Hydraulics Flashcards
What are the three hydraulic systems?
The aircraft has three hydraulic systems: A, B and Standby.
What are some components of Hydraulic System A?
• Ailerons
• Rudder
• Elevator and Elevator Feel
• Flight Spoilers (Two on Each Wing)
• GROUND SPOILER
• Alternate Brakes
• No. 1 Thrust Reverser
• Autopilot A
. NORMAL NWS
• LANDING GEAR
• PTU
What are some components of Hydraulic System B?
• Ailerons
• Rudder
• Elevator and Elevator Feel
• Flight Spoilers (Two on Each Wing)
• Leading Edge Flaps and Slats
• Normal Brakes
• No. 2 Thrust Reverser
• Autopilot B
• Alternate Nose Wheel Steering
• Landing Gear Transfer Unit
• Autoslats
• Yaw Damper
• Trailing Edge Flaps
How are the hydraulic reservoirs pressurized?
System A and B reservoirs are pressurized by regulated bleed air. System B reservoir pressure also pressurizes the Standby System reservoir.
What condition is indicated by RF (white) on the Lower Display Hydraulic indicator and when is it valid?
The REFILL (RF) indication is displayed (white) when hydraulic quantity is below
76%. This indication is valid only:
• when aircraft is on ground with both engines shutdown, or
• after landing with flaps up during taxi-in
Hydraulic quantity is also displayed at each reservoir in the main wheel well.
What is the normal pressurization range of System A and B?
Normal pressure for Hydraulic System A and B is 3000 +/- 200 psi. Maximum system pressure is 3500 psi.
What precautions, if any, should be taken when turning on the ELEC HYD pumps?
Placing both ELEC Hydraulic Pump Switches to ON simultaneously may create an amperage surge resulting in hydraulic pump motor circuit breakers tripping in the E/E compartment.
Staggering switch selection to ON avoids this condition.
Fuel 1675
In the event of a System A Engine Driven Pump leak, what prevents a total system fluid loss?
If a leak develops in the engine-driven pump or its related lines, a standpipe in the reservoir prevents a total system fluid loss.
How much System A fluid is available if the fluid is at the top of the standpipe?
With fluid level at the top of the standpipe, the reservoir quantity displayed indicates approximately 20% full.
With zero indicated on the System B reservoir, can the PTU still operate?
Yes
What’s the purpose of the PTU?
The purpose of the PTU is to provide Hydraulic System B fluid at a flow rate (approximately 6.5 GPM) and pressure sufficient to provide normal rates of operation for the Autoslats and
Leading Edge Devices (LED) in the event the Hydraulic System B Engine-Driven Pump output pressure drops below a specific value.
What could cause variations in the Hydraulic Quantity Indications?
• the system becomes pressurized after engine start.
• Landing Gear or Leading Edge Devices:
- System A: Retraction of the landing gear may result in up to a 20% drop in
hydraulic fluid quantity.
- System B: Extension of the Leading Edge Devices may result in up to 20% drop in hydraulic fluid quantity.
• Cold Soaking:
- During long periods of cruise flight, thermal contraction may cause additional quantity drops of 5 to 10%.
- After prolonged cruise flights with low temperatures, thermal contraction may cause as much as a 20% drop.
NOTE: Cold Soaked fluid reductions for System A are cumulative with landing gear retraction quantity reductions, and Cold Soak fluid reductions for System B are
cumulative with Leading Edge Device quantity reductions.
What happens when placing a FLT CONTROL switch to STBY RUD?
Positioning either FLT CONTROL switch to STBY RUD:
- activates the standby electric motor-driven pump
- shuts off the related hydraulic system pressure to ailerons, elevators and rudder by closing the Flight Control Shutoff Valve
- opens the Standby Rudder Shutoff Valve
- deactivates the related FLT CONTROL LOW PRESSURE light when the Standby Rudder Shutoff Valve opens
- allows the Standby System to power the rudder and thrust reversers
- illuminates the STBY RUD ON, FLT CONT annunciator, and MASTER CAUTION lights
What would cause the automatic operation of the Standby Hydraulic System?
Automatic operation is initiated when the following conditions exist:
- flaps extended, and
- airborne, or wheel speed greater than 60 kts, and
- loss of System A or B, with the respective FLT CONTROL switch positioned to ON
OR:
- the main PCU Force Fight Monitor (FFM) trips
When does the STANDBY HYD LOW QUANTITY light illuminate?
The STANDBY HYD LOW QUANTITY (amber) light illuminates when the standby reservoir is approximately half empty.
