Hydraulics Flashcards
Hydraulic operating pressure, minimum pressure & maximum pressure
Normal = 3000psi
Minimum = 2800psi
Maximum = 3500psi
Where are the hydraulic reservoirs and electric pump’s located?
The wheel well
How are hydraulic reservoirs pressurised and at what pressure?
Bleed air, 40-50psi
How is the stdby hydraulic system replenished and pressurised?
Connected to the Hyd B system
What type of hydraulic fluid is used?
BMS 3-11 type 4
What type of hydraulic fluid is used?
BMS 3-11 type 4
EMDP
Electric motor driven pump
EDP
Engine driven pump
How is the hydraulic low pressure light activated?
Illuminates when pressure drops below 1300psi, detected via the pressure module
How is the PTU activated?
Pressure module pressure switch sends a low pressure signal to the PTU when the EDP pressure drops below 2350psi for more than 0.5 seconds
How is the EMDP cooled and lubricated?
Via its own hydraulic fluid supply
What transfer bus powers the HYD A EMDP?
XFR Bus #2
What transfer bus powers the HYD B EMDP?
XFR BUS #1
What transfer bus powers the STDBY EMDP?
XFR BUS #2
EMDP output vs EDP
EMDP has 6x lower capacity output than the EDP
EMDP operating limits
- 5 minute period - max 5 starts
- When switched off wait 30 seconds before restarting the pump
How is the STDBY EMDP cooled?
Cooled by airflow from outside the aircraft
Minimum amount of fuel in the main tank to provide cooling for hydraulic heat exchangers
760kg in the associated tank
Cockpit hydraulic overheat light parameters
Illuminates at 113 degrees Celsius
Resets at 85-102 degrees Celsius
What does the cockpit EDP switch control?
Controls the position of the depressurising valve
Function of the pressure module
-Protects from overpressure
-low pressure warning
-Transmits pressure readouts to DEU
What does a flight control package contain?
-Flight spoiler shut off valve
-Flight control shut off valve
-Pressure switch (low pressure warning)
-Optional compensator cartridge
What is the purpose of the flight control package compensator cartridge?
Maintains 40-70psi of hydraulic pressure to primary flight controls when hydraulics are off. Providing gust protection.
Cockpit hydraulic flight control switch functions:
Off: Ailerons, Elevator and rudder are hydraulically isolated. Low pressure light illuminates.
Stby: Ailerons, elevator and rudder are hydraulically isolated. Low pressure light is inhibited. Stby rudder is activated.
Hydraulic A reservoir, in case of a leak in the EDP line and EMDP line:
EDP line: Reservoir quantity will reduce to 20% (standpipe reaching up to the first 20% of the reservoir, EDP prone to leaks)
EMDP line: Reservoir quantity will reduce to 0%
Hydraulic B reservoir, how much fluid is left if there is a leak?
Around 5 litres remain for PTU operation
(EDP and EMDP have a common standpipe)
If there is a leak in the standby line what will occur to hydraulic levels?
Hydraulic B reservoir will drop to 70%
At what quantity will RF (Refill) be displayed?
76%
Hydraulic reservoir quantities:
Hyd A: 25.8L (100%: 21.6L)
Hyd B: 40.6L (100%: 31.1L)
Stby: 13.3L
Function of the PTU
Supplies additional volume of hydraulic fluid needed to operate autoslats and leading edge flaps at normal rate when system B EDP volume is lost
What is the function of the landing gear transfer unit?
Designed to raise the gear at a normal rate after EDP A volume is lost
What does the standby hydraulic system supply?
- Standby rudder PCU
- Standby yaw damper
- Leading edge flaps and slats (Extension only)
- Thrust reversers
Where is the standby EMDP located?
On the right aft wing to body fairing and cooled by outside air
What is the power supply for the standby EMDP?
AC transfer bus 2
When does the standby low quantity light illuminate?
Fluid quantity less than 50%
