PP Turbine Engines

At what point in an axial-flow turbojet engine will the highest gas pressures occur?

At the turbine entrance.
Within the burner section.
At the compressor outlet.

One function of the nozzle diaphragm in a turbine engine is to?

Decrease the velocity of exhaust gases.
Center the fuel spray in the combustion chamber.
Direct the flow of gases to strike the turbine blades at the desired angle.

What is the profile of a turbine engine compressor blade?

The leading edge of the blade.
A reduced blade tip thickness.
The curvature of the blade root.

The fan rotational speed of a dual axial compressor forward fan engine is the same as the

low-pressure compressor.
forward turbine wheel.
high-pressure compressor.

The abbreviation P_t7used in turbine engine terminology means

the total inlet pressure.
pressure and temperature at station 7.
the total pressure at station 7.

The blending of blades and vanes in a turbine engine

is usually accomplished only at engine overhaul.
should be performed parallel to the length of the blade using smooth contours to minimize stress points.
may sometimes be accomplished with the engine installed, ordinarily using power tools.

What turbine engine section provides for proper mixing of the fuel and air?

Combustion section.
Compressor section.
Diffuser section.

In a gas turbine engine, combustion occurs at a constant

volume.
pressure.
density.

Which statement is true regarding jet engines?

At the lower engine speeds, thrust increases rapidly with small increases in RPM.
At the higher engine speeds, thrust increases rapidly with small increases in RPM.
The thrust delivered per pound of air consumed is less at high altitude than at low altitude.

Some high-volume turboprop and turbojet engines are equipped with two-spool or split compressors. When these engines are operated at high altitudes, the

low pressure rotor will increase in speed as the compressor load decreases in the lower density air.
throttle must be retarded to prevent overspeeding of the high-pressure rotor due to the lower density air.
low pressure rotor will decrease in speed as the compressor load decreases in the lower density air.

Turbine nozzle diaphragms located on the upstream side of each turbine wheel, are used in the gas turbine engine to

decrease the velocity of the heated gases flowing past this point.
direct the flow of gases parallel to the vertical line of the turbine blades.
increase the velocity of the heated gases flowing past this point.

Where is the highest gas pressure in a turbojet engine?

At the outlet of the tailpipe section.
At the entrance of the turbine section.
At the entrance of the burner section.

An exhaust cone placed aft of the turbine in a jet engine will cause the pressure in the first part of the exhaust duct to

increase and the velocity to decrease.
increase and the velocity to increase.
decrease and the velocity to increase.

What is the function of the stator vane assembly at the discharge and of a typical axial-flow compressor?

To straighten airflow to eliminate turbulence.
To direct the flow of gases into the combustion chambers.
To increase air swirling motion into the combustion chambers.

The turbine section of a jet engine

increases air velocity to generate thrust forces.
utilizes heat energy to expand and accelerate the incoming gas flow.
drives the compressor section.

When starting a turbine engine,

a hot start is indicated if the exhaust gas temperature exceeds specified limits.
an excessively lean mixture is likely to cause a hot start.
release the starter switch as soon as indication of light-off occurs.

In the dual axial-flow or twin spool compressor system, the first stage turbine drives the

N₁ and N₂ compressors.
N₁ compressor.
N₂ compressor.

Which of the following may be used to mark turbine engine components exposed to high temperatures?

Grease or wax pencil.
Layout dye.
Graphite lead pencil.

When starting a turbine engine, a hung start is indicated if the engine

exhaust gas temperature exceeds specified limits.
fails to reach idle RPM.
N₁ is normal, but N₂ is low.

What are the two basic elements of the turbine section in a turbine engine?

Impeller and diffuser.
Hot and cold.
Stator and rotor.

Which of the following acts as a diffuser in a turbine engine and converts velocity to pressure?

Impeller.
Manifold.
Stators.

The function of the exhaust cone assembly of a turbine engine is to

collect the exhaust gases and act as a noise suppressor.
swirl and collect the exhaust gases into a single exhaust jet.
straighten and collect the exhaust gases into a solid exhaust jet.

What are the two functional elements in a centrifugal compressor?

Turbine and compressor.
Bucket and expander.
Impeller and diffuser.

What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?

Perform a full power engine run to check fuel flow.
Recalibrate the fuel nozzles.
Retrim the engine.

