JET ENGINE PROPULSION – TYPICAL EXAMINATION QUESTIONS
In 1930, who first patented a design for a reaction (jet) type motor suitable for aircraft propulsion?
a)Sir Frank Whittle
b)Sir Henry Royce
c)Hon. Charles Rolls
d)Henry Ford
What is the operating cycle sequence for a jet engine
a)Induction, compression, combustion, exhaust
b)Induction, combustion, compression, exhaust
c)Combustion, induction, compression, exhaust
d)Induction, compression, exhaust, combustion
A simple jet engine is made up of four main sections, what are these four main sections called?
a)The compressor, combustor, turbine and exhaust
b)The compressor, fuel pump, oil pump, and turbine
c)The intake, fuel pump, oil pump, and turbine
d)The intake, compressor, turbine, and mounts
How is the thrust of a jet engine determined?
a)By the mass air flow and jet pipe pressure
b)By the mass air flow and velocity
c)By the air temperature and velocity of the mass airflow
d)By the change in velocity of hte mass airflow
Compressors
How is the compression ratio of a jet engine determined?
a)By the diameter of the compressors
b)By the length of the compressors
c)By the diameter between atmospheric pressure and compressor outlet pressure
d)By dividing compressor outlet pressure by atmospheric pressure
A jet engine's compressor is driven by:
a)The gearbox
b)The turbine
c)Air pressure at the air intake
d)Residual pressure in the tailpipe
What is an advantage centrifugal compressors have compared to axial flow compressors?
a)There are fewer parts in a centrifugal compressor
b)Centrifugal compressor never surge
c)Centrifugal compressor are cheaper to make
d)All of the above
Combustion
Approximately how much of the airflow through the combustion section is used for combustion?
a)82%
b)43%
c)92%
d)18%
Approximately how much of the combustion energy is used for thrust?
a)82%
b)40%
c)60%
d)18%
Which part of a jet engine produces the energy for thrust?
a)The compressors
b)The combustors
c)The turbine
d)The Exhaust
What is a disadvantage that individual can type and can-annular type combustion chambers have?
a)The turbine gas flow can be slower
b)Turbine blade temperature fluctuations can occur
c)They are very difficult to start, accelerate, decelerate and stop
d)Turbine speed can be lower
What type of combustion chambers did the Whittle type jet engines have?
a)Annular type combustion chambers
b)Can-annular type combustion chambers
c)Individual can type combustion chambers
d)Continual type combustion chambers
Turbine
A turbine is made up of a number of stages, each stage consisting of nozzle guide vanes (NGV's) and rotor blades. How are these arranged?
a)NGV's are on top of rotor blades
b)Rotor blades are on top of NGV's
c)NGV's are in front of rotor blades
d)Rotor blades are in front of NGV's
The function of the turbine in a turbojet engine is to?
a)Energise the gas stream
b)Drive the compressor
c)Drive the gas stream into the atmosphere
d)Vaporise the fuel as much as possible
The jet engine turbine is a series of convegent and divergent ducts. What happens to pressure, temperature and velocity of the air passing through a divergent duct?
a)Presure increases, temperature reduces, velocity increases
b)Pressue reduces, temperature increases, velocity increases
c)Pressure increases, temperature increases, velocity reduces
d)Pressure reduces, temperature reduces, velocity increases
What is the function of the Turbine Blades?
a)To compress the received air in the engine intake
b)To drive the shaft using spent exhaust gasses
c)To drive out the hot exhaust gasses
d)To drive the shaft using air sucked into the inlet vane
Engine Types
Turbofan (Bypass)
How is the bypass ratio of a bypass type jet engine determined?
