29 Questions
What component in a turbine-powered aircraft converts the variable engine rpm to an alternator input speed of 12,000 rpm?
CSD
How does the Quick Attach/Detach (QAD) adapter facilitate the maintenance of a turbine aircraft?
Allows quick removal and replacement of the generator and CSD assembly
What is the purpose of the Integrated Drive Generator (IDG) in modern turbine-powered aircraft?
To reduce the weight and size of the traditional two-unit system
Which component cannot be replaced separately from the Integrated Drive Generator (IDG)?
Generator
What is the typical rotation speed range of older alternators in turbine-powered aircraft?
$8000$ to $9000$ rpm
What does the Constant Speed Drive (CSD) in a turbine aircraft contain that helps in RPM conversion?
Hydraulic trim units and a differential assembly
What is the purpose of oil cooling in a generator section?
To increase the speed of the rotor
In case of a complete failure of engine-driven generators, what powers emergency generators in aircraft?
Airstream-driven generator
What type of alternators are emergency generators typically equipped with?
Permanent magnet alternators
What is the function of the hydraulic motor-driven emergency generator system on larger transport aircraft like the Airbus A330?
To restore essential power during a loss of normal electrical power
Why do emergency AC generation systems on aircraft typically use hydraulic motors?
To avoid battery usage
What is the key advantage of emergency generators being constructed with permanent magnet rotors?
Elimination of battery dependency
What causes the external power relay to open?
Tripping the operational generators
What happens when the GCB of the second aircraft engine closes?
The BTB trips
How are the essential AC loads supplied under normal operating conditions?
From the no. 1 generator bus
What happens when one of the generators becomes inoperative?
The BTB closes to allow power distribution
What is the purpose of connecting both generator buses together by closing the BTB?
To enable power supply from the serviceable generator to all system loads
What does supplying power via auxiliary contacts of a tripped GCB to the BTB's close coil achieve?
Closes the BTB
What is the purpose of the three-phase contactor in an aircraft AC external power system?
To monitor the input voltage and phase rotation of the external power source.
Why is the external power contactor de-energized when an onboard generating source is brought online?
To prevent any conflicts between different sources of power.
What happens when any inconsistency in the input external power is detected?
The three-phase contactor inhibits the application of power to aircraft systems.
Why is it important to remove ground power when onboard generating sources are brought online?
To enable the aircraft to switch between different power sources seamlessly.
What role does the external AC power schematic play in an aircraft's electrical system?
It ensures a continuous and stable supply of power to the aircraft systems.
Why is the DC external power receptacle designed with two large pins and a smaller pin?
To enable interlock sensing and polarity check
What purpose does the plug design with different-sized prongs serve?
To prevent incorrect insertion of the plug in the receptacle
Why is the smaller pin in the DC external power receptacle shorter than the main pins?
To prevent arcing at the pins during plug withdrawal
What safety feature is implemented by the DC external power receptacle design?
Preventing reverse polarity or reverse phase sequence issues
Why is it important for the external power relay to de-energize before the main pins are disengaged during plug withdrawal?
To prevent damage to the aircraft's electrical components
What event triggers the de-energization of the external power relay?
Removal of the plug from the receptacle while in use
Study Notes
Hydraulic Motor and Generator
- The pump supplies hydraulic pressure to a hydraulic motor, which varies the ratio of input rpm to output rpm to maintain a constant output rpm to drive the generator and maintain an AC frequency of 400 Hz.
- Quick Attach/Detach (QAD) adapter allows for quick removal and replacement of the generator and CSD assembly in a matter of minutes.
Integrated Drive Generator (IDG)
- The IDG contains both the generator and the CSD in one unit, reducing weight and size compared to traditional two-unit systems.
- The generator is an integral part of the IDG and cannot be replaced separately.
- The CSD converts variable engine rpm to an alternator input speed of 12,000 rpm.
- Oil cooling allows for a higher-speed rotor within the generator section, resulting in a lighter, more compact generator.
Emergency Power Generation
- Emergency power generation is installed on many aircraft to supply essential power in the event of losing all normal power generation.
- Emergency generators are typically permanent magnet alternators and do not require battery power to function.
- Hydraulic electrical generating system (HEGS) uses a hydraulic motor-driven emergency generator system to provide emergency or standby electrical power.
Hydraulic Electrical Generating System (HEGS)
- The system consists of a hydraulic motor-driven generator designed to restore the essential power network in case of the loss of both normal main generator buses.
- The generator is driven by a hydraulic motor supplied by an airstream-driven hydraulic pump.
External and Ground Power
- External AC power systems incorporate circuits that monitor input voltage and phase rotation.
- If any inconsistency in input external power is sensed, the application of power to aircraft systems is inhibited by the three-phase contactor.
- The DC external power receptacle has specific design features to prevent incorrect connection and ensure safe power supply.
Test your knowledge on hydraulic systems, generators, and CSD assemblies in the context of turbine aeroplane aerodynamics, structures, and systems as per CASA Part 66 training materials.
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