POWERPLANT - Turbine Engines

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

1. layout dye.

2. commercial felt tip marker.

3. wax or grease pencil.

4. chalk.

5. graphite lead pencil.

a. 1,2, and 3.

b. 3 and 5.

c. 4and 5.

b. 3 and 5.

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

a. a specified slot 1800 away.

b. a specified slot 900 away in the direction of rotation.

c. the same slot.

c. the same slot.

The blending of blades and vanes in a turbine engine

a. is usually accomplished only at engine overhaul.

b. should be performed parallel to the length of the blade using smooth contours to minimize stress points.

c. may sometimes be accomplished with the engine installed, ordinarily using power tools

b. should be performed parallel to the length of the blade using smooth contours to minimize stress points.

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

a. Decrease the velocity of exhaust gases.

b. Center the fuel spray in the combustion chamber.

c. Direct the flow of gases to strike the turbine blades at the desired angle.

c. Direct the flow of gases to strike the turbine blades at the desired angle.

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

a. low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.

b. throttle must be retarded to prevent overspeeding of the high-pressure rotor due to the lower density air.

c. low-pressure rotor will decrease in speed as the compressor load decreases in the lower density air.

a. low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.

A gas turbine engine comprises which three main sections?

a. Compressor, diffuser, and stator.

b. Turbine, combustion, and stator.

c. Turbine, compressor, and combustion.

c. Turbine, compressor, and combustion.

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

a. increase and the velocity to decrease.

b. increase and the velocity to increase.

c. decrease and the velocity to increase

a. increase and the velocity to decrease.

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

a. number of compressor stages.

b. rotor diameter.

c. air inlet velocity.

a. number of compressor stages.

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

a. number of compressor stages.

b. rotor diameter.

c. air inlet velocity.

a. number of compressor stages.

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

a. fuel control must be replaced.

b. EGT controller is out of adjustment.

c. compressor may be contaminated or damaged.

c. compressor may be contaminated or damaged.

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

a. Dual-stage, centrifugal-flow.

b. Split-spool, axial-flow.

c. Single-spool, axial-flow.

b. Split-spool, axial-flow.

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

a. The engine manufacturer.

b. The operator (utilizing manufacturer data and trend analysis) working in conjunction with the FAA.

c. The FAA.

a. The engine manufacturer.

Which statements are true regarding aircraft engine propulsion?

1. An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air.

2. Turbojet and turbofan engines impart a relatively large amount of acceleration to a smaller mass of air.

3. 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.

a. 1,2,3

b. 1,2

c. 1.3

b. 1,2

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

a. profile.

b. creep.

c. galling.

b. creep.

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

a. the soak method.

b. field cleaning.

c. the purging process.

b. field cleaning.

The stators in the turbine section of a gas turbine engine

a. increase the velocity of the gas flow.

b. decrease the velocity of the gas flow.

c. increase the pressure of the gas flow.

a. increase the velocity of the gas flow.

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

a. A rise in the engine fuel flow.

b. A rise in oil pressure.

c. A rise in the exhaust gas temperature.

c. A rise in the exhaust gas temperature.

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

a. Combustion.

b. Turbine.

c. Exhaust.

c. Exhaust.

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

a. foreign object damage to the compressor section.

b. the need for less frequent abrasive grit cleaning of the engine.

c. erosion damage to the compressor and turbine sections.

c. erosion damage to the compressor and turbine sections.

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

a. Combustion section.

b. Compressor section.

c. Diffuser section

a. Combustion section.

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

a. Rotor and stator.

b. Compressor and manifold.

c. Stator and diffuser

a. Rotor and stator.

Three types of turbine blades are

a. reaction, converging, and diverging.

b. impulse, reaction, and impulse-reaction.

c. impulse, vector, and impulse-vector.

b. impulse, reaction, and impulse-reaction.

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

a. vent some of the air overboard to prevent a

compressor stall.

b. control excessively high RPM to prevent a

compressor stall.

c. vent high ram air pressure overboard to prevent a compressor stall.

a. vent some of the air overboard to prevent a

compressor stall.

An advantage of the axial-flow compressor is its

a. low starting power requirements.

b. low weight.

c. high peak efficiency.

c. high peak efficiency.

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

a. The FAA.

b. The operator working in conjunction with the FAA.

c. The engine manufacturer.

c. The engine manufacturer.

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

a. Low voltage, high amperage glow plug.

b. Self-ionizing or shunted-gap type plug.

c. Recessed surface gap plug.

b. Self-ionizing or shunted-gap type plug.

