Topic 06 - Reverse Thrust, Thrust Augmentation, and Auxiliary Power Units

Question 1

the addition of a __________________ capability has improved the aircraft handling to the extent that landing a modern aircraft on a wet and/or icy runway in crosswind conditions is relatively straight forward

Answer 1

reverse thrust

Question 2

the usual method of operating the reverse thrust system is to select it _________________ as the weight of the aircraft is firmly on the main wheels or during ________________

Answer 2

immediately, touchdown

Question 3

three basic thrust reversal systems in use

Answer 3

• clamshell doors
• bucket doors (external doors)
• blocker doors

Question 4

all types of basic thrust reversal systems operate either ________________ or ___________________

Answer 4

hydraulically, pneumatically

Question 5

the reverse thrust system turn thrust into which direction?

Answer 5

direction of the drag

Question 6

in the clamshell doors system, the reverser doors are usually ____________________ and uses _________________________ as its power source

Answer 6

pneumatically operated, high pressure compressor air

Question 7

__________________ move the reverser doors from their stowed (forward thrust) position to their deployed (reverse thrust) position

Answer 7

pneumatic rams

Question 8

in their stowed position, the clamshell doors _______ ‘cascade vanes’, which are ___________ when the doors move to the deployed state

Answer 8

cover, revealed

Question 9

while deployed, the clamshell doors shut off the _______________________, forcing the gas to escape through the ______________ in a forward direction, so that the forward motion of the aircraft is opposed by the reverse thrust generated

Answer 9

normal exhaust gas exit, cascade vanes

Question 10

why do the lower cascade vanes aim the exhaust at an angle instead of pure forward motion?

Answer 10

to minimize the chances of debris and hot gases to be re-ingested into the engine intake during the use of reverse thrust

Question 11

the ‘bucket reverser’ system is normally ______________ operated

Answer 11

hydraulically

Question 12

in a bucket reverser system, the ____________________ is shaped like two halves of a bottomless bucket, hinged to enable them to swing _____________ when selected, deflecting the exhaust gas forward

Answer 12

rear portion of the engine exhaust pipe, rearwards

Question 13

another name for blocker reversers

Answer 13

cold stream reverser

Question 14

type of basic thrust reversal system that is only used on high bypass ratio fan jet engines

Answer 14

cold stream reverser or blocker system

Question 15

the essential difference between the blocker system and both the clamshell door and bucket reversing systems

Answer 15

while the latter use the hot exhaust as the means of reverse thrust, the blocker system blocks and diverts the cold bypass air stream only

Question 16

operation of all thrust reverser systems is initiated by movement of ________________ in the cockpit where each engine with a reverse thrust capability has it

Answer 16

reverse thrust levers

Question 17

in the case of a blocker system, the speed and direction of an ‘____________’ is determined by operation of the reverse thrust lever

Answer 17

air motor

Question 18

the output of the air motor
drives flexible shafts which
______________ the blocker
doors, which by their movement, either expose or cover _________________, which direct the bypass air where it is required

Answer 18

open or close, cascade vanes

Question 19

some form of warning is fitted so that the pilot has information about the position of reverser doors where the warning can be ___________________ positioned somewhere on the ____________________, or __________________________

Answer 19

amber lights, forward instrument array, captions which appear on the ECAM system

Question 20

meaning of ECAM

Answer 20

electronic centralized aircraft monitoring

Question 21

the warnings will be shown whenever the reverser doors are ______________ and away from their __________________

Answer 21

unlocked, ‘stowed’ (forward thrust) position

Question 22

_____________ have to be built into the reverse thrust system which will protect the aircraft in case of a malfunction or incorrect handling

Answer 22

safeguards

Question 23

five safeguards built into the selection of reverse thrust

Answer 23

1. reverse thrust cannot be selected on an engine until the throttle lever of that engine is at idle
2. reverse thrust cannot normally be activated on an aircraft until that aircraft has its weight on the main wheels
3. with reverse thrust selected, engine power cannot be increased above idle power until the reverse thrust doors are in the deployed (reverse thrust) position
4. if, while forward thrust is selected, the reverser doors inadvertently move to the deployed (reverse thrust) position, the throttle will automatically close to idle
5. if, while the reverse thrust is selected, the reverser doors inadvertently move to the stowed (forward thrust) position, the reverse thrust lever will automatically go to the reverser deploy position

Question 24

types of thrust augmentation

Answer 24

• water injection system
• afterburning

Question 25

in conditions of high altitude and/or high ambient temperature, the use of a water injection system can restore the thrust of a ____________ engine, and boost the output of a _____________ engine

Answer 25

turbojet, turbo-propeller

Question 26

the power output of a gas turbine engine depends upon the __________ flowing through it and its ____________

Answer 26

mass of air, acceleration

Question 27

in conditions of high altitude and/or high ambient temperature, the density of the airflow through the engine, and therefore the mass of that airflow, _____________, causing a ____________ of engine power output

Answer 27

decreases, reduction

Question 28

water injection system: to restore, or as is sometimes the case, boost, the power output of an engine, the airflow passing through that engine can be cooled by ________________ into it

Answer 28

spraying water

Question 29

the amount of water carried for use in these water injection systems can be large, approximately __________________ of water per engine, which had to be all used up during a __________________________

Answer 29

300 gallons, three-minute takeoff and climb

Question 30

what is the water flow rate for a water injection system?

