Hydraulics

Question 0

What is the purpose of the PTU? (Power Transfer Unit)

Answer 0

To back up the #2 Main Hydraulic system. It is powered by the #1 Main Hydraulic system.

SDM 12-3

Question 1

What powers the #3 hydraulic system?

Answer 1

A gas-charged accumulator. Accumulator pressure is maintained by a DC Motor-Driven Pump (DCMP).
(A pressure switch controls the DCMP operation to maintain pressure 2600-3250 psi).
SDM 12-3

Question 2

What powers the PTU (Power Transfer Unit)?

Answer 2

The #1 Main hydraulic system.
Operation of the PTU requires normal operation of the #1 Main hydraulic system and normal fluid quantity in the #2 Main hydraulic system.
SDM 12-8

Question 3

What systems are powered by the #1 hydraulic system?

Answer 3

B - Brakes
A - Anti-Skid
R - Rudder
F - Flaps
P - PTU (Power Transfer Unit)
I  - Inboard Roll Spoilers
E - Elevator                                                              SDM 12-4

Question 4

What backs up the #1 hydraulic pump?

Answer 4

The Standby Hydraulic Pump.

SDM 12-7

Question 5

When will the STBY HYD PUMP turn on automatically?

Answer 5

• When the #1 engine fails, or
• Whenever the flaps are selected to any position greater than zero degrees, and the parking brake is released.

SDM 12-7

Question 6

Will the green ON switchlight illuminate if the STBY HYD PUMP is automatically activated?

Answer 6

No. (Only when the pump is activated manually using the switchlight).

SDM 12-7

Question 7

What systems are powered by the #2 hydraulic system?

Answer 7

L - Landing Gear
O - Outboard Roll Spoilers
S - Steering
E - Emergency/Park Brake
R - Rudder
E - Elevator                                                                 SDM 12-4

Question 8

When will the PTU turn on automatically?

Answer 8

Anytime the flaps are selected greater than zero degrees, and the parking brake is released.

SDM 12-8

Question 9

How do the hydraulic systems protect from fluid loss?

Answer 9

The affected system’s isolation valve closes.

SDM 12-9

Question 10

If hydraulic systems #1 & #2 fail, will brakes be available?

Answer 10

There are approximately six applications of emergency brake available from the emergency brake accumulator.

E & A 11.14

Question 11

Will the green ON switchlight illuminate if the PTU is automatically activated?

Answer 11

Yes.
The ON segment (green) of the PTU Switchlight illuminates whenever the PTU is activated either automatically or manually.

SDM 12-8

Question 12

What systems are powered by the #3 hydraulic system?

Answer 12

Elevators.

SDM 12-4

Question 13

What is the purpose of the #3 Main Hydraulic system?

Answer 13

To provide hydraulic pressure to the elevator, in the event of #1 and/or #2 Main hydraulic system(s) failure, or failure of both engines.

SDM 12-3

Question 14

What is the minimum hydraulic quantity for dispatch in each system?

Answer 14

40%

FSM 3.3.10