Aircraft Mufflers

Pilot observed smoke in the cockpit, declared emergency and landed normally. Inspection of the right engine compartment revealed the mufflers aft wall was missing and exhaust was directed onto the battery box. Hot exhaust melted the battery and battery contactor, clock fuse holder, both battery cables and boots. The gascolator push/pull control knob was melted.

Editorial Staff

Thursday, September 15, 2016 at 12:00 AM ET

Verified

Key Takeaways:

Multiple aircraft models experienced various exhaust system failures, including missing muffler walls, cracked spot welds, internal separations, and missing tailpipes.
These failures led to significant safety hazards such as cockpit smoke, melted electrical components, and carbon monoxide warnings.
The causes of these failures ranged from material fatigue, manufacturing defects, and issues with previous repairs, to design flaws causing component chafing.

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Cessna Model 150E
Aft Muffler Wall Failure

Pilot observed smoke in the cockpit, declared emergency and landed normally. Inspection of the right engine compartment revealed the muffler’s aft wall was missing and exhaust was directed onto the battery box. Hot exhaust melted the battery and battery contactor, clock fuse holder, both battery cables and boots. The gascolator push/pull control knob was melted. All electrical wiring in the engine compartment was destroyed.

The owner recalls engine backfiring when a student performed the ignition test IAW AD 76-07-12 at too high an rpm, which likely aggravated an already weak muffler (p/n 04504004), causing the failure.