A FADEC on a gas turbine engine ?
Registration > lift > off
When a turbo prop aeroplane decelerates during the intial part of the landing roll a constant speed propeller within the beta range ?
Most high bypass unmixed turbofan engines are equipped with a cold exhaust reverser fan reverser only in order to ?
A booster or lp compressor in a twin spool turbofan Rotates at same rotor speed as fan, rotates at same rotor speed as hp turbine, rotates at a rotor speed different from both fan, hp compressor hp turbine, rotates at same rotor speed as hp compressor. If engine a twin spool turbofan, it highly likely that there will be a hp compressor, lp compressor, a fan. the lp comp the fan will be driven from same turbine, on same shaft, will therefore be at same speed. 
The function of swirl vanes round fuel nozzles to 1 increase air pressure at fuel nozzles 2 reduce average axial flow speed in order to stabilise flame front 3 generate a swirl of incoming air to enhance mixing of fuel with air the combination that regroups all of correct statements 2, 3,, 2,, 2, 3, only. 
The take off of a jet aeroplane may be performed with 'reduced thrust' in order to Reduce maintenance costs, save fuel, reduce take off noise, reduce risk of engine failure during take off. 
In an ignition system during a normal start of a gas turbine engine igniter activation Should commence prior to fuel entering combustion chamber, should commence after fuel has entered combustion chamber, should commence prior to starter motor engagement to prevent a hot start, commences upon starter motor engagement, is deactivated at a rotor speed of approximately5% below idle rpm. Question Turbine Engines 34 Answer 8
A gas turbine engine r at ground idle a period of time prior to shutdown to Prevent seizure of rotor blades in their seals, prevent vapour lock in fuel control and/or fuel lines, prevent seizure of engine bearings, allow engine oil to cool. This allows to gas generator the power turbine discs more time to cool than if engines were immediately shut down. the danger that rotor will cool (and will shrink) more rapidly than blades, they could be seized in their seals. Question Turbine Engines 34 Answer 9
The purpose of variable pass valves in a high bypass turbofan engine between lp compressor and hp compressor hpc to Prevent fan stall lp compressor stall during engine start low rotor speeds, provide sufficient air to hp compressor during engine start, prevent fan surge at high rotor speeds (high rpm), prevent hp compressor stall during engine start. A bypass valve another name a bleed valve. it can also be called a blow off valve, anti stall valve, or an acceleration valve. Question Turbine Engines 34 Answer 10
If a gas turbine engine fuel/oil heat exchanger located downstream of hp fuel pump internal leakage of heat exchanger will cause oil level to Rise, rise the fuel nozzles eventually to become clogged, fall, fall the oil jets eventually to become clogged. The oil in fuel/oil heat exchanger (located in tanks) always at a higher pressure than fuel, but question states located downstream of hp fuel pump , so it a secondary fuel/oil heat exchanger in order to avoid fuel icing in fuel regulation system. in this heat exchanger you will have high pressure fuel relatively low pressure oil so any internal leak will transfer fuel to oil system, raising indicated oil level. Question Turbine Engines 34 Answer 11
The compressor pressure ratio of an axial flow compressor primarily determined the Number of stages, rotor diameter, compressor inlet temperature design value, compressor inlet pressure design value. Question Turbine Engines 34 Answer 12
In a theoretical gas turbine cycle combustion takes place at constant Pressure, energy, temperature, volume. Question Turbine Engines 34 Answer 13
When a gas turbine engine accelerates from idle to take off thrust and compressor rpm too high in comparison with air inlet velocity this may result in A compressor stall, stagnation, supersonic airflow at compressor blade trailing edges, a compressor blade airflow angle of attack that too small. Like stall of a wing, compressor stall caused a breakdown of airflow. a compressor stall most likely to occur when air flow stagnates in rear stages of compressor. a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow. when incoming speed low angle of attack will be high. when angle of attack gets too high blade stalls. so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow). you can prevent this dumping some late stage air to atmosphere (via bleed valves). Question Turbine Engines 34 Answer 14
Which of following parameters remains constant in a divergent subsonic gas turbine engine intake Total temperature, static pressure, dynamic pressure, static temperature. Question Turbine Engines 34 Answer 15
The most favourable conditions to apply flexible take off procedure are 1 high take off mass2 low take off mass3 high outside temperature4 low outside temperature5 high atmospheric pressure6 low atmospheric pressurethe combination grouping all correct answers 2, 4, 5,, 3, 5, 2, 3, 6, 2, 4, 6. Question Turbine Engines 34 Answer 16
Assuming jet pipe not choked equation to calculate jet engine thrust t with mass flow m airspeed vv and jet velocity vj T = m(vj vv), t = m(vv vj), t = m(vv + vj), t = mvj Question Turbine Engines 34 Answer 17
