CHƯƠNG 5: TUABIN
245. What condition does the twist in a turbine blade provide to axial airflow
leaving the trailing edge?
A. A constant axial r.p.m. from base to tip
B. A constant axial velocity from base to tip
C. A lower axial velocity from base to tip
246. How do the turbine nozzle stator vanes become a point of increasing
gas velocity within the engine?
A. Their trailing edges converge to form a nozzle.
B. Their leading edges converge to form a nozzle.
C. Their trailing edges diverge to form a nozzle.
247. From which source is the air used to cool turbine blades and stator
vanes extracted?
A. The secondary combustor airflow
B. The compressor
C. Inlet ram air
248. A flight engine will more likely have what type turbine wheel installed to
drive its compressor?
A. Impulse-axial
B. Reaction-axial
C. Impulse-reaction
249. The three main types of turbine blades are.
A. impulse, vector, and impulse-vector.
B. reaction, converging, and diverging.
C. impulse, reaction, and impulse-reaction.
1
250. What are the two main basic components of the turbine section in a gas
turbine engine?.
A. Stator and rotor.
B. Hot and cold.
C. Impeller and diffuser.
Explanation. Jeppesen A&P Powerplant Textbook 3-25.
251. Turbine impulse blading forms a.
A. constant area duct.
B. divergent duct.
C. convergent duct.
Explanation. Rolls Royce - The Jet Engine (New) Page 135 diagram.
252. The turbine section.
A. increases air velocity to create thrust.
B. uses heat energy to expand and accelerate the gas flow.
C. drives the compressor section.
Explanation. Jeppesen A&P Powerplant Textbook 3-25.
253. Where do stress rupture cracks usually appear on turbine blades?.
A. Across the blade root, parallel to the fir tree.
B. Across the leading or trailing edge at a right angle to the edge.
C. Along the leading edge, parallel to the edge. Explanation. Jeppesen
A&P Powerplant Textbook 4-25.
254. 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 has a shroud or duct which provides cooling air
to the turbine blades.
C. The turbine wheel is enclosed by a protective shroud to contain the
blades in case of failure.
2
255. Turbine nozzle diaphragms located on the upstream side of each turbine wheel,
are used 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.
256. Reduced blade vibration and improved airflow characteristics in turbines are
brought by.
A. shrouded turbine rotor blades.
B. impulse type blades.
C. fir tree blade attachment.
257. What term is used to describe a permanent and cumulative deformation of
turbine blades?.
A. Stretch.
B. Creep.
C. Distortion.
258. What is the major function of the turbine assembly in a turbojet engine?.
A. Directs the gases in the proper direction to the tailpipe.
B. Supplies the power to turn the compressor.
C. Increases the temperature of the exhaust gases.
259. Gas pressure through the turbine section will generally.
A. increase.
B. remain the same.
C. decrease.
260. A condition known as 'hot streaking' in turbine engines is caused by
A. a partially clogged fuel nozzle.
B. excessive fuel flow.
C. a misaligned combustion liner.
3
261. Temperature through the turbine stages generally.
A. remains the same.
B. decreases.
C. increases.
262. Shrouded blades allow.
A. smaller inlets to be used.
B. higher turbine inlet temperatures.
C. thinner more efficient blade sections to be used.
263. Continued and/or excessive heat and centrifugal force on turbine engine
rotor blades is likely to cause.
A. galling.
B. creep.
C. profile.
Explanation. Jeppesen A&P Powerplant Textbook 4-22.
264. N.G.V's (Nozzle guide vanes) form.
A. convergent ducts.
B. parallel ducts.
C. divergent ducts.
Explanation. Jepperson Gas Turbine Powerplants Page 3-38 refers.
265. Dirt particles in the air going 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.
4
266. Reduced blade vibration and improved airflow characteristics in gas turbines are
brought about by.
A. shrouded turbine rotor blades.
B. fir tree blade attachment.
C. impulse type blades.
267. A purpose of the shrouds on the turbine blades of an axial flow engine is to.
A. reduce air entrance.
B. increase tip speed.
C. reduce vibration.
268. Hot section inspections for many modern turbine engines are required.
A. on a time or cycle basis.
B. only when an over temperature or overspeed has occurred.
C. only at engine overhaul.
269. Why do some turbine engines have more than one turbine wheel attached to a
single shaft?.
