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Primary cause of internal exhaust failures

Aviation Mechanic Powerplant (AMP) practice question 2 of 8 on Engine Exhaust and Reverser Systems. ACS element AM.III.L.R3 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat is given as the primary cause of internal exhaust system failures, such as broken baffles and diffusers?

  1. AErosion and carburization
  2. BThermal and vibration fatigue
  3. CImproper clamp torque at slip joints
Show the answer and explanation

Correct answer: A. Erosion and carburization

  • A — correct Unlike other exhaust failures, internal failures are caused primarily by erosion and carburization resulting from the extreme thermal conditions inside the system.
  • B — incorrect Thermal and vibration fatigue cracking in areas of stress concentration is given as the cause of heat exchanger surface failures, not of internal baffle and diffuser failures.
  • C — incorrect Loose or improperly torqued connections produce external leaks at mated joints; they are not described as the cause of internal baffle and diffuser breakup.

BACKGROUND

Internal failures of baffles, diffusers, and similar parts can cause partial or complete engine power loss by restricting the flow of exhaust gases. If pieces of the internal baffling break loose and partially or totally block the flow of exhaust gases, engine failure can occur. As opposed to other failures, erosion and carburization caused by the extreme thermal conditions are the primary causes of internal failures. Engine backfiring and combustion of unburned fuel within the exhaust system are probable contributing factors. Local hot-spot areas caused by uneven exhaust gas flow can also result in burning, bulging, or rupture of the outer muffler wall.

STUDY TIP

Keep the failure causes separated by location: internal parts fail from erosion and carburization, while external manifolds and stacks fail from fatigue at welded or clamped points. Disassemble as needed to inspect internal baffles and diffusers.

KEY POINTS

  • Internal baffle or diffuser breakup can block exhaust flow and cause engine power loss.
  • Erosion and carburization from extreme heat are the primary causes of internal failures.
  • Backfiring and combustion of unburned fuel in the system are contributing factors.

SOURCES

  • sources/amp-powerplant/ch03.txt "Internal Muffler Failures"
Practice the Aviation Mechanic Powerplant (AMP) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON ENGINE EXHAUST AND REVERSER SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.