ATPL BOOK Flashcards
What is a surge line?
Defines the minimum value of stable airflow that can be obtained at various engine speeds.
Running line occurs before as a buffer
What are the three variables that affect the angle of attack in the compressor?
- Speed of the intake airflow
- Compressor RPM
- Direction of the intake airflow
What prevents compressor surge and stalls?
Variable inlet guide vanes/stators
Blow off or bleed valves
Multi spool engines
What is a safety coupling?
Back up device for the negative torque system, in the event of NTS failure the safety uncouples the reduction gear from the power section.
Leads to reduce drag
How to reduce blade tip flutter?
Lower speed or by reducing RPM
What are the methods that gas generators use to control the propeller-driven by their own turbine?
Prop controller
- Integrated control of both fuel flow and rpm
- Direct control of gas generator fuel flow
- Direct control of propeller blade angle.
How does the CSU work?
The cockpit power lever selects a required blade angle for the thrust demanded. Automatic functions then adjust fuel flow to achieve the required propeller RPM
WHat determines the appropriate torque setting?
Ambient Conditions
Prop RPM
Airspeed
Turbo prop performance at low speeds?
- Performs best at low speeds before the effects of high prop tip speeds reduce propeller effenciency
- Extremely capable of producing thrust at low speeds
- Propulsive force by impairing a lesser acceleration to a larger mass of air.
What type of fuel does all jets use?
kerosene
liquid hydrocarbons
Refinery fuel qualities?
- Ease of flow
- Ability to start
- complete and rapid combustion under all conditions
- Highest possible calorific value
- non-corrosiveness
- lubrication
- minimal fire hazard
What would fuel with a high specific gravity mean?
The fuel will have more mass per unit.
What is a fuel shut-off valve?
Allows fuel supply to the engine to be terminated in the event of a engine malfunction.
What do boost pumps do?
Draw fuel to the delivery lines for the engine.
Is there a bypass valve in the centre tank?
No this means if the pump fails in the cenztre tank the fuel is unusable.
What does the fuel control unit do?
Meters appropriate amount of fuel in response to thrust levers setting, measured engine speed.
What is the purpose of the fuel heater unit?
Ensures high pressure fuel is free from ice crystals, which can form in cold fuel.
What are different engine-associated instruments available to a jet engine? To represent a gas turbine engine
- N1 and N2 RPM
- Oil pressure and temperature
- Fuel Flow in high pressure delivery line
- EGT
- Engine vibrations
What are two indicators for engine power and thrust?
Engine pressure ratio gauge
Torque Gauge
Why are fuel flow gauges important?
Verify the supply of fuel to the engines on start and shutdown.
Can work with the FMS to identify expected arrival fuel.
What is the turbine engine basic starting procedure?
- Rotate the engine core with a starter untill a specified engine speed is reached
- Activate igniters
- Open the high pressure fuel supply
How is a hot start indicated?
Engine temperature rising rapidly to set limit.
How does a hung start occur?
High temperature accompanied by low RPM
Normally due to the excessive back pressure through the compressor stages.
What is the remedy for a hot and hung start?
Terminate ignition and fuel and continue cranking the starter to clear the fuel.
How can a flameout occur?
When idle rpm is set below self-sustaining rpm, and the throttle is closed in flight.
How is the air turbine starter rotated?
Compressed air is delivered normally by an auxiliary power unit.
Compressed air for the other engines start is normally tapped from a bleed air supply from the first engine.
How is reverse thrust restricted from deployed
Squat switches or wheel speed transducers, there are high-speed limitations of reverse thrust as well.
What is an artificial feel?
Power control systems have an artificial feel to prevent overstress of the aircraft, usually done by a centering spring and additional resistance to control movement.
What is q feel?
A hydraulic system that prevents over corrections provides resistance to the hydraullic operated control collums, through pitot and static pressures.
In the event of a power control failure what redundancy systems are in place.
Multiple hydraulic jacks driven from separate hydraulic systems. each hydraulic system will have its own power source.
Manual revision is also available
What is lift augmentation devices’ purpose?
To give an additional lift to the wing.
What are the types of lift augmentation devices fitted to jet transport aircraft?
Trailing edge flaps, leading-edge flaps, and slats
Explain trailing edge flaps?
- Increases camber of the wing
- Increase total wing area
- Hydraulically actuated
- Move CP rearward which therefore nose-down moment giving steeper approaches
- Lift increase
- Drage increases
- Slots can be involved to further energize airflow
Purpose of the rudder ratio changer?
Receives inputs from the air data computer and provides control signals to the actuator, then the actuator then dampens the inputs to the rudder.
Explain yaw dampeners?
There are two yaw dampeners operating continuously inflight (left and right). They are powered by the centre and left the hydraulic system, if one of the hydraulic systems is failed the yaw dampening is halfed.
What are three stabilizer trim controls?
Electric
Alternate
automatic
How is electric trim operated?
Each pilot has dual electric trim switches mounted on each control wheel., they must be pressed simultaneously to operate.
How is alternate trim operated?
Provides back up to pitch trim, alternate stabilizer trim switches are provided, and similar to the electric trim must be pressed at the same time.