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

a. increases.

b. decreases.

c. remains constant.

a. increases.

When starting a turbine engine,

a. a hot start is indicated if the exhaust gas

temperature exceeds specified limits.

b. an excessively lean mixture is likely to cause a hot start.

c. release the starter switch as soon as indication of light-off occurs.

a. a hot start is indicated if the exhaust gas temperature exceeds specified limits.

Hot section inspections for many modern turbine engines are required

a. only at engine overhaul.

b. only when an over temperature or over speed has occurred.

c. on a time or cycle basis.

c. on a time or cycle basis.

What are the two functional elements in a centrifugal compressor?

a. Turbine and compressor.

b. Bucket and expander.

c. Impeller and diffuser.

c. Impeller and diffuser.

Hot spots in the combustion section of a turbojet engine

are possible indicators of

a. faulty igniter plugs.

b. dirty compressor blades.

c. malfunctioning fuel nozzles.

c. malfunctioning fuel nozzles.

How does a dual axial-flow compressor improve the

efficiency of a turbojet engine?

a. More turbine wheels can be used.

b. Higher compression ratios can be obtained.

c. The velocity of the air entering the combustion

chamber is increased.

b. Higher compression ratios can be obtained.

(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,

a. only No. 1 is true.

b. only No. 2 is true.

c. both No. 1 and No. 2 are true.

c. both No. 1 and No. 2 are true.

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,

a. only No. 1 is true.

b. only No. 2 ¡s true.

c. neither No. 1 nor No. 2 is true.

c. neither No. 1 nor No. 2 is true.

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

a. changing the velocity of the airflow.

b. changing the compressor diameter.

c. increasing the pressure ratio.

a. changing the velocity of the airflow.

Which of the following factors affect the thermal

efficiency of a turbine engine?

1. Turbine inlet temperature.

2. Compression ratio.

3. Ambient temperature.

4. Speed of the aircraft.

5. Turbine and compressor efficiency.

6. Altitude of the aircraft.

a. 3, 4, 6.

b. 1,2,5.

c. 1.2.6.

b. 1,2,5.

The velocity of supersonic air as it flows through a

divergent nozzle

a. increases.

b. decreases.

c. is inversely proportional to the temperature.

a. increases.

Where do stress rupture cracks usually appear on turbine blades?

a. Across the blade root, parallel to the fir tree.

b. Along the leading edge, parallel to the edge.

c. Across the leading or trailing edge at a right

angle to the edge length.

c. Across the leading or trailing edge at a right angle to the edge length.

In a gas turbine engine, combustion occurs at a constant

a. volume.

b. pressure.

c. density.

b. pressure.

What is meant by a double entry centrifugal compressor?

a. A compressor that has two intakes.

b. A two-stage compressor independently connected to the main shaft.

c. A compressor with vanes on both sides of the impeller.

c. A compressor with vanes on both sides of the impeller.

The pressure of supersonic air as it flows through a

divergent nozzle

a. increases.

b. decreases.

c. is inversely proportional to the temperature.

b. decreases.

What is the proper starting sequence for a turbojet engine?

a. Ignition, starter, fuel.

b. Starter, ignition, fuel.

c. Starter, fuel, ignition.

b. Starter, ignition, fuel.

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

a. Annular, variable, and cascade vane.

b. Can, multiple-can, and variable.

c. Multiple-can, annular, and can-annular.

c. Multiple-can, annular, and can-annular.

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

a. after the engine has reached self-accelerating

speed.

b. only after the engine has reached full idle RPM.

c. when the ignition and fuel system are activated.

a. after the engine has reached self-accelerating speed.

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

a. Can.

b. Can annular.

c. Annular.

a. Can.

What is the function of the stator vane assembly at the

discharge end of a typical axial-flow compressor?

a. To straighten airflow to eliminate turbulence.

b. To direct the flow of gases into the combustion

chambers.

c. To increase air swirling motion into the combustion

chambers.

a. To straighten airflow to eliminate turbulence.

Some engine manufacturers of twin spool gas turbine

engines identify turbine discharge pressure in their

maintenance manuals as

a. Pt7.

b. Pt2.

c. Tt7.

a. Pt7.

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

a. prevent engine oil contamination and subsequent

engine bearing wear or damage.

b. facilitate flight line inspection of engine inlet and

compressor areas for defects or FOD.

c. prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.

c. prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.

