Hydraulics Flashcards
What happens to the EDP after an engine flame out?
In the event of engine flameout, the FADEC automatically commands the unload of the respective EDP, which reduces the hydraulic system pressure. This depressurization reduces the torque loads on the engine and facilitates a windmill restart (812 14-11-10 Pg 2)
What facility does Hydraulic System 2 have on the ground with the electric pump switch in AUTO?
Same functions as Hyd 1 System (812 14-11-10 Pg 2) During landing operations, the Electric Hydraulic Pumps remain activated for 60 seconds to avoid abrupt hydraulic pressure variations in an event of engine failure. ACMP active if Flaps selected to any position greater than 0° and:
- Thrust levers set to takeoff thrust, or
- Ground speed greater than 50 kt.
During takeoff when thrust levers are set to TOGA, the Electric Hydraulic Pumps will be activated for 60 s to avoid abrupt hydraulic pressure variations in an event of engine failure.
PLUS (B12 14-11-10 Pg 5)
Electric Hydraulic Pump 2 will be automatically activated when the following conditions occur.
- Engine 1 running and parking brake released;
- During Engine 1 start (once N2 reaches 40%) if parking brake has been applied within the last 6 min.
NOTE: The Electric Hydraulic Pump 2 will be automatically turned off after 6 min have elapsed from parking brake application.
What is the system logic for operation of PTU?
Automatically started when all the following conditions are met:
- Flaps not set to zero or Landing Gear not up and locked;
- EDP 1 not fail;
- Hydraulic reservoir 2 quantity above 12%.
PTU will not be activated if the airplane is on ground. (81214-11-10 Pg 5 & 6)
Why are the pump un-loader/ flow limiter valves fitted to System 3?
Hydraulic system 3 has two dedicated valves (Pump Un-Loader & Flow Limiter Valves) which are used only in an electrical emergency to avoid overload in the RAT. (812 14-11-10 Pg 8)
In flight, with AUTO selected, when will system 1 and 2 electric hydraulic pumps come on?
In flight, with the selector knob set to AUTO position, the Hydraulic System logic activates the electric pump in case of:
EDP or engine fail, or
Flaps selected to any position greater than 0°. (812 14-11-10 Pg 3)
Other than system load transience, what does the System 3 Hydraulic Accumulator do?
In an Electrical Emergency, the Hydraulic System 3 accumulator will provide hydraulic power to the associated flight controls from the beginning of RAT deployment until the ACMP 3A is powered by the AC ESS BUS. (B12 14-11-10 Pg 8)
When will the fluid shut off valves be closed and how?
If the fluid temperature reaches 125°(, the shutoff valve (SOV) automatically actuates. In the event of hydraulic system overheat (fluid temperature above 145°(), the HYO 2 OVERHEAT EICAS warning message will be displayed. In this case, the SOV can be manually actuated through a guarded pushbutton on the hydraulic system control panel. (B12 14-11-10 Pg 2 & 4)
Why does System 3A pump only have a two-position Electric Hydraulic Pump 3A (ACMP 3A) is the primary power source switch?
Electric Hydraulic Pump 3A (ACMP 3A) is the primary power source for Hydraulic System 3 and it is powered by the AC ESS BUS. There is no automation associated with this pump. So in normal operation, the flight crew will turn the pump ON and OFF during engine start and shut down, respectively. (812 14-11-10 Pg 7)
What is the indication of an EDP failure?
HYO 1 (2) EDP FAIL on EICAS (812 14-11-15 Pg 1) plus associated indications (grey circle and a white windmill beneath an amber cross) on the MFD Hydraulic Synoptic Page (B12 14-11-05 Pg 6)
What provides positive pressure for the reservoirs?
A mechanical piston pressurizes the hydraulic system reservoirs, which supply fluid to the pump. (B12 14-11-10 Pg 2 & 4)
Inbound and Outboard brakes hyd systems and what’s buses
Hyd 1 out DC ESS BUS 1
Hyd 2 in DC ESS BUS 2
4 BCM Functions
Antiskid
Touchdown
Locked wheel
Automatic wheel braking
What is the purpose of the Pump Unloader Valve (PUV) during RAT deployment? What is the role of the Flow Limiter Valve (FLV)?
The PUV reduces pressure during RAT startup to decrease the electrical power required.
The FLV reduces flow to lower electrical power demands on Pump 3A during RAT deployment.
When does the PTU (Power Transfer Unit) activate automatically (AUTO switch position)?
The PTU activates automatically when:
ENG 2 or EDP 2 fails,
Flaps are extended or the landing gear is not up and locked,
EDP 1 is operational,
and
Hydraulic reservoir 2 is above 12%.
Under what condition does Electric Pump 3B run automatically?
Pump 3B runs automatically only when Pump 3A fails, not due to engine or EDP failure.