A. To facilitate balancing of the turbine assembly.
B. To extract more power from the exhaust gases than a single wheel
canabsorb.
C. To help stabilize the pressure between the compressor and the turbine.
270. When aircraft turbine blades are subjected to excessive heat stress, what type of
failures would you expect?.
A. Bending and torsion.
B. Stress rupture.
C. Torsion and tension.
271. Which of the following conditions is usually not acceptable to any extent in
turbine blades?.
A. Cracks.
B. Dents.
5
C. Pits.
272. The forces driving a turbine round are due to.
A. impulse only.
B. reaction only.
C. impulse and reaction.
Explanation. Rolls Royce The Jet Engine Page 50 Refers.
273. Nozzle guide vanes give a.
A. pressure increase, velocity decrease.
B. pressure increase, velocity increase.
C. pressure decrease, velocity increase.
Explanation. Jeppesen Gas Turbine Powerplant Page 3-35 refers.
274. Shrouding of stator blade tips is to.
A. minimise vibration.
B. ensure adequate cooling.
C. prevent tip turbulence.
Explanation. Jeppesen Gas Turbine Powerplant Page 3-43 refers.
275. Why are two or more turbine wheels coupled?.
A. To keep turbine rotor diameter small.
B. So power output is doubled.
C. To simplify dynamic balancing.
Explanation. Rolls Royce The Jet Engine page 45 refers.
276. Running clearance on a turbine disk is kept to a minimum to reduce.
A. temperature loss.
B. aerodynamic buffeting.
C. tip losses.
Explanation. Jeppesen Gas Turbine Powerplants Page 3-18 refers.
6
277. Two basic types of turbine blades are.
A. impulse and vector.
B. reaction and impulse.
C. tangential and reaction.
Explanation. Jeppesen Gas Turbine Powerplants Page 3-40 refers.
278. Why are nozzle guide vanes fitted?.
A. To decrease velocity of the gas flow.
B. To increase velocity of the gas flow.
C. To increase velocity of the air flow.
Explanation. Jeppesen Gas Turbine Powerplants Page 3-38 refers.
279. A turbine disk is.
A. a disk at the core of the engine that the blades are attached to.
B. a segmented or complete shroud on blade tips that reduces leakage.
C. a shroud around the stators of the turbine.
Explanation. The turbine blades are mounted to the disc which absorbs the
centrifugal force.
280. When carrying out a borescope the damage on turbine blades that would
indicate a failure is.
A. speckling.
B. tip curl.
C. colour changes.
Explanation. Jeppesen Gas Turbine Powerplants figure 5-23 page 178 and figure
5-26 page 185 refers.
281. The active clearance control system aids turbine engine efficiency by.
A. automatically adjusting engine speed to maintain a desired EPR.
B. adjusting stator vane position according to operating conditions and
power requirements.
C. ensuring turbine blade to engine case clearances are kept to a
minimumby controlling case temperatures.
7
282. Turbine rear struts.
A. straighten the gas flow.
B. increase the velocity of the gas flow.
C. increase the pressure of the gas flow.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant page 3-34 refers.
283. Bowing of turbine blades indicates an.
A. over-temperature condition.
B. over-speed condition.
C. under-temperature condition.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant page 5-30 refers to bowing
as part of the ageing process. Over temp is the only answer relevant to aging
(temperature creep).
284. On an impulse-reaction turbine blade it is.
A. impulse at the root and reaction at the tip.
B. reaction at the root and impulse at the tip.
C. impulse and reaction all the away along the blade.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant page 3-40 refers. Rolls
Royce pg.50 para.10 and figure5.6 stagger angle.
285. Turbine creep effects.
A. turbine blades.
B. turbine disks.
C. N.G.Vs.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant Page 5-28 refers.
286. Creep is.
A. not found in turbines.
B. a temporary deformation of turbine.
C. a permanent deformation of turbine.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant Page 5-28 refers.
8
287. Creep, overall.
A. has no effect on turbine diameter.
B. increases turbine diameter.
C. decreases turbine diameter.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant Page 5-28 refers.
288. How are turbine disks attached to the shaft in gas turbine engine?.
A. Splined.
B. Curvic couplings.
C. Bolted.
Explanation. Jeppesen Aircraft gas Turbine Powerplant page 3-41 refers.