Using standard atmospheric conditions, the standard sea level temperature is

a. 59°F

b. 59°C.

c. 29°C.

a. 59°F

Main bearing oil seals used with turbine engines are

usually what type(s)?

a. Labyrinth and/or carbon rubbing.

b. Teflon and synthetic rubber.

c. Labyrinth and/or silicone rubber.

a. Labyrinth and/or carbon rubbing.

Hot spots on the tail cone of a turbine engine are possible indicators of a malfunctioning fuel nozzle or

a. a faulty combustion chamber.

b. a faulty igniter plug.

c. an improperly positioned tail cone.

a. a faulty combustion chamber.

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

a. Turn off the fuel and continue engine rotation with the starter.

b. Continue engine start rotation and discharge a fire

extinguisher into the intake.

c. Continue starting attempt in order to blow out the

fire.

a. Turn off the fuel and continue engine rotation with the starter.

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

a. High scavenge pump oil flow.

b. Engine main bearing distress.

c. Turbine damage and/or loss of turbine efficiency

b. Engine main bearing distress.

The stator vanes in an axial-flow compressor

a. convert velocity energy into pressure energy.

b. convert pressure energy into velocity energy.

c. direct air into the first stage rotor vanes at the proper angle.

a. convert velocity energy into pressure energy.

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

a. decrease the velocity of the heated gases flowing

past this point.

b. direct the flow of gases parallel to the vertical line of the turbine blades.

c. increase the velocity of the heated gases flowing past this point.

c. increase the velocity of the heated gases flowing past this point.

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

a. allow the turbine wheel to cool before the case contracts around it.

b. prevent vapor lock in the fuel control and/or fuel lines.

c. prevent seizure of the engine bearings.

a. allow the turbine wheel to cool before the case contracts around it.

What is meant by a shrouded turbine?

a. The turbine blades are shaped so that their ends form a band or shroud.

b. The turbine wheel is enclosed by a protective shroud to contain the blades in case of failure.

c. The turbine wheel has a shroud or duct which

provides cooling air to the turbine blades.

a. The turbine blades are shaped so that their ends form a band or shroud.

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

a. Stator vanes and rotor vanes.

b. Variable guide vanes and/or compressor bleed valves.

c. Pressurization and dump valves.

b. Variable guide vanes and/or compressor bleed valves.

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

speed compressor

a. always turns at the same speed as the high speed

compressor.

b. is connected directly to the high speed compressor.

c. seeks its own best operating speed.

c. seeks its own best operating speed.

Where is the highest gas pressure in a turbojet engine?

a. At the outlet of the tailpipe section.

b. At the entrance of the turbine section.

c. In the entrance of the burner section.

c. In the entrance of the burner section.

A purpose of the shrouds on the turbine blades of an axialflow engine is to

a. reduce vibration.

b. increase tip speed.

c. reduce air entrance.

a. reduce vibration.

Which of the following can cause fan blade shingling in a

turbofan engine?

1. Engine over speed.

2. Engine over temperature.

3. Large, rapid throttle movements.

4. FOD.

a. 1,2

b. 1,2,3,4

c. 1,4.

c. 1,4.

What term is used to describe a permanent and cumulative

deformation of the turbine blades of a turbojet engine?

a. Stretch.

b. Distortion.

c. Creep.

c. Creep.

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

a. High frontal area.

b. Less expensive.

c. Greater pressure ratio.

c. Greater pressure ratio.

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

a. N(2) compressor.

b. N(1) compressor.

c. low pressure compressor

a. N(2) compressor.

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

a. buckets.

b. rotors.

c. stators.

c. stators.

The non-rotating axial-flow compressor airfoils in an

aircraft gas turbine engine, are called

a. pressurization vanes.

b. stator vanes.

c. bleed vanes.

b. stator vanes.

Standard sea level pressure is

a. 29.00" Hg.

b. 29.29" Hg.

c. 29.92" Hg.

c. 29.92" Hg.

Severe rubbing of turbine engine compressor blades will usually cause

a. bowing.

b. cracking.

c. galling.

c. galling.

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

a. Directs the air into the first stage rotor blades at the proper angle.

b. Converts velocity energy into pressure energy.

c. Converts pressure energy into velocity energy.

a. Directs the air into the first stage rotor blades at the proper angle.

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

a. fir-tree blade attachment.

b. impulse type blades.

c. shrouded turbine rotor blades.

c. shrouded turbine rotor blades.

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

a. electrical heating elements inside the inlet guide vanes.

b. engine bleed air ducted through the critical areas.

c. electrical heating elements located within the engine air inlet cowling.

b. engine bleed air ducted through the critical areas.

