B747-400 Hydraulic System Questions with 100% Correct Answers

B747-400 Hydraulic System Questions with
100% Correct Answers
Describe the hydraulic system, what it powers and name the general components
Correct Answer Hydraulic system consists of 4 independent systems operating at 3000
PSI powering:

(PASS- SELF - BRAKES)

- Primary flight controls
- stabilizer trim
- Landing gear
- flaps
- spoilers
- breaks

- Autopilot servos
- elevator feel
- Steering



The system consists of:

- 4 engine driven hydraulic pumps (one for each engine).
- 4 reservoirs
- 2 electrical demand pumps (system 2 & 3)
- 2 Pneumatic demand pumps (system 1 & 4)
- 2 electrical Auxiliary pumps (system 1 & 4)
- 4 SOVs (one for each engine)
- Numerous Hydraulic actuators for primary and secondary flight controls and the
landing gear

What pressure does the hydraulic system operate at? Correct Answer 3000 PSI

How is the hydraulic SOV operated? Correct Answer Manually by the engine fire switch

What is the purpose of Demand Pumps? Correct Answer As the name suggests,
demand pumps will operate if the engine driven pumps fail or are under high demand
(such as when flaps extend or are already extended)

How are the Demand pumps operated? Correct Answer Electrically for system 2 and 3
and pneumatically for system 1 and 4.