Hydraulics

Question 1

What are the normal hydraulic pressures? And if the RAT is online?

Answer 1

3000 PSI normally
2500 when RAT is powering blue system

Question 2

What are the hydraulic system pressure limits?

Answer 2

3000 PSI +/- 200 PSI

Question 3

How does the hydraulic system generate pressure?

Answer 3

Green system - engine driven pump or PTU
Blue system - electric driven pump or RAT
Yellow system - engine driven pump or PTU. Electric pump can also pressurise the system. Crew members can also use a hand pump to pressurise the yellow system in order to operate cargo doors when no elec power is available.

Question 4

What are the redundancies of the hydraulic system?

Answer 4

Green - PTU
Blue - RAT
Yellow - PTU, Elec pump, Hand pump

Question 5

What is the hydraulic accumulator & which system supplies it?

Answer 5

Way if storing hydraulic pressure for use when no other means of hydraulic pressure is available. Powered by yellow system & will provide 7 full brake applications. Can be recharged by yellow elec pump.

Question 6

What are the hydraulic priority valves?

Answer 6

They cut off power to heavy load users if hydraulic pressure in a system gets low. Prioritise pressure to Landing gear, slats/flaps, emergency generator

Question 7

How are the hydraulic reservoirs pressurised & what is the redundancy?

Answer 7

Normally bleed air from Engine 1 pressurised reservoirs automatically. If engine 1 fails or or bleed air delivered is too low the system automatically takes air from cross bleed duct to prevent hydraulic pumps from cavitating

Question 8

Which hydraulic system have fire shutoff valves?

Answer 8

Green & Yellow

Question 9

Which hydraulic abnormal procedures are located within the QRH?

Answer 9

Dual hydraulic summaries

Question 10

Explain how the PTU functions during engine start procedure?

Answer 10

PTU is inhibited during first engine start & it self tests at the beginning of 2nd engine start

Question 11

When does the PTU operate?

Answer 11

The PTU operates anytime the pressure between the green & yellow hydraulic systems is greater than 500 PSI. It is inhibited during first engine start & for 40 seconds after cargo door operation.

Question 12

Draw the hydraulic system as shown in QRH

Question 13

Draw the hydraulic system as displayed on systems page

Question 14

Name the main systems on GREEN hydraulics

Question 15

Name the main systems on BLUE hydraulics?

Question 16

Name the main systems on YELLOW hydraulics?

Question 17

Why with Green & Blue failure do we put gear down at 200 kts?

Answer 17

To get into direct law and have better pitch authority as only one elevator working

Question 18

Why with Green and Yellow failure is flap 3 selected before gear down?

Answer 18

Loss of horizontal stabiliser means aircraft is trimming with elevator. Once gear is down trimming will be lost so better to be flap 3 and trimmed out before putting gear down otherwise you’ll be fighting it out of trim down the approach