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?

a. Turbine blades.

b. Casings.

c. Inlet guide vanes.

a. Turbine blades.

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

a. a rich flameout.

b. a lean die-out.

c. high EGT.

b. a lean die-out.

Newton's Law of Motion, generally termed the "Law of

Momentum," states:

a. Acceleration is produced when a force acts on a mass. The greater the mass, the greater the amount of force needed.

b. For every action there is an equal and opposite reaction.

c. Every body persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.

a. Acceleration is produced when a force acts on a mass. The greater the mass, the greater the amount of force needed.

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

a. straighten the airflow and eliminate turbulence.

b. increase the velocity and prevent swirling and

eddying.

c. decrease the velocity, prevent swirling, and decrease

pressure.

a. straighten the airflow and eliminate turbulence.

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

a. Number of stages in compressor.

b. Compressor inlet pressure.

c. Compressor inlet temperature.

a. Number of stages in compressor.

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

a. collect the exhaust gases and act as a noise suppressor.

b. swirl and collect the exhaust gases into a single exhaust jet.

c. straighten and collect the exhaust gases into a solid exhaust jet.

c. straighten and collect the exhaust gases into a solid exhaust jet.

What is the profile of a turbine engine compressor blade?

a. The leading edge of the blade.

b. A reduced blade tip thickness.

c. The curvature of the blade root.

b. A reduced blade tip thickness.

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

1. Speed of the aircraft.

2. Compression ratio.

3. Turbine inlet temperature.

4. Altitude of the aircraft.

5. Ambient temperature.

6. Turbine and compressor efficiency.

a. 1,3,6.

b. 1,4,5.

c. 4. 5. 6.

b. 1,4,5.

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

a. Scoring.

b. Cracking.

c. Galling.

b. Cracking.

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

a. Reaction.

b. Impulse.

c. Impulse-reaction.

c. Impulse-reaction.

The two types of centrifugal compressor impellers are

a. single entry and double entry.

b. rotor and stator.

c. impeller and diffuser.

a. single entry and double entry.

Newton's First Law of Motion, generally termed the Law of Inertia, states:

a. To every action there is an equal and opposite reaction.

b. Force is proportional to the product of mass and acceleration.

c. Everybody persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.

c. Everybody persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.

The turbine section of a jet engine

a. increases air velocity to generate thrust forces.

b. utilizes heat energy to expand and accelerate the incoming gas flow.

c. drives the compressor section

c. drives the compressor section

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

a. low-pressure compressor.

b. forward turbine wheel.

c. high-pressure compressor.

a. low-pressure compressor.

The Brayton cycle is known as the constant

a. pressure cycle.

b. temperature cycle.

c. mass cycle.

a. pressure cycle.

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

a. 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.

b. The valve controls compressor stall by dumping compressor bleed air from the compressor discharge port under certain conditions.

c. 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.

a. 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.

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

the engine

a. exhaust gas temperature exceeds specified limits.

b. fails to reach idle RPM.

c. RPM exceeds specified operating speed.

b. fails to reach idle RPM.

The abbreviation Pt7 used in turbine engine terminology means

a. the total inlet pressure.

b. pressure and temperature at station No. 7.

c. the total pressure at station No. 7.

c. the total pressure at station No. 7.

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

a. Faulty cooling shield.

b. Over temperature condition.

c. Overspeed condition.

b. Over temperature condition.

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

a. Impeller and diffuser.

b. Hot and cold.

c. Stator and rotor.

c. Stator and rotor.

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

a. burner cans.

b. turbine inlet guide vanes.

c. turbine blades.

b. turbine inlet guide vanes.

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

a. Bending and torsion.

b. Torsion and tension.

c. Stress rupture.

c. Stress rupture.

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

a. increases.

b. decreases.

c. remains constant.

b. decreases.

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

a. To increase pressure and reduce velocity.

b. To convert pressure to velocity.

c. To reduce pressure and increase velocity.

a. To increase pressure and reduce velocity.

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

a. Compressor inlet air temperature.

b. Turbine inlet temperature.

c. Burner-can pressure.

b. Turbine inlet temperature.

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

a. N(1) and N(2) compressors.

b. N(2) compressor.

c. N(1) compressor.

b. N(2) compressor.

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

a. Compressor inlet air temperature.

b. Compressor RPM.

c. Turbine inlet temperature.

c. Turbine inlet temperature.

(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,

a. only No. 1 is true.

b. only No. 2 is true.

c. neither No. 1 nor No. 2 is true.

c. neither No. 1 nor No. 2 is true.