FAA POWERPLANT MECHANIC KNOWLEDGE EXAM PRACTICE
QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALE Q&A INSTANT DOWNLOAD PDF.
115 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze and diagnose powerplant system malfunctions using schematic and performance data
2 Evaluate fuel metering and ignition system parameters for correct operation across flight regimes
3 Apply thermodynamic and mechanical principles to optimize engine performance and safety
4 Interpret maintenance data and regulatory requirements to ensure airworthiness
5 FAA Powerplant Mechanic Knowledge Exam Practice Questions And Correct Answers
6 Verified Answers
7 Plus Rationale Q&A Instant Download Pdf.
8 Foundations of Aerospace Engineering - Powerplant Systems
9 Applied Aerospace Engineering - Powerplant Systems
10 Advanced Aerospace Engineering - Powerplant Systems
11 Aerospace Engineering - Powerplant Systems Review
Page 1
,Q1 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
During a hot-section inspection of a turbofan engine, you observe that the turbine
blades exhibit signs of severe sulfidation. Which fuel sulfur specification and
operational condition most likely contributed to this damage?
A. High sulfur content combined with prolonged low-power operation at high ambient
temperatures CORRECT
B. Low sulfur content combined with repeated thermal cycling above the turbine inlet
temperature limit
C. High sulfur content combined with continuous high-power operation at low ambient
temperatures
D. Low sulfur content combined with lean combustion at high altitude cruise
RATIONALE: Sulfidation (hot corrosion) occurs when sulfur impurities in fuel react with sodium
and other contaminants at elevated temperatures, typically during low-power operation when
turbine metal temperatures are high but combustion efficiency is low. High sulfur fuel and hot,
humid conditions accelerate this. Low sulfur fuel reduces risk; high-power operation tends to
keep temperatures uniform and may burn off deposits.
Q2 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A reciprocating engine exhibits a sudden drop in oil pressure accompanied by a
rise in oil temperature. The oil filter inspection reveals metallic particles. Which
failure mode is most consistent with these symptoms?
A. Main bearing oil starvation due to a clogged oil pickup screen
B. Crankshaft journal scoring due to inadequate oil viscosity at high temperature
C. Connecting rod bearing failure causing increased friction and debris generation CORRECT
D. Oil pump gear wear leading to reduced oil volume and pressure
RATIONALE: A connecting rod bearing failure generates metallic debris that can be seen in the
filter, and the resulting increased friction raises oil temperature while the damaged bearing allows
oil to escape, reducing pressure. Oil starvation (A) would not typically produce metallic debris
immediately; (B) might cause scoring but not sudden debris; (D) would cause pressure loss but
not necessarily temperature rise or metallic particles.
Page 2
,Q3 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
You are analyzing a turbine engine fuel control system. The power lever is
advanced, but the engine does not accelerate properly. The compressor discharge
pressure (CDP) sensor reads high, and the fuel flow is lower than scheduled.
Which component failure is most likely?
A. Stuck fuel metering valve in the open position
B. Leaking CDP sense line to the fuel control CORRECT
C. Faulty compressor discharge pressure sensor sending an erroneously high signal
D. Blocked fuel nozzle causing backpressure
RATIONALE: A leaking CDP sense line would cause the fuel control to sense a lower than actual
compressor discharge pressure, leading to under-fueling during acceleration. However, if the
sensor itself reads high (C), the control would schedule more fuel, not less. A stuck metering
valve open (A) would cause excess fuel, not low flow. Blocked nozzles (D) would raise fuel
pressure but not necessarily reduce flow as sensed by the control.
Q4 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
In a constant-speed propeller system, the propeller governor is set to maintain
2400 RPM. During a climb, the manifold pressure is increased, but the RPM
remains constant. Which statement correctly describes the action of the
governor?
A. The governor increases blade angle to absorb the additional engine power, maintaining RPM.
CORRECT
B. The governor decreases blade angle to increase RPM, but the RPM stays constant due to
overspeed protection.
C. The governor increases fuel flow to raise RPM, but the propeller load prevents RPM change.
D. The governor reduces blade angle to increase propeller efficiency, but RPM is limited by the
engine governor.
