01/18/23 Hydraulics Flashcards
What are the three Hydraulic Systems?
A, B, and Standby Systems
Which components powered by System A are unique to this system?
• Ground Spoilers
• Alternate Brakes
• No. 1 Thrust Reverser
• Autopilot A
• Normal Nose Wheel Steering
• Landing Gear
• Power Transfer Unit (PTU)
System A (all components)
• Ailerons
• Rudder
• Elevator and Elevator Feel
• Flight Spoilers (Two on Each Wing)
• Ground Spoilers
• Alternate Brakes
• No. 1 Thrust Reverser
• Autopilot A
• Normal Nose Wheel Steering
• Landing Gear
• Power Transfer Unit (PTU)
Which components powered by System B are unique to this system?
• 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
System B (components)
• 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?
Regulated bleed air.
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?
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.
A mechanical quantity indicator (externally mounted on the reservoir) indicates fluid quantity using a needle indicator and calibrations where zero is empty, RFL is refill, and F is full.
What is the normal pressurization range of System A and B?
3000 +/- 200 psi
Normal pressure for Hydraulic System A and B is 3000 +/- 200 psi.
What precautions, if any, should be taken when turning on the ELEC HYD pumps?
Stagger ELEC HYD pump switch selection, ELEC PUMP B then ELEC PUMP A when turning ON ELEC PUMP A then ELEC PUMP B turning OFF. Avoids circuit breaker trip and possible fluid transfer.
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.
In the event of a System A Engine Driven Pump leak, what prevents a total system fluid loss?
standpipes in each system prevents a total system fluid loss.
(System A) If a leak develops in the engine-driven pump or its related lines, a standpipe in the reservoir prevents a total system fluid loss. With fluid level at the top of the standpipe, the reservoir quantity displayed indicates approximately 20% full.
How much System A fluid is available if the fluid is at the top of the standpipe?
approximately 20% full
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
If a leak develops in either pump, line or component of System B, the quantity decreases until it indicates approximately zero and System B pressure is lost. The System B reservoir has one standpipe which supplies fluid to both the engine-driven pump and the electric motor-driven pump. However, with fluid level at the top of the standpipe, fluid remaining in the System B reservoir is sufficient for Power Transfer Unit operation.
What could cause variations in the Hydraulic Quantity Indications?
During normal operations, variations in hydraulic quantity indications occur when:
• the system becomes pressurized after engine start.
• Landing Gear retracted or Leading Edge Devices extended.
• Cold Soaking.
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
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 2350 psi.
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.
