Hydraulics Flashcards
What happens if centre hydraulic system quantity is sensed low?
- Centre 1 elec pump is automatically isolated to provide hydraulic pressure to the RESERVE BRAKES & STEERING
- The ISLN light for C HYD SYS on the rear panel illuminates
What systems power the Flight controls?
- All 3
What does the RAT do?
- Provides hydraulic pressure to the flight controls portion of the Centre Hydraulic System
- Provides adequate hydraulic power for flight controls at speeds above 130kt
- Deploys automatically when both engines fail (Engines drop BLW idle)
- Cannot be stowed in flight
- In right wheel well
What does the Pitch enhancement system do and when does it activate?
- Auto activates if the Left & Centre HYD systems fail and trim switches are used
- A pump in the right system uses trapped left system fluid to operate the stabilizer
- Elec trim is available at approx 1/4th of the rate
- Alternate and auto trim inop
What systems have reservoirs? Are they pressurised?
- Each system has own reservoir
- PRESSURIZED from bleed air
How is the centre hydraulic system demand pump powered?
- By the Pneumatic system
Does the centre Air Demand pump ever Auto operate?
- Yes when there is a large demand on the centre system such as when operating the landing gear, flaps/slats and ground spoilers
- Pump also operates whenever system pressure is low
- Air supply valve opens and pump operates to provide additional system pressure
What Hydraulic pump is load shed and when?
- The C2 pump
- Load shed when on GND and only one source of electrical power
- APU, EXT PWR or 1 ENG GEN
Does an autopilot become inop when the left hydraulic system fails?
- Yes the Left autopilot
When will an RF appear on the hydraulic system quantity?
- Below 0.75
When does the QTY light illuminate on the overhead panel and what other indication do you get with this?
- Below .48
- Also illuminates HYD QUANTITY EICAS advisory message
When does the RAT deploy automatically?
- When both engines fail in flight (both sensed below idle)
- Provides adequate power for operation of the flight controls portion of the centre hydraulic system at airspeeds ABV 130kts
When does the tail skid extend and retract and what powers it?
- Extends and retracts with LDG gear
- Powered by the Centre HYD system
Using Alternate Gear extension does the tailskid extend?
- No
When do the gear doors stay open?
- If there is no pressure in the centre hydraulic system after an Alternate gear extension
- GEAR DOORS displays on EICAS
Is anti skid available in the alternate brake system?
- Yes provided in normal and alternate systems
- NORMAL - Each making gear wheel is provided with individual anti skid protection
- ALTERNATE - Provided to laterally paired wheels
How are the nose and main gear held in the up and locked position?
- Nose gear - up locks
- Main Gear - door structure
What does the green PRESS light on the RAT panel indicate?
- RAT is deployed and RAT is producing hydraulic pressure
When does Auto braking application commence on touchdown?
- Both thrust levers retarded to idle
- Wheels have spun up
- Nose attitude is less then 1 degree
What does touchdown protection provide?
- Ensures rear wheel brakes do not have hydraulic pressure at touchdown
How does the braking system provide hydro planning protection?
- Compares IRS ground speed to wheel speed and decreases aft wheel brake pressure when ground speed is greater then wheel speed
How does the braking system provide locked wheel protection?
- Compares the speed of each fore and aft wheel pair
- Releases hydraulic pressure from the slower wheel when the speed difference is greater than 25kts
What powers the Elevators?
- Right, Center & Left systems
- Can still power if 2 systems lost