Answer 30

100 gal/min

Question 31

the fuel flow through each engine at takeoff was _________________, or approximately ______________ for water injection systems

Answer 31

9,000 lb/hr, 22 gal/min

Question 32

water to fuel flow ratio through the engine during 3 min takeoff and climb when the water injection was being used

Answer 32

4.5:1

Question 33

for a typical early design turbojet engine, 100% of power continues to be available, even up to ________, which is ___________ and at ambient temperatures higher than this, the power available __________

Answer 33

25°C, ISA + 10°, drops off

Question 34

the reason for limiting the thrust restoration of the turbojet to that of its rated performance is that although the airflow mass could be increased by increasing the ______________, the maximum compressor outlet pressure has to be limited to prevent the engine compressor case ___________, under the excessive pressures generated by using such a procedure

Answer 34

compressor speed, splitting

Question 35

for a typical early design turbo-propeller engine the power output has been boosted by ______ when a power augmentation system is operated

Answer 35

15%

Question 36

in the case of the turboprop engine, if the water is injected into the _______________, the mass flow through the engine is ______________ relative to that flowing through the compressor

Answer 36

combustion chamber, increased

Question 37

in the turboprop engine, the increased mass flow through the turbine is not used to increased ________________ and its _______________

Answer 37

compressor RPM, output pressure

Question 38

in the turboprop engine, the increase in mass flow is absorbed by ________________ to increase the mass of air being thrust rearwards, while maintaining the engine rotational speed at no more than the _____________

Answer 38

coarsening the propeller pitch, normal maximum

Question 39

some centrifugal compressor engines, and some small American designed axial flow compressor engines, used a system of injecting the water into the _____________ where the water distribution was not of the best, and the quantity of water injected had to be limited, so as not to cause an ______________

Answer 39

engine intake, engine flame out

Question 40

injection of water into the combustion chamber _____________ the mass flow through the turbine relative to that through the compressor

Answer 40

increases

Question 41

because a relatively lower level of energy is being extracted from the turbine, even though there is an increased mass flow through it, there is a related decrease in the amount of ____________ and ____________________ across the turbine meaning that there is an ___________ in the amount of energy available either ____________ the turbine

Answer 41

pressure, temperature dropped, increase, at or after

Question 42

the extra amount of energy available at or after the turbine can be used to generate extra thrust, either by driving the propeller at a _______________, in the case of a turboprop engine or, in case of turbojet engine, by __________________________

Answer 42

coarser pitch, increasing the pressure at the propelling nozzle

Question 43

a pure water injection system does have some drawbacks, not least because the water must all be used up on takeoff if it is not to __________________ as the aircraft climbs to altitude

Answer 43

freeze in the tanks

Question 44

the injection fluid should not freeze, thus, ____________ is added to the water which serves primarily as an ________________

Answer 44

methanol, anti-freeze

Question 45

by injecting __________ into the combustion chamber, the turbine gas temperature is lowered dramatically

Answer 45

coolant

Question 46

lowering the turbine gas temperature would _________ the amount of power potentially available, because the turbojet is a ___________ which relies on there being a large temperature drop across its turbine

Answer 46

lower, heat engine

Question 47

the bonus obtained by using methanol in the injection system is that because it is an alcohol fuel, and thus, ________ to the temperature of the gases, raising the ______ back to its original level

Answer 47

adds, TGT

Question 48

in order to regulate the amount of heat added, the quantity of water methanol injected into the engine must be carefully regulated, this is done by a ________________________

Answer 48

water methanol control system

Question 49

the proportion of methanol added to the water must also be carefully controlled with a ratio of ______ methanol and ______ water (by volume) ensures that the TGT limits should never be exceeded during use of the water methanol system

Answer 49

40%, 60%

Question 50

thrust augmentation by ______________, or as it is sometimes called, _________, makes use of the unburnt oxygen which remains in the engine exhaust gases, to release more heat energy

Answer 50

afterburning, reheat

Question 51

afterburning is achieved by injecting fuel somewhere between the ___________ and the _________________ and burning it

Answer 51

turbine, propelling nozzle

Question 52

_______________ is used to improve takeoff, climb, and combat performance whose use is mainly restricted to military aircraft

Answer 52

afterburning

Question 53

in afterburning, what is used to ignite the unburnt oxygen and fuel mixture after the combustion chamber?

