3272-15 (15.6)

An increase in turbine diameter is caused by. prolonged high temperatures and centrifugal loads. products of combustion. over speed.

Which of the following is most likely to occur in the turbine section of a gas turbine engine?. Pitting. Galling. Cracking.

Aluminium deposits on the turbine show up as. white powder traces. white or silver speckles. black stains.

An impulse/reaction turbine is designed to ensure. greater axial velocity at the blade root. uniform axial velocity from blade root to tip. greater axial velocity at the blade tip.

Excessive turbine temperatures can lead to. turbine blade creep and an increase in the diameter of the turbine. not a serious problem as long as engine oil pressure is within limits. a serious fire risk in the engine.

What are blue and golden deposits evidence of, on a turbine blade?. Aluminium. Magnesium. Titanium.

Necking and mottling of turbine blades. is due to thermal stress. is formed during manufacture. is due to bending when the gas hits the blades.

During a borescope check of the H.P turbine blades. dry motor the engine at minimum speed. hand turn the turbine wheel. attach a device to the accessory gearbox and rotate slowly.

The turbine section of a jet engine. converts dynamic pressure into mechanical energy. circulates air to cool the engine. extracts heat energy to drive the compressor.

The temperature and centrifugal loads which the turbine is subjected to during normal engine operation causes. fatigue failure. elastic stretching. creep loading.

Impulse-reaction turbine blades form. tip half reaction, root half Impulse. 1 stage impulse, 1 stage reaction. tip half Impulse, root half reaction.

A fir tree root. attaches turbine blades to the turbine disk. allows compressor cooling air to alleviate thermal stress. allows individual turbine blades to be changed without engine disassembly.

The passage between adjacent nozzle guide vanes forms a. convergent duct. divergent duct. parallel duct.

As the hot gasses flow through an impulse turbine blading, the velocity. will decrease. remains constant. will increase.

What is the normal range of turbine efficiency?. 90% - 95%. 70% - 85%. 30% - 40%.

Turbine engine components are never manufactured by. electrical resistance welding. argon arc welding. gas welding.

How is a radial turbine driven?. By impulse. By change of momentum and angle of airflow. By reaction.

Turbine disk growth is due to. a permanent change in disk diameter. an overall increase in blade length. a build up of carbon deposits.

A nozzle guide vane is. hollow in construction to allow for thermal expansion. hollow in construction to allow for flow of cooling air. solid in construction to support the guide vane.

A slow constant growth in a turbine blade is known as. primary creep. secondary creep. tertiary creep.

The function of the exhaust cone assembly of a turbine engine is to. swirl and collect the exhaust gases into a single exhaust jet. collect the exhaust gases and act as a noise suppressor. straighten and collect the exhaust gases into a solid exhaust jet.

The struts on the exhaust cone. straighten the gas flow only. support the exhaust cone and straighten the gas flow. support the exhaust cone only.

What is the maximum practical angle through which the gas flow can be turned during thrust reversal?. 180°. 50°. 135°.

A supersonic duct is. convergent then divergent along its length. divergent then convergent along its length. a convergent duct that is choked at the largest end at mach 1.

Noise from the jet wake when untreated by suppression is. high frequency, high decibel. low frequency, low decibel. low frequency, high decibel.

Hot spots on the tail cone of a turbine engine are possible indicators of a malfunctioning fuel nozzle or. a faulty igniter plug. an improperly positioned tail cone. a faulty combustion chamber.

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

A convergent-divergent nozzle. requires the aircraft to be travelling at supersonic speeds. makes maximum use of pressure thrust. produces a type of thrust known as kinetic thrust.

The velocity of supersonic air as it flows through a divergent nozzle. is inversely proportional to the temperature. increases. decreases.

The Jet Pipe of a gas turbine engine. protects the airframe from heat damage. is convergent in shape to increase the velocity as much as possible. has an inner cone to protect the rear turbine disc.

For what purpose is the propelling nozzle of a gas turbine engine designed?. To increase the velocity and decrease the pressure of the gas stream leaving the nozzle. To decrease the velocity and increase the pressure of the gas stream leaving the nozzle. To increase the velocity and pressure of the gas stream leaving the nozzle.

If the exit area of the nozzle was too large, the effect is. exit velocity lower causing loss of thrust. will choke at a lower gas temperature. exit velocity lower, negligible effect on thrust.

A choked nozzle. increases thrust. decreases thrust. has no effect on the thrust.

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

Reverse thrust can only be selected when the throttle is. closed. 75% power position. open.

