B777 central hydraulic system

[Pitch Up Authority]

I am puzzled about the C Hydraulic system.
In case of HYD QTY LOW R+C the QRH suggests that a leak in the brake system might be the reason.
For any problem in the C system we usually keep the C1 ACMP running as it is dedicated to the reserve system. This is of course useless when the leak is in the brake system so you switch it off.
The question is. How do you drop the MLG and Nose gear? The MLG drops by gravity but you must first unlock the uplock to do that.The alternate gear extension uses C HYD and a separate DC pump but how does it work if there is no more HYD QTY? In case of QTY loss in C+R the C reservoir will empty all to the bottom.

[VNAV PATH]

There is a dedicated pipe on the upper part of the hydraulics reservoir which is full of fluid even when reservoir is empty

This fluid is used for the dedicated alternate pack extension (fluid+ dedicated pump)

[Pitch Up Authority]

Thanks. They could mention this in the FCOM. I have been breaking my head on this and could not find anything on the web.

Do you have a copy of the MML?

[VNAV PATH]

http://nsa38.casimages.com/img/2015/05/25/150525063606621642.jpg (http://www.casimages.com/i/150525063606621642.jpg.html)


Gear extension including door release valves and uplock release actuators.
These components as well alternate pack are in wheel wells.


Indeed, FCOM should write it in 5 words...