Powerplant IV FINAL EXAM

Which section of a gas turbine engine is responsible for driving the fan?

Turbine section

Which type of gas turbine engine is most efficient in the 300 to 400 mph speed range?

Turboprop

What is the purpose of convergent and divergent shaped ducts in supersonic inlets?

To control and drop the air flow to subsonic speeds

What is the role of increasing the forward speed of the aircraft in determining the amount of air passing through a gas turbine engine?

It increases the amount of air passing through the engine

What is the role of increasing the density of the ambient air in determining the amount of air passing through a gas turbine engine?

It increases the amount of air passing through the engine

What is the primary function of the accessory section in a gas turbine engine?

To provide space for mounting accessories

Where is the accessory gear box typically located in a turbofan engine?

On the bottom of the engine

Where is bleed air typically extracted from in a gas turbine engine?

The compressor outlet

What is the purpose of the diffuser in a centrifugal-flow compressor?

To compress air while it continues in its original direction of flow

Where is the combustion section located in relation to the compressor and turbine sections?

 

Directly between the compressor and turbine

What is the purpose of the fuel drainage system in a combustion chamber?

To drain off unburned fuel after engine shutdown

Which type of combustion chamber is typically used on turboshaft and APUs?

Can-type

What is the purpose of the shroud in an annular combustion chamber?

To prevent flame contact with the combustion chamber

What is the purpose of the pre-swirl vanes in a can-annular combustion chamber?

To provide a swirling motion to the fuel spray

What are the advantages of using an annular combustion chamber in modern turbine engines?

Both Answers are correct

Higher efficiency AND Better atomization of fuel

What is the purpose of the gas generator turbine?

To absorb kinetic energy from the exhaust gases

Which type of turbine blade is also referred to as a bucket?

 

Impulse turbine blade

What is the function of the turbine inlet nozzle assembly?

To deflect gases in the direction of turbine rotation

What is the function of the turbine nozzle guide vanes?

To increase the efficiency of the air stream striking the blades

What is the difference between the turbine inlet nozzle assembly and turbine nozzle guide vanes from the previous questions?????

 

Different names for the same component

What material is commonly used for the turbine shaft?

Steel

What is the benefit of using single crystal blades?

Better strength and heat properties

Why would it be necessary to use multiple turbine stages?

To drive heavy rotational loads

What is the purpose of the thermocouple bosses in the outer shell or duct of the exhaust section?

To measure exhaust temperature

What are the principles of convergent and divergent ducts for subsonic gas velocities? 

Convergent increases velocity and decreases pressure, while divergent decreases velocity and increases pressure

What is the recommended method for repairing corrosion pitting on compressor stator vanes?

Blending

What are examples of blade damage in axial-flow and centrifugal-flow engines?

All of the above;

Damage to the outer half of the blade

Nicks and dents in the critical band

Cracks in the leading edges

Why is it important to follow the manufacturer's maintenance and overhaul manuals when performing repairs or inspections on turbine engines?

To ensure proper functioning of the engine

What is the recommended method for cleaning turbine blades during a hot section inspection?

Ultrasonic cleaning

What is the purpose of using a borescope inspection during a hot section inspection?

To check for cracks and warping

What is the importance of following the manufacturer's detailed assembly instructions during engine maintenance?

All of the above;

To extend the engine's service life

To prevent foreign material from entering the engine

To ensure efficient maintenance

Which marking material is recommended for parts directly exposed to the engine's gas path?

All answers are correct;

Felt tip marker and chalk

What method is recommended for inspecting combustion chambers for cracks?

Fluorescent penetrant inspection

Which type of crack is considered the most severe in combustion chambers?

Stress rupture cracks

What is the recommended method for reinstalling turbine blades after inspection?

Numbering the blades and reinstalling them in the same slots

What is the flat rating of a turbine engine?

The guaranteed thrust under specific operating conditions

Why is it important to monitor EGT during takeoff?

To prevent damage to the engine

What is the purpose of the N1 indicator in a turbine engine?

To indicate engine speed

Why is it impractical to measure turbine inlet temperature in most engines?

Because it is too hot

Why are tachometers usually calibrated in percent rpm?

To make it easier to compare different types of engines

What is the purpose of following manufacturer's operating instructions for starting and operating a turbine engine?

To avoid a hot or hung start

What is the appropriate action to take in case of an engine fire during start or ground operation?

Move the fuel lever to the off position and continue cranking or motoring the engine until the fire has been expelled from the engine.

How is the takeoff power for a turboprop engine calculated?

By determining the maximum allowable exhaust gas temperature and torquemeter pressure

What is the purpose of a continuity check in an aircraft EGT circuit?

To eliminate any error caused by one or more inoperative aircraft thermocouples

Why is regular testing and maintenance important for an EGT system?

All answers are correct;

To ensure the accuracy of the EGT indicator

To prevent potential errors in the system

To troubleshoot any issues that may arise

An APU is usually rotated during start by?