Given p0 = static ambient pressure t0 = static ambient temperaturem = air mass flowvv = true air speedvj = jet efflux exhaust velocitypj = jet efflux exhaust static pressuretj = jet efflux exhaust static temperaturea = exhaust cross sectional areathe thrust t of a jet engine T = m(vjvv ) + a(pj p ), t = m(vvvj ) + a(t jt ), t = m(vvvj ) + a(pj p ), t = m(vj vv ) + a(tj t ). Thrust = air mass flow.(jet exhaust velocity true air speed) + exhaust cross sectional area.(jet exhaust static pressure static ambient pressure) thrust equal to change in momentum of air entering leaving (it measured the acceleration of air through engine). Question Turbine Engines 34 Answer 18
The axial compressor of a gas turbine engine usually has more stages than its driving turbine because The power output of a turbine stage higher than power consumption of a compressor stage, compressor consumes much more power than turbine, bleed air taken from compressor, turbine speed much higher than compressor speed. Question Turbine Engines 34 Answer 19
On a fadec gas turbine engine during normal flight power the fadec's sensors comes from The fadec power source(s) on engine, aircraft battery, aircraft generator, apu generator. The fadec has its own independent power supply (generator), which separate from aircraft generator to ensure that fadec system has electrical power as long as engine running, regardless of any problems or faults with aircraft system. Question Turbine Engines 34 Answer 20
In a gas turbine combustion chamber Secondary air required cooling of inner casing, gas pressure increases in an axial (downstream) direction, axial velocity of gas stream greatest behind swirl vanes, gas temperature highest at chamber outlet. The combustion system's purpose to provide a smooth stream of uniformly heated gas, with least loss of pressure the maximum release of heat. the combustion chamber made from two tubes. one the flame tube, which inside air casing, between two an air gap, through which any air that does not go into combustion chamber passes (secondary air). air enters combustion chamber at around 500 ft/sec, is diffused to around 80 ft/sec. even at this speed, slow flame (at 1/2 ft/sec) would be blown away, so a region of low pressure created round it to keep it alright. Question Turbine Engines 34 Answer 21
If there a single input data failure on a fadec gas turbine engine The engine continues to operate normally, engine stops, engine set at a fail safe thrust, electronic engine control unit uses a constantdata value computation. Question Turbine Engines 34 Answer 22
Concerning fuel system high pressure shut off valve hpsov of a gas turbine engine Ignition activated before fuel delivered the hpsov to fuel nozzles, hpsov located between hp fuel pump the fuel control unit, manual hpsov control from cockpit not possible with fadec equipped engines, hpsov mounted in wing front spar near pylon. Question Turbine Engines 34 Answer 23
Derated or reduced take offs save engine life primarily due to Reduced low cycle fatigue damage, maximum oil temperature not being exceeded, reduced corrosion of hp turbine blades, reduced creep damage due to higher egt levels during take off. Low cycle fatigue where stress high enough deformation to occur. this deformation will occur in turbine since it most sensitive to high temperatures. Question Turbine Engines 34 Answer 24
The diagram shown in annex represents a twin spool turbofan positions before and after air intake are located at numbers 1054 Question Turbine Engines 34 Answer 25
What the average compression ratio of a centrifugal compressor axial compressor radial compressor a centrifugal compressor will provide a compression ratio of 5 1 per stage (maximum), which relatively high compared to an axial compressor that achieves a ratio of only 1.2 1 per stage. Question Turbine Engines 34 Answer 26
If engine compressor air bled off engine anti icing or a similar system turbine temperature Will rise, will be unchanged, may rise or fall depending on which stage of compressor used the bleed the rpm of engine at moment of selection, will fall. Gorny21 the ratio of tertiary airflow around combustion flame tube that cools turbine decreases, thus less cooling flow as warm air diverted anti icing so egt will increase as a result. Question Turbine Engines 34 Answer 27
Increasing frequency of variations in thrust setting during normal operation detrimental to life of hp turbine blades because Low cycle fatigue damage more severe, egt limit would be exceeded more often, fatigue due to vibration more severe, creep will be more severe. It commonly known that a metal subjected to repetitive or flunctuating stress will fail at a stress much lower than its ultimate strength. failures occuring under cyclic loading are generally termed 'fatigue'. the endurance of gas turbine engine to high temperature particularly marked the creep resistance of hp turbine blade alloy. in turbine engines, low cycle fatigue generally caused repeated loading cycles caused operation (i.e. starting or takeoff conditions). if a turbine blade goes through one takeoff max power setting, it may be fine. if it subjected to 8000 of them, it may fail due to fatigue. Question Turbine Engines 34 Answer 28
An axial compressor when operating below its design speed has A tendency to stall in front stages, a tendency to stall in rear stages, a tendency to stall in centre stages, no tendency to stall. axial compressor radial compressor the stall of a blade occurs in same way as a wing stalls, if angle of attack exceeds a set value blade/wing will stall. the first stage of blades on a compressor are rotor blades. when it turns, air push rearwards increasing velocity onto blades behind, but also pressure. if horizontal flow low it results in a large angle of attack, as this most likely at front of compressor, it will tend to stall at front. Question Turbine Engines 34 Answer 29
