Auxiliary Power Unit (APU)
Index
- About Auxiliary Power Unit (APU).
- Starting procedure of Airbus A320 Auxiliary Power Unit (APU).
- Why CSD not used in Auxiliary Power Unit (APU)?
- How many switches in Airbus A320 to shutdown Auxiliary Power Unit (APU)?
- How to shut down Airbus A320 Auxiliary Power Unit (APU) in case of APU fire?
- Where is the APU on Airbus A320?
- Can A320 fly without Auxiliary Power Unit (APU)?
- What happens if APU fails in flight?
- Can you start engine without APU?
- Does the APU run during flight?
- Is APU DC or AC?
- What are main components of APU?
- Purpose of Airbus 320 APU (Auxiliary Power Unit) starter motor.
An Auxiliary Power Unit (APU) is a small gas turbine engine installed on an aircraft that provides electrical power and pneumatic power while the aircraft is on the ground. It is typically used to start the main engines, power the aircraft's electrical systems, and provide climate control before takeoff.
The APU is usually located in the tail section of the aircraft and is connected to the aircraft's electrical and hydraulic systems. It is started using a battery or a pneumatic starter, and once it's running, it can power the electrical system, which in turn can start the aircraft's main engines.
In addition to providing electrical power, the APU can also provide pneumatic power to air conditioning to cool the aircraft's cabin, start engines etc.
The APU is a valuable part of modern aircraft as it allows the aircraft to operate independently of ground-based electrical and pneumatic system. This can be useful for remote airports or when there is a power outage at the airport. The APU can also provide backup power in the event of an engine failure, allowing the aircraft to make a safe landing.
Starting procedure of Airbus A320 Auxiliary Power Unit (APU).
The Airbus A320 has a standard starting procedure for the Auxiliary Power Unit (APU) that involves several steps. Here is a general overview of the APU starting procedure for the Airbus A320:
- Check that the APU master switch is in the OFF position.
- Turn on the battery master switch and verify that the battery voltage is adequate for starting the APU.
- Set the APU start switch to the ON position. This sends a signal to the APU to begin the start sequence.
- Observe the APU EGT (Exhaust Gas Temperature) indicator to monitor the APU's temperature as it starts.
- Once the EGT indicator starts to rise, turn on the APU generator switch to begin generating electrical power.
- When the APU RPM (Revolutions Per Minute) indicator stabilizes, the APU is considered started and is now providing compressed air and electrical power to the aircraft systems.
- When the APU RPM reaches 95%, turn on the APU Generator switch on the overhead panel.
- When the APU RPM stabilizes at 100%, verify that the APU Bleed switch is in the OFF position.
- Check the APU parameters on the E/WD and SD screens to ensure that they are within normal ranges.
- Set the APU bleed air switch to the ON position to supply air to the air conditioning and pressurization systems.
- Check the APU operating parameters, such as oil pressure, oil temperature, and fuel flow, to ensure they are within the normal range.
- If the APU is required for engine start, wait for the APU to stabilize before starting the engines.
- Once the APU is running and stable, the APU master switch can be set to the ON position to transfer the electrical load to the APU.
It's important to note that the exact starting procedure may vary depending on the specific model of the Airbus A320 and the airline's standard operating procedures. Pilots should always refer to the aircraft manufacturer's operating manual and the airline's specific procedures to ensure a safe and efficient APU start.
Why CSD not used in Auxiliary Power Unit (APU)?
In the context of aircraft systems, CSD stands for Constant Speed Drive. A CSD is a device used to maintain a constant speed of a generator or hydraulic pump, regardless of the speed of the engine or motor that drives it.
While CSDs are commonly used in the main engine systems of aircraft, they are generally not used in the APU. This is because the APU operates at a constant speed and does not require a CSD to maintain a constant speed of the generator or hydraulic pump.
APUs typically have a single-speed generator or hydraulic pump that is directly connected to the APU's turbine. Since the APU runs at a constant speed, the generator or hydraulic pump also runs at a constant speed, eliminating the need for a CSD.
Additionally, adding a CSD to the APU system would increase its weight and complexity, which could negatively impact the aircraft's performance and increase maintenance requirements. For these reasons, APUs generally do not use CSDs.
Instead of using CSDs, APUs typically use a combination of control systems and other devices to regulate their speed and provide the required power to aircraft systems.
For example, the APU's control system can regulate fuel flow and other parameters to maintain the desired operation, while the generator is designed to provide a constant voltage and frequency output to the aircraft's electrical system.