RATIONALE: In a constant-speed propeller, the governor adjusts blade angle to maintain a set
RPM. When power is increased (higher manifold pressure), the governor increases blade angle
(higher pitch) to increase the load on the engine, preventing an overspeed. This keeps RPM
constant while converting the increased power into thrust. Decreasing blade angle would allow
RPM to rise, not stay constant.
Page 3
, Q5 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A technician is performing a magneto timing check on a reciprocating engine. The
magneto is found to fire 20° before top center (BTC) at idle, but the specified
timing is 25° BTC. Which adjustment is required?
A. Retard the magneto timing to fire later (closer to TDC)
B. Advance the magneto timing to fire earlier (more BTC) CORRECT
C. Replace the magneto because it is worn out
D. Adjust the breaker point gap to a larger gap to correct timing
RATIONALE: Firing at 20° BTC is later than the specified 25° BTC, so the timing must be
advanced to fire earlier (more degrees before TDC). This is typically done by adjusting the
magneto's position or breaker point gap. Retarding (A) would make it fire later, worsening the
error. Replacing (C) is unnecessary. Adjusting the point gap (D) might affect timing, but the
primary adjustment is to rotate the magneto to advance timing.
Q6 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A turbojet engine is operating at a constant RPM at sea level. If the aircraft enters
an area of higher ambient temperature (e.g., flying from cold to warm air) without
any throttle change, what is the immediate effect on thrust?
A. Thrust increases because higher temperature increases exhaust velocity.
B. Thrust decreases because air density is lower, reducing mass flow through the engine.
CORRECT
C. Thrust remains constant because RPM is constant and fuel flow is unchanged.
D. Thrust increases because higher temperature improves combustion efficiency.
RATIONALE: Thrust in a turbojet is proportional to mass flow times exhaust velocity. Higher
ambient temperature reduces air density, so for the same RPM and compressor geometry, the
mass flow of air into the engine decreases, leading to lower thrust. Exhaust velocity may not
change enough to compensate. Fuel flow may be adjusted by the control to maintain RPM, but
the reduced mass flow dominates.
Page 4
QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALE Q&A INSTANT DOWNLOAD PDF.
115 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze and diagnose powerplant system malfunctions using schematic and performance data
2 Evaluate fuel metering and ignition system parameters for correct operation across flight regimes
3 Apply thermodynamic and mechanical principles to optimize engine performance and safety
4 Interpret maintenance data and regulatory requirements to ensure airworthiness
5 FAA Powerplant Mechanic Knowledge Exam Practice Questions And Correct Answers
6 Verified Answers
7 Plus Rationale Q&A Instant Download Pdf.
8 Foundations of Aerospace Engineering - Powerplant Systems
9 Applied Aerospace Engineering - Powerplant Systems
10 Advanced Aerospace Engineering - Powerplant Systems
11 Aerospace Engineering - Powerplant Systems Review
Page 1
,Q1 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
During a hot-section inspection of a turbofan engine, you observe that the turbine
blades exhibit signs of severe sulfidation. Which fuel sulfur specification and
operational condition most likely contributed to this damage?
A. High sulfur content combined with prolonged low-power operation at high ambient
temperatures CORRECT
B. Low sulfur content combined with repeated thermal cycling above the turbine inlet
temperature limit
C. High sulfur content combined with continuous high-power operation at low ambient
temperatures
D. Low sulfur content combined with lean combustion at high altitude cruise
RATIONALE: Sulfidation (hot corrosion) occurs when sulfur impurities in fuel react with sodium
and other contaminants at elevated temperatures, typically during low-power operation when
turbine metal temperatures are high but combustion efficiency is low. High sulfur fuel and hot,
humid conditions accelerate this. Low sulfur fuel reduces risk; high-power operation tends to
keep temperatures uniform and may burn off deposits.
Q2 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A reciprocating engine exhibits a sudden drop in oil pressure accompanied by a
rise in oil temperature. The oil filter inspection reveals metallic particles. Which
failure mode is most consistent with these symptoms?
