SkyDrill

Share of ram airflow entering the cowling

Aviation Mechanic Powerplant (AMP) practice question 11 of 13 on Reciprocating Engine Induction and Cooling Systems. ACS element AM.III.J.K8 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONAbout how much of the total ram airflow approaching an airborne engine nacelle enters the cowling to provide engine cooling?

  1. A50 to 60 percent
  2. B75 to 85 percent of the airflow
  3. C15 to 30 percent
Show the answer and explanation

Correct answer: C. 15 to 30 percent

  • A — incorrect This is far more than the share that actually enters the cowling; most of the approaching air flows over the outside.
  • B — incorrect Most of the approaching air passes over the outside of the cowling rather than through it.
  • C — correct Of the total ram airflow approaching the airborne engine nacelle, only about 15 to 30 percent enters the cowling to provide engine cooling.

BACKGROUND

Of the total ram airflow approaching an airborne engine nacelle, only about 15 to 30 percent enters the cowling to provide engine cooling, and the remainder flows over the outside of the cowling. Because so much air stays outside, the external shape of the cowl must be faired so that air flows smoothly over it with a minimum loss of energy. The cowling performs two functions: it streamlines the bulky engine to reduce drag, and it forms an envelope around the engine that forces air to pass around and between the cylinders to absorb heat dissipated by the cylinder fins. Cowl panels are made from sheet aluminum or composite material with a smooth external surface to permit undisturbed airflow. Cowl panels are inspected for scratches, dents, and tears, since such damage weakens the panel, increases drag by disrupting airflow, and invites corrosion.

STUDY TIP

Remember the two jobs of the cowling, streamlining and forcing air through, and pair them with the fact that only a minority of the ram air ever goes inside.

KEY POINTS

  • Only about 15 to 30 percent of approaching ram air enters the cowling.
  • The cowling both streamlines the engine and forces air around the cylinders.
  • Dents and tears in cowl panels disrupt airflow, add drag, and start corrosion.

SOURCES

  • amp-powerplant/ch06.txt "Maintenance of Engine Cowling"
Practice the Aviation Mechanic Powerplant (AMP) test →Timed 100-question exam, by ACS area, or review your misses. Free.
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.