136 Questions
What material is used to cover the ducts in the cross-wing manifold first?
Fibreglass
How are the epoxy impregnated fibreglass sheets applied around the ducts in the cross-wing manifold?
Wrapped
What is used to bring the joints of the manifold components tightly together?
V-band type clamp
Which type of seal is placed between the mating faces of each component in the cross-wing manifold?
Crush type seal
What is used to secure the insulation blanket around the bare metal of the manifold joints?
Clamp
Why is fibreglass insulation preferred for ducts in the cross-wing manifold?
It hardens and is durable
What is the purpose of temperature compensators in aircraft pneumatic ducting?
To prevent thermal expansion issues
How do temperature compensators limit the amount of duct growth?
By using bellows acted on by higher duct pressure
What is the key function of bleed air shut-off valves in aircraft?
To stop the flow of bleed air
Which component helps to absorb expansion and contraction differentials in pneumatic ducting?
Temperature compensators
What is the primary purpose of the slip joint in a temperature compensator?
To allow the ducts to grow
How are temperature compensators designed to counteract thermal expansion issues?
By limiting duct growth through bellows action
What is the main function of the cross-wing manifold in an aircraft's pneumatic system?
To control air to pneumatic supply systems
Why are aircraft cross-wing manifolds typically constructed from stainless steel?
To resist fatigue and corrosion from high pressures and temperatures
What is the purpose of insulating the cross-wing manifold in an aircraft's pneumatic system?
To prevent heat transmission to the aircraft structure
Which of the following components is NOT typically found in a typical engine pneumatic system?
Temperature regulator valve
What is the material used for constructing aircraft cross-wing manifolds resistant to?
Corrosion and fatigue from high pressures and temperatures
Which component is responsible for controlling the air supply to pneumatic systems in an aircraft?
Shut-off valve
What is the main function of the airflow around an engine nacelle as described in the text?
Venting flammable vapours overboard
Why is icing protection of compressor rotor blades rarely necessary according to the text?
Centrifugal action removes ice
What benefit does keeping the airflow to a minimum around the nacelle provide according to the text?
Lessens engine drag
How does a pneumatic anti-ice system differ from a nacelle cooling system based on the text?
Nacelle cooling prevents ice formation, while anti-ice removes flammable vapours.
What is the main function of the Variable Stator Vanes (VSVs) in an aircraft engine?
Controlling the airflow to the high pressure compressor (HPC)
What component sends high pressure compressor 9th stage air to the low pressure turbine stage 1 nozzles during engine start and acceleration?
Transient Bleed Valve (TBV)
What is the purpose of controlling the HPC inlet guide vanes (IGVs) and VSVs of the HPC?
Avoiding HPC stall during engine start
Which component of an aircraft engine helps absorb expansion and contraction differentials in pneumatic ducting?
Temperature Compensators
What does the Transient Bleed Valve (TBV) prevent during engine start and acceleration?
High pressure compressor (HPC) stall
Why are Variable Stator Vanes (VSVs) important in ensuring engine performance?
To control airflow to the high pressure compressor (HPC)
What is a common source of pneumatic power for many aircraft systems?
Air
Which material is commonly used to construct pneumatic anti-ice systems?
Stainless steel
Which device is responsible for preventing compressor stalls in aircraft engines?
Compressor surge control system
What component is responsible for controlling the supply of air to pneumatic systems on an aircraft?
Air regulator
What is the main function of the compressor bleed surge control system on a Boeing 737 CFM56-7 engine?
Preventing surging and stalls
What is the purpose of the compressor bleed valve system?
To duct excess air overboard when the bleed air valves are open
What triggers the speed sensitive valve in the compressor bleed valve system?
Engine RPM
When does the speed sensing valve flyweights position the sensing valve to close the 5th and 10th stage bleed valves?
Below 94% RPM
What happens when the 5th and 10th stage bleed valves are open in the compressor bleed valve system?
Excess air is ducted overboard
What is the role of the speed sensitive valve mounted on the forward face of the accessory gearbox?
To respond to engine RPM
How does the compressor bleed valve system operate at less than 94% RPM?
By forcing open the 5th and 10th stage bleed valves
Where are shut-off valves typically located in an aircraft's system?
On the engine pylon
What is the primary function of engine shut-off valves in an aircraft's system?
Control airflow to and from the engine
In which system are reverse flow or one-way check valves typically incorporated?
Pneumatic systems
What is the purpose of reverse flow or one-way check valves in a pneumatic system?
Prevent loss of manifold pressure
Where would you find a reverse flow valve located in an aircraft's pneumatic system?
APU external air source connection
When do bleed air shut-off valves typically come into play in an aircraft system?
During engine shutdown
How do bleed air shut-off valves contribute to fuel efficiency in an aircraft engine?
By controlling the supply of bleed air to save fuel
During what stage of engine operation does the bleed air shut-off valve system allow bleed air to flow?
During engine start and up to 13,000 RPM
What happens if a bleed air shut-off valve fails to operate as intended?