If during inspection at engine overhaul, bail or roller bearings are found to have magnetism but otherwise have no defects, they

cannot be used again.
are in an acceptable service condition.
must be degaussed before use.

A turbine engine compressor which contains vanes on both sides of the impeller is a

double entry centrifugal compressor.
double entry axial-flow compressor.
single entry axial-flow compressor.

What is the first engine instrument indication of a successful start of a turbine engine?

A rise in engine RPM.
A rise in oil temperature.
A rise in the exhaust gas temperature.

Some engine manufacturers of twin spool gas turbine engines identify turbine discharge pressure in their maintenance manuals as

P_t₇
P_t₂
T_t₇

Who establishes the recommended operating time between overhauls (TBO) of a turbine engine used in general aviation?

The engine manufacturer.
TBO does not apply to turbine engines.
The aircraft manufacturer.

The basic gas turbine engine is divided into two main sections: the cold section and the hot section.

(1) The cold section includes the engine inlet, compressor, and turbine sections.

(2) The hot section includes the combustor, diffuser, and exhaust sections.

Regarding the above statements,

only 1 is true.
only 2 is true.
neither 1 nor 2 is true.

(1) Welding and straightening of turbine engine rotating airfoils does not require special equipment.

(2) Welding and straightening of turbine engine rotating airfoils is commonly recommended by the manufacturer.

Regarding the above statements,

only 1 is true.
only 2 is true.
neither 1 nor 2 is true.

Turbine engine components exposed to high temperatures generally may not be marked with

layout dye, commercial felt tip marker, or chalk.
wax, grease pencil, or a graphite lead pencil.
commercial felt tip marker or grease pencil.

Who establishes mandatory replacement times for critical components of turbine engines?

The FAA.
The component manufacturer.
The engine manufacturer.

Main bearing oil seals used with turbine engines are usually what type(s)?

Labyrinth and/or carbon rubbing.
Teflon and synthetic rubber.
Labyrinth and/or silicone rubber.

How does a dual axial-flow compressor improve the efficiency of a turbojet engine?

More turbine wheels can be used.
Higher compression ratios can be obtained.
The velocity of the air entering the combustion chamber is increased.

Three types of turbine blades are

impulse, converging, and impulse-converging.
impulse, reaction, and impulse-reaction.
impulse, diverging, and impulse-diverging.

Which statement is true regarding aircraft engine propulsion?

An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air.
An engine driven propeller imparts a relatively large amount of acceleration to a smaller mass of air.
In modern turboprop engines, nearly 50 percent of the exhaust gas energy is extracted by turbines to drive the propeller and compressor with the rest providing exhaust thrust.

An advantage of the axial-flow compressor is the

low starting power requirements.
low weight.
high peak efficiency.

What is one purpose of the stator blades in the compressor section of a turbine engine?

Stabilize the pressure of the airflow.
Control the direction of the airflow.
Increase the velocity of the airflow.

What is the purpose of the diffuser section in a turbine engine?

To increase pressure and reduce velocity.
To convert pressure to velocity.
To reduce pressure and increase velocity.

Where do stress rupture cracks usually appear on turbine blades?

Across the blade root, parallel to the fir tree.
Along the leading edge, parallel to the edge.
Across the leading or trailing edge at a right angle to the edge length.

In which type of turbine engine combustion chamber is the case and liner removed and installed as one unit during routine maintenance?

Can.
Can-annular.
Annular.

The diffuser section of a jet engine is located between

the burner section and the turbine section.
station 7 and station 8.
the compressor section and the burner section.

When the leading edge of a first-stage turbine blade is found to have stress rupture cracks, which of the following should be suspected?

Faulty cooling shield.
Overtemperature condition.
Overspeed condition.

Turbine blades are generally more susceptible to operating damage than compressor blades because of

the high probability of carbon deposits.
exposure to high temperatures.
less exposure to solution during engine pressure wash.

Which of the following is the ultimate limiting factor of turbine engine operation?

Compressor inlet air temperature.
Turbine-inlet temperature.
Burner-can pressure.

The recurrent ingestion of dust or other fine airborne particulates into a turbine engine can result in

foreign object damage to the compressor section.
the need for less frequent abrasive grit cleaning of the engine.
erosion damage to the compressor and turbine sections.

Which of the following engine variables in the most critical during turbine engine operation?