a)By the diameter of the fan
b)By the diameter of the fan and the length of hte compressors
c)By the difference between atmospheric pressure and bypass pressure
d)By dividing the bypass mass air flow by the core engine mass airflow
In the turbofan engine, some of the air is not compressed fully. This air is made to bypass the combustion chamber and the overall jet velocity is thereby reduced. An important consequence is that:
a)The residual thrust is higher
b)The propulsive efficiency at higher aircraft speed is improved
c)All the residual thrust is removed
d)The propulsive efficiency at lower aircraft speeds is improved
In a bypass engine, part of the air is fully compressed and is passed into the combustion chamber, whilst the remainder is compressed to a lesser extent and is ducted around the hot sections. Which type of engine normally employs this system?
a)Turbofan
b)Turboprop
c)Turboshaft
d)Turbojet
The illustration above shows the typical layout of one type of jet engine. What is this layout called?
a)Turbojet
b)Low by-pass
c)Medium by-pass
d)High by-pass
The illustration below shows the typical layout of one type of jet engine. What is this layout called?
a)Turbojet
b)Low by-pass
c)Medium by-pass
d)High by-pass
Turbojet
Which application or type of operation best suits the turbojet engine?
a)In high speed aircraft where low frontal area is an advantage
b)In static engines in industrial use
c)In low speed aircraft operating at low altitudes
d)In helicopters
The illustration above shows the typical layout of one type of jet engine. Which part of the engine is the combustor?
a)W
b)X
c)Y
d)Z
The illustration above shows the typical layout of one type of jet engine. Which part of the engine is the compressor?
a)W
b)X
c)Y
d)Z
The illustration above shows the typical layout of one type of jet engine. Which part of the engine is the exhaust?
a)W
b)X
c)Y
d)Z
Turboprop
Which of these is a turboprop engine?
a)RB211
b)Dart
c)Adour
d)Spey
Which of these statements applies to a turboprop engine?
a)It has one less turbine than the turbojet
b)It has very high residual thrust
c)It has an extra turbine compared with the turbo jet
d)It is very inefficient at low aircraft speeds
A turbo-prop engine is..?
a)High torque, low speed
b)Low torque, high speed
c)High speed, high cost
d)Low cost, high torque
Why do turbo-prop engines drive the propeller through a reduction gearbox?
a)Turbo-prop engines aren't strong enough to take the thrust of the propeller
b)Turbo-prop engine shafts rotate too fast for a propeller
c)Turbo-prop engine shafts are too short to mount a propeller
d)Turbo-prop engine shafts rotate too slow for a propeller
The illustration above shows one layout of a turbo-prop engine. Which part is indicates?
a)The output drive shaft
b)The intake duct
c)The thrust strut
d)The reduction gearbox
The illustration above shows one layout of a turbo-prop engine. Which part is indicated?
a)The output drive shaft
b)The intake duct
c)A thrust strut
d)The reduction gearbox
The illustration above shows one layout of a turbo-prop engine. Which part is indicated?
a)The output drive shaft
b)The intake duct
c)The thrust strut
d)The reduction gearbox
Turboshaft
Which of these is a turboshaft engine?
a)Harrier's Pegasus
b)The Lynx Helicopter's Gem
c)Concorde's Olympus
d)Boeing 747's RB211
A turbo-shaft engine is..?
a)High power, large size
b)Small size, high power
c)Low power, light weight
d)High power, heavy weight
What type of engine is shown above:
a)Turbojet
b)Turboshaft
c)Turbofan
d)Turboprop
Fuel System
What is the nominal air to fuel ratio (by weight) supplied to an engine?
a)10:01
b)02:01
c)15:01
d)01:02
In a hydro mechanically controlled jet engine fuel system, what components in a fuel control unit controls engine speed?
a)The float chamber
b)The accelerator pump
c)The choke valve
d)The throttle valve
A gear type pump is positive displacement. What does positive displacement mean?
a)Flow will occur when the pump is rotating
b)Flow will stop when the pump stops rotating
c)Flow is relative to pump speed
d)All of the above
A centrifugal type pump is non-positive displacement. What does non-positive displacement mean?
