Licensing Examination Practice

Illinois Aircraft Mechanic Powerplant Licensing Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary function of a reciprocating aircraft engine’s

crankshaft?

• Support the camshaft
• Convert reciprocating motion into rotary motion
• Compress air in the cylinders
• Act as a fuel pump

Rationale: The crankshaft converts the up-and-down motion of the pistons

into rotary motion to drive the propeller.

• What component is used to prevent detonation in an aircraft engine?
• Turbocharger 1 / 4

• Spark plug heat range selection
• Oil filter
• Carburetor float

Rationale: Using the proper spark plug heat range helps prevent pre-

ignition and detonation in aircraft engines.

• Which of the following is the main purpose of an aircraft engine

magneto?

• Charge the battery
• Provide electrical spark to ignite the fuel-air mixture
• Regulate fuel flow
• Control engine temperature

Rationale: A magneto generates electrical current independently of the

aircraft battery to ignite the fuel-air mixture in the cylinders.

• During a preflight inspection, you notice a slight oil leak at the lower

crankcase. What is the most appropriate action?

• Ignore if the level is adequate
• Report and repair before flight
• Add oil and continue
• Clean the engine and monitor

Rationale: Any oil leaks should be corrected prior to flight to prevent

engine damage or failure. 2 / 4

• Which of the following types of carburetors is commonly used in light

aircraft engines?

• Fuel injection
• Float-type carburetor
• Turbocharger
• Rotary vane

Rationale: Float-type carburetors are widely used in light aircraft to

regulate fuel flow to the engine.

• What is the purpose of a turbocharger in an aircraft engine?
• Reduce fuel consumption
• Increase engine power by compressing intake air
• Cool the engine
• Provide ignition timing

Rationale: Turbochargers compress intake air, allowing more air-fuel

mixture into the cylinders, increasing engine power.

7. Detonation in an aircraft engine can cause:

• Reduced oil consumption
• Excessive cylinder head temperature and possible engine damage
• Smooth engine operation
• Improved fuel economy

Rationale: Detonation causes uncontrolled combustion, leading to

overheating and potential mechanical damage. 3 / 4

• What is the function of the propeller governor on a constant-speed

propeller?

• Start the engine
• Lubricate the propeller hub
• Maintain a selected propeller RPM
• Regulate fuel flow

Rationale: The propeller governor adjusts blade pitch to maintain a

constant engine RPM.

9. The most critical component in a radial engine lubrication system is:

• Oil filter
• Scavenge and pressure pumps
• Cylinder head
• Magneto

Rationale: Proper operation of pressure and scavenge pumps ensures all

engine parts receive adequate lubrication.

• What does the term “TBO” (Time Between Overhaul) signify for

an aircraft engine?

• Maximum flight time
• Recommended operating hours before engine overhaul
• Time until first inspection
• Oil change interval
• / 4