In conclusion, while CSDs are useful devices for regulating the speed of engine-driven accessories, they are not typically used in APUs due to their size, weight, power requirements, complexity, cost, and potential impact on efficiency. Instead, APUs are designed to be simple, reliable, and highly efficient, using control systems and other devices to regulate their speed and provide the required power to aircraft systems.
How many switches in Airbus A320 to shutdown Auxiliary Power Unit (APU)?
There are typically two switches that are used to shut down the Auxiliary Power Unit (APU) on an Airbus A320 aircraft:
APU Master Switch: This switch is located on the overhead panel and is used to turn off the APU. When the switch is turned off, the APU will shut down, and its exhaust gas temperature and RPM will begin to decrease. This switch also controls the APU generator and bleed air systems.
APU Fire Switch: This switch is also located on the overhead panel as well as on 108 VU and is used to shut down the APU in case of a fire or other emergency. When the switch is moved to the SHUT OFF position, the APU fuel valve is closed, and the APU will shut down.
It's important to note that the exact location and labeling of the switches may vary slightly depending on the specific aircraft configuration and airline operating procedures. Additionally, there may be other procedures and checks that need to be performed before and after shutting down the APU to ensure safe and proper operation.
How to shut down Airbus A320 Auxiliary Power Unit (APU) in case of APU fire?
In case of an APU fire on an Airbus A320 aircraft, the following procedure should be followed to shut down the APU:
- The APU FIRE switch on the overhead panel or 108VU should be selected to the SHUT OFF position. This will close the APU fuel valve and shut down the APU.
- The APU BLEED switch on the overhead panel should be set to the OFF position to prevent any further spread of the fire.
- The APU fire extinguishing system should be activated by pushing the APU Fire Extinguisher pushbutton on the overhead panel. This will discharge the APU fire bottle and release the fire extinguishing agent into the APU compartment.
- The APU Generator switch on the overhead panel should be set to the OFF position.
- The APU Master switch on the overhead panel should be set to the OFF position.
- The APU status on the overhead panel should be checked to ensure that it is off.
- The APU fire condition should be monitored and managed using the appropriate procedures and equipment, such as the fire extinguisher system, fire detection system, and emergency equipment.
It's important to note that the exact procedures for handling an APU fire may vary depending on the airline's operating procedures, the specific aircraft configuration, and the nature of the fire. It's always best to follow the procedures outlined in the aircraft's operating manual and to consult with the appropriate personnel to ensure safe and effective management of the situation.
Manufacturer of the Airbus A320 Auxiliary Power Unit (APU).
The Auxiliary Power Unit (APU) for the Airbus A320 family of aircraft is typically manufactured by Honeywell Aerospace. The APU model commonly used on the A320 is the Honeywell GTCP 131-9A.
Honeywell Aerospace is a major aerospace manufacturer and a leader in APU technology. The company produces a wide range of APUs for various aircraft models and applications, including commercial airliners, military aircraft, and business jets. Their APUs are known for their reliability, efficiency, and performance.
Where is the APU on Airbus A320?
On an Airbus A320 aircraft, the Auxiliary Power Unit (APU) is located in the tail cone section of the fuselage. It is mounted in a compartment at the rear of the aircraft, below the empennage (vertical stabilizer).
The APU intake is located on the lower left side of the tail cone, while the exhaust is located on the right side or center of tail of the aircraft. The APU is connected to the aircraft's electrical, pneumatic, and hydraulic systems, and provides power and air conditioning while the aircraft is on the ground or in flight.
The APU compartment is equipped with fire detection and extinguishing systems, as well as other safety features to ensure safe and reliable operation. It's important to follow the proper procedures and precautions when operating and servicing the APU to ensure the safety of personnel and the aircraft.
Can A320 fly without Auxiliary Power Unit (APU)?
Yes, an Airbus A320 aircraft can fly without the Auxiliary Power Unit (APU) if necessary. The APU is not a critical component for flight and is primarily used to provide electrical power, air conditioning, and pneumatic power when the engines are not running or not providing enough power.
During normal operations, the APU is typically used on the ground before engine start, and during flight to provide electrical power and air conditioning to the cabin. However, if the APU is not available or not required, the aircraft's electrical, pneumatic, and hydraulic systems can still be powered by the engines or by external power sources, such as ground power units.
In the event of an APU failure or shutdown, the pilot can still operate the aircraft normally and safely using alternate power sources and procedures. It's important to follow the appropriate operating procedures and checklists to ensure the safety and reliability of the aircraft during these situations.