Compressor inlet air temperature.
Compressor RPM.
Turbine-inlet temperature.

Reduced blade vibration and improved airflow characteristics in gas turbines are brought about by

fir-tree blade attachment.
impulse type blades.
shrouded turbine rotor blades.

Which turbine engine compressor offers the greatest advantages for both starting flexibility and improved high altitude performance?

Dual-stage, centrifugal-flow.
Split-spool, axial-flow.
Single-spool, axial-flow.

Jet engine turbine blades removed for detailed inspection must be reinstalled in

a specified slot 180 degrees away.
a specified slot 90 degrees away in the direction of rotation.
the same slot.

An advantage of the centrifugal-flow compressor is its high

pressure rise per stage.
rain efficiency.
peak efficiency.

The highest heat-to-metal contact in a jet engine is the

burner cans.
turbine inlet guide vanes.
turbine blades.

Which two elements make up the axial-flow compressor assembly?

Rotor and stator.
Compressor and manifold.
Stator and diffuser.

The two types of centrifugal compressor impellers are

single entry and double entry.
rotor and stator.
impeller and diffuser.

Between each row of rotating blades in a turbine engine compressor, there is a row of stationary blades which act to diffuse the air. These stationary blades are called

buckets.
rotors.
stators.

Standard sea level pressure is

29.00″ Hg.
29.29″ Hg.
29.92″ Hg.

Using standard atmospheric conditions, the standard sea level temperature is

59 degrees F.
59 degrees C.
29 degrees C.

When aircraft turbine blades are subjected to excessive heat stress, what type of failures would you expect?

Banding and torsion.
Torsion and tension.
Stress rupture.

In an axial-flow compressor, one purpose of the stator vanes at the discharge end of the compressor is to

straighten the airflow and eliminate turbulence.
increase the velocity and prevent swirling and eddying.
decrease the velocity, prevent swirling, and decrease pressure.

Compressor field cleaning on turbine engines is performed primarily in order to

prevent engine oil contamination and subsequent engine bearing wear or damage.
facilitate flight line inspection of engine inlet and compressor areas for defects or FOD.
prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.

Hot section inspections for many modern turbine engines are required

only at engine overhaul.
only when an overtemperature or overspeed has occurred.
on a time or cycle basis.

A purpose of the shrouds on the turbine blades of an axial-flow engine is to

reduce vibration.
increase tip speed.
reduce air entrance.

In a dual axial-flow compressor, the first stage turbine drives

N₂ compressor.
N₁ compressor.
low pressure compressor.

What should be done initially if a turbine engine catches fire when starting?

Turn off the fuel and continue engine rotation with the starter.
Continue engine start rotation and discharge a fire extinguisher into the intake.
Continue starting attempt in order to blow out the fire.

What is the proper starting sequence for a turbojet engine?

Ignition, starter, fuel.
Starter, ignition, fuel.
Starter, fuel, ignition.

A weak fuel to air mixture along with normal airflow through a turbine engine may result iin

a rich flameout.
a lean die-out.
high EGT.

What is used in turbine engines to aid in stabilization of compressor airflow during low thrust engine operation?

Stator vanes and rotor vanes.
Variable guide vanes and/or compressor bleed valves.
Pressurization and dump valves.

In a turbine engine with a dual-spool compressor, the low speed compressor

always turns at the same speed as the high speed compressor.
is connected directly to the high speed compressor.
seeks its own best operating speed.

What is the function of the inlet guide vane assembly on an axial-flow compressor?

Directs the air into the first stage rotor blades at the proper angle.
Converts velocity energy into pressure energy.
Converts pressure energy into velocity energy.

Which of the following is a good indication of a malfunctioning fuel nozzle when inspecting the exhaust section of an aircraft turbine engine?

Buckling of the combustion liner.
Hotspots on the tail cone.
Carbon buildup in the exhaust.

The stator vanes in an axial-flow compressor

convert velocity energy into pressure energy.
convert pressure energy into velocity energy.
direct air into the first stage rotor vanes at the proper angle.

The velocity of subsonic air as it flows through a convergent nozzle

increases.
decreases.
remains constant.

The velocity of supersonic air as it flows through a divergent nozzle

increases.
decreases.
is inversely proportional to the temperature.

The pressure of subsonic air as it flows through a convergent nozzle

increases.
decreases.
remains constant.

