EPU Flashcards
Hydrazine Leak detector
Mustard yellow under right wing through access door 3208 - turns purple/black when leak in fuel/EPU system
EPU nitrogen bottle pushes ______ into EPU for EPU start and as required for normal EPU operations
Hydrazine
EPU Fired indicator shows
3 balck triangles with 3 white triangles (grey - not fired)
EPU automatic activation when:
main and stby generator failure, or Dual hydraulic system failures <1000psi
HYDRAZN light
indicated EPU is commanding hydrazine, and indicated primary spped control failure
AIR Light
when EPU commanded on with safety pin removed, stays on whole EPU augmented by hydrazine
EPU run light
turbine speed is in proper range, and EPU driven hydraulic pump discharge pressure above 2000 psi
only time hydrazine not required
EPU/GEN test switch
EPU Fuel % remain
operates on battery bus power, ensure 95-102%
purpose of EPU
provides hydraulic pressure to system A and Emergency electrical power to ac/dc busses but requires dc power from battery bus
____ and _____ are unpowered when EPU operates
Nonessential and essential DC buses
EPU requires ___ seconds to come up to speed, FLCS powered by _____ durig gen failure and _____ during engine failure during the spool up time
2 seconds ; FLCS PMG (pemanent magnetic generator) for gen failure ; Hydraulic system B for engine failure
EPU Exhaust
Lower inboard side of right strake Nitrogen,hydrogen,ammonia,water can reach 1600 degrees flammable ammonia oder
Hydrazine only mode time
<10 minutes, 15% per minute (if EPU is main source of hydraulic power, loss of EPU is loss of A/C control)
engine bleed air for EPU helps____
minimize hydrazine use with thrust above 75% rpm
________ moves control valves that keeps the EPU turbine power unit rpm constant by controlling the amount of bleed air or hydrazine
Electronic speed controller
how do you know the tertiary system is controlling the speed controller?
blinking EPU run light, steady HYDRAZN light
how does the EPU generator function
it powers the emergency ac and dc buses and the battery bus
prior to EPU check make sure
EPU pin is inserted, 100% oxygen, EPU GEN/EPU PMG lights are off
EPU check
ensure EPU pin is inserted and 100% Oxygen
EPU GEN/EPU PMG lights are off
EPU switch off
EPU safety pin removed
EPU NORM (once ground crew is out of the way)
Engine rpm - increase 5% above idle
EPU/GEN TEST Switch
EPU/GEN TEST switch - EPU/GEN and hold
EPU AIR light - on
EPU GEN/EPU PMG lights - off
FLCS PWR lights - on (ABCD)
EPU run light should stay on for ___ seconds, if it does not illuminate within ____ seconds, release the test switch, increase the throttle by 5%, and test again
5 second ; 10 seconds
4 situations start the EPU automatically:
dual hydraulic failure (<1000 psi)
main and stby generator failure
engine lost
PTO Shaft Shear