289. Fir tree turbine blade attachment locates the blade.
A. allows slight movement.
B. radially.
C. axially.
Explanation. Rolls Royce The Jet Engine page 52 Para 19 refers.
290. What is the hottest component in an operating turbine
A. Turbin outlet nozzle vannes
B. Turbine inlet nozzle vanes.
C. Turbine blade tip
291. Creep may occur to turbine blades due to.
A. prolonged low RPM use.
B. over-temp with excessive centrifugal loads.
C. high back pressures.
Explanation. Creep is irreversible Rolls Royce the Jet Engine Page 56 refers.
292. Forces driving the turbine are due to.
A. aerodynamic lift imposing impulse on blades.
9
B. momentum and directional acceleration of gases.
C. expansion of gases.
Explanation. Rolls Royce The Jet Engine Page 49-50 refers.
293. Impulse turbine blades run cooler than reaction blades because.
A. impulse spin faster radially.
B. temperature drop across N.G.V is greater.
C. converging rotors increase velocity.
Explanation. Impulse blades have total pressure drop in N.G.V's hence air is colder
as it enters turbine RR Page51 refers.
294. An increase in turbine diameter is caused by.
A. prolonged high temperatures and centrifugal loads.
B. products of combustion.
C. over speed.
Explanation. This is known as creep.
295. Which of the following is most likely to occur in the turbine section of a gas
turbine engine?.
A. Pitting.
B. Galling.
C. Cracking.
Explanation. A turbine bearing is under great heat stress, cracking is the only
possible choice here.
296. Aluminium deposits on the turbine show up as.
A. white or silver speckles.
B. white powder traces.
C. black stains.
Explanation. CAIPs E L/3-10 refers. It also says titanium speckles are blue or gold.
297. An impulse/reaction turbine is designed to ensure.
A. greater axial velocity at the blade root.
10
B. uniform axial velocity from blade root to tip.
C. greater axial velocity at the blade tip.
Explanation. Jeppesen Gas turbine Powerplant page 3-40 refers.
298. Excessive turbine temperatures can lead to.
A. turbine blade creep and an increase in the diameter of the turbine.
B. not a serious problem as long as engine oil pressure is within limits.
C. a serious fire risk in the engine.
Explanation. Jeppesen gas turbine Powerplant Page 5-28 discusses the causes
ofcreep.
299. What are blue and golden deposits evidence of, on a turbine blade?.
A. Titanium.
B. Aluminium.
C. Magnesium.
Explanation. Aluminium and magnesium leave white powder deposits so by
elimination the answer is titanium.
300. Necking and mottling of turbine blades.
A. is due to thermal stress.
B. is formed during manufacture.
C. is due to bending when the gas hits the blades.
Explanation. Necking could occur due to creep which is a function of thermal
stress and centrifugal loads, and turbine blades do show signs of discolouration
after use,the latter is not normally a defect.
301. Impulse blades operate cooler than reaction blades because.
A. impulse blades rotate at higher speeds.
B. the N.G.V's cool the air.
C. the airflow has a higher velocity through a impulse turbine N.G.V.
Explanation. Impulse turbine N.G.Vs accelerate gases faster than their
reaction counterparts therefore the pressure and temperature is reduced more in
the impulseturbine.
11
302. During a borescope check of the H.P turbine blades.
A. dry motor the engine at minimum speed.
B. hand turn the turbine wheel.
C. attach a device to the accessory gearbox and rotate slowly.
Explanation. All large GTE have a hand turning tool adaptor fitted to the
accessoryor high speed gearbox.
303. The turbine section of a jet engine.
A. converts dynamic pressure into mechanical energy.
B. circulates air to cool the engine.
C. extracts heat energy to drive the compressor.
Explanation. The shape and size of the turbine blades determines the amount
ofenergy extracted from the dynamic pressure of the airflow.
304. The temperature and centrifugal loads which the turbine is subjected to during
normal engine operation causes.
A. fatigue failure.
B. elastic stretching.
C. creep loading.
Explanation. Creep is a permanent deformation caused by high centrifugal loads
atcontinuous high temperature.
