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How an augmentor draws cooling air

Aviation Mechanic Powerplant (AMP) practice question 8 of 13 on Reciprocating Engine Induction and Cooling Systems. ACS element AM.III.J.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONIn an augmentor cooling system, what draws additional cooling air over the engine?

  1. AA blower driven by the engine accessory section
  2. BRam air forced in by the propeller slipstream
  3. CA low-pressure area created by the exhaust gas
Show the answer and explanation

Correct answer: C. A low-pressure area created by the exhaust gas

  • A — incorrect Augmentors use exhaust gas velocity rather than any engine-driven blower to move cooling air.
  • B — incorrect The point of an augmentor is that cooling is not entirely dependent on prop wash.
  • C — correct Exhaust gas mixing with engine compartment air in the inner augmentor tubes forms a high-temperature, low-pressure, jet-like flow, and that low-pressure area draws additional cooling air over the engine.

BACKGROUND

Some aircraft use augmentors to provide additional cooling airflow. Each nacelle has two pairs of tubes running from the engine compartment to the rear of the nacelle, and the exhaust collectors feed exhaust gas into the inner augmentor tubes. There the exhaust gas mixes with air that has passed over the engine and heats it, forming a high-temperature, low-pressure, jet-like exhaust that draws more cooling air over the engine. Air entering the outer shells is heated by contact with the augmentor tubes but is not contaminated with exhaust gases, so it can be used for cabin heating, defrosting, and anti-icing. Vanes in the augmentors control the volume of air and are usually left in the trail position to permit maximum flow.

STUDY TIP

Remember that the augmentor is an exhaust-powered pump for cooling air, and that the outer shell air stays clean enough for cabin heat.

KEY POINTS

  • Exhaust gas in the inner augmentor tubes creates a low-pressure area that pulls cooling air over the engine.
  • Outer shell air is heated but uncontaminated and feeds cabin heat, defrost, and anti-icing.
  • Augmentor vanes control air volume and are normally left in trail for maximum flow.

SOURCES

  • amp-powerplant/ch06.txt "Reciprocating Engine Cooling Systems"
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MORE ON RECIPROCATING ENGINE INDUCTION AND COOLING 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.