaust gas leaks, posing a significant risk of carbon monoxide exposure in the cabin or heat shroud, often triggering CO warnings.
Detection of these critical flaws can be challenging, with some cracks being hidden or only visible upon component removal during maintenance.

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Cessna 150L

Cracked Flange

During a scheduled inspection, a crack was found at the forward muffler flange. Crack is approximately 75 percent around the circumference. There is separation along the crack. Exhaust trails were found inside shroud and well down into hot-air ducting. Muffler identified as having three small pin holes in 2008. Heat system incapacitated at that time for safety reasons; muffler remained in service.

Part total time: Unknown

Cessna 172S Skyhawk SP

Cracked Spot Welds

Sitting on the ramp idling, crew received a high CO warning after a couple of minutes. Crew shut down engine and CO warning ceased. Inspected muffler and found spot welds pulling out from muffler liner and releasing exhaust into heat shroud.

Part total time: 151.0 hours

Cessna 182B

Cracked Right Exhaust

Exhaust-type cabin heater inspection carried out. Found exhaust cracked at right-hand inlet flange radius. Exhaust muffler, left-hand and right-hand exhaust header pipes removed. Sent to manufacturer for repair and fit inspection.

Part total time: 50.0 hours

Piper PA-28-181 Archer II/III

Carbon Monoxide Alert

Crew received carbon monoxide warning in flight. They made a precautionary landing. Visual inspection of exhaust system revealed a crack in the aft muffler in the transition from forward muffler. The muffler was replaced. No CO warning was noted on run-up.

Part total time: 131.0 hours

Piper PA-44-180 Seminole

Invisible Crack

During replacement of the right engine’s #3 exhaust riser, the tech removed the aft muffler, revealing it had a large, four-inch crack. The crack was not visible unless the muffler is removed, because the forward muffler blocks the view of the aft muffler’s front side.

Part total time: Unknown

Tecnam P2006T

Deteriorated Ball Joints

On complying with AD 2015-02-09, found exhaust pipes leaking at the ball joints where they connect to the muffler. One side of one ball joint lip on the muffler had deteriorated substantially, from about 0.065 in. to 0.023 in. All ball joints showed signs of leaking and heat corrosion.

Part total time: Unknown