AAS Flashcards
Important
Function of a starter generator system?
Book 1
- A DC motor is used in a starter generator system to start the aircraft engine
- It can then be used as a generator to supply the aircraft DC bus and recharge the battery.
- Still used in light aircraft’s where weight is a major consideration
What advantages does Bleed Air have over other starting systems?
Book 1
It has many advantages over other starting systems, and is comparatively light, simple and economical to operate
What are the main components of a typical air starting system?
Book 1
The main components of a typical air starting system are a starter motor and a start control valve.
Important
Bleed air sources - the starter motor is rotated by 3 main power sources, these are?
Book 1
- air taken from an external ground supply
- an auxiliary power unit (APU)
- bleed air from a running engine
Important
What is the purpose / function of an APU in an automatic starting system used in modern aircraft’s?
Book 1
- Forms integral part of the engine starting system
- Supply low pressure air
- Commands / controls signals to components in the engine control system
The APU supplies Low Pressure air for the air starting motor
Label the components in the Starter Circuit Diagram
Book 1
- Auxillary Power Supply Control Unit
- APU Starter Motor
- APU
- Air Starter Motor
- Turbofan Engine
What are the components of a Engine Ignition System?
Book 1
The engine ignition system supplies the electrical power necessary to operate the engine igniters during start/relight sequences.
The system includes two
high energy (HE) ignition units, two HE igniter leads and two igniter plugs.
Important
What does the Gas Turbine Start caption (GTS) indicate in the cockpit?
Book 1
The captions come on to indicate that the APU is running and ready to supply Low Pressure air
What is a “ENG START “START-ON-OFF” switch in the cockpit.
Book 1
The switch that controls the main power supply to the APU and engine starting system
What is an “IGNITION “NORMAL-ISOLATE” switch in the cockpit?
Book 1
This switch
controls the power supply to the engine ignition system
What is a “ROT” or Rotation caption in the cockpit.
Book 1
During a start/relight sequence, the captions come on to indicate that the engine low pressure
section rotating assembly is turning at more than 100 RPM (in the correct
direction).
What is the Auxiliary Power System Control Unit (APSCU)?
Book 1
The APSCU is the brains behind the starting system.
It contains components and circuits to control and monitor the APU and engine start sequences.
To control and monitor the APU and engine start sequences
What is the central component of a Jet Engine Ignition System?
Book 1
The central component of the jet engine ignition system is the High Energy
Ignition Unit (HEIU)
Where are the ignition switches located in a Jet Engine ignition system?
Book 1
The ignition and relight switches are located in the aircraft cabin, usually close to the throttles.
They connect bus voltage to the ignition relay and HEIUs
What is the purpose of
High Tension Ignition Leads in a Jet Engine Ignition System?
Book 1
The high tension ignition leads are located on the aircraft engine, connected between the
HEIUs and the igniter plugs.
They conduct the high voltage from HEIUs to the igniters
What occurs if a flame-out happens during flight?
Book 1
The engine continues to rotate due to airflow; ignition source is needed to re-ignite the fuel/air mixture
What are the four main precautions when dealing with High Energy Ignition Units (HEIU)?
Book 1
- do not touch the HEIU when operating
-
allow the recommended amount of time to elapse before
handling the HEIU or disconnecting associated circuitry - when removing the HEIU, disconnect the input plug before the output plug
- when installing the unit, connect the output plug before the input plug
Electrical isolation
Removal - Disconnect input first
Installation - Connect output first
Do not touch when operating
Allow the recommended time to elapse before touching it
A typical magneto ignition system contains what components?
Book 1
- magneto
- auxiliary starting device
- ignition switch
- ignition harness
- spark-plugs
Label the components in the Rotating Magnet Magneto
Book 1
- Secondary Winding
- Primary Winding
- Magneto Switch
- Distrubition
- Rotor
Due to the magneto producing high voltages, without an external power source. What are some safety requirements to ensure electrical safety?
Book 1
Always place the magneto ignition switch in the cockpit to the OFF
position, thus short-circuiting the contact breaker points
What is the purpose of the Auxiliary starting device?
Book 1
A fundamental weakness of all magnetos is that the strength of the spark is proportional
to the rotor speed.
It is therefore necessary to provide auxiliary means for boosting the magneto output during
the engine starting period.
i.e. It boosts the strength of the spark
What is the source of high pressure oil for the controlling the proppeller?
Book 2
In both PGM and Beta mode.
The source of high pressure oil for controlling the propeller is the propeller governor.
What is the purpose of the unfeather pump, in a propeller control system?
Book 2
The unfeather pump provides oil pressure for moving the
blades out of the feather position on the ground and for air starting the engine
What two basic modes of the propeller control system?
Book 2
- Propeller governing mode (alpha range or flight range)
- Beta mode (ground range).