40 Questions
What is the purpose of lubricating quick release terminals with white petroleum jelly?
To prevent corrosion forming on the contacts
Why must an aircraft battery be securely mounted in the aircraft?
To reduce the risk of the battery becoming dislodged during flight
What type of nuts are commonly used to secure the battery in place?
Wing nuts and hexagonal nuts
What is the first step to take when installing a new battery in an aircraft?
Refer to the aircraft maintenance manual
Why should the positive lead be connected first when installing a battery?
To prevent a spark from occurring
What should be checked before installing a new battery in an aircraft?
The vent and drain lines, and the neutralising jar
Which terminal of the battery is typically connected to the aircraft structure?
The negative terminal
What should be done first when removing a battery from an aircraft?
Disconnect the negative lead
What is the main purpose of the reverse current cut-out relay?
To automatically disconnect the battery from the generator when the generator voltage is less than the battery voltage
What would happen if the reverse current cut-out relay was not used in the generator circuit?
The battery would discharge through the generator, driving it as a motor
What is the purpose of the current winding, L4, in the three-unit regulator?
To carry the entire line current in series with the line
What happens to contact C3 when the generator is not operating?
It is held open by the spring S3
What is the effect of the coil spring, S3, on the voltage winding, L5?
It holds the contact points open until the generator voltage is more than the battery voltage
What happens to the magnetic field of L4 when the generator slows down or the generator voltage decreases?
It opposes the magnetic field of L5
What is unique about contact C3 compared to C1 and C2?
It does not vibrate
What is the effect of the charging current passing through L4 on the contacts C3?
It holds the contacts tightly closed
What is the normal operating temperature for the cooling oil?
93 °C (200 °F)
How is the oil level typically monitored in a constant-speed drive?
Through a sight glass
What happens in the event of an in-flight oil loss or over-temperature condition?
A warning indicator illuminates on the flight deck
What is the purpose of the electrically activated generator-drive disconnect mechanism?
To disconnect the CSD input shaft from the CSD input spline
How can the CSD disconnect be activated?
Either manually or automatically
What happens to the CSD after disconnection?
It can only be reconnected on the ground
What is the main function of the hydraulic transmission in an IDG installation?
To govern the rotational speed of the alternating current generator
What components work together to control the power used to drive the alternating current generator?
The differential, variable displacement hydraulic units, and fixed displacement hydraulic units
What is the frequency output of a rotary inverter?
400 Hz
What is a major disadvantage of a rotary inverter compared to a static inverter?
Lower surge capability
What should be done if the control box on top of a rotary inverter appears to be defective?
Send it to a repair shop
What is the input voltage range for a rotary inverter?
26 to 29-V DC
What is an advantage of a static inverter compared to a rotary inverter?
Less maintenance required
What is the output voltage of a static inverter?
115 V, single-phase
Why are rotary inverters being replaced by static inverters?
More maintenance required
What feature do rotary inverters have that allows them to automatically start and stop?
Automatic load demand
What is the primary source of power for an AC bus?
Main generator
What type of systems are supplied power by essential buses?
Essential lighting, flight control systems, communication and navigation systems
What is the purpose of load shedding in an aircraft?
To prevent overloading the active generator during partial generator system failure
What is the function of a Bus Tie Breaker (BTB) in a twin-engine split bus system?
To couple power from one bus to the other during generator failure
What is the main difference between a basic DC generation bus system and a basic twin-engine split DC bus system?
The number of generators used
What is the primary purpose of an AC bus system?
To supply power to essential systems
What is the function of the inverter in a basic DC generation bus system?
To provide AC voltage to the aircraft
What is the term for non-essential buses that supply power to low-priority electrical systems?
Shed buses
Study Notes
Battery Connections and Installation
- Quick-release terminals are lubricated with white petroleum jelly to prevent corrosion and ensure serviceability.
- Batteries must be securely mounted in the aircraft using a mounting cradle and bolts, and secured with lockwired nuts or clamps.
- Battery installation procedures:
- Ensure the correct type of battery is used, referring to the aircraft maintenance manual.
- Check the mounting tray, box, or compartment and surrounding area are clean and free of corrosion or contamination.
- Check the vent and drain lines are in good condition and not blocked.
- Check the neutralizing jar is serviceable.
CSD/IDG Operation and Indications
- Normal operating temperature for the cooling oil is approximately 93°C (200°F).
- Oil level should be monitored periodically to maintain correct cooling capacity.
- A warning indicator will illuminate on the flight deck in the event of an in-flight oil loss or over-temperature condition.
- The CSD can be disengaged and inspected upon landing.
- The CSD disconnect is switched manually from the aircraft’s flight deck or automatically by a generator control unit.
Generator and Electrical Systems
- IDG installation consists of an alternating current generator and a hydraulic transmission with mechanical control governing the rotational speed of the generator.
- The power used to drive the generator is controlled and transmitted from the aircraft engine through the combined effects of the differential, variable displacement hydraulic units, and fixed displacement hydraulic units.
- The reverse current cut-out relay automatically disconnects the battery from the generator when the generator voltage is less than the battery voltage.
- The AC bus is fed from its respective main generator and supplies power to essential and non-essential systems.
- Load shedding involves isolating non-essential systems during partial generator system failure to prevent overloading the active generator.
DC and AC Bus Systems
- Basic DC generation bus system: a single generator charges the battery and supplies power to the aircraft.
- Basic twin-engine split DC bus system: each generator powers its own individual bus, and if one generator fails, the failed generator is isolated from its bus, and the power on the other bus is coupled to that bus by a Bus Tie Breaker (BTB).
- Basic twin-engine split AC bus system: AC generators supply their individual buses, and fans provide air cooling for the generators.
Inverters
- Rotary inverters:
- Supply 115 V, single-phase or three-phase, or 200 V, three-phase AC power at 400 Hz.
- Have automatic load demand and shut down when the load is removed.
- Disadvantages include lack of frequency control, low surge capability, and lower efficiency.
- Require more scheduled maintenance than static inverters due to mechanical parts.
- Static inverters:
- Serve the same functions as rotary inverters but have no moving parts.
- Are subject to less maintenance problems than rotary inverters.
- Can produce 115 V, single-phase alternating current with a frequency of 400 Hz.
Learn about the proper installation and connection of batteries in aircraft, including secure mounting, corrosion prevention, and correct battery type.
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