AAS Flashcards
In an electrically controlled landing gear system - what is the purpose of the ground safety microswitch?
Prevent the accidental retraction of the landing gear on the ground
What is another name for the ‘ground safety microswitch’?
WOW switch
In an equipment cooling system - which component supplies the alarm signal?
Low flow sensor
In a mechanical hydraulic servo actuator - what controls the direction of movement?
Control valve
In a fire extinguishing system - what device is responsible for pyrotechnically releasing the extinguishing agent from the bottle?
Squib
What are the 2 significant sections of the Air Cycle Machine?
Compressor and turbine
In an air cycle machine - the turbine extracting energy results in what?
The temperature and pressure of the air reducing
In a fire detection system - where is the power supplied from?
28 VDC vital bus
In a landing gear indication system - ‘down and locked’ is indicated by?
A diagram of a miniature wheel
Under normal flight conditions (ie cruise) - the landing gear warning system is designed to provide the aircrew with what?
A visual and / or audio warning that the landing gear is in transit
What is an aircrafts undercarriage safety circuit designed to ensure?
That the undercarriage cannot be retracted when the aircraft is on the ground
When on the ground - the compression of the undercarriage struts hold the weight on the wheels micro-switch contacts:
a) Locked
b) Closed
c) Open
d) Suspended
c) Open
In an anti-skid brake system - the skid control valve relaxes the brake applications by?
Dumping fluid into the reservoir return line whenever the solenoid is energised
An anti-skid brake system comprises of the following components?
- Brake / rudder pedals
- Brake control servo valve
- Skid control valve
- Skid control box
- Skid control generators
The signal from the skid control generator is?
Received, interpreted and analysed by the skid control box
3 major types of flight control servomotors are?
- Electro-pneumatic
- Electro-mechanical
- Electro-hydraulic
Prior to performing maintenance on a fire extinguishing system what must you ensure?
All applicable circuit breakers are pulled
During maintenance - fire detection systems must be inspected for what?
- System integrity
- Security of components
- Visible faults
2 smoke detection systems used on aircrafts are?
- Light refracting
- Light detecting
What are the primary detecting elements in a light refracting smoke detector?
- Pilot light
- Light trap
- Photo diode
What are the basic requirements of an aircraft fuel system?
Supply clean fuel under positive pressure at all aircraft attitudes and altitudes
What is the function of fuel selector valves?
To transfer fuel between tanks and direct fuel to one or more engines
Where is a fuel boost pump normally located?
Bottom of the fuel tank
In what situation should a fuel boost pump NOT be operated?
If the electrical circuit breaker is tripped
On aircrafts that use a starter generator - once the engine has reached self-sustaining speed - what happens to the starter generator?
It operates as a generator to supply the electrical system power
What rotates an air starter generator?
Bleed air from a running engine
When starting an engine with bleed air - the SCV is opened by what?
Operation of the solenoid
On propeller engines, the term ‘Synchronising’ refers to what?
Matching the engine RPMs
On propeller engines, the term ‘Synchrophasing’ refers to what?
Maintaining a blade phase angle so the pilot can minimise noise and vibration
In an electrically controlled landing gear system - where is the ground safety micro-switch fitted?
On the shock absorber struts of one of the main landing gear legs
In an equipment cooling system - which component is used to monitor the cooling quality of air through the system?
Low flow sensor
In a mechanical hydraulic servo actuator - how are the pilots controls linked to the actuator?
Via direct mechanical linkage to the control valve
What is a precaution associated with fire bottle cartridges?
Do not touch the electrical pins
How is the core of the heat exchanger cooled in a brake turbine air cycle air conditioning system?
Ram air
In a fire detection system - where is power supplied from?
28 VDC vital bus
The landing warning system is designed to warn the aircrew in what situation?
Attempting to land without the undercarriage down and locked
An aircraft undercarriage safety circuit is designed to ensure what?
Undercarriage cannot be retracted when the aircraft is on the ground
What is the function of the ‘lever lock release’ push button on the front of the landing gear control lever box?
Allows emergency unlocking of the landing gear control lever (even when the aircraft is on the ground)
In an anti-skid system - the touch down protection circuit will only allow the brakes to be applied in what situation?
When the weight is ON the wheels and wheel speed if OVER 25kph
What component within the anti-skid brake system develops a voltage which represents the wheels rotational speed?
Skid control generator
Prior to electrically re-connecting a fire extinguishing bottle you must carry out what?
A ‘no voltage’ check
A thermocouple fire detection system operates on what principle?
Rate of temperature rise
Where is the reference thermocouple (cold junction) in a thermocouple fire detection system located?
In an area that is relatively protected from the initial flame, but is still in the same fire zone
Common name for the Fenwal and Walter kidde fire sensors?
Fire-wire
In the Systron-Donner sensor/responder fire detecting system illustrated below, if the sensor was damaged and the helium gas was depleted?
The integrity switch contacts would open and ‘No’ fire indication would be visible during test
refraction smoke detection system, when a smoke level of about 10% is present in the chamber, some of the pilot light is reflected off the smoke and onto the what?