The pressure of supersonic air as it flows through a divergent nozzle

increases.
decreases.
is inversely proportional to the temperature.

Anti-icing of jet engine air inlets is commonly accomplished by

electrical healing elements inside the inlet guide vanes.
engine bleed air ducted through the critical areas.
electrical heating elements located within the engine air inlet cowling.

Generally, when starting a turbine engine, the starter should be disengaged.

after the engine has reached self-accelerating speed.
only after the engine has reached full idle RPM.
when the ignition and fuel system are activated.

What is the primary advantage of an axial-flow compressor over a centrifugal compressor?

High frontal area.
Less expensive.
Greater pressure ratio.

The purpose of a bleed valve, located in the beginning stages of the compressor, in an aircraft gas turbine engine is to

vent some of the air overboard to prevent a compressor stall.
control excessively high RPM to prevent a compressor stall.
vent high ram air pressure overboard to prevent a compressor stall.

What is meant by a double-entry centrifugal compressor?

A compressor that has two intakes.
A two-stage compressor independently connected to the main shaft.
A compressor with vanes on both sides of the impeller.

What is the major function of the turbine assembly in a turbojet engine?

Directs the gases in the proper direction to the tailpipe.
Supplies the power to turn the compressor.
Increases the temperature of the exhaust gases.

Stator blades in the compressor section of an axial-flow turbine engine.

increase the air velocity and prevent swirling.
straighten the airflow and accelerate it.
decrease the air velocity and prevent swirling.

A gas turbine engine comprises which three main sections?

Compressor, diffuser, and stator.
Turbine, combustion, and stator.
Turbine, compressor, and combustion.

What type of turbine blade is most commonly used in aircraft jet engines?

Reaction.
Impulse.
Impulse-reaction.

What is the primary factor which controls the pressure ratio of an axial-flow compressor?

Number of stages in compressor.
Compressor inlet pressure.
Compressor inlet temperature.

The non-rotating axial-flow compressor airfoils in an aircraft gas turbine engine are called

rotor blades.
stator vanes.
disc rims.

(1) In a turbine engine axial-flow compressor, each consecutive pair of rotor and stator blades constitutes a pressure stage.

(2) In a turbine engine axial-flow compressor, the number of rows of stages is determined by the amount of air and total pressure rise required.

Regarding the above statements,

only 1 is true.
only 2 is true.
both 1 and 2 are true.

The air passing through the combustion chamber of a turbine engine is

used to support combustion and to cool the engine.
entirely combined with fuel and burned.
speeded up and heated by the action of the turbines.

The stators in the turbine section of a gas turbine engine

increase the velocity of the gas flow.
decrease the velocity of the gas flow.
increase the pressure of the gas flow.

The compressor stators in a gas turbine engine act as diffusers to

decrease the velocity of the gas flow.
increase the velocity of the gas flow.
increase the velocity and decrease the pressure of the gas.

Newton’s second law of motion, generally termed the law of momentum, states:

Acceleration is produced when a force acts on a mass. The greater the mass, the greater the amount of force needed.
For every action there is an equal and opposite reaction.
Every body persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.

The procedure for removing the accumulation of dirt deposits on compressor blades is called

the soak method.
field clearning.
the purging process.

Which of the following may be used to accomplish internal inspection of an assembled turbine engine?

infrared photography.
Ultrasound.
A borescope.

What is the possible cause when a turbine engine indicates no change in power setting parameters, but oil temperature is high?

High scavenger pump oil flow.
Engine main bearing distress.
Turbine damage and/or loss of turbine efficiency.

Newton’s first law of motion, generally termed the law of inertia, states:

To every action there is an equal and opposite reaction.
Force is proportional to the product of mass and acceleration.
Every body persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.

A turbine engine hot section is particularly susceptible to which kind of damage?

Erosion.
Cracking.
Elongation.

Dirt particles in the air being introduced into the compressor of a turbine engine will form a coating on all but which of the following?

Turbine blades.
Castings.
Inlet guide vanes.

Severe rubbing of turbine engine compressor blades will usually cause

bowing.
cracking.
galling.

Which of the following influences the operation of an automatic fuel control unit on a turbojet engine?

Burner pressure.
Mixture control position.
Exhaust gas temperature.

