Powerplant Theory and Maintenance Flashcards
7 cards from real AMT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Powerplant Theory and Maintenance flashcards as text
What is the primary cause of reciprocating engine 'valve float'?
Answer: Excessive engine RPM preventing the valve spring from closing the valve in time
Valve float occurs at excessive RPM when valve springs cannot return the valve to its seat before the next cycle, causing power loss and potential engine damage.
In turbine engine terminology, what does 'EPR' (Engine Pressure Ratio) represent?
Answer: The ratio of turbine discharge pressure to compressor inlet pressure
EPR is the ratio of turbine exhaust total pressure to compressor inlet total pressure and is used as an indicator of engine thrust output.
Which condition would most likely cause a reciprocating engine to run rough at idle but smoothly at higher power settings?
Answer: A fouled or defective spark plug
A fouled spark plug has the greatest effect at low power (idle) because there is less combustion energy to compensate; the engine typically smooths out at higher power.
What is the purpose of 'trimming' a turbine engine?
Answer: Adjusting the engine to produce the correct thrust at specified conditions
Engine trimming is the adjustment of the fuel control unit to ensure the engine produces the correct rated thrust at specified ambient conditions.
During an annual inspection of a turbine engine, blue-gray staining found on a combustion liner is most likely caused by:
Answer: Improper fuel nozzle spray patterns causing localized rich burning
Blue-gray staining on a combustion liner typically indicates a distorted fuel spray pattern from a worn or clogged nozzle, causing localized rich combustion and hot spots.
What effect does increased altitude have on a naturally aspirated reciprocating engine's power output?
Answer: Power decreases because air density decreases, reducing volumetric efficiency
As altitude increases, air density decreases, reducing the mass of the fuel-air charge per cylinder and therefore reducing engine power output.
The function of the engine's oil temperature regulator (thermostatic bypass valve) is to:
Answer: Bypass the oil cooler when oil temperature is below the desired range
The thermostatic bypass valve allows cold oil to bypass the oil cooler so the engine reaches operating temperature faster, then routes oil through the cooler once the desired temperature is reached.