The compressor bleeds more air from stages 5 and 10
What percentage of air entering the combustor flows into the snout for the twin spool gas turbine engine internal cooling system?
20%
In the internal cooling system, what is the purpose of the remaining air that is proportioned into secondary vortex generation, combustor cooling, and flame dilution?
Cooling
Which components of the engine require cooling air in the internal cooling system?
Combustors and turbines
What is the main purpose of the internal cooling system for an aircraft engine?
To prevent overheating of engine components
Which portion of air entering the combustor is responsible for secondary vortex generation in the engine?
Snout
What happens to the remaining air that is not diverted into the snout in the engine's internal cooling system?
Is used for cooling purposes
How is induced cooling achieved for engine accessories during ground operation?
By allowing compressor bleed air to flow through nozzles in the cooling air outlet duct
What is the role of a blower fan driven by the accessory gearbox in engine cooling systems?
To accelerate ambient air through the fan
What system would typically cool engine accessories with air ducted from blower motors?
Generator cooling system
What is the purpose of a valve that controls airflow in an engine accessory cooling system?
To ensure induced cooling only during ground running
How does a blower motor-driven system contribute to engine cooling during ground operation?
By drawing ambient air for accelerated cooling
Why is combustor cooling air necessary in a gas turbine engine?
To minimize heat transfer to the combustor outer casing
What is the primary purpose of dilution air entering the rear area of a combustor?
To reduce gas temperature before entering the turbine
How does turbine disc cooling contribute to turbine operation?
Reduces thermal expansion rates and thermal fatigue
What limits the maximum turbine inlet temperature in a gas turbine engine?
Turbine blades' ability to withstand heat
Why are closer operating tolerances maintained in a turbine area with continuous cooling?
To reduce thermal fatigue and increase efficiency
What is the main benefit of combustor cooling air in a gas turbine engine?
Preventing excessive heat radiation within the engine nacelle
How is hot gas intrusion prevented in the turbine disc cavities?
By continuously supplying cooling air over the inter-stage seals and into the disc cavities
What is the purpose of multi-pass internal air film cooling in turbine vanes and blades?
To enhance the cooling of turbine vanes and blades
Why is continuous cooling air supply required over the inter-stage seals and turbine disc cavities?
To oppose the inward flow of mainstream gas
What is the function of turbine inter-stage seals in turbine disc cooling?
To control turbine disc inter-stage cooling
In turbine blade cooling, what happens once the cooling air has completed its task?
It is discharged into the mainstream gas
Why is multi-pass internal air film cooling important for both vanes and blades in turbines?
To improve cooling effectiveness
What is the primary function of the airflow around an engine nacelle?
To cool and ventilate the nacelle
Why is it important to keep the airflow around the nacelle to a minimum?
To minimize engine drag
Which system provides surface heating where ice is likely to form in an aircraft engine?
Pneumatic anti-ice system
Why is icing protection of compressor rotor blades rarely necessary?
Because of centrifugal action
Which components or areas might need anti-ice protection according to the text?
First stage compressor inlet guide vanes
What is the purpose of purging the nacelle with atmospheric air according to the text?
To protect against flammable vapors
How is induced cooling for engine accessories typically achieved during ground operation?
By allowing compressor bleed air to flow through nozzles in the cooling air outlet duct
What is a typical method used to cool engine accessories with air ducted from blower motors?
Having a blower fan driven by the accessory gearbox to accelerate air
What is the function of the valve in the engine accessory cooling system?
To control the airflow only during ground running
What is the role of compressor bleed air in cooling engine accessories?
To draw atmospheric air through intake louvres using a low pressure area
What is the primary source of cooling for engine accessories during flight?
Ram air delivered through scoops in nacelle cowling
How does induced cooling differ from ram air cooling for engine accessories?
Induced cooling draws ambient air with nozzles, while ram air uses external airflow
When the Anti-Ice Switch is turned OFF, what happens to the blue and amber lights mentioned in the text?
The blue light remains on while the amber light is extinguished
In the context of the Anti-Ice System, what occurs when the four limit switches are repositioned as described in the text?
Both lights are extinguished
What is indicated by the blue light staying on and the amber light coming on during valve transit in the Anti-Ice System when switched OFF?
Correct operation
What is the significance of four limit switches being mechanically repositioned in the Anti-Ice System after valve closure?
Preparing for next operation command
What happens when the transition to the closed position is complete in the Anti-Ice System?
Both lights are extinguished
What holds the piston up against spring tension during the bleed band operation when the compressor discharge air pressurizes the actuator cavity?
Modulator diaphragm
When does the actuator valve close in the bleed band operation according to the description?
At cruise or high power settings
What causes an upward movement that opens the actuator valve, allowing P3 air pressure to dump from the actuator cavity during bleed band operation?
Pressure drop on the modulated air side of the diaphragm
What action does the FCU take when the power lever is retarded during the bleed band operation?
Uncover the atmospheric pressure port
What is locked in by the slider during the bleed band operation according to the provided text?
Modulated air
How do operators know that the anti-ice system is activated in the cockpit?