A. Main bearing oil starvation due to a clogged oil pickup screen
B. Crankshaft journal scoring due to inadequate oil viscosity at high temperature
C. Connecting rod bearing failure causing increased friction and debris generation CORRECT
D. Oil pump gear wear leading to reduced oil volume and pressure
RATIONALE: A connecting rod bearing failure generates metallic debris that can be seen in the
filter, and the resulting increased friction raises oil temperature while the damaged bearing allows
oil to escape, reducing pressure. Oil starvation (A) would not typically produce metallic debris
immediately; (B) might cause scoring but not sudden debris; (D) would cause pressure loss but
not necessarily temperature rise or metallic particles.
Page 2
,Q3 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
You are analyzing a turbine engine fuel control system. The power lever is
advanced, but the engine does not accelerate properly. The compressor discharge
pressure (CDP) sensor reads high, and the fuel flow is lower than scheduled.
Which component failure is most likely?
A. Stuck fuel metering valve in the open position
B. Leaking CDP sense line to the fuel control CORRECT
C. Faulty compressor discharge pressure sensor sending an erroneously high signal
D. Blocked fuel nozzle causing backpressure
RATIONALE: A leaking CDP sense line would cause the fuel control to sense a lower than actual
compressor discharge pressure, leading to under-fueling during acceleration. However, if the
sensor itself reads high (C), the control would schedule more fuel, not less. A stuck metering
valve open (A) would cause excess fuel, not low flow. Blocked nozzles (D) would raise fuel
pressure but not necessarily reduce flow as sensed by the control.
Q4 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
In a constant-speed propeller system, the propeller governor is set to maintain
2400 RPM. During a climb, the manifold pressure is increased, but the RPM
remains constant. Which statement correctly describes the action of the
governor?
A. The governor increases blade angle to absorb the additional engine power, maintaining RPM.
CORRECT
B. The governor decreases blade angle to increase RPM, but the RPM stays constant due to
overspeed protection.
C. The governor increases fuel flow to raise RPM, but the propeller load prevents RPM change.
D. The governor reduces blade angle to increase propeller efficiency, but RPM is limited by the
engine governor.
RATIONALE: In a constant-speed propeller, the governor adjusts blade angle to maintain a set
RPM. When power is increased (higher manifold pressure), the governor increases blade angle
(higher pitch) to increase the load on the engine, preventing an overspeed. This keeps RPM
constant while converting the increased power into thrust. Decreasing blade angle would allow
RPM to rise, not stay constant.
Page 3
, Q5 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A technician is performing a magneto timing check on a reciprocating engine. The
magneto is found to fire 20° before top center (BTC) at idle, but the specified
timing is 25° BTC. Which adjustment is required?
A. Retard the magneto timing to fire later (closer to TDC)
B. Advance the magneto timing to fire earlier (more BTC) CORRECT
C. Replace the magneto because it is worn out
D. Adjust the breaker point gap to a larger gap to correct timing
RATIONALE: Firing at 20° BTC is later than the specified 25° BTC, so the timing must be
advanced to fire earlier (more degrees before TDC). This is typically done by adjusting the
magneto's position or breaker point gap. Retarding (A) would make it fire later, worsening the
error. Replacing (C) is unnecessary. Adjusting the point gap (D) might affect timing, but the
primary adjustment is to rotate the magneto to advance timing.
Q6 ANALYZE AND DIAGNOSE POWERPLANT SYSTEM MALFUNCTIONS USING SCHEMATIC
AND PERFORMANCE DATA
A turbojet engine is operating at a constant RPM at sea level. If the aircraft enters
an area of higher ambient temperature (e.g., flying from cold to warm air) without
any throttle change, what is the immediate effect on thrust?
A. Thrust increases because higher temperature increases exhaust velocity.
B. Thrust decreases because air density is lower, reducing mass flow through the engine.
CORRECT
C. Thrust remains constant because RPM is constant and fuel flow is unchanged.
D. Thrust increases because higher temperature improves combustion efficiency.
RATIONALE: Thrust in a turbojet is proportional to mass flow times exhaust velocity. Higher
ambient temperature reduces air density, so for the same RPM and compressor geometry, the
mass flow of air into the engine decreases, leading to lower thrust. Exhaust velocity may not
change enough to compensate. Fuel flow may be adjusted by the control to maintain RPM, but
the reduced mass flow dominates.
Page 4
