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FADEC handling of compressor inlet conditions

Aviation Mechanic Powerplant (AMP) practice question 11 of 12 on Engine Instrument Systems. ACS element AM.III.D.K9 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONOn a turbine engine with full authority digital engine control (FADEC), what reads the compressor inlet air temperature and pressure and sends that information to the engine controls?

  1. AA mechanical aneroid linkage
  2. BThe engine computer
  3. CThe flight engineer's panel
Show the answer and explanation

Correct answer: B. The engine computer

  • A — incorrect An aneroid and linkage drive an analog manifold pressure gauge on a reciprocating engine; it is not what feeds a digital control.
  • B — correct On FADEC engines, the computer reads the compressor inlet temperature and pressure information and sends it to the engine controls.
  • C — incorrect A crewmember reading and converting values belongs to earlier systems; the digital control does this automatically.

BACKGROUND

Gas turbine engines are sensitive to the temperature and pressure of the air at the compressor inlet, so correct values for ambient conditions matter when thrust is computed. The engine senses the actual air temperature and pressure at the compressor inlet, which for a stationary aircraft is the static field or true barometric pressure rather than the altimeter setting reported by the tower. On engines with full authority digital engine control (FADEC), the computer reads this information and sends it to the engine controls. Temperature sensed is the total air temperature (TAT), which several onboard computers use, and the engine controls set the engine computers according to it. FADEC installations also provide a means of checking the engine, with the results displayed on the flight deck.

STUDY TIP

Note that FADEC replaces manual readings and settings: the computer takes the inlet conditions itself and passes them to the engine controls.

KEY POINTS

  • FADEC computers read compressor inlet air temperature and pressure.
  • That information is sent to the engine controls automatically.
  • FADEC also provides engine checks whose results appear on the flight deck.

SOURCES

  • FAA-H-8083-32B ch10 "Ambient Conditions"
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MORE ON ENGINE INSTRUMENT 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.