SkyDrill

Classifying a 40 inches Hg turbosupercharged engine

Aviation Mechanic Powerplant (AMP) practice question 6 of 13 on Reciprocating Engine Induction and Cooling Systems. ACS element AM.III.J.K3 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONAn engine whose turbosupercharger raises manifold pressure to about 40 "Hg at sea level is best classified as which of the following?

  1. AA normalized engine that regains lost pressure
  2. BA ground-boosted, truly supercharged engine
  3. CA naturally aspirated engine with ram air boost
Show the answer and explanation

Correct answer: B. A ground-boosted, truly supercharged engine

  • A — incorrect Normalizing systems only recover the pressure lost with altitude and are never used to boost manifold pressure above 30 "Hg.
  • B — correct To be a true supercharger the system must boost manifold pressure above 30 "Hg; a sea level-boosted system that reaches about 40 "Hg at sea level is a ground-boosted, truly supercharged installation.
  • C — incorrect Ram air alone cannot raise manifold pressure to about 40 "Hg; an engine with no compressor is nonsupercharged.

BACKGROUND

Induction systems for reciprocating engines are broadly classified as supercharged or nonsupercharged. Some systems only normalize the air pressure entering the engine, regaining the pressure lost as altitude increases; these are not ground boost systems and are never used to boost manifold pressure above 30 "Hg. A true supercharged engine, called a ground boosted engine, boosts manifold pressure above ambient, that is, above 30 "Hg. Some ground-boosted or sea level turbosupercharged systems are designed to operate from sea level up to their critical altitude and can develop more power at sea level than an engine without turbosupercharging, typically by raising manifold pressure to around 40 "Hg.

STUDY TIP

Use 30 "Hg as the dividing line. Above it at sea level means ground boosted and truly supercharged; at or below it the system is only normalizing.

KEY POINTS

  • A true supercharger boosts manifold pressure above 30 "Hg.
  • Normalizing systems only restore the pressure lost with altitude.
  • Sea level-boosted systems can reach around 40 "Hg and make more power at sea level.

SOURCES

  • amp-powerplant/ch03.txt "Supercharged Induction Systems"
  • amp-powerplant/ch03.txt "Ground-Boosted Turbosupercharger System"
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.