Terms in this set (36)
What are the two main purposes of an APU?
1. Provide power to the entire electrical system
2. Provide high pressure air for engine starts and air conditioning operation
Does APU bleed air or APU electric have priority?
What monitors and controls all APU operations (start, shutdown, speed, bleed air, etc)?
The APU Electronic Control Box (ECB)
What happens when the APU MASTER SW pb is selected to ON?
1. Electrically powers the APU system (Blue ON light)
2. ECB performs a power up test
3. ECAM APU System Page comes up (if on AC power)
4. APU air intake flap opens
5. APU fuel isolation valve opens
6. APU fuel pump operates (if no pressure)
Where is the APU intake flap?
Bottom of the aft fuselage, beneath the APU compartment.
After the APU MASTER SW pb is selected on, the APU computer will not permit an APU start until what happens?
The APU intake flap is fully open.
What two things are required for the APU starter motor to engage?
1. The APU intake flap must be fully open
2. The APU START pb must be selected ON
How is the APU starter motor powered?
The starter is an electrically powered DC motor.
During a normal APU start when is starter cut out and ignition turned off?
approximately 60% N
Are the aircraft batteries required for APU start or operation?
No, however, on the ground when the APU is the sole source of power, the batteries must be selected ON to ensure a power source for extinguisher discharge in the event of an APU fire.
After the APU has been started and is on speed (~95% N) the green AVAIL appears in what three locations?
1. APU START pb
2. ECAM APU system page
3. E/WD memo section
Fuel for the APU typical comes from which tank?
The left wing tank inner cell
When does the APU fuel pump turn ON?
When the APU MASTER SW pb is selected ON, the ECB senses whether there is pressure in the Engine 1 Feed Line (Left Engine), if not, the APU fuel pump is automatically activated.
What happens when the amber FUEL LO PR appears on the APU System Page?
The APU automatically shuts down
What happens when the green LOW OIL LEVEL appears on the APU System page?
Nothing. However, if a low oil pressure is detected, the APU will automatically shutdown.
What should the flight crew do if the LOW OIL LEVEL message appears on the ECAM APU System page prior to starting the APU?
Contact maintenance control
In flight, when the APU is the sole source of power, what will load shed?
The Main Galley bus
How is the APU Bleed Valve controlled?
By the APU BLEED pb. The bleed valve is commanded open when the pb is selected ON.
The APU bleed air duct is directly connected to what side of the aircraft's Pneumatic System Manifold?
The left side.
Can the APU bleed air be used for wing anti-ice?
Although it is technically possible, its use is prohibited (no precooler for APU bleed air)
When the APU bleed valve is open and supplying bleed air, the APU AVAIL in the ECAM memo section is replaced with what message?
If APU bleed air was in use prior to a normal shutdown, will the APU continue to run after the APU MASTER SW pb has been selected to OFF?
Yes. Typically for a short cool down period (approx 2 min, bypassed for auto shutdown)
During the cool down cycle can you still use the APU?
Yes. Press the APU MASTER SW pb back to ON.
What does an amber FAULT light in the APU MASTER SW pb indicate?
An APU auto shutdown has occurred
What does an amber FAULT light in the APU BLEED pb indicate?
An APU bleed leak has been detected
Does the APU generator have a constant speed drive?
No. The constant generator output is controlled by the ECB.
What happens with an APU FIRE on the ground?
The APU will automatically shutdown and the halon bottle will be automatically discharged. In addition, an external horn located in the nose gear will sound.
What happens with an APU FIRE in flight?
Nothing automatic. The flight crew must manually shutdown the APU and discharge the halon bottle.
Are there any situations in flight that would cause the APU to automatically shutdown?
Yes. For operational exceedances (low oil pressure, high oil temperature, overspeed, etc).
The APU can provide electrical power up to what altitude?
Maximum certified altitude. However, above 25,000 feet the generator becomes less effective in its ability to generate 100% of its rated output.
What is the maximum flight altitude for an inflight APU start?
1. 39,200 feet with at least one IDG powering the aircraft
2. 25,000 feet when the aircraft is on battery power only
The APU can provide pneumatic air to operate two packs up to what altitude?
The APU can provide pneumatic air to operate one pack up to what altitude?
What is different about an APU Battery Start?
Everything is the same except the ECAM display is not on.
The APU generator can provide electrical power to what altitude?
The maximum certified aircraft altitude of approximately FL390
Can APU bleed air be used for supplying the packs during takeoff?
Yes, to avoid the thrust reduction that occurs when the engines supply bleed air for the packs. Thus, enabling improved takeoff performance.