Explain automatic trim?
Trim controlled by the autopilot
What is the purpose of an alerion lockout (inhibit system) ?
Permits full travel of the outboard alerions at low speeds, but at high speeds they are locked and controls for roll are off inboard alerions.
Explain how spoilers are used in a roll?
They help to provide roll control and operate as speed brakes, Signals resulting from movement of the control wheels are sent to the spoiler control which then determines the required spoiler panel deflection and selects the appropriate spolier panel actuator.
If the speed brakes are in the armed position what does this mean?
all 6 spoilers will deploy at the landing and then move to the up positions when all conditions are satissifed.
What are speed brakes conditions?
Appropriate hydraulic pressure, no tilt condition and both thrust leavers idle or reverse.
What is the source of air for, pressurisation systems and air conditioning systems?
Bleed air tapping from the engine compressor
Air is already heated and pressurised, which enables high mass flow rate.
What is the certification requirements for aircraft in regarded to pressure differential?
Must be capable of withstanding 1.33 times the maximum design pressure differential.
What is the basic control of the pressurisation system?
Constant amount of incoming air being balanced against a variable rate of outflow air.
What does a non-return valve do in the pressurisation system?
Prevents pressure loss with an engine failure.
What is the purpose of an isolation valve? In the pressuirisation system
Allows the pilot to shutoff the air from any source in the event of overpressurisation or inlet air contamination, or to meet take off performance demands.
What occurs if cabin altitude exceeds 10,000ft?
An automatic warning device
Purpose of the pressurization controller?
Provide cabin pressure regulation, pressure relief vacuum relief, and the means for selecting the desired altitude.
This is all accomplished by a safety and outflow valve.
What would happen if maximum permissible defferential pressure occurred?
A safety valve will open to lower pressure.
How may total decompression occur?
Failure of a component but moist likely structural failure.
What is a negative pressure differential?
Outside pressure will be greater than inside pressure, to mitigate this an inward pressure relief valve is fitted to allow ambient air to enter the cabin, which normally occurring at an increase of negative pressure of 0.5psi
Negative pressure relief valve
What are the two types of cooling systems?
Vapour Cycle Cooling
Air cycle cooling
Explain the vapour cooling system?
- Vapour cycle cooling systems have greater cooling capacity the air cycles, usauly employed in ground operations.
- Uses a refrigerant fluid
- Heat will flow from a point of higher temp to a point of lower temp
- Gas is compressed temperature is raised above outside temperature
- Heat will flow from the higher to lower temperature, thus reducing the heat content of the gas.
- Gas is then transported to the area to be coolwed and allowed to expand.
- Heat will now flow from air to the gas. The gas is then transported back to the compressor to recycle.
Purpose of the vapour cycle?
The vapour cycle extracts heat from the cabin air, transferring it through a refrigerant and then dumping overboard.
What does an air cycle cooling system consist of?
Expansion turbine
air to air heat exchanger
compressor
various control mechanisms
Explain the air cycle cooling system?
Air passes through the systems turbine and is expanded and cooled. And delivered to the cabin and desired temperature sensed by the tmeperature sensors and the mixixng valve directs suitable amount of air to the desired area.
Need for ventilation in and aircraft?
Implies supplying fresh air and exhausting stale air. Fresh air is required for oxygen and remove of carbon dioxide and odours.
Purpose of the humidity controller?
Keeps humidity within the aircraft in the comfort zone (30 - 70% humidity). A sensing element know as a humidistat monitors the humidity levels and when necessary signals valves that allow water to be injected by humidifiers..
Purpose of air recirculation?
To reduce the need for engine bleed air, well over half air is recirculated. Air is exhausted and duct through filters and returned to the common manifold for mixing.
What do air conditioning packs do?
Cool cabin air by an air cycle machine process. Ram air doors and exit doors operate automatically to control the ram air to the pack heat exchangers. There are three standy by modes should fully automatic mode fail.
How is the cargo comparrtment heated?
Three cargo compartments are heated by air from the cabin flowing down through the compartment side alls, supplemented by air from the pneumatic system ducted under the compartment doors.
What is the difference between DC generators and DC motors?
The generator accepts mechanical rotary inputs and outputs DC electricity,
Where a DC motor accepts DC electricity as its input and outputs a rotary motion.
Are starter generators to only to be used on DC systems?
YEs
Explain an alternator?
The output of the alternator is alternating current, the alternating current is rectified by diodes so the system outputs DC.
A/C voltage is either 14 - 28V.
Regulating deviced used to regulate the voltage.
Current from the regulator makes the gernator field always DC and alternator on a line above 1,000 - 2000RPM
Explain a regulating device in an alternator?
Modern regulators are solid state electronic devices that very accurately sense a change in the line voltage and cause a change in the alternator field current to regulate the output voltage over a wider engine RPM range.
What is the backup generators’ source of power?
Air-driven generators
Hydraulically driven generators
Auxiliary power unit driven generators.
Explain Bus Bars?
Bus bars are major terminals to which generators supply electric power to where consumers of that power are connected.
