How many hydraulic systems are on the plane?
- 3 independent systems
- HYD 1, HYD 2, and HYD 3
what systems use hydraulic power?
- flight controls
- spoilers
- landing gear
- nose wheel steering
- wheel brakes
- thrust reversers
can hydraulic fluid be transferred between each system?
No
how many hydraulic pumps are on the plane?
- 6 total
- 2 EDP Engine Driven Pumps
- 4 ACMP ACmotor pumps
what are the basic components of the hydraulic system?
- reservoir
- pumps
- accumulator
what is the purpose of the accumulator?
- helps to maintain constant pressure by covering transient demands
- helps to avoid pump cavitation
when will ACMP 1 or 2 automatically activate?
-Ground
Flaps >0 and
-TL set to T/O or
-Groundspeed >50k
-Flight
Engine failure or EDP failure
Flaps >0
what are some important items controlled by HYD 2 system?
- landing gear
- nose wheel steering
- inboard breaks
what is the PTU
- Power transfer unit
- mechanical pump that used HYD 1 power to provide HYD 2 pressure to assist with gear operation
what is the primary purpose of the PTU?
to allow landing gear retraction in the event of an engine 2 or EDP 2 failure
when will the PTU automatically activate?
-during takeoff and landing with the flaps >0 if
engine 2 fails or EDP 2 fails
how is single engine taxi possible if nose wheel steering is on HYD 2?
releasing the parking break activates ACMP 2
what is the primary purpose of HYD 3 system?
backup for the flight controls
why are HYD ACMP 3A&B pump switch positions ON&AUTO respectively?
- HYD ACMP 3A pump is primary and has no automation
- HYD ACMP 3B pump is backup and automatically activates if ACMP 3A fails
what, if any, HYD ACMP will function if the RAT is the only power source
HYD ACMP 3A only
in an electrical emergency what provides hydraulic pressure to flight controls until the RAT becomes online?
- HYD 3 accumulator
- After 8 seconds the RAT will power ACMP 3A
in an electrical emergency can HYD 3 system power requirements overload the RAT?
No. a flow limiter valve is used to reduce flow and limits pump electrical power draw to prevent a RAT stall