305. Impulse-reaction turbine blades form.
A. tip half reaction, root half Impulse.
B. 1 stage impulse, 1 stage reaction.
C. tip half Impulse, root half reaction.
Explanation. Turbine blades move from impulse at the root to reaction at the
tip.
306. A fir tree root.
A. allows compressor cooling air to alleviate thermal stress.
B. attaches turbine blades to the turbine disk.
C. allows individual turbine blades to be changed without
enginedisassembly.
12
Explanation. Rolls Royce the Jet Engine Page 52 para 19 refers.
307. The passage between adjacent nozzle guide vanes forms a.
A. convergent duct.
B. divergent duct.
C. parallel duct.
Explanation. Rolls Royce The Jet Engine page 51 paragraph 13 refers.
308. As the hot gasses flow through an impulse turbine blading, the velocity.
A. will decrease.
B. remains constant.
C. will increase.
Explanation. In an 'Impulse bladed turbine' the turbine blades form parallel
ducts therefore the velocity will remain constant figure 5-5 of RR the Jet
Engine shows the contour of impulse turbine blades.
309. What is the normal range of turbine efficiency?
A. 90% - 95%.
B. 70% - 85%.
C. 30% - 40%.
Explanation. Rolls Royce The Jet Engine page 51 Para 11 refers to 92%.
310. Turbine engine components are never manufactured by.
A. electrical resistance welding.
B. argon arc welding.
C. gas welding.
Explanation. Both Argon arc and Electron beam welding are referred to in
RR the Jet Engine so we assume gas welding is not used, this is probably due
to carburisation of the weld.
311. How is a radial turbine driven?.
A. By impulse.
B. By change of momentum and angle of airflow.
13
C. By reaction.
Explanation. Radial turbines are effectively reversed centrifugal
compressors.
312. Turbine disk growth is due to.
A. a permanent change in disk diameter.
B. an overall increase in blade length.
C. a build up of carbon deposits.
Explanation. The turbine disc does not include the blades.
313. A nozzle guide vane is.
A. hollow in construction to allow for thermal expansion.
B. hollow in construction to allow for flow of cooling air.
C. solid in construction to support the guide vane.
Explanation. Air is tapped from the H.P compressor and passed through the
N.G.Vto cool it.
314. A slow constant growth in a turbine blade is known as.
A. primary creep.
B. secondary creep.
C. tertiary creep.
14
CHƯƠNG 6: ỐNG XẢ
315. The engine exhaust duct is another name for what?
A. Tailcone
B. Tailpipe
C. Exhaust nozzle
316. In what shape is the tailpipe of a business jet constructed?
A. Divergent
B. Convergent
C. Convergent-divergent
317. Subsonic aircraft with gas turbine engines installed will most likely have
what type of tailpipe?
A. Fixed area
B. Variable area
C. Variable geometry
318. What percentage of forward thrust will an engine in thrust reverser
mode be capable of producing?
A. 20 to 30
B. 30 to 40
C. 40 to 50
319. On the ground, the reverser is deployed when the engine is at what
power setting?
A. Idle
B. Cruise
C. Takeoff
320. What older engine type would most likely have a noise suppressor unit
installed?
A. Turboprop
B. Turbojet
C. Turboshaft
15
321. How would noise from the jet wake be described if it was not treated by
noise attenuating materials?
A. Low frequency, high decibel
B. High frequency, high decibel
C. Low frequency, low decibel
322. A turbine engine compressor case would most likely be made of what
type of construction material?
A. Cobalt
B. Aluminum
C. Nickel-alloy
323. Where would Inconel® most generally be used in a turbine engine?
A. Compressor blades
B. Compressor cases
C. Turbine blades
324. The righthand side of a turbine engine is at which of the following?
A. 9 o’clock
B. 6 o’clock
C. 3 o’clock"
325. The function of the exhaust cone assembly of a turbine engine is to.
A. swirl and collect the exhaust gases into a single exhaust jet.
B. collect the exhaust gases and act as a noise suppressor.
C. straighten and collect the exhaust gases into a solid exhaust jet.
326. A nozzle is 'choked' when the gas flow or air flow at the throat is.
A. sonic.
B. subsonic.
C. supersonic.
Explanation. Rolls Royce The Jet Engine page 14; refers.
