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:

Muffler and exhaust system failures are a recurring issue across various aircraft models, leading to serious safety concerns such as cockpit smoke, carbon monoxide warnings, and extensive component damage including melted electrical systems.
Common causes for these failures include structural fatigue, cracked welds (both original and from previous repairs), and design flaws leading to component chafing.
Incidents show that failures can occur on relatively low-time parts or shortly after overhaul, indicating persistent issues with component integrity and design.

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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.