Hydraulics Flashcards
How many hydraulic systems are on the airplane?
3 independent systems
HYD 1, 2 and 3
What systems use hydraulic power?
- Flight Controls
- Spoilers
- Landing gear
- nose wheel steering
- wheel brakes
- thrust reversers
Can hydraulic fluid be transferred between systems?
No
How many hydraulic pumps are on the airplane?
Six:
- 2 EDPs (engine driven pumps)
- 4 ACMP ( AC motor pumps)
What are the basic components of the hydraulic systems?
- reservoir
- pumps
- accumulator
What do accumulators do?
Maintain constant pressure and prevent pump cavitation
When will ACMP 1 or 2 activate automatically on the ground?
When flaps are > 0 and:
- TL set for takeoff, or
- GS > 50 kts
When will ACMP 1 or 2 automatically activate when in the air?
- engine failure or EDP failure
- flaps > 0
Name some important systems controlled by HYD 2
- Landing gear
- nose wheel steering
- inboard brakes
What is the PTU?
- power transfer unit
- mechanical pump that uses HYD 1 power to provide HYD 2 pressure
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?
When engine 2 or EDP 2 fails and:
- Flaps > 0 or landing gear not up and locked
- EDP 1 not failed
- HYD 2 reservoir quantity > 12%
With ACMP 1 and 2 in AUTO how is single engine taxi on engine 1 possible if nosewheel steering is on HYD 2?
- releasing parking brake activates ACMP 2
What is the purpose of HYD 3?
Backup for the primary flight controls
What are HYD ACMP 3A and B pump switches ON and AUTO respectively?
- HYD ACMP 3A is primary and has no automation
- HYD ACMP is the backup and automatically activates if ACMP 3A fails
What HYD ACMP will function if the RAT is the only power source?
HYD ACMP 3A
In an electrical emergency what provides hydraulic pressure to flight controls until the RAT comes 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. HYD 3 system pressure is unloaded automatically to prevent a RAT stall