16
327. The struts on the exhaust cone.
A. straighten the gas flow only.
B. support the exhaust cone and straighten the gas flow.
C. support the exhaust cone only.
328. A nozzle is 'choked' when the engine inlet airflow is.
A. subsonic.
B. supersonic.
C. subsonic or supersonic.
329. What is the maximum practical angle through which the gas flow can
be turned during thrust reversal?.
A. 180°.
B. 50°.
C. 135°.
Explanation. Rolls Royce The Jet Engine page 160 refers.
330. A supersonic duct is.
A. convergent then divergent along its length.
B. divergent then convergent along its length.
C. a convergent duct that is choked at the largest end at mach 1.
331. Noise from the jet wake when untreated by suppression is.
A. high frequency, high decibel.
B. low frequency, low decibel.
C. low frequency, high decibel.
332. Hot spots on the tail cone of a turbine engine are possible indicators of
a malfunctioning fuel nozzle or.
A. a faulty igniter plug.
B. an improperly positioned tail cone.
C. a faulty combustion chamber.\
17
333. 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. decrease and the velocity to increase.
C. increase and the velocity to increase.
334. A convergent-divergent nozzle.
A. requires the aircraft to be travelling at supersonic speeds.
B. makes maximum use of pressure thrust.
C. produces a type of thrust known as kinetic thrust.
335. The velocity of supersonic air as it flows through a divergent nozzle.
A. decreases.
B. increases.
C. is inversely proportional to the temperature.
336. The Jet Pipe of a gas turbine engine.
A. protects the airframe from heat damage.
B. has an inner cone to protect the rear turbine disc.
C. is convergent in shape to increase the velocity as much as possible.
337. For what purpose is the propelling nozzle of a gas turbine engine
designed?.
A. To increase the velocity and decrease the pressure of the gas
stream leaving the nozzle.
B. To decrease the velocity and increase the pressure of the gas
stream leaving the nozzle.
C. To increase the velocity and pressure of the gas stream leaving the
nozzle.
338. If the exit area of the nozzle was too large, the effect is.
A. exit velocity lower causing loss of thrust.
B. will choke at a lower gas temperature.
C. exit velocity lower, negligible effect on thrust.
18
339. A choked nozzle.
A. increases thrust.
B. decreases thrust.
C. has no effect on the thrust.
340. The exhaust section is designed to.
A. increase temperature, therefore increasing velocity.
B. decrease temperature, therefore decreasing pressure.
C. impart a high exit velocity to the exhaust gases.
341. Reverse thrust can only be selected when the throttle is.
A. closed.
B. 75% power position.
C. open.
Explanation. Rolls Royce The Jet Engine page 160 refers.
342. A Convergent-Divergent nozzle.
A. makes maximum use of Pressure thrust.
B. produces a type of thrust known as kinetic thrust.
C. requires the aircraft to be travelling at supersonic speeds.
Explanation. Jeppesen Gas Turbine Powerplants Page 3-49 refers.
343. On front fan engines, to obtain thrust reversal, the.
A. hot and cold streams are reversed.
B. hot stream is reversed.
C. cold stream is reversed.
Explanation. Rolls Royce The Jet Engine page 159 refers.
344. Exhaust noise can be reduced by.
A. lowering the vibration frequency.
B. increasing the mixing rate.
C. increasing the jet velocity.
19
345. Operating thrust reversers at low ground speeds can sometimes cause.
A. sand or other foreign object ingestion, hot gas re-ingestion.
B. hot gas re-ingestion, compressor stalls.
C. sand or other foreign object ingestion, hot gas re-ingestion,
compressor stalls.
Explanation. Jeppesen A&P Technician Propulsion Textbook 6-10.
346. Thrust reversers utilizing a pneumatic actuating system, usually
receive operating pressure from.
A. the engine bleed air system.
B. high pressure air reservoirs.
C. an on-board hydraulic or electrical powered compressor.
347. The purpose of cascade vanes in a thrust reversing system is to.
A. turn the exhaust gases forward just after exiting the exhaust nozzle.
B. form a solid blocking door in the jet exhaust path.
C. turn to a forward direction the fan and/or hot exhaust gases that have
been blocked from exiting through the exhaust nozzle.
