View Full Version : B777 Alternate/Reserves Braking System
Hello Gents,
simple question: what is meant with Reserve Braking in the Triple? I am a bit confused about it! Do they mean the fluid below the standpipe which is used for landing (nose wheel steering......etc.)?
Many thanks in advance
JammedStab
30th Jun 2015, 15:24
Hello Gents,
simple question: what is meant with Reserve Braking in the Triple? I am a bit confused about it! Do they mean the fluid below the standpipe which is used for landing (nose wheel steering......etc.)?
Correct. This is of course if the Center hydraulic system has been lost subsequent to the right system being lost.
Normally the right hydraulic supplies the normal brakes. If this is lost, there is an automatic switchover to Alternate Brakes powered by the center system
There is a standpipe in the Center hydraulic reservoir to supply the fluid to the center system that has just lost its fluid. That means that fluid below the standpipe has not leaked out and is used by the primary C1 pump as a reserve hydraulic source to power alternate brakes and nosewheel steering.
Remember that when the center system fluid gets to standpipe level, it indicates as zero. But you still have the reserve amount left for the Reserve operation.
VNAV PATH
30th Jun 2015, 16:18
Do not make confusion between different pipes and servitudes: landing gear alternate extension system and nose steering/alternate brakes.
Your FCOM and QRH giving more when saying "nose steering OR alternate brakes may be not operative" or when EICAS advisory message showing RESERVE BRAKES/STEERING.
Nose gear isolation valve (NG ISLN VLV) and reserve isolation valve (RSV ISLN VLV) are commanded by CHIS (center hydraulics isolation system)
http://nsa37.casimages.com/img/2015/06/30/150630060825522305.jpg (http://www.casimages.com/i/150630060825522305.jpg.html)
Thank you for your reply:ok:
flying the Triple Seven now for