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
After engine overhaul, a break-in run is performed. What oil type should NOT be used during engine break-in?
Answer: Synthetic oil
Synthetic oil is too slippery during break-in and prevents cylinder walls from seating properly; mineral oil is required for new or overhauled engines.
A reciprocating engine exhibits detonation during high-power operation. Which of the following will most effectively reduce detonation?
Answer: Enriching the fuel-air mixture
Enriching the mixture reduces cylinder temperatures and lowers the tendency for detonation by decreasing peak combustion temperatures.
When checking valve clearance (tappet clearance) on a reciprocating engine, the piston of the cylinder being checked must be positioned at:
Answer: TDC on the compression stroke
Valve clearance is checked with the piston at TDC on the compression stroke so that both intake and exhaust valves are fully closed.
An EGT gauge shows all cylinders rise normally during leaning except one which rises sharply then drops off. What does this indicate?
Answer: That cylinder has a partially clogged fuel injector
A clogged injector delivers less fuel, so that cylinder reaches peak EGT much earlier in the leaning process and then goes excessively lean before the others.
During a ground run, manifold pressure is 2 inches Hg higher than standard atmosphere with the throttle closed. What does this indicate?
Answer: Throttle plate is not fully closing
A throttle plate that does not fully close allows high-pressure air to leak into the intake manifold, raising manifold pressure above atmospheric.
What parameter is monitored to detect early signs of internal engine bearing failure using oil analysis?
Answer: Copper and silver levels
Copper and silver are typical bearing overlay and plating materials; elevated levels in oil analysis indicate bearing wear before catastrophic failure occurs.
A turbine engine's N1 speed is normal but N2 speed is lower than expected at a given power setting. What is the most likely cause?
Answer: Slippage in the reduction gearbox
If N1 (low-pressure compressor/fan) is normal but N2 (high-pressure spool) is low, a slipping or damaged reduction gearbox is the likely cause.