348. A convergent exhaust nozzle produces mainly.
A. momentum and pressure thrust.
B. momentum thrust.
C. pressure thrust.
Explanation. Rolls Royce The Jet Engine Page 218.
349. The rearward thrust capability of an engine with the thrust reverser
system deployed is.
A. equal to or less than its forward capability, depending on ambient
conditions and system design.
B. less than its forward capability.
C. equal to its forward capability.
Explanation. Jeppesen A&P Technician Propulsion Textbook 6-10.
20
350. Which statement is generally true regarding thrust reverser systems?.
A. Engine thrust reversers on the same aircraft usually will not
operate independently of each other (must all be simultaneously).
B. It is possible to move some aircraft backward on the ground using
reverse thrust.
C. Mechanical blockage system design permits a deployment position
aft of the exhaust nozzle only.
Explanation. Jeppesen A&P Technician Propulsion Textbook 6-9.
351. What is the proper operating sequence when using thrust reversers to
slow an aircraft after landing?.
A. Advance thrust levers up to takeoff position as conditions require,
select thrust reverse, de-select thrust reverser, retard thrust levers to
ground idle.
B. Retard thrust levers to ground idle, raise thrust reverser levers as
required, and retard thrust reverser levers to ground idle.
C. Select thrust reverse, advance thrust reverser levers no higher than
75% N1, and retard thrust reverser levers to idle at approximately
normal taxi speed.
352. Most exhaust system failures result from thermal fatigue cracking in the
areas of stress concentration. This condition is usually caused by.
A. the high temperatures at which the exhaust system operates.
B. improper welding techniques during manufacture.
C. the drastic temperature change which is encountered at altitude.
353. Thrust reversal on a high bypass engine is achieved by.
A. blocker doors.
B. clamshell configuration.
C. bucket type doors.
354. If damage is found to the reverse thrust cascade vanes and they need
replacing, you can.
A. replace damaged vanes with 45 degree vanes.
B. only replace vanes with new ones that have the correct part as the
originals removed.
C. interchange the cascade vanes as they are interchangeable.
21
355. When should thrust reversers be used?.
A. At low RPM and low forward speed.
B. At high RPM and high forward speed.
C. At high RPM and low forward speed.
Explanation. Thrust reversers cannot be actuated if the throttles are set
above idle and they can only be used on the ground.
356. If the area of the nozzle was too large the effect is.
A. will 'choke' at mach 1.
B. exit velocity lower causing loss of the thrust.
C. exit velocity lower, negligible effect on thrust.
Explanation. Jeppesen Aircraft Gas Turbine Powerplant page 2-20 and
others.
357. Lobe type exhaust noise suppressors are made from.
A. heat resistant alloy.
B. composite Material.
C. steel.
Explanation. Rolls Royce The Jet Engine Page 205 refers.
358. What indication does the pilot receive that thrust reversers have
deployed?.
A. An audible warning.
B. A sequence of lights.
C. A feeling of rapid deceleration.
Explanation. Boeing 757/767 use the word 'rev' in amber for unlocked and
green for deployed on the upper EICAS screen.
359. What angle are the exhaust gasses turned through in a clamshell type
thrust reverser?.
A. 180 degrees.
B. 135 degrees.
C. 45 degrees.
22
360. The purpose of a propelling nozzle is to.
A. increase the velocity of the air and increase thrust.
B. decrease the velocity of the exhaust to increase static pressure.
C. direct the air onto the turbines.
Explanation. The convergence of the propelling nozzle in a subsonic pure jet
engine is set so that max speed is just below Mach 1.
361. If a thrust reverser is deployed at lower than normal landing speed.
A. exhaust gases can be ingested into the engine.
B. the thrust reverser will be ineffective.
C. if the EGT gets too high the thrust reverser will automatically
restow.
Explanation. Exhaust gas ingestion is a problem for thrust reverser systems
when stationary or very slow.
362. The size of the exhaust section is dictated by.
A. cone or diffuser size and location.
B. size of engine only.
C. size and location of the engine.
Explanation. The exhaust section is of a certain diameter and can be of
different lengths depending on the location of the engine within the fuselage
or wing root (IE English Electric Lightning).