An electric starter

Fuel is normally supplied to an APU from

The airplanes main fuel supply

Frequently, an aircraft auxiliary power unit (APU) generator

Is identical to the engine-driven generators

Usually, the most load placed on an APU occurs when

The bleed air valve is opened

Fuel scheduling during APU start and under varying pneumatic bleed and electrical loads is maintained by

Automatically by the APU fuel control system

The function of an APU plenum is to

Stabilize the pressure before of the air before it enters the compressor

Standard sea level pressure is:

29.92 in. Hg

When in operation the speed of an APU

Remains at or near rated speed regardless of the load condition

An APU uses aircraft fuel, supplied under pressure by

Electric boost pump

An APU can provide redundancy to aircraft systems by

Providing a back up electrical and pneumatic source

Where is the highest temperature in a turbine engine with respect to the metal parts?

Turbine inlet nozzle vanes

What is the name given to the thermodynamic cycle of a APU gas turbine engine uses to produce electrical or pneumatic power?

Continuous combustion cycle

T or F:
Compressor inlet screens are used on Turboprops and APUs to prevent all FOD from entering the intake of the engine

False

T or F:
APUs are installed in the aircraft and are used to supply electrical power, air hydraulic pressure, and fuel to the aircraft engines when the main engines are not running.

False

T or F:
APU’s are small gas turbine engines or reciprocating-engine that power a generator, hydraulic pump, and air pump.

True

An APU can be operated:

Both A and B;
While the aircraft is in flight and While the aircraft is on the ground

T or F:
An APU is usually manually controlled

False

T or F:

An APU can only be operated while on the ground?

False

An APU is usually rotated during start by:

An electrical starter

Most APU’s have automatic controls for starting, stopping and maintaining operation within safe limits because:

They provide the correct sequencing of the start cycle

Where is the highest gas pressure in a turbojet engine?

At the outlet of the compressor section

The pressure of subsonic air as it flows through a convergent duct :

Decreases Pressure

Name the four basic types of Combustion Sections used in aircraft turbine engines?

Can type, Reverse-flow type, Annular type and Can-annular type

The exhaust section of a turbine engine is designed to

Impart a high exit velocity to the exhaust gases

Using Standard Day Conditions, What is the standard sea level temperature?

59 degrees F

Using Standard Day Conditions, What is the standard sea level pressure?

29.92 in. Hg

What are the two types of compressors used in turbine engines?

Axial and centrifugal flow

Where is the highest temperature in a turbine engine with respect to the metal parts?

Turbine inlet nozzle vanes

What are the three types of turbine blades?

Impulse, reaction and impulse-reaction

What is the name given to the thermodynamic cycle of a gas turbine engine to produce thrust?

Brayton cycle

What is the effect of a blocked inlet screen on a turbine engine?

Decreased engine performance

What is the function of a variable geometry inlet in a turbine engine?

 

To adjust the shape of the inlet for different flight conditions

In which type of engine are inlet screens generally not used?

 

Turbofan engines with steel or titanium compressor blades

What is the purpose of a compressor inlet screen?

 

To prevent FOD ingestion

What is the main objective of a bellmouth inlet?

 

To obtain high aerodynamic efficiency

What is the purpose of the inlet cowl on a turbofan engine?

 

To provide an airflow path into the engine

What is the function of deflector doors in engine inlets?

 

To deflect ice and dirt away from the intake

What is the primary source of thrust in a high-bypass engine?

 

The secondary airstream

What is the function of the fan hub or spinner in a high-bypass engine?

 

To provide warm bleed air for anti-icing

What is the function of the abraidable rub strip in a high-bypass engine?

 

To allow the fan blades to rub during flightpath changes

What is the purpose of a cabin heater exhaust shroud?

 

To induce airflow through the exhaust ejectors

What is the purpose of an exhaust system on a reciprocating engine?

 

To dispose of exhaust gases with safety

Which type of exhaust system is typically used on modern aircraft?

 

Collector system

What material is the exhaust collector ring typically made of?

 

Corrosion-resistant steel

What is the purpose of the augmentor vane actuator on a radial engine?

 

To control vane positions

What are the primary inspection areas of three types of exhaust systems?

 

Exhaust gas leakage, external surfaces, and internal baffles

What is the importance of regular inspections for exhaust systems?

 

To prevent carbon monoxide hazards

What is the best approach for inspecting an inaccessible component of an exhaust system?

 

Remove the component and check for leaks

What are the potential consequences of using galvanized or zinc-plated tools on an exhaust system?

 

Cracks and eventual failure

What is the purpose of a converging nozzle in a turboprop engine?

 

To increase the velocity of the exhaust gases

What is the purpose of an insulating blanket on an exhaust nozzle assembly?

 

To shield the surrounding area from high heat

What is the purpose of the convergent component of the exhaust nozzle?

 

To increase gas velocity

What is the purpose of the exhaust nozzle in an aircraft engine?

 

To provide increased thrust

What is the term used to describe the pressure difference between the inside of the nozzle and the ambient air?

 

Pressure thrust

What is the purpose of locking the thrust reverser system in the stowed position?

 

To prevent deployment during maintenance