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Exhaust shroud heater operation

Aviation Mechanic Airframe (AMA) practice question 4 of 15 on Environmental Systems. ACS element AM.II.G.K4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONIn an exhaust shroud heating system on a single-engine light aircraft, how is the air sent to the cabin heated?

  1. AExhaust gas is ducted into the cabin.
  2. BA fuel burner heats the air stream.
  3. CAmbient air passes over the exhaust.
Show the answer and explanation

Correct answer: C. Ambient air passes over the exhaust.

  • A — incorrect Exhaust gas entering the cabin is the hazard the system is inspected against; even a slight exhaust crack can admit fatal carbon monoxide.
  • B — incorrect Burning fuel in a separate chamber describes a combustion heater, not an exhaust shroud heater.
  • C — correct Ambient air is directed into a shroud that encases part of the exhaust system, is warmed by the exhaust, and then passes through a firewall heater valve into the cabin.

BACKGROUND

Most single-engine light aircraft use exhaust shroud heating systems. Ambient air is directed into a metal shroud, or jacket, that encases part of the engine exhaust system, where the air is warmed and then directed through a firewall heater valve into the cabin. The arrangement requires no electrical or engine power and uses heat that would otherwise be wasted. The major concern is that exhaust gases could contaminate the cabin air, since even the slightest crack in an exhaust manifold could admit enough carbon monoxide to be fatal. Inspection usually involves pressurizing the exhaust system with air and checking for leaks with a soapy solution, and such checks can be performed as often as every 100 hours.

STUDY TIP

Tie the shroud heater to its inspection: the same wall that transfers heat is the only thing separating exhaust gas from cabin air. Expect questions about pressurizing the exhaust for leak checks and about carbon monoxide detectors in the flight deck.

KEY POINTS

  • Ambient air is warmed inside a shroud around the exhaust and ducted to the cabin.
  • A firewall heater valve controls the heated air entering the cabin.
  • Exhaust leaks admit carbon monoxide, so leak checks and a CO detector are required.

SOURCES

  • sources/ama-airframe/ch16.txt "Exhaust Shroud Heaters"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.