OLA APU Flashcards
What does APU provide on the ground?
Bleed air for engine start
Bleed air for air conditioning
Electrical power
Why may APU be used for takeoff?
May be used to supply bleed air during takeoff when optimum performance is required
What does APU provide in the air?
Backup for the electrical system
Bleed air for air conditioning
Assists in engine starting
What does the APU Master switch do?
Controls electrical power supply for APU operation and fault protection, and controls the start and shutdown sequences. Electronically opens the APU air intake flap
It also brings up the SD page
When does APU page automatically disappear?
15 seconds after start cycle is complete
What does the APU Bleed pb control?
APU bleed valve
When switched on, the APU bleed valve opens, the crossbleed valve (if auto) opens, and the engine bleed valves close
The theory being that APU bleed has priority over engine bleed and so the crossbleed allows it to serve both sides, and the engine bleed valves close to allow APU to supply all
Where can you check the status of the APU air intake flap?
With the APU SD page. FLAP OPEN
What happens if there is insufficient pressure in the left side fuel tank pumps when APU is operating?
The APU fuel pump will start automatically
What will cause APU fuel supply to stop?
APU master PB off
APU fire PB pushed
APU SHUTOFF PB on external power panel pushed
Automatic shutdown caused by a fault
What has priority between APU bleed air and engine bleed air?
APU bleed air
(Consider for example when boosting takeoff performance while using APU for bleed, to give engines maximum power)
What does ECB stand for?
Electronic Control Box
What does the ECB do?
Controls and monitors all modes of APU operation, such as start, speed and temperature, bleed air, normal shutdown and automatic shutdown
What speed does ECB regulate APU to?
100%
This is reduced to 99% when there is an air conditioning demand and ambient temperature is between -18 and 35 degrees
When is AVAIL in green displayed on APU SD page?
N speed above 95%
When is AVAIL displayed on the APU START pb?
N is above 99.5%, or 2 seconds after N reaches 95%
When do amber Xs replace the bleed air pressure reading on APU SD page?
ADIRS 1 or 2 not available (or off)
Data from ECB not valid or not transmitted
When is there a small arrow above the APU GEN box on the APU SD page?
When the APU GEN line contactor is closed
When do APU N indications become amber?
102%
When do APU N indications become red?
107%
What N is required for automatic APU shutdown?
107%
When does APU EGT indication display in amber?
When EGT max minus 33 degrees is reached
When does APU EGT indication display in red?
When EGT has reached EGT max
What is the APU EGT max?
It varies, and is calculated by the ECB as a function of rotational speed during start, and ambient temperature when APU is running
What is the highest EGT Max for APU start?
1090 degrees
