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Combustion heater ventilating air

Aviation Mechanic Airframe (AMA) practice question 5 of 15 on Environmental Systems. ACS element AM.II.G.K5 · 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 aircraft combustion heater, what name is given to the air that is warmed and sent into the cabin?

  1. ACombustion chamber air
  2. BVentilating air
  3. CHeater exhaust air
Show the answer and explanation

Correct answer: B. Ventilating air

  • A — incorrect Combustion air is burned with fuel inside the sealed inner chamber and is kept completely separate from the air sent to the cabin.
  • B — correct Ventilating air is the handbook's term for the air that is warmed by passing between the combustion chamber and the outer shroud and is then sent into the cabin.
  • C — incorrect The exhaust from combustion is funneled overboard and never enters the cabin.

BACKGROUND

A combustion heater is a heat source independent of the aircraft engines, although it burns fuel drawn from the aircraft main fuel system. Ambient air and fuel are ignited in an air-tight inner combustion chamber located inside the heater's cylindrical outer shroud, and the exhaust from that combustion is funneled overboard. Ventilating air, normally taken in through a ram air intake, passes between the combustion chamber and the outer shroud, absorbs heat by convection, and is channeled into the cabin. Combustion air is scooped from outside the aircraft or from the heater compartment and is delivered by a blower that ensures the correct quantity and pressure. On the ground, a ventilating air fan controlled by a landing gear squat switch draws in ventilating air; once airborne, ram airflow is sufficient and the fan stops.

STUDY TIP

Keep the heater's two air streams straight: combustion air burns and goes overboard, ventilating air only picks up heat and goes to the cabin. Many combustion heater questions hinge on that separation.

KEY POINTS

  • Ventilating air is warmed between the combustion chamber and outer shroud, then sent to the cabin.
  • Combustion air is separate and its exhaust goes overboard.
  • A ground ventilating fan is controlled by the landing gear squat switch.

SOURCES

  • sources/ama-airframe/ch16.txt "Combustion Heaters — Ventilating Air System"
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MORE ON ENVIRONMENTAL SYSTEMS

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.