FAA Aviation Mechanic Powerplant (AMP)Engine InspectionEasy
During an annual inspection, a technician finds a small crack in the exhaust muffler shroud of a normally aspirated reciprocating engine that uses a cabin heat system drawing air around the muffler. Why is this discrepancy considered critical and requiring immediate correction?
- AIt will cause the exhaust gas temperature gauge to read inaccurately
- BIt could allow carbon monoxide to enter the cabin heating air supply, endangering occupants
- CIt will reduce engine power output significantly
- DIt only affects fuel economy and is not a safety concern
Show answer & explanationAnswer & explanation
Correct answer: B. It could allow carbon monoxide to enter the cabin heating air supply, endangering occupants
Exhaust system cracks near the muffler shroud used for cabin heat are a critical safety concern because they can allow carbon monoxide, a toxic and undetectable gas, to enter the cabin heating air, posing a serious risk to occupants.
Why the other options are wrong
- A. EGT probe accuracy is unrelated to shroud cracks in this location.
- C. Minor exhaust cracks generally have negligible effect on power output.
- D. This significantly understates the serious safety risk involved.
Exhaust System Inspection
Inspection of exhaust components for cracks, leaks, and corrosion, critical when the muffler is used as a heat source for cabin air.
- Cracks near cabin heat muffler shrouds risk carbon monoxide entering the cabin
- CO is colorless, odorless, and highly toxic
- Exhaust systems require inspection each annual/100-hour inspection per Appendix D
Memory trick: 'A cracked muffler can turn cabin heat into a silent killer'