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Effect of dirt on compressor blades

Aviation Mechanic Powerplant (AMP) practice question 5 of 13 on Turbine Engines. ACS element AM.III.B.K6 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat can result from an accumulation of dirt and other foreign deposits on turbine engine compressor components?

  1. ALower exhaust gas temperature and quick acceleration
  2. BHigh exhaust gas temperature and poor acceleration
  3. CNo change until the blades begin to crack or erode
Show the answer and explanation

Correct answer: B. High exhaust gas temperature and poor acceleration

  • A — incorrect Deposits degrade performance rather than improve it; EGT rises and acceleration becomes unsatisfactory.
  • B — correct Unsatisfactory acceleration and high exhaust gas temperature can result from foreign deposits on compressor components.
  • C — incorrect Performance deteriorates from the loss of aerodynamic efficiency alone, well before any cracking occurs.

BACKGROUND

A large volume of air is drawn into the compressor, and centrifugal force throws dirt particles outward so they build up as a coating on the casing, the vanes, and the compressor blades. The atmosphere near the ground carries tiny particles of dirt, oil, soot, and other foreign matter that feed this buildup. Accumulated dirt reduces the aerodynamic efficiency of the blades, in a manner similar to an aircraft wing under icing conditions, with resulting deterioration in engine performance. If enough material is allowed to accumulate, the end result is inefficiency. The condition is remedied by periodic inspection, cleaning, and repair of compressor components.

STUDY TIP

Link dirt buildup to lost blade efficiency, and lost efficiency to hotter running and sluggish acceleration. The wing-icing comparison is a useful memory hook.

KEY POINTS

  • Dirt builds up on the compressor casing, vanes, and blades from air drawn in near the ground.
  • Deposits reduce blade aerodynamic efficiency much like ice on a wing.
  • The result is unsatisfactory acceleration and high exhaust gas temperature.

SOURCES

  • FAA-H-8083-32B ch10 "Compressor Section" (Turbine Engine Maintenance)
Practice the Aviation Mechanic Powerplant (AMP) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON TURBINE ENGINES

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.