What happens if APU fails in flight?
If the Auxiliary Power Unit (APU) on an Airbus A320 aircraft fails in flight, it will typically result in the loss of the APU generator, which provides electrical power to the aircraft's electrical system. The aircraft's other power sources, such as the engines or an external power unit, will need to be used to provide electrical power to the aircraft systems.
In addition to the loss of electrical power, the failure of the APU can also result in the loss of air conditioning and pneumatic power provided by the APU. However, the aircraft's systems will automatically switch to alternative sources of air conditioning and pneumatic power, such as engine-driven compressors and bleed air.
The APU failure will trigger a series of alerts and warnings in the cockpit, and the pilots will need to follow the appropriate procedures and checklists to manage the situation. Depending on the nature and severity of the APU failure, the pilots may need to divert to an alternate airport or make an emergency landing.
It's important to note that the APU failure is a relatively rare event, and Airbus aircraft are designed and tested to operate safely and reliably with various types of failures and malfunctions. The pilots are trained to manage these situations and ensure the safety of the aircraft and its passengers.
Can you start engine without APU?
Yes, an Airbus A320 aircraft can start its engines without the Auxiliary Power Unit (APU) running, as long as an external power source (Jet Starter) is available. An external power source, such as a ground power unit (GPU), can provide electrical power to the aircraft's electrical system and allow the engines to be started.
The aircraft's engines can be started using either the pneumatic start system, which uses high-pressure air from the APU or external power source to spin the engine's turbine and initiate combustion, or the crossbleed start system, which uses bleed air from a running engine to start a second engine.
It's worth noting that starting the engines without the APU can result in longer engine start times and may require additional coordination between the pilots and ground personnel to ensure that the external power source is properly connected and supplying sufficient power. Additionally, the APU provides backup power and can be used in case the external power source fails.
Does the APU run during flight?
No, the Auxiliary Power Unit (APU) does not run during flight on an Airbus A320 or any other commercial aircraft. The APU is primarily used on the ground to provide electrical power, air conditioning, and other systems to the aircraft when the engines are not running.
During flight, the aircraft's electrical system is powered by the engines, which generate electrical power through the engine-driven generators. The air conditioning and other systems are also powered by the engines, which provide compressed air through the engine bleed air system.
Once the engines are started and running, the APU is typically shut down to conserve fuel and reduce maintenance costs. However, in certain situations, the APU may be used during flight as a backup power source or to provide additional electrical power or air conditioning. For example, if one or more of the engine-driven generators fail, the APU can be started and used to provide electrical power to the aircraft systems. However, this is a rare occurrence and is typically managed by the pilots using specific procedures and checklists.
Is APU DC or AC?
The Auxiliary Power Unit (APU) on an Airbus A320 is a source of AC (alternating current) electrical power. The APU generates electrical power through an alternator, which produces AC electrical power at a frequency of 115 volts and 400 hertz. This electrical power is used to power various systems on the aircraft, including the air conditioning, lighting, and other electrical systems, when the engines are not running or during specific phases of flight.
The APU also has a DC (direct current) electrical system, which is used to power the APU starter motor, APU fuel solenoid, and APU battery charger. The APU battery charger converts the AC electrical power generated by the alternator to DC electrical power to charge the APU battery.
What are main components of APU?
The Auxiliary Power Unit (APU) on an aircraft is a self-contained unit that provides electrical power, air conditioning, and other essential systems when the main aircraft engines are not running. The main components of an APU can vary depending on the specific model, but typically include:
Turbine engine: The turbine engine is the heart of the APU, which produces the mechanical energy to drive the generator and compressor.
Generator: The generator is driven by the turbine engine and produces AC electrical power to power the aircraft's electrical systems.
Compressor: The compressor draws in outside air and compresses it to a high pressure, which is then used to drive various systems on the aircraft, such as the air conditioning and pneumatic systems.
Fuel system: The fuel system is used to deliver fuel to the turbine engine for combustion and power generation.
Electronic control unit: The electronic control unit monitors and controls the APU's functions and systems, including the fuel system, compressor, and generator.
Battery: The battery provides the initial power to start the APU, and also serves as a backup power source for critical aircraft systems.
Exhaust system: The exhaust system is used to expel the hot gases produced by the turbine engine during operation.
Air intake: The air intake system provides cool air to the compressor for use in driving the various systems on the aircraft.