Answer 53

electric or catalytic igniter plug

Question 54

while afterburning is mainly restricted to military aircraft, the one notable exception was ___________, which was the only passenger carrying aircraft using ________________

Answer 54

Concorde, four high ratio turbojets with afterburners

Question 55

fuel is introduced into the jet pipe through ______________ centrally disposed around the axis of flow that enables cooler turbine discharge gas to flow along the ___________, to cool the jet pipe which is required because the afterburner temperature may be in excess of _________

Answer 55

discharge nozzles, jet pipe walls, 1,700 ° C

Question 56

an afterburning jet pipe is fitted with a ________________, the area of which is restricted during ______________________, and is opened fully to allow for the increased volume of gas which is produced during the _________________

Answer 56

variable area propelling nozzle, non-afterburning operation, afterburning operation

Question 57

the operation of the afterburner is usually initiated by the pilot moving the ____________ through a ________________

Answer 57

throttle lever, detent or ‘gate’

Question 58

control of the nozzle is _____________ and when the fuel from the afterburner is ignited, the pressure in the jet pipe, which is called the _____________, will __________

Answer 58

automatic, P6 pressure, increase

Question 59

igniting fuel from the afterburner causes a change in pressure ratio across the turbine where the pressure before the turbine is commonly called ________________, so the pressure ratio across the turbine is ___________

Answer 59

P3 pressure, P3 to P6

Question 60

the variable area propelling nozzle is automatically opened so as to restore the correct ____________

Answer 60

P3:P6 ratio

Question 61

because of low flame rate, the velocity of the gas stream through the afterburner must be also reduced by using a ____________ which is positioned _____________ the afterburner section

Answer 61

diffuser, before

Question 62

the increase in thrust obtained due to the use of an afterburner depends entirely upon the ________________________, before and after the extra fuel is burnt

Answer 62

ratio of the absolute jet pipe temperatures

Question 63

the increase in velocity of the gas stream in the jet pipe is equal to the ________________

Answer 63

square root of the temperature ratio

Question 64

the fuel consumption goes _________________ when the afterburner is selected, so its use is normally limited to _____________ only

Answer 64

up dramatically, short periods

Question 65

the first recorded use of an APU was on a scout aircraft, ______________, in the _________________

Answer 65

Night Hawk, Great War in 1916

Question 66

for the first recorded use of an APU, a ___________________ was used in this

Answer 66

gasoline fueled piston engine

Question 67

because of the APU, the aircraft was no longer dependent on ___________________________

Answer 67

expensive ground support equipment

Question 68

the APU can provide necessary power for operation of an aircraft’s ____________, ___________, and ___________ systems

Answer 68

electrical, hydraulic, pneumatic

Question 69

unlike the main engine, APUs are ______________ to the propulsion system and does not produce thrust to drive the aircraft forward, instead they generate ______________ and in some cases, _______________ for various systems such as for air-conditioning

Answer 69

not connected, electrical power, compress air

Question 70

while earlier aircraft used the ____________ to drive their APUs, it soon became obvious that the __________________ was safer, lighter, quieter, and more reliable

Answer 70

piston engine, gas turbine engine

Question 71

the gas turbine engine APU uses the ______ fuel as the main engines use, so the problem of fuel storage and fuel management systems is _______________

Answer 71

same, minimized

Question 72

the type of gas turbine engine normally used to drive APUs isa ___________ engine with a ___________ which drives the accessories via a ___________

Answer 72

turboshaft, free turbine, gearbox

Question 73

some aircraft use air bled from the APU’s compressor to power the aircraft’s _______________, but it is also common for the ____________ to drive a separate load compressor to supply bleed air

Answer 73

pneumatic system, free turbine

Question 74

the APU is normally positioned in the ____________ where its operation will not harm personnel working in proximity to the aircraft

Answer 74

tail of the aircraft

Question 75

the APU of modern aircraft can be operated in the air, thus providing a ____________________ to the aircraft systems in the event of an _____________

Answer 75

back-up source of power, engine failure

Question 76

the ability of the APU to operate while airborne has become more important with the introduction of _________________ which are now flying long haul routes under ETOPS regulations

Answer 76

twin engine aircraft,

Question 77

ETOPS abbreviation meaning

Answer 77

extended twin operations

Question 78

while other aircraft APUs may or may not have the ability to be started while the aircraft is in flight, ETOPS compliant aircraft APUs must be capable of being started at _____________

Answer 78

all altitudes

Question 79

what is ETOPS?

Answer 79

aviation regulation concerning long distance routes that are more than 60 mins from the nearest suitable airport

Question 80

what happens when ETOPS compliant aircraft APUs malfunction?

Answer 80

the aircraft cannot be released for ETOPS flight and must fly a longer route

Question 81

the APU’s turboshaft engine is started by an _____________ powered from the _________, although some later model have a ____________________ to preserve the aircraft batteries

Answer 81

electric starter motor, aircraft battery, dedicated auxiliary power unit battery