363. On a Clamshell door type thrust reverser. The Clamshell doors redirect
the exhaust gas stream.
A. 0 degrees to the thrust line.
B. 45 degrees to the thrust line.
C. 90 degrees to the thrust line.
Explanation. 45 degrees to the thrust line is an alternative to 'turned through
135 degrees'.
364. Normal gas turbine engine's exhaust duct is.
A. divergent.
B. convergent/divergent.
C. convergent.
23
Explanation. The exhaust nozzle consists of a parallel duct then the
propelling nozzle which is always convergent.
365. As the air flows out at the outflow of a choked nozzle.
A. velocity increases and pressure decreases.
B. velocity and pressure decrease.
C. velocity decreases and pressure increases.
Explanation. A choked nozzle has a shock wave in it and air is at Mach 1.
After the shock the air must be decreased in speed and pressure is rising.
366. Main bearing oil seals used with turbine engines are usually what
type(s)?.
A. Teflon and synthetic rubber.
B. Labyrinth and/or carbon rubbing.
C. Labyrinth and/or silicone rubber. Explanation. Jeppesen A&P
Powerplant Textbook 3-5.
367. If, during inspection at engine overhaul, ball or roller bearings are
found to have magnetism but otherwise have no defects, they.
A. are in an acceptable service condition.
B. cannot be used again.
C. must be degaussed before use.
Explanation. Jeppesen A&P Powerplant Textbook 4-26.
368. A carbon seal has which type of sealing arrangement?.
A. Full contact with race.
B. Full contact with casing.
C. Full contact with labyrinth.
Explanation. Rolls Royce The Jet engine page 92 refers.
369. The highest turbine bearing temperature takes place.
A. all the time.
B. at start-up.
C. at shut-down.
24
370. The function of a labyrinth seal is to create.
A. a restricted leakage of air between fixed and rotating components.
B. an airtight seal between fixed and rotation components.
C. an airtight seal between fixed adjacent casing surfaces.
Explanation. Jeppesen Gas Turbine Powerplants Page 5-36 Refers.
371. The bearings of a compressor rotor are usually.
A. ball and roller.
B. plain.
C. sintered.
Explanation. Jeppesen Gas Turbine Powerplant Page 4-49/50 refers.
372. Bearing seal failure would most probably cause.
A. high oil temperature.
B. high oil consumption.
C. low oil pressure.
Explanation. Jeppesen Gas Turbine Powerplants Page 5-36 refers.
373. Why are oil seals pressurised?.
A. To ensure minimum oil loss.
B. To ensure oil is forced into the bearings.
C. To ensure that the oil is prevented from leaving the bearing
housing.
Explanation. Pressurised labyrinth seals stop oil leaking out of the bearing
housing between rotating shafts and stationary casing. Note that oil is always
scavenged out of theses housings therefore answer c must be wrong.
374. What bearing is used to take axial loads on a main rotation shaft of a
gas turbine engine?
A. Plain bearing.
B. Roller bearing.
C. Ball bearing.
25
375. Seals on a gas turbine engine restrict leakage of oil by.
A. spring pressure.
B. closely tolerated contacting components.
C. air pressure.
376. An abradable lining in the fan case.
A. prevents fan blade tip rub.
B. produces less leakage at tips for anti-ice.
C. provides acoustic medium.
Explanation. The prime purpose is to optimise fan performance, but it is also
an acoustic lining.
377. Squeeze film bearings are usually found on.
A. H.P compressor section.
B. the turbine section.
C. LP compressor section.
378. Taper roller bearings accept loads in which direction?.
A. Axial loads only.
B. Radial and axial in both directions.
C. Radial and axial in one direction only.
379. Some labyrinth seals.
A. control the outflow of air at the turbine.
B. are self lubricating.
C. are spring loaded.
Explanation. Labyrinth seals can be air seals as well as oil seals.
380. The purpose of 'squeeze film' type bearing is to.
A. increase the flow of oil to the rolling element.
B. minimise the effect of vibration.
C. improve outer race cooling.
26
381. In a jet engine the rotating assembly oil seals are maintained oil tight by
means of.
A. a garter seal.
B. an annular expander ring.
C. air pressure.
Explanation. Air pressure acts across a labyrinth seal to hold the oil in the
bearing chamber.
27
