Hydraulics Flashcards
What are the hydraulic system pressure limitations?
3000 +/- 200 psi
How does the hydraulic system generate pressure?
The Green System is powered by an engine driven pump or if needed by the PTU. The Yellow System is pressurised by an engine driven pump or again by the PTU should an engine fail. An electric pump can pressurise the yellow system at any time, but mainly is used to allow for cargo door operation on the ground. The Blue System is powered by an electric pump, or by the RAT following a pump failure.
What is the hydraulic pressure with the RAT online?
2500 psi.
What do the priority valves do?
Protect against low pressure. They cut off hydraulic power to heavy load users.
How are the hydraulic reservoirs usually pressurised?
Bleed air from engine 1 usually pressurises the hydraulic reservoirs. If engine 1 fails or bleed air is too low, the system automatically takes the air from the cross bleed duct to prevent the pumps cavitating.
Which systems have fire shutoff valves?
Green and Yellow Systems.
How does the PTU operate during engine start?
The PTU is inhibited during the first engine start, it then self tests at the beginning of the second engine start.
What is the hydraulic accumulator?
A way of storing hydraulic pressure for use when no other means of hydraulic pressure is available. It also helps to maintain a constant pressure by covering transient demands during normal operation of the system. The yellow system accumulator will provide 7 full brake applications in the event of a system failure. The accumulator can be recharged by using the yellow electric pump.
Which hydraulic system is used for normal braking?
Green.
Which hydraulic system is used for alternate braking?
Yellow.
What alternate braking methods do we have?
- Alternate braking with anti-skid.
- Alternate braking without anti-skid.
- Alternate braking on accumulator (max 7 applications)
Is anti-skid available on alternate brakes?
It may be available depending on electrical/hydraulic supply.
Do we have a system to manually select alternate brakes?
Yes, by switching the A/SKID & N/W STRG switch OFF.
Is autobrake available on alternate braking?
No.
If an instructor was going to fail a hydraulic system, which one would you want them to fail and why?
BLUE, Less dependent on it for the aircraft control ability and performance. B+Y is the least worst dual hydraulic in the case of further loss.