Photo diode
To ensure aircrew know that a light detecting smoke detector is operating what iluminates?
The small green indicator light above the window is illuminated
2 types of turbine engine starting systems? And common aircraft application?
- Starter generator system (Commonly found on light aircrafts where weight is a major concern - CT4)
- Air / Bleed air starting (Jet engines)
Components of a typical air starting system?
- Starter motor
- SCV (Start control valve)
What is an SCV?
What does it do?
Start control valve
(Like a butterfly valve)
Controls the flow of low pressure air (from the ground cart) to the starter motor
In reference to bleed air sources, the starter motor is rotated by what?
- Air taken from an external ground supply
- An auxiliary power unit (APU)
- Bleed air from a running engine
What is a HEIU?
What is its function?
High energy ignition unit
- Central component of the jet engine ignition system
- Produces the high energy spark necessary to ignite the fuel / air mix at engine start
Components of a gas turbine engine dual high energy ignition system?
- Relight switch
- Ignition switch
- Bus
- Ignition relay
- High energy ignition unit x 2
- High tension ignition leads x 2
- Ignitor plug
- Gas turbine engine
Surface discharge plug commonly used on modern aircrafts in place of a spark plug?
Flash over - Semi-conducting pellet
HEIUs are rated in what?
Joules
2 classifications of HEIUs?
High joule (12 joule)
Low joule (3-6 joule) units
HEIU safety precautions?
- After use, allow recommended amount of time (typically 5 minutes) to elapse before handling or disconnecting!!!!!!!!!
- Do not touch HEIU when operating
- When removing HEIU, disconnect the input plug before the output plug !!!!!
- When installing, connect the output plug before connecting the input plug !!!!
- HEIU and igniter plugs to be earthed
- Do not test in confined spaces where flammable vapours may be present
- Consult relevant pubs
2 types of reciprocating (piston) engine ignition systems?
- Coil ignition
- Magneto ignition
Common issues with a coil ignition systems?
- Timing can be out
- Contact can wear down and throw the timing
- Distributor is mechanical / overall maintenance is increased
Components of a coil ignition system?
- Battery
- Ignition switch
- Ignition coil
- Distributer
- Distributor
- Capacitor
- Spark plugs
Components of a typical magneto ignition system?
- Magneto
- Auxiliary starting device
- Ignition switch
- Ignition harness
- Spark plugs
4 ratings for aircraft lamps?
- Voltage
- Current in amperes
- Wattage
- Candle power or CP.
4 types of lamps in aircrafts?
- Incandescent
- Incandescent sealed beam
- Light emitting diodes (LED)
- Capacitor-discharge flash tube.
Exterior lighting system in aircrafts are divided into 5 different groups - what are these groups?
- Navigation
- Formation
- Anti-collision
- Landing / taxi
- Ice inspection
Navigation lights positioning on aircrafts?
- Green light located on the starboard (right hand) wingtip
- Red light located on the port (left hand) wingtip
- White light located on the rear of the aircraft (tail).
2 types of anti-collision lights?
- Rotating beacon
- Strobe light
2 basic types of landing lights?
- Fixed
- Retractable
Taxi lights
- Used on the taxiway while taxiing at night or when visibility conditions are poor
- Typically 250W
Light aircrafts: located on the nose of the landing gear assembly
Larger aircrafts: have multiple taxi lights and are located on areas such as above the main wheel well or on the top of the wing
Ice inspection lights
- Lights are recessed into each side of the fuselage or sometimes mounted on the top of the engine cowlings
- Controlled by the use of toggle switch
- If ice is detected, the aircrew can turn on the de-icing system to remove the ice
Internal lighting on aircrafts are divided into 4 main categories - what are they?
- Cockpit / instrument
- Aircrew / passenger
- Servicing lighting
- Emergency
In reference to internal lighting, cockpit / instruments - what 5 basic methods are used to provide instrument and panel lighting?
- Integral instrument lighting
- Trans-illuminated panel lighting
- Flood-lighting
- Ultra- violet lighting
- Post and bridge lighting
In reference to warning lights, what does each colour represent?
Red - Warning lights - Failure occurring in a major system
Amber - Caution lights - abnormal but not necessarily dangerous condition exists
Green - advisory lights - system is in a normal state
Mandatory requirements of a fire detection unit?
- Are durable and resistant to damage from all of the environmental factors
which may exist in the location where it is installed - Include an accurate and effective method for testing to ensure the
integrity of the system - Are easy to inspect, remove and install
- Are designed so the possibility of false indications is unlikely
- Accurately indicate that a fire has been extinguished and indicate if a fir
re-ignites - Require a minimum of electrical power and operate from the aircraft
electrical system without inverters or other special equipment
Basic construction of a thermocouple fire detection sensor?
A thermocouple sensor consists of two dissimilar metals (e.g.: chromel and
constantan) joined at both ends to form two junctions. If one junction is
heated, current proportional to the difference in temperature between the
two junctions will flow in the circuit.
What is negative torque?
Adjusts the pitch angle of the props so it doesn’t speed the engine
Where is the target of the synchro phasor?
