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23 Cards in this Set

  • Front
  • Back
What are the purposes of the APU
The APU provides bleed air for the ECS, main engine starting and electrical power on the ground and in flight
What has priority, APU electrical loads or pneumatics
Electrical loads take priority over pneumatics
How is the APU cooled
It is cooled by drawing airflow over the APU engine and the oil cooler then exhausting the air
What are the APU operating time limits with the inspection doors open
10 mins with the APU unloaded and 5 mins with it loaded
What is the source and pressure of APU bleed air
The APU bleed air comes from the single stage centrifugal compressor and it normally provides apprx 55 psi
When does the APU oil pass through the APU oil cooler
When the APU oil Temp exceeds a pre-determined higher than normal operating range the oil will be route through the oil Cooller. Below that temp the Oil Cooler is bypassed
Will the APU perform a protective shutdown on the ground for a low oil pressure condition? In flight?
On the ground yes but not in flight
May the APU oil be replenished using the Auto Replenishment System
How is the APU oil filled manually and can it be overfilled by using this method
By removing the gravity fill cap and filling the until the sight guage indicates full. It will overflow and therefore cannot be overfilled manually
How many EGT probes are fitted to the APU engine
2 probes connected to a single temp sensing unit
Should an APU speed sensor fail, what are the cockpit indications? If the 2nd sensor then fails, what will occure to the APU in flight
If either RPM sensor fails, the APU FAULT advisory message will be triggered and the APU will continue to operate normally. If both sensors fail the APU will auto shutdown and a restart would be inhibited
What is the effect of te APU EGT probe failure(s)
Loss of one probe has no effect
Loss of both probes on the grnd will induce an auto shutdown
Loss of both probes in flight will not cause an auto shutdown
What is the purpose of the SCV (surge control valve) and when does it function
To control APU surge potential when operating under electrical load at altitudes above 16,375 ft
When can the APU accept an electrical load in flight and on the ground
2 seconds after the APU reaches 99% RPM. ELectrical loading is not available if the RPM drops below 95%
When can the APU accept a pneumatic laod in flight and on the ground
Flight- 2 secs after reaching 99% and below 37,000
Ground- 60 secs after reaching 99%
When the APU switch is moved to "OFF" what is the shutdown sequence
The APU enters it's cooldown mode, the RPM reduces to 70% for 60 secs then shutsdown
What will be the normal position of the APU door with the APU operating on the ground
100% open 47 deg
When is the door position indicated on the status page
When there is a fault and door position does not agree with the FADEC command.
How is normal APU operation indicated in the cockpit
A green APU symbol on the AC electrical synoptic page, the beled air/anti-ice page and RPM and EGT indications on the STAT page
Id there an automatic discharge of the fire agent in the event of an APU fire
What conditions must be met to re-start the APU after a protective shutdown
The BATT MASTER switch must be on.
The switch on the APU panel must be reset to the OFF position before selecting start
Will the APU perform a protective shutdown when an APU fire is detected
What is the max altitude that the APU can be started
37,000 ft