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Result of fuel flow increasing too rapidly on acceleration

Aviation Mechanic Powerplant (AMP) practice question 3 of 20 on Engine Fuel and Fuel Metering Systems. ACS element AM.III.I.K8 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONDuring a rapid acceleration of a turbine engine, fuel flow increases too rapidly for the mass airflow through the engine. What is the likely result?

  1. AA lean flameout as the fuel is cooled
  2. BAn immediate drop in turbine inlet temperature
  3. CA rich blowout or compressor stall
Show the answer and explanation

Correct answer: C. A rich blowout or compressor stall

  • A — incorrect Lean flameout occurs at the opposite extreme, when fuel quantity is reduced proportionally below the air quantity, not when fuel flow is excessive.
  • B — incorrect Excessive fuel relative to mass airflow can exceed the limiting temperature of the turbine blades, so a drop in turbine temperature is not the expected result.
  • C — correct The handbook states that if fuel flow increases too rapidly during acceleration an over-rich mixture can be produced, with the possibility of a rich blowout or compressor stall.

BACKGROUND

The turbine engine fuel system must let the pilot increase or decrease power at will, and that control comes from varying the fuel flow to the combustion chambers. The quantity of fuel must be adjusted automatically to correct for changes in ambient temperature or pressure. If the fuel becomes excessive in relation to mass airflow, the limiting temperature of the turbine blades can be exceeded, or a compressor stall and rich blowout can occur. Rich blowout happens when the oxygen in the air supply is insufficient to support combustion and the mixture is cooled below combustion temperature by the excess fuel. Lean flameout is the opposite extreme, occurring when fuel quantity is reduced proportionally below the air quantity.

STUDY TIP

Keep the two failure modes straight by the word in front of them: rich blowout comes from too much fuel, lean flameout from too little. Acceleration schedules exist precisely to keep fuel flow from outrunning airflow.

KEY POINTS

  • Excess fuel relative to mass airflow can overtemperature the turbine or cause compressor stall.
  • Rich blowout occurs when excess fuel starves the mixture of oxygen and cools it below combustion temperature.
  • Lean flameout occurs when fuel flow falls proportionally below airflow.

SOURCES

  • amp-powerplant/ch02.txt "Turbine Engine Fuel System—General Requirements"
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MORE ON ENGINE FUEL AND FUEL METERING 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.