On the de-icing platter
What is the differential pressure switch and engine throttle micro?
Most common thermal switch fire detection sensor?
And its operation?
Spring bow thermal sensor
Operation:
- Expansion tube heats up
- Springs expand
- Contacts are pushed together
- Set off the alarm
2 types of Tubular Sensors (Fire-Wire)?
And describe the operation of each?
Fenwel sensor
Operation:
Walter Kidde Sensor
Operation:
Explain the operation of a thermal switch overheat detection system?
Requirements of a fuel tank?
- Clean
- Continuous flow
- Constant pressure
What is the normal spark rate of a typical jet engine ignition system?
Between 60 and 100 sparks per minute
What are the 2 types of reciprocating (piston) engine ignition systems?
- Coil ignition
- Magneto ignition
What controls a prop control system?
Prop governor
Prop control system: 2 basic modes?
- Propeller governing mode (alpha range or flight range)
- Beta mode (ground range)
Description of anti-collision lights?
They are a high intensity red or white light that flashes on and off at a typical frequency of 80 - 90 cycles per minute
Speed lever in cockpit: 3 positions?
- Low
- Cruise
- High
Typical flashing frequency of strobe lights?
70 times per minute
(Strobe lights at a disco in the 70s)
What is a Trans-Illuminated Panel?
- Sometimes known as edge lighting
- Method used to illuminate etched inscriptions on cockpit panels to make them readable under night conditions
- When the lamps (located just under the surface of the panel) are
turned on, all of the writing and arrows are illuminated. This makes them stand out against the black background.
Define dome lights?
- Type of flood-light
Usually situated overhead to illuminate an area such as:
- the cockpit
- passenger
- cargo
- galley area
- Dome lights can usually be selected to provide white light
Define floor lights?
These are another type of flood-light and, as the name suggests, are mounted at floor level to illuminate walkways and stairways.
Auxiliary starting devices?
- Booster coils
- Induction vibrators
- Impulse coupling
3 basic types of magnetos?
- Rotating magnet
- Rotating armature
- Polar induction
In a rotating magnet magneto schematic system, what position is the switch in then it is in the ON position?
ON - switch is open
OFF - switch is closed and circuit is complete / this will short circuit as these is an earth connected on both ends
Ignition switch has 4 positions, what are they?
- Off
- Left
- Right
- Both
Magneto safety precautions?
- Always place the magneto ignition switch to OFF in the cockpit (short circuiting the contact breaker)
- If the ignition switch connection to the magneto is disconnected - fit auxiliary earth lead to magneto connection to short circuit the contact breaker / or disconnect secondary winding of the magneto coil
2 main groups of propellers?
- Fixed
- Variable
2 types of fixed propellers?
Fixed pitch: needs to be removed and replaced to change the pitch
Adjustable (ground) pitch: Can be adjusted by technicians on the ground by moving the prop blades
2 types of variable propellers?
Controllable: Change pitch by the pilot moving a lever and adjusting it as they please
- Electric
- Hydro-mechanical
Constant speed: Automatically changes pitch of the blades to maintain constant engine speed
(when the governor senses a change in engine RPMs it will direct the pitch the change accordingly)
Feathering - what is it? And what are the methods typically used?
Prop blades are parallel to the direction of flight (thick edge of prop to face direction of travel)
- Used to eliminate drag
- Prevent damage to airframe and engine
Methods:
- Mechanical
- Electrical
Reverse thrust: what is it?
Reversing the direction of the propulsion of the propeller
- Useful for ground handling the aircraft as it can be used to manoeuvre backwards
- Can be used to slow the aircraft down upon landing, shortening the roll / reduces the required amount of brakes required and increases life span
- Requires weight on the wheels
Define:
- propeller synchroniser
- Propeller synchrophaser
Synchroniser:
- Automatically matches speed of one engine with another
- controlled by the synchroniser control
Box
Synchrophaser:
- Automatically matches speed as above
- Also allows the pilot to select the phase relationship to minimise noise and vibration
4 most common types of flight controls?
- Mechanical flight controls
- Mechanical-hydraulic flight controls
- Electrical-hydraulic with mechanical input
- Electrical-hydraulic (fly-by-wire)
Mechanical hydraulic flight control system: hydraulic oil is supplied to the servo-actuator at what PSI?
Approx 3000 PSI
Definition of a servo-actuator?
- A type of motor for moving or controlling a mechanism or system
- Automatic source of energy
Servo-actuators: convert signals into control surface movements by what 3 methods?
- Hydraulic pressure
- Pneumatic pressure
- Electrical motor movement
Therefore, the 3 main types of servo motors are:
- Electro-pneumatic
- Electro-mechanical
- Electro-hydraulic
Electro-hydraulic landing gear system: safety precautions
- Keep clear of undercarriage doors and components during retraction and extension
- Ensure undercarriage cannot be retracted or extended whilst performing work in the area
- Trade sup must be present to coordinate retraction / extension cycles
- Must be trained and authorised to be in charge of a hydraulic test rig
Anti-collision lights: Typical frequency of flashing?
80-90 cycles per minute
