Engine Testing & Diagnostics Flashcards
7 cards from real ACS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Engine Testing & Diagnostics flashcards as text
During a pre-takeoff run-up, the engine idles smoothly but surges at mid-throttle. What is the most likely cause?
Answer: Accelerator pump defect in the carburetor
The accelerator pump provides an extra fuel shot during throttle advancement; a defective pump causes a lean surge at mid-throttle as the main jets take over.
What is the correct procedure when an engine fire occurs during start on a reciprocating aircraft engine?
Answer: Continue cranking with mixture at idle cutoff and throttle full open to draw fire into engine
Continuing to crank with mixture cut off and throttle full open creates airflow that can draw burning fuel back into the induction system and extinguish the fire.
An engine cylinder head temperature (CHT) gauge shows one cylinder consistently 50°F hotter than the others in level cruise. What should be inspected first?
Answer: Cylinder baffling and cooling fins for that cylinder
Damaged or missing baffling disrupts cooling airflow to individual cylinders and is the most common cause of a single cylinder running consistently hotter.
When using a borescope to inspect cylinder combustion chambers, what condition would require immediate removal from service?
Answer: Cracks radiating from the exhaust valve seat
Cracks radiating from the exhaust valve seat indicate serious structural damage that could lead to valve failure or cylinder head separation in flight.
An aircraft engine fails to develop full static RPM during a pre-takeoff run-up. The magneto check is normal. What should be checked next?
Answer: Propeller pitch setting and governor operation
A constant-speed propeller set to too coarse a pitch or a malfunctioning governor will prevent the engine from reaching full static RPM despite normal ignition.
What does a sudden drop in fuel flow during an engine operational test with no corresponding change in throttle position indicate?
Answer: Fuel vapor lock or cavitation in the fuel system
Vapor lock causes intermittent fuel starvation as fuel vaporizes in the fuel lines, creating a pocket that temporarily reduces liquid fuel flow.
After replacing a cylinder on a reciprocating engine, the cylinder head temperature on the new cylinder is abnormally low compared to adjacent cylinders at the same power setting. What does this most likely indicate?
Answer: The new cylinder is not receiving ignition on both plugs
A cylinder with no ignition (both plugs misfiring) will not combust fuel normally, resulting in low CHT because little or no combustion heat is being generated.