Rise in exhaust gas temperature
Which component controls the amount of airflow in an anti-ice system based on the temperature of tapped air?
Air regulator valves
What indicates a normal response to a gas turbine engine losing compressor air when an anti-ice system is activated?
Temperature rise in exhaust gas
In a typical anti-ice system, what happens after air flows through the air regulator?
It passes through the anti-ice valve towards the nose cone area
How do bimetallic spring coils contribute to the operation of an anti-ice system?
Control airflow based on outside temperature
What occurs when the Anti-Ice Switch is turned OFF based on the text?
Both blue and amber lights are extinguished
What happens to the valve status during the transition to the closed position in the Anti-Ice System?
Valve closes completely
Why are the blue and amber lights used in the Anti-Ice System according to the text?
To indicate valve opening and closing
What changes occur to the lights during valve transition in the Anti-Ice System based on the provided information?
Blue light turns off, amber light lights up
What happens to the limit switches once the valves in the Anti-Ice System reach the closed position?
They reset for next activation
Which lights are initially illuminated upon selecting 'OFF' in the Anti-Ice System according to the text?
Blue only
What happens when the anti-ice switch is turned on in the described system?
The limit switches control the motors and valves, illuminating an amber light in the cockpit.
How does the rotary movement of the valve disc affect the airflow through the valve?
Reduces airflow by partially covering the ports through the stator plate.
What is the function of the limit switches in the Anti-Ice System described?
To control the flow of AC power to the motors and valves.
How does anti-ice air affect engine performance in some configurations?
It can raise intake air temperature, thereby affecting engine performance.
What role does AC power play in activating components of the Anti-Ice System?
It actuates motors and valves via limit switches to regulate airflow.
What is the main purpose of a variable vane actuating system in a gas turbine engine?
To minimize compressor acceleration and deceleration stall problems
Which type of gas turbine engines are often fitted with a variable vane actuating system?
Engines with high compression ratios or inherent stall problems
In what situations are surge bleed valves typically activated in a gas turbine engine?
When there is a risk of compressor stall
Which statement best describes the purpose of a variable angle compressor vane system?
Automatically varies the area and shape of the compressor air path
What does the compressor bleed valve system do during start and up to 13,000 RPM or 94% engine speed?
Unloads the compressor by bleeding air from the fifth and tenth stages
What controls the compressor bleed valve system based on speed in the described system?
Speed sensitive valve
What happens if low-speed ground idle or engine shutdown are selected in the system?
Compressor bleed valves open to unload the compressor
How does the spring tension on the main actuator piston behave when not opposed by P3 air?
Pushes the piston down
What is the function of the bleed band in relation to the compressor bleed valve system?
Covers and uncovers compressor bleed ports
What is the significance of the relationship between a compressor's total entry area and total exit area?
Balances airflow velocity and pressure
Why might a compressor stall at very low speeds even if it is balanced at governed speed?
Insufficient compressor exit area
What does the EEC control in the engine air system to prevent stall?
Compressor airflows
How does the bleed valve aid in deceleration?
By relieving some airflow from the front compressor
What component does the EEC use to operate the air valves and actuators?
Hydro-mechanical FCU
Why is it important for the rear compressor to pick up speed quickly?
To assist in engine acceleration
What sub-system of the engine air system is responsible for controlling compressor airflow?
Turbine clearance control
What effect does closing the bleed valve have on the low pressure compressor?
Increases its speed
How does the EEC change turbine blade tip clearances to prevent stall?
By regulating cooling air onto the turbine case
How does exhaust from the first stage turbine help in turbine operation?
By increasing remaining turbine stages' speed
What is the main role of the engine air system's hydro-mechanical FCU?
Controlling actuator movements in turbine clearance control
Why does the bleed valve open during starting?
To give good acceleration characteristics to the engine
What is the purpose of the Transient Bleed Valve (TBV) in a gas turbine engine system?
To prevent high pressure compressor (HPC) stall during engine start and acceleration.
What role do the Variable Bleed Valves (VBVs) play in a gas turbine engine system?
Letting some low pressure compressor (LPC) discharge air bypass the engine and mix with fan discharge air.
What is the function of the High Pressure Turbine Active Clearance Control (HPTACC) system in a gas turbine engine?
Sending HPC 4th stage and 9th stage air to the HPT shroud support.
What is the main function of the Low Pressure Turbine Active Clearance Control (LPTACC) system?
Sending fan discharge air to the LPT case.
How does the Transient Bleed Valve (TBV) contribute to preventing high pressure compressor (HPC) stall?
By sending HPC 9th stage air to the LPT stage 1 nozzles.
What is the primary function of a Variable Bleed Valve (VBV) in a gas turbine engine system?
Letting some LPC discharge air bypass the engine and mix with fan discharge air.
Learn about the process of insulating ducts with fibreglass, including the layering and baking of epoxy impregnated fibreglass sheets. Explore the durability and benefits of this type of insulation. Figure 2 provides a sectioned view of a cross-wing manifold duct.
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