APU Limits Flashcards
Normal APU RPM range when providing bleed air?
100 +/- 3% RPM
Continuous APU EGT operating range?
200°-715°C
APU RPM red line (over speed)?
110%
APU automatic shutdown protection for over speed?
110 (+/-1) %
When is APU Auto Shutdown Protection disabled?
During Start Cycle
APU Starting Limit: below _____ RPM, APU EGT can peak as high as _____ for up to _____.
Below 60% RPM, APU EGT can peak as high as 980°C for up to 2 seconds.
During APU-Assisted engine starts, APU EGT can peak as high as?
760°C for 2 seconds.
APU start is unsuccessful if APU RPM does not exceed ___ within ___?
60% within 30 seconds.
APU start is unsuccessful if APU EGT does not decrease towards continuous operating range as RPM increases above?
60%
After an unsuccessful APU start, wait _____ between each attempt with up to _____ attempts, then wait _____ for APU to cool down.
1 minute between attempts, with up to 3 attempts, then wait 20 minutes for APU to cool down.
Do not operate APU longer than ____ with the APU generator off?
5 minutes with the APU generator off.
After the APU is used for starting or motoring an aircraft engine, the APU must run unloaded for?
2 minutes prior to shut down.
On the ground with engines at IDLE, leave APU running if aircraft is modified with?
OBOGS or for cockpit cooling if temp is above 85°F.
After a successful ground APU start and shutdown, wait?
10 minutes after APU shutdown before attempting another APU start.
After a successful inflight APU start and shutdown, wait?
2 minutes from initiating the previous start before attempting another APU start.
APU starts can be made up to an altitude of?
15,000 feet and in most cases up to 20,000 feet.
The APU can supply sufficient bleed air for an inflight engine start at altitudes up to?
10,000 feet, and in most cases up to 15,000 feet.
The APU will continue to operate for _____ in negative-G flight?
10 seconds in negative-G flight.
APU EGT Yellow Band
715-760*C (Max 2” during engine start)
APU EGT Red Lind
760*C
APU EGT Red Line
760*C
Reasons for APU Auto Shutdown in Flight
High RPM or Low Oil Pressure
Reasons for APU Auto Shutdown on Ground
- High RPM
- Low Oil Px
- High EGT
- APU Fire Warning System activated
- Overcurrent in APU component circuits
