Tech - Hydraulic Flashcards
Q1. How is Yellow Hyd. Sys pressurized?
A1. The Yellow hydraulic system is pressurized by a pump driven by engine 2. An electric pump can also pressurize the yellow system, which allows yellow hydraulics to be used on the ground when the engines are stopped. Crew members can also use a hand pump to pressurize the yellow system in order to operate the cargo doors when no electrical power is available.
Q2. In which of the hydraulic systems, engine driven pumps are installed?
A2. Green and Yellow.
Q3. Name some of the major users of the GREEN system?
A3. Some of the major users of Green system :- –> Landing Gear –> Slats/Flaps –> Normal Brakes –> Rev Eng 1 –> Yaw Damper 1 –> Stabilizer –> Some Flt. Control surfaces
Q4. Name some of the major users of the BLUE system?
A4. Some of the major users of Blue system :- –> Emerg. Gen. –> Slats –> Rudder –> Some Flt. control surfaces
Q5. Name some of the major users of the YELLOW system?
A5. Some of the major users of Yellow system :- –> Flaps –> Alt./Parking brake –> Rev Eng 2 –> Yaw Damper 2 –> Rudder –> Stabilizer –> Nose Wheel Steering
Q6. Name the components in Green Hyd. system?
A6. Components in Green Hydraulic system :- –> Eng 2 Pump –> PTU –> Green Reservoir –> Eng 1 FSOV –> Accumulator –> Priority Valve
Q7. When does Blue Pump energize,{with the a/c on the ground and the blue electric pump switch in AUTO}?
A7. The Blue pump energizes on the ground with the Blue Elec. pump s/w in AUTO when either engine is running or if the crew has pressed the BLUE PUMP OVRD P/b on the Maintenance panel
Q8. What is the purpose of the priority valve installed in Hydraulic Systems?
A8. The priority valves cut off hydraulic power to heavy load users if hydraulic pressure in a system gets low. In the event of low hydraulic pressure, the priority valves maintain the operation
of essential systems by cutting off hydraulic power to heavy load users.
Q9. What happens to the yellow hydraulic system when a cargo door is being opened or closed?
A9. When a crewman sets the lever of the cargo door manual selector valve to open or close, it inhibits the operation of other yellow system function (Except Alternate braking & Eng 2 Reverser). The ‘OFF’ Light comes on in the Yellow Elec. pump P/b s/w.
Q10. What is the purpose of the engine fire shutoff valves?
A10. Each of the Green and Yellow systems has a FSOV in its line upstream of its EDP. The flight crew can close it by pushing the ENG 1(2) FIRE P/b . The FSOV isolates the hydraulic system from its respective engine to prevent the spread of fire.
Q11. What is the PTU and what is its purpose?
A11. PTU is short for Power Transfer Unit. It is s bi-directional power transfer unit which enables the Yellow system to pressurize the Green system & vice versa.
It comes into action automatically when the differential pressure between the Green and the Yellow systems is greater than 500 psi.
Q12. Is it possible to pressurize the green hydraulic system on the ground via the PTU?
A12. Yes.
Q13. During cockpit preparation if you start yellow electric pump, will green hyd. Sys. get pressurized via PTU?
A13. Yes.
Q14. When does the PTU operate?
A14. The PTU operates when the differential pressure between the Green and Yellow systems is more than 500 psi.
Q15. Will the PTU operate during Cargo Door operation?
A15. No.
Q16. What are the conditions when PTU will not run {inhibited}, even if there is a differential pressure between Green & Yellow is more than 500 psi?
A16. The following are the conditions when the PTU is inhibited from operating :-
–> PTU inhibited during first engine start
–> If Green/Yellow Reservoir overheats
–> If Green/Yellow reservoir has low air pressure
–> If Green/yellow reservoir has low fluid level
–> Parking Brake ON and only one ENG MAST ON
–> NWS in towing position and Parking brake ON
Q17. When is the PTU self tested?
A17. PTU is self tested during the second engine start.