Aircraft Engines and Operations Quiz

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Questions and Answers

What is the location of the APU fire detection displays and controls?

Wheelwell bay (correct)

APU compartment

Screw-jack compartment

Flight deck

Which is not an authentic indication for the 'APU on fire'?

Master warning light illuminates, and status message and warning display on EICAS

APU fire extinguisher is operated (correct)

APU fire handle illuminates

Aural warning is activated

After starting, at what speed does the APU run regardless of loads imposed on it?

Rated speed (correct)

Maximum speed

Guaranteed speed

Normal speed

What system automatically maintains the APU on-speed?

Load control valve Signup and view all the answers

Which load needs to be modulated to maintain a safe operating temperature of a heavily loaded APU?

Electrical Signup and view all the answers

What protects a heavily loaded APU running near its maximum EGT?

Overtemperature controller, EGT stabilizer Signup and view all the answers

What is a typical cool-down period for an APU?

5 minutes Signup and view all the answers

Why is it important for an APU to have a proper cool-down period?

To minimize the possibilities of Thermal shock Signup and view all the answers

What is the main cause of jet engine noise?

Turbulence produced when hot, high velocity jet exhaust mixes with the cold, lower velocity ambient air Signup and view all the answers

What type of noise is produced from a jet engine exhaust?

White noise Signup and view all the answers

Who is responsible for treating engine fan cowls with acoustic panels to suppress noise?

Original manufacturer Signup and view all the answers

What type of noise suppression method involves breaking the primary exhaust stream into multiple small jets with their own discharge nozzles?

Multi-tube suppressors Signup and view all the answers

How does a corrugated perimeter design type of silencer affect the shape of the exhaust stream?

Alters Signup and view all the answers

What is not a function of thrust reversers?

Once they are deployed, the pilot has absolute control over the drag on the aircraft Signup and view all the answers

What is not a function of a thrust reverser?

They must be repacked after each use Signup and view all the answers

What is the purpose of a corrugated perimeter design in a jet engine silencer?

To alter the shape of the exhaust stream Signup and view all the answers

What is the primary purpose of thrust reversers on a jet aircraft?

To increase braking and directional control during landing Signup and view all the answers

Which of the following is not a function of thrust reversers?

Providing the pilot with absolute control over the aircraft's drag Signup and view all the answers

Study Notes

Engine Performance

Equivalent Shaft Horsepower (ESHP) is concerned with Turboprop and Turboshaft engines.
Economical operation of an engine is referred to as THP (Thermal Horsepower).
Thrust Specific Fuel Consumption (TSFC) is the ratio between fuel flow and thrust of an engine.

Engine Efficiency

Engine efficiency is the ratio of output power to input energy.
Component efficiency, thermal efficiency, and propulsive efficiency are different aspects of engine efficiency.
100% propulsive efficiency would occur if aircraft speed equals exhaust velocity.

Turbofan Engines

High-bypass turbofan engines have the fan mounted to the turbine section.
A bypass engine is also referred to as a subsonic engine.
Thrust ratio is the comparison of thrust produced by the fan to the thrust produced by the engine core exhaust.

Centrifugal and Axial Flow Compressors

Disadvantages of centrifugal flow compressors include high starting requirements, large frontal area, and high cost manufacturing.
Axial flow compressors have the advantage of increased pressure rise with an increase in the number of stages.

Combustion Section

The combustion section is located between the compressor diffuser and turbine section.
The primary function of the combustion section is to burn the fuel-air mixture.
About 2/3 of the energy produced by the combustion section is used to drive the gas generator compressor.

Reverse-Flow Combustors

Reverse-flow combustors are designed to reduce the length of the engine.
Annular combustors require less cooling air than can-annular combustors.

APU (Auxiliary Power Unit)

The gas generator, combustion section, and compressor turbine comprise the gas generator in a turboprop engine.
The power turbine is an additional turbine wheel that is placed in the exhaust stream from the gas generator.
The gas generator section performs only one function, i.e., converting fuel energy into kinetic energy.

Thrust and Propulsion

Thrust is derived from Newton's second law of motion.
The converging and diverging duct mentioned in Bernoulli's principle is called a C-D duct.

Turbine Blades

Creep is a gradual deformation of turbine blades due to centrifugal load and elevated operating temperature.
Turbine blades are also known as buckets.
Reaction turbine blades produce a turning force.

Cooling Systems

Cooling air is directed over each side of the disk.
Open-ended blades are used on low-speed turbines.
Film cooling is a type of cooling where bleed air is directed in through hollow blades.

Turbine Cracks

Stress cracks usually appear as minute hairline cracks on or across the leading or trailing edge at a right angle to the blade length.
Typical causes of stress rupture cracks include excessive temperature and centrifugal loading.

Noise Reduction

Jet engine noise is mainly the result of turbulence produced when hot, high-velocity jet exhaust mixes with cold, lower-velocity ambient air.
A corrugated perimeter design type of silencer alters the shape of the exhaust stream as it leaves the engine.

Thrust Reversers

Thrust reversers aid in braking and directional control during normal landing.
They can even be deployed in air to hasten emergency descent.

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Description

Test your knowledge on aircraft engines and operations with questions about equivalent shaft horsepower, economical operation terms, and thrust specific fuel consumption. See how well you understand different engine types and their efficiency.