Types of buses in heavy aircraft consists of bus that may not be switched off, and bus annotated as emergency essential busses.
What are current limiters?
Heavy-duty resistive fuse designed to restrict current flow for a period before breaking the circuit if current remains excessive.
What are relays and solenoids?
A remotely controlled switching device, usually a control circuit switched by the pilot to cause a relay to operate somewhere else in the aircraft.
A solenoid is a heavy-duty relay
What is a rheostat?
Variable resistance device used to control current flow in a circuit.
What is a potentiometer?
Variable resistance device to control voltage in a circut.
What is a diode?
Semiconductor device, which has many uses in radio and computers, has a low resistance current flow in one direction and a high resistance flow in the other direction.
Heavy-duty diodes are used to rectify AC electrical power to produce DC.
What is a transistor?
Semiconductor devices that can be used as amplifiers or switches.
What is a capacitor?
A device that can be charged or discharged. In a circuit, it will block DC or act as a short-term accumulator. A capacitor will pass AC depending on its value and the frequency of the AC
What is a suppressor?
The capacitor can be used as a suppressor, is passing the changing component of the power to the earth
ie suppressing the AC and the electronic noise associated with the AC
What is a transformer?
A transformer is an AC device that allows voltage changes with only minimal losses. AC voltage at a particular frequency can be changed into a different value of AC at the same frequency with that AC.
What is an inductor (choke)
An inductor is an AC device often used as a resistor in AC circuits. They are used in DC circuits to help filter voltage changes.
What kind of electrical systems to large airline aircraft use?
Constant frequency AC systems
What is frequency wild AC?
AC generation that disregards frequency variations. Some electrical components are no frequency sensitive, anti-ice, de-ice, heating and lighting
1Modern ACW generating systems are fitted with rotating rectifier brushless generators, what are their advantages over brush types?
No brush so no wear or arcing, improving reliability and safety and providing significant maintenance cost saving.
Purpose of the generator?
Is the heart of any electrical system, and has the capacity to provide power for normal services.
What is the Constant speed drive (CSD)?
The generator is required to be at a constant frequency. A CSD unit is required to convert the varying speed drive from the engine into a constant speed for the generator.
What is the purpose of the mechanical governers is the CSD?
Maintain a constant output rotation speed, with fine adjustments from the frequency controller.
How is there protection of the CSD systems?
A facility for disconnecting the engine drive from the CSD in the event of a generator or gearbox failure is provided. Should an electrical fault occur the circuit breaker system would protect each circut.
What is a guarded switch within the CSD?
A switch provided to the pilots labelled GEN DISC, which activates a solenoid which pulls a dog clutch open effectively breaking the drive between the engine gearbox and the CSD.
Once generator is disconnected in cannot be reset.
Benefits of three-phase AC supply over a single phase?
Increases the current available and therefore more power available to the equipment. Connection to phase-sensitive motors and transformers is critical. If not monitored properly could lead to opposition rotation of the motor and an incorrect phase sequence could lead to burnout.
What is the purpose of the frequency regulator?
Signals to the CSD so that the generator output frequency is maintained at 400 +/- 4 Hz
What is the purpose of the voltage regulator?
Maintains a constant output voltage of the generator irrespective of the electrical load.
Done through continual adjustments to the DC current flowing in the generator fields.
When does the generator failure warning light come on?
When the associated circuit breaker is tripped or the generator fails.
What does the synchronizing unit ensure?
Bus tie breaker cannot be closed until the generators are phase aligned. The circuit is so designed that the sync push switch can be pressed, but the bus tie breaker will not close until the system is in phase.
What are emergency power supplies for AC power?
Static or rotary inverters, powered by the battery can be used to generate emergency AC but are limited to the capacity of the battery.
Standby AC generator sytems separate from the primary generating systems are driven by:
- A ram air turbine
- The auxiliary power unit
- Pneumatic air system
- The aircraft hydraulic system.
What is the desired effect of a turbofan?
Increase the power-weight ratio when compared to a turbojet and improve specific fuel consumption
Greater efficiency and less noise
How does a turboprop operate?
axial flow or centrifugal or both to drive the propeller through a suitable drive system
What determines thermal efficiency?
Conversion of fuel energy into kinetic energy
Why does the propulsive efficiency of a turboprop decrease at high speeds?
Due to the drag experienced from compressibility
What is the purpose of each compressor stage?
Airflow velocity is increased by a rotor and then converted to a pressure increase through the diffusing action of both rotor and stator
How will a compressor blade stall?
Increasing the angle of attack will increase compression-like lift but will exceed a critical angle of attack eventually and stall.
Decreasing airflow at a given engine speed will increase blade angle. Similar can happen if engine RPM becomes too high.
Any action that decreases airflow will increase blade angle.
How is noise suppressed in reverse thrust?
Through a noise suppressor, operate by breaking the large volume flow into individual smaller streams
What does an outflow valve do in a pressurization system?
Specific control of cabin pressure acheved by regulating the release of cabin air through an outflow valve.
What is ACW service bus?
Supplies power inflight and on the ground during aeroplane servicing operations
