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23 Cards in this Set
- Front
- Back
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What are the purposes of the APU
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The APU provides bleed air for the ECS, main engine starting and electrical power on the ground and in flight
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What has priority, APU electrical loads or pneumatics
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Electrical loads take priority over pneumatics
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How is the APU cooled
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It is cooled by drawing airflow over the APU engine and the oil cooler then exhausting the air
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What are the APU operating time limits with the inspection doors open
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10 mins with the APU unloaded and 5 mins with it loaded
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What is the source and pressure of APU bleed air
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The APU bleed air comes from the single stage centrifugal compressor and it normally provides apprx 55 psi
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When does the APU oil pass through the APU oil cooler
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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
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Will the APU perform a protective shutdown on the ground for a low oil pressure condition? In flight?
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On the ground yes but not in flight
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May the APU oil be replenished using the Auto Replenishment System
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Yes
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How is the APU oil filled manually and can it be overfilled by using this method
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By removing the gravity fill cap and filling the until the sight guage indicates full. It will overflow and therefore cannot be overfilled manually
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How many EGT probes are fitted to the APU engine
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2 probes connected to a single temp sensing unit
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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
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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
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What is the effect of te APU EGT probe failure(s)
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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 |
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What is the purpose of the SCV (surge control valve) and when does it function
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To control APU surge potential when operating under electrical load at altitudes above 16,375 ft
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When can the APU accept an electrical load in flight and on the ground
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2 seconds after the APU reaches 99% RPM. ELectrical loading is not available if the RPM drops below 95%
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When can the APU accept a pneumatic laod in flight and on the ground
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Flight- 2 secs after reaching 99% and below 37,000
Ground- 60 secs after reaching 99% |
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When the APU switch is moved to "OFF" what is the shutdown sequence
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The APU enters it's cooldown mode, the RPM reduces to 70% for 60 secs then shutsdown
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What will be the normal position of the APU door with the APU operating on the ground
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100% open 47 deg
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When is the door position indicated on the status page
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When there is a fault and door position does not agree with the FADEC command.
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How is normal APU operation indicated in the cockpit
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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
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Id there an automatic discharge of the fire agent in the event of an APU fire
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No
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What conditions must be met to re-start the APU after a protective shutdown
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The BATT MASTER switch must be on.
The switch on the APU panel must be reset to the OFF position before selecting start |
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Will the APU perform a protective shutdown when an APU fire is detected
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yes
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What is the max altitude that the APU can be started
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37,000 ft
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