A Convergent-Divergent nozzle. makes maximum use of Pressure thrust. produces a type of thrust known as kinetic thrust. requires the aircraft to be travelling at supersonic speeds.

On front fan engines, to obtain thrust reversal, the. hot and cold streams are reversed. cold stream is reversed. hot stream is reversed.

Exhaust noise can be reduced by. lowering the vibration frequency. increasing the jet velocity. increasing the mixing rate.

Operating thrust reversers at low ground speeds can sometimes cause. sand or other foreign object ingestion, hot gas re-ingestion. hot gas re-ingestion, compressor stalls. sand or other foreign object ingestion, hot gas re-ingestion, compressor stalls.

The purpose of cascade vanes in a thrust reversing system is to. turn the exhaust gases forward just after exiting the exhaust nozzle. form a solid blocking door in the jet exhaust path. turn to a forward direction the fan and/or hot exhaust gases that have been blocked from exiting through the exhaust nozzle.

A convergent exhaust nozzle produces mainly. momentum and pressure thrust. momentum thrust. pressure thrust.

The rearward thrust capability of an engine with the thrust reverser system deployed is. equal to or less than its forward capability, depending on ambient conditions and system design. less than its forward capability. equal to its forward capability.

Which statement is generally true regarding thrust reverser systems?. Engine thrust reversers on the same aircraft usually will not operate independently of each other (must all be simultaneously). It is possible to move some aircraft backward on the ground using reverse thrust. Mechanical blockage system design permits a deployment position aft of the exhaust nozzle only.

What is the proper operating sequence when using thrust reversers to slow an aircraft after landing?. Advance thrust levers up to takeoff position as conditions require, select thrust reverse, de- select thrust reverser, retard thrust levers to ground idle. Retard thrust levers to ground idle, raise thrust reverser levers as required, and retard thrust reverser levers to ground idle. Select thrust reverse, advance thrust reverser levers no higher than 75% N1, and retard thrust reverser levers to idle at approximately normal taxi speed.

Most exhaust system failures result from thermal fatigue cracking in the areas of stress concentration. This condition is usually caused by. the high temperatures at which the exhaust system operates. improper welding techniques during manufacture. the drastic temperature change which is encountered at altitude.

Thrust reversal on a high bypass engine is achieved by. clamshell configuration. blocker doors. bucket type doors.

If damage is found to the reverse thrust cascade vanes and they need replacing, you can. replace damaged vanes with 45 degree vanes. only replace vanes with new ones that have the correct part as the originals removed. interchange the cascade vanes as they are interchangeable.

When should thrust reversers be used?. At low RPM and low forward speed. At high RPM and high forward speed. At high RPM and low forward speed.

Lobe type exhaust noise suppressors are made from. heat resistant alloy. composite Material. steel.

What indication does the pilot receive that thrust reversers have deployed?. An audible warning. A sequence of lights. A feeling of rapid deceleration.

What angle are the exhaust gasses turned through in a clamshell type thrust reverser?. 180 degrees. 135 degrees. 45 degrees.

The purpose of a propelling nozzle is to. increase the velocity of the air and increase thrust. decrease the velocity of the exhaust to increase static pressure. direct the air onto the turbines.

If a thrust reverser is deployed at lower than normal landing speed. exhaust gases can be ingested into the engine. the thrust reverser will be ineffective. if the EGT gets too high the thrust reverser will automatically restow.

The size of the exhaust section is dictated by. cone or diffuser size and location. size of engine only. size and location of the engine.

As the air flows out at the outflow of a choked nozzle. velocity increases and pressure decreases. velocity and pressure decrease. velocity decreases and pressure increases.

Main bearing oil seals used with turbine engines are usually what type(s)?. Teflon and synthetic rubber. Labyrinth and/or silicone rubber. Labyrinth and/or carbon rubbing.

If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism but otherwise have no defects, they. are in an acceptable service condition. cannot be used again. must be degaussed before use.

A carbon seal has which type of sealing arrangement?. Full contact with race. Full contact with labyrinth. Full contact with casing.

The highest turbine bearing temperature takes place. all the time. at start-up. at shut-down.

Indentations on bearing races caused by high static loads are known as. fretting. galling. brinelling.

The function of a labyrinth seal is to create. a restricted leakage of air between fixed and rotating components. an airtight seal between fixed and rotation components. an airtight seal between fixed adjacent casing surfaces.

The bearings of a compressor rotor are usually. ball and roller. plain. sintered.

Bearing seal failure would most probably cause. high oil temperature. high oil consumption. low oil pressure.