Engine Inspection is the powerplant subject area that asks whether you can look at an engine and tell what the evidence in front of you means. AM.III.C questions put you at a compression gauge, an oil screen, a cracked combustor liner, or a stained exhaust clamp and ask what condition produced what you see. The FAA is not checking whether you can recite an inspection interval here; it is checking whether you can read damage. Expect reciprocating and turbine hardware mixed together in the same block of questions.
This area covers routine and troubleshooting inspection of both reciprocating and turbine engines, and the technical detail comes straight out of the Powerplant Handbook, FAA-H-8083-32. On the reciprocating side, the differential compression test appears in nearly every form: where you hear the escaping air tells you which component is leaking. Air at the exhaust stack points to an exhaust valve, air at the carburetor or induction inlet points to an intake valve, and air at the crankcase breather or oil filler points to worn rings or a scored cylinder wall. You will also see oil screen and filter inspection, where metal found in the screen is a symptom you must identify by type and quantity rather than a simple pass or fail, and cylinder hold-down hardware, where you are checking through-bolts and hold-down nuts for looseness and correct torque rather than for cosmetic condition. On the turbine side the questions shift to damage vocabulary and hot-section evidence. You are expected to know the standard defect names, because repair and blend limits in the manual are written against those exact words: a nick is a sharp, V-shaped depression in a blade edge, distinct from a dent, a gouge, or a score. Discoloration and cracking on combustion liners and nozzle vanes trace back to localized hot spots, most often caused by a fuel nozzle that is no longer spraying an even pattern. Foreign object damage is expected in the compressor, where anything drawn through the inlet strikes first. Magnetic chip detectors round out the lubrication questions, collecting ferrous particles so wear is found before a bearing fails. Exhaust system inspection closes the area: a light-colored deposit trailing from a slip joint or clamp is the classic sign of a gas leak, and exhaust leaks are urgent because of carbon monoxide and fire risk, not noise.
ACS AM.III.C is tested on the FAA Powerplant written test, one of 1,355 ACS-tagged questions in the Powerplant bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
While performing a differential compression test, air is heard escaping from the engine exhaust outlet. This indicates a leaking
Local heat discoloration and small cracks found on turbine engine combustion liners and nozzle vanes are generally the result of
A defect described as a sharp, V-shaped depression in the edge of a turbine compressor blade is properly called a
Metal particles found on a reciprocating engine oil screen during inspection most likely indicate
Magnetic chip detectors are installed in turbine engine lubrication systems to
During inspection of an exhaust system, a streak of light-colored deposit trailing from a slip joint or clamp most often indicates
When inspecting reciprocating engine cylinder hold-down nuts and through-bolts, the technician should primarily check for
ACS code: AM.III.C
Correct answer: exhaust valve
Rationale: Air heard at the exhaust outlet means it is leaking past the exhaust valve. Air at the carburetor/intake indicates an intake valve leak, and air at the crankcase breather indicates worn or broken piston rings. Listening for the escape point localizes the leak during inspection.
ACS code: AM.III.C
Correct answer: high operating temperatures and thermal stress
Rationale: Combustion liners and turbine nozzle vanes operate in the hottest gas path. Repeated heating and cooling produces thermal stress that leads to localized discoloration, warping, and cracking. FOD typically dents or nicks compressor blades, and fuel-borne moisture is not the usual cause of hot-section cracking.
ACS code: AM.III.C
Correct answer: nick
Rationale: Standardized inspection terminology defines a nick as a sharp, V-shaped depression in an edge or surface, typically caused by foreign objects. A score is a deeper scratch from a harder material, and a pit is a small, rounded cavity often from corrosion. Using correct terms ensures accurate defect reporting.
ACS code: AM.III.C
Correct answer: internal engine wear or component failure
Rationale: The oil screen and filter trap particles circulating in the oil. Metal contamination signals abnormal internal wear or impending failure of bearings, gears, or other components, and must be investigated. Oil oxidation produces sludge or varnish, and fuel dilution thins the oil rather than introducing metal.
ACS code: AM.III.C
Correct answer: capture ferrous particles for early wear detection
Rationale: A magnetic chip detector uses a magnet to collect ferrous debris from the oil so technicians can detect internal wear before it becomes a failure. It performs an inspection/monitoring function and does not regulate oil pressure or separate water from the oil.
ACS code: AM.III.C
Correct answer: an exhaust gas leak at that joint
Rationale: Escaping hot exhaust gas leaves a tell-tale light-gray or sooty streak downstream of the leak point, signaling a faulty joint, clamp, or crack that must be corrected. General heat oxidation discolors the whole surface uniformly, and exhaust clamps are not lubricated, so a streak points to a leak.
ACS code: AM.III.C
Correct answer: proper torque and security
Rationale: Cylinder hold-down hardware must remain at the specified torque to keep the cylinder properly seated and sealed; inspection verifies torque and security per the manufacturer's data. Paint color and serial-number matching are not the function of hold-down fasteners, so torque and security are the key checks.
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