a)When the pump is rotating, flow will occur
b)Whent he pump stops rotating, flow will stop
c)Flow is relative to pump speed
d)Flow can vary at a constant pump RMP
A multi plunger (swash plate) type pump is a positive displacement pump through which flow can be varied at a constant RPM. How is the variable flow achieved?
a)By altering the variable size inlet ports
b)By altering the variable size outlet ports
c)By altering the angle of the swash plate
d)By varying the number of pistons in use
Lubrication
Jet engine mainline bearing chambers have oil inside. How are the bearing chambers sealed to prevent oil loss?
a)'O' ring seals
b)Metal to metal seals
c)Metal to nylon seals
d)Air supported seals
Oil specifications include the property of viscosity. What does low viscosity mean?
a)Synthetic type oil
b)A thinner consistency
c)Mineral type oil
d)A thicker consistency
The mainline bearings in a jet engine are usually ball or roller type bearings, how is the oil delivered to these bearings?
a)By direct jet and centrifugal distribution
b)By splash
c)By pressure feed through internal drillings
d)By jet and pressure feed
What is the purpose of the oil system within a Gas Turbine Engine?
a)To increase the temperature in the combustion chamber.
b)To cool the rotating shaft.
c)To mix with the fuel to aid combustion
d)To provide lubrication to the shaft bearing chambers
There are two basic types of oil system, a wet sump system and a dry sump system. What type of oil systems do jet engines use?
a)Wet sump only
b)Mostly wet sump
c)Mostly dry sump
d)Dry sump only
Ignition
In a modern jet engine ignition system, what type of igniters are used?
a)Surface discharge
b)Gap type sparkplugs
c)Standard vehicle spark plugs
d)Surgace discharge or gap type igniters
In a modern jet engine ignition system, the igniters are switched on at start up and at what other operating condition?
a)Take off
b)Heavy rain conditions
c)Landing
d)All of the above
In a magneto, one purpose of the capacitor (condenser) is to?
a)Reduce pitting of the contact breaker points
b)Make the primary current flow evenly
c)Reduce erosion at the sparking plug gaps
d)Make the secondary current flow evenly
Cooling
Jet engines have two types of cooling systems, active and passive systems. How does a passive system work?
a)The cooling flow is relative to engine RPM
b)The cooling flow is controlled by a valve
c)The cooling flow only goes to the turbine
d)The cooling flow only goes to the compressor
Jet engines turbine blades feature film cooling, ie a barrier of air. How does film cooling work?
a)The cool air keeps hot gases from the turbine blade material
b)The cooling air is mixed with the turbine gasses to cool it down
c)The cooling air is mixed with fuel to bring down the flame temperature
d)The cooling air keeps the inside of the turbine casings cool
Thrust Augmentation
Which is a type of Jet engine augmentation system?
a)Rocket booster – single use
b)Supercharging – Increases the pressure in the inlet manifold
c)Water injection – cools the turbine
d)Turbo charging – Driven by expelled exhaust gasses
Which sentence is true? Afterburning….
a. ... is restricted for take-off and combat.
b. ...adds more fuel to the reheat section of theengine to produce more power.
c. ...results in an extremely high fuel consumption rate.
d. ...produces visible shock waves in the exhaust plume.
b, c, and d only
a, b and d only
a and c only
a, b, c and d
In a typical reheat system, oxygen is required in the jet pipe for combustion. Where does the reheat oxygen come from?
a)Slipstream air is scooped into the jet pipe
b)From on board oxygen bottles
c)Oxygen is pumped in with the extra fuel
d)Reheat uses unburnt oxygen from the combustion chambers
Why is the jet pipe rear nozzle controlled to open when reheat is selected?
a)To prevent jet pipe pressure affecting the engine
b)It uses less fuel
c)It allows cooling air into the fuel gutters and spray tubes
d)To allow the flame to escape
How does water injection increase power in a jet engine?