The compressor blades in a rotating gas turbine engine are held in position The mountings the resultant of aerodynamic centrifugal forces, abradable seals aerodynamic forces, a centrifugal latch, mountings thermal expansion only. Question Turbine Engines 34 Answer 30
Some gas turbine engines have multiple stages in hp and lp turbines Because one stage does not generate sufficient shaft power, to facilitate balancing of turbine assembly, to help stabilise pressure between compressor the turbine, to reduce noise in propelling nozzle. Question Turbine Engines 34 Answer 31
In which part of a gas turbine engine are high temperature requirements most critical the materials used The combustion chamber front part of hp turbine, the last part of hp compressor front part of hp turbine, the turbine exhaust nozzle, the combustion chamber exhaust nozzle. Usually titanium alloy the material used the combustion chamber high pressure turbine. Question Turbine Engines 34 Answer 32
A twin spool engine with an inlet air mass flow of 500 kg/s and a hp compressor mass flow of 250 kg/s has a bypass ratio of bypass ratio = bypass mass flow / hp compressor mass flow 500 250 = 250 250 / 250 = 1 Question Turbine Engines 34 Answer 33
A 'fan' stage of a ducted fan turbine engine driven The low pressure turbine, airflow drawn across it the high pressure compressor, high pressure compressor through reduction gearing, high pressure turbine. Question Turbine Engines 34 Answer 34
The oil supply to gas turbine engine bearings maintained in event of main oil filter becoming clogged Differential pressure opening bypass valve of main oil filter, hp fuel pump, scavenge pumps, a back up oil system. Question Turbine Engines 34 Answer 35
One of purposes of compressor bleed valves to Decrease airflow across rear compressor stages, whilst that across early stages increased, limit acceleration period of engine, increase airflow across rear compressor stages, whilst that across early stages decreased, decrease load on compressor when engine approaching maximum rpm. Bleed valves are fitted to prevent compressors stalling. like stall of a wing, compressor stall caused a breakdown of airflow. the bleed valve removes excesss volume of air at low compressor speeds to increase flow over front compressor blades reduce flow over latter stages. as speed of compressor increases bleed valve closes. Question Turbine Engines 34 Answer 36
Turbine blade stages may be classed as either 'impulse' or 'reaction' in an impulse blade section pressure i across nozzle guide vanes ii across rotor blades (i) drops (ii) remains constant, (i) rises (ii) remains constant, (i) remains constant (ii) drops, (i) remains constant (ii) rises nozzle guide vanes = stator. the pressure drops across stator blades remains constant across rotor blades. Question Turbine Engines 34 Answer 37
One advantage of having three instead of two spools in some high bypass turbofan engine that Fewer variable stator vanes variable inlet guide vanes are required to prevent compressor stall at low rotor speeds, fewer variable stator vanes variable inlet guide vanes are required to prevent compressor stall at high rotor speeds, there a lower fuel consumption due to a higher overall pressure ratio, there a lower fuel consumption more thrust due to higher overall pressure ratio. Variable inlet guide vanes (v.i.g.v.s) are fitted to engines which have a particular problem with inherent compressor stall at low rpm or during engine acceleration or deceleration. the vanes are fitted just in front of first rotor stage, they can be automatically pivoted around their own axis to vary path of airflow going into compressor, so maintaining proper relationship between compressor rotational speed airflow in front compressor stages. at low compressor speeds v.i.g.v.s are angled to impart greatest amount of swirl to air, thereby correcting relative airflow to obtain optimum angle of attack over rotor blades. this optimum angle of attack allows a smooth rapid engine acceleration. on a three spools high bypass turbofan engine, an additional intermediate pressure compressor stage added reduces risk of compressor stall at low rotor speeds. Question Turbine Engines 34 Answer 38
The compressor surge effect during acceleration prevented the Fuel control unit (f.c.u.), variable setting type nozzle guide vanes, surge bleed valves, inlet guide vanes. With modern engines there are various ways to control surge, one of them the use of blow off valves (also called compressor bleed valves). on all modern turbine engines with electronic fuel control systems valves are controlled the fuel control unit. the end result will be that blow off valve will reduce pressure in compressor to prevent surge. Question Turbine Engines 34 Answer 39
Creep in a gas turbine engine The permanent increase in length of metal parts due to a combination of tensile stress high temperatures over a prolonged period, expansion of metal parts due to temperature increase, elastic increase in length of metal parts due to tensile stress high temperatures, crack formation in metal parts due to cyclic mechanical loads high temperatures. Question Turbine Engines 34 Answer 40
About a twin spool compressor The low pressure spool runs at a lower rpm than high pressure spool, both spools run at same rpm, the low pressure spool runs at a very high rpm, thus preventing onset of compressor stall, when operating at very high rpm's, later stages within high pressure spool will have a large negative angle of attack.
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