NIFE - Engine Exam Review
Questions with 100% Correct
Detailed Answers
What is an advantage of the can design? - Answer- Strong, durable, easy to maintain
What is a disadvantage to the can design? - Answer- Malfunction can lead to cold spots
What is an advantage to the annular combustion chamber? - Answer- Even heat
distribution to the turbine
What is the disadvantage to the annular combustion chamber? - Answer- Hard to
maintain - have to repalce the whole thing
What's the purpose of the trurbine section? - Answer- Transform 75% of the heat
energy to drive compressor and accessories. Remaining 25% used for thrust.
In the turbine, which comes first - rotor or stator? - Answer- Stator, then the rotor.
What is the most highly stressed part of the engine? - Answer- Turbine
What is the malfunction that can happen in the turbines? - Answer- Creep
How are the turbine blades attached? - Answer- Fir tree configuration
What's the purpose of the exhaust section? - Answer- Direct the flow of hot gases
rearward to cause a high exit velocity to the gasses while preventing turbulence
What is the shape of the exhaust? - Answer- Nozzle (subsonic: convergent, supersonic:
convergent-divergent)
How much more thrust do you get from an afterburner? - Answer- 50%, but costs 300%
in fuel consumption
What are the four components of the afterburner and what do they do? - Answer- Spray
bars - introduce fuel. Flame holder - creates turbulent eddies to mix fuel and hold flame.
Screech liner - shock absorber, variable exhaust nozzle - prevents back presure
What causes a stall? - Answer- Excessive angle of attack
, What is the angle of attack in an engine? - Answer- Angle between the chordline of the
blade and the relative wind
What makes up the relative wind in an engine? - Answer- The resulting vector of the
compressor RPM and the inlet airflow. Decrease in inlet airflow will cause the angle of
the relative wind to increase
What are signs of a compressor stall? - Answer- Loud bangs, increase in turbine
temperature, engine RPM drops
What are mechanical malfunctions that can lead to a compressor stall? - Answer- FOD,
Failed fuel control unit, vairiable inlet guide vane failure, or variable exhaust nozzle
failure
What's the difference between stall prevention and stall avoidance? - Answer-
Prevention - manufacturer (viarable inlet guide/stator vane, dual spool compressor,
bleed valves, variable exhaust nozzle) Avoidance - pilot can control (avoid erratic/abrupt
PCL movements, avoid severe weather, avoid abrupt changes in attitude, maintain
minimums)
What is interstage bleed air used for? - Answer- Compressor stability
How do you recover from an engine stall? - Answer- Reduce attitude of aircraft, retard
PCL
How do you construct a turbojet? - Answer- Gas generator + inlet + exhaust
What is thrust specific fuel consumption? - Answer- Amount of fuel you need to get 1lb
of thrust. Lower is more efficient.
How is a turbo fan constructed? - Answer- gas generator + ducted fan + exhaust
How does a turbo fan increase its thrust? - Answer- Accelerating more air (increases
the mass portion of the Thrust = m * a)
How can you attach a ducted fan? - Answer- Free power turbine or attached to low-
pressure compressor
What is a bypass ratio? - Answer- Amount of air that goes around the engine to what
goes through. Strike fighter low (1:1), cargo would be high (like 5:1)
Describe turbojet thrust, TSFC and specific weight - Answer- 100% of thrust comes
from exhaust. Very high TSFC (inefficient) and lowest specific weight (most simple
design)
Questions with 100% Correct
Detailed Answers
What is an advantage of the can design? - Answer- Strong, durable, easy to maintain
What is a disadvantage to the can design? - Answer- Malfunction can lead to cold spots
What is an advantage to the annular combustion chamber? - Answer- Even heat
distribution to the turbine
What is the disadvantage to the annular combustion chamber? - Answer- Hard to
maintain - have to repalce the whole thing
What's the purpose of the trurbine section? - Answer- Transform 75% of the heat
energy to drive compressor and accessories. Remaining 25% used for thrust.
In the turbine, which comes first - rotor or stator? - Answer- Stator, then the rotor.
What is the most highly stressed part of the engine? - Answer- Turbine
What is the malfunction that can happen in the turbines? - Answer- Creep
How are the turbine blades attached? - Answer- Fir tree configuration
What's the purpose of the exhaust section? - Answer- Direct the flow of hot gases
rearward to cause a high exit velocity to the gasses while preventing turbulence
What is the shape of the exhaust? - Answer- Nozzle (subsonic: convergent, supersonic:
convergent-divergent)
How much more thrust do you get from an afterburner? - Answer- 50%, but costs 300%
in fuel consumption
What are the four components of the afterburner and what do they do? - Answer- Spray
bars - introduce fuel. Flame holder - creates turbulent eddies to mix fuel and hold flame.
Screech liner - shock absorber, variable exhaust nozzle - prevents back presure
What causes a stall? - Answer- Excessive angle of attack
, What is the angle of attack in an engine? - Answer- Angle between the chordline of the
blade and the relative wind
What makes up the relative wind in an engine? - Answer- The resulting vector of the
compressor RPM and the inlet airflow. Decrease in inlet airflow will cause the angle of
the relative wind to increase
What are signs of a compressor stall? - Answer- Loud bangs, increase in turbine
temperature, engine RPM drops
What are mechanical malfunctions that can lead to a compressor stall? - Answer- FOD,
Failed fuel control unit, vairiable inlet guide vane failure, or variable exhaust nozzle
failure
What's the difference between stall prevention and stall avoidance? - Answer-
Prevention - manufacturer (viarable inlet guide/stator vane, dual spool compressor,
bleed valves, variable exhaust nozzle) Avoidance - pilot can control (avoid erratic/abrupt
PCL movements, avoid severe weather, avoid abrupt changes in attitude, maintain
minimums)
What is interstage bleed air used for? - Answer- Compressor stability
How do you recover from an engine stall? - Answer- Reduce attitude of aircraft, retard
PCL
How do you construct a turbojet? - Answer- Gas generator + inlet + exhaust
What is thrust specific fuel consumption? - Answer- Amount of fuel you need to get 1lb
of thrust. Lower is more efficient.
How is a turbo fan constructed? - Answer- gas generator + ducted fan + exhaust
How does a turbo fan increase its thrust? - Answer- Accelerating more air (increases
the mass portion of the Thrust = m * a)
How can you attach a ducted fan? - Answer- Free power turbine or attached to low-
pressure compressor
What is a bypass ratio? - Answer- Amount of air that goes around the engine to what
goes through. Strike fighter low (1:1), cargo would be high (like 5:1)
Describe turbojet thrust, TSFC and specific weight - Answer- 100% of thrust comes
from exhaust. Very high TSFC (inefficient) and lowest specific weight (most simple
design)