a)It heats the air flow into the engine allowing more fuel to be added
b)It makes the combustion burn slower
c)It cools the air flow in the combustor allowing more fuel to be added
d)It allows less fuel to be used
Which of the following statements applies to the process of afterburning, as used in some jet engines? It provides extra thrust without:
a)Increasing the exhaust velocity
b)Increasing the engine's frontal area
c)Removing any more oxygen from the exhaust gases
d)The use of additional fuel
Which is a type of Jet engine augmentation system?
a)Rocket booster – single use
b)Supercharging – Increases the pressure in the inlet manifold
c)Water injection – cools the turbine
d)Turbo charging – Driven by expelled exhaust gasses
How does reheat increase jet engine thrust?
a)It heats the air flow into the engine allowing more fuel to be added
b)It makes the combustion burn fuel faster
c)It allows less fuel to be burnt more efficiently
d)It increases the exhaust jet velocity
Which aircraft was the only passenger aircraft in service with reheat?
a)Concorde
b)Lightning
c)Boeing 777
d)Airbus A380
What is the function of the Spray tubes in the afterburner?
a)To control the afterburner internal pressure
b)To inject water to control the afterburner temperature
c)To add more air to the combustion process
d)To add more fuel to the combustion process
Vectored Thrust
What was the most successful VSTOL aircraft ever made and put into service?
a)Short SC 1
b)McDonald Douglas Phantom
c)BAe Harrier
d)BAe Tornado
Complete the sentence: Vectored thrust…?
a)Does not control the angular velocity of the aircraft
b)Is a method of extracting more power from the internal combustion engine.
c)Is a means of Jet engine afterburner
d)Manipulates the direction of thrust from its engine
What is thrust vectoring?
a)Guiding an aircraft to an intercept position
b)Changing the direction of the thrust from a jet engine
c)Flying an aircraft during combat manoeuvring
d)Changing altitude in flight
Thrust Reversing
Thrust reversers generally fall into four types, what are these types?
a)Translating cowl, pivot doors, clamshell doors and target doors
b)Translating cowl, balanced doors, clamshell doors and target doors
c)Transmission cowl, pilot doors, clamshell doors and target doors
d)Transmission cowl, pilot doors, crab shell doors and bucket doors
e)
Which type of thrust reverser is fitted to the Tornado?
a)Translating cowl
b)Pivot doors
c)Transmission cowl
d)Target doors
Reverse thrust is simply a method of altering what?
a)Increasing thrust without increasing the engines rontal area
b)The cooling of the engine
c)Jet reaction
d)The primary airflow
The drawing indicates which type of thrust reverser system?
a)Ramjets
b)Clamshell doors
c)Translating Cowl
d)Retractable ejector
Which type of thrust reverser is fitted to the C17 Galaxy?
a)Translating cowl
b)Pivot doors
c)Clamshell doors
d)Target doors
Which type of thrust reverser is fitted to the VC10?
a)Translating cowl
b)Pivot doors
c)Clamshell doors
d)Target doors
What is thrust reversing?
a)Turning the engine round to point in the opposite direction
b)Making the engine shafts rotate in the opposite direction
c)Redirecting the engine exhaust stream in a forward direction
d)Driving the aircraft wheels backwards
How is thrust reverser deployment commanded?
a)Automatically on landing
b)By the pilot on landing
c)By command from the control tower
d)By engine power on touch down
The illustration above shows one type of thrust reverser, which type is it?
a)Translating cowl
b)Pivot doors
c)Clamshell doors
d)Target doors
Which type of thrust reverser is fitted to the Sentinel?
a)Translating cowl
b)Pivot doors
c)Clamshell doors
d)Target doors
The illustration above shows one type of thrust reverser, which type is it?
a)Translating cowl
b)Pivot doors
c)Clamshell doors
d)Target doors
Ramjet
Which of the following statements applies to the ramjet engine
a)It has only one turbine
b)It has only one compressor
c)It is most efficient at subsonic speeds
d)It has no moving parts
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