If a turbine engine is unable to reach takeoff EFR before its EGT limit is reached, this is an indication that the

fuel control must be replaced.
EGT controler is out of adjustment.
compressor may be contaminated or damaged.

The Brayton cycle is known as the constant

pressure cycle.
temperature cycle.
mass cycle.

Continued and/or excessive heat and centrifugal force on turbine engine rotor blades is likely to cause

profile.
creep.
galling.

If the RPM of an axial-flow compressor remains constant, the angel of attack of the rotor blades can be changed by

changing the velocity of the airflow.
changing the compressor diameter.
increasing the pressure ratio.

The compression ratio of an axial-flow compressor is a function of the

number of compressor stages.
rotor diameter.
air inlet velocity.

Which of the following variables affect the inlet air density of a turbine engine?

Speed of the aircraft, compression ratio, and ambient temperature.
Speed of the aircraft, altitude of the aircraft, and ambient temperature.
Compression ratio, turbine inlet temperature, and turbine and compressor efficiency.

Which of the following factors affect the thermal efficiency of a turbine engine?

Ambient temperature, speed of the aircraft, and altitude of the aircraft.
Turbine inlet temperature, compression ratio, and turbine and compressor efficiency.
Turbine inlet temperature and ambient temperature.

Why do some turbine engines have more than one turbine wheel attached to a single shaft?

To facilitate balancing of the turbine assembly.
To help stabilize the pressure between the compressor and the turbine.
To extract more power from the exhaust gases than a single wheel can absorb.

The exhaust section of a turbine engine is designed to

impart a high exit velocity to the exhaust gases.
increase temperature, therefore increasing velocity.
decrease temperature, therefore decreasing pressure.

Which of the following types of combustion sections are used in aircraft turbine engines?

Annular, variable, and cascade vane.
Can, multiple-can, and variable.
Multiple-can, annular, and can-annular.

A cool-off period prior to shutdown of a turbine engine is accomplished in order to

allow the turbine wheel to cool before the case contracts around it.
prevent vapor lock in the fuel control and/or fuel lines.
prevent seizure of the engine bearings.

What type igniter plug is used in the low tension ignition system of an aircraft turbofan engine?

Low voltage, high amperage glow plug.
Self-ionizing or shunted-gap type plug.
Recessed surface gap plug.

What is meant by a shrouded turbine?

The turbine blades are shaped so that their ends form a band or shroud.
The turbine wheel is enclosed by a protective shroud to contain the blades in case of failure.
The turbine wheel has a shroud or duct which provides cooling air to the turbine blades.

What term is used to describe a permanent and cumulative deformation of the turbine blades of a turbojet engine?

Stretch.
Distortion.
Creep.

What is the purpose of the dump valve used on aircraft gas turbine engines?

The fuel is quickly cut off to the nozzles and the manifolds are drained preventing fuel boiling off as a result of residual engine heat.
The valve controls compessor stall by dumping compressor bleed air from the compressor discharge port under certain conditions.
Maintains minimum fuel pressure to the engine fuel control unit inlet and dumps excessive fuel back to the inlet of the engine-driven fuel pump.

At what stage in a turbine engine are gas pressures the greatest?

Compressor inlet.
Turbine outlet.
Compressor outlet.

In what section of a turbojet engine is the jet nozzle located?

Combustion.
Turbine.
Exhaust.

(1) Accumulation of contaminates in the compressor of a turbojet engine reduces aerodynamic efficiency of the blades.

(2) Two common methods for removing dirt deposits from turbojet engine compressor blades are a fluid wash and an abrasive grit blast.

Regarding the above statements,

only 1 is true.
only 2 is true.
both 1 and 2 are true.

Hot spots in the combustion section of a turbojet engine are possible indications of

faulty igniter plugs.
dirty compressor blades.
malfunctioning fuel nozzles.

Which of the following can cause fan blade shingling in a turbofan engine?

Engine overtemperature.
Large, rapid throttle movements.
Engine overspeed and/or FOD.

Compressor stall is caused by

a low angle of attack airflow through the first stages of compression.
a high angle of attack airflow through the first stages of compression.
rapid engine deceleration.

A condition known as “hot streaking” in turbine engines is caused by

a partially clogged fuel nozzle.
a misaligned combustion liner.
excessive fuel flow.

PP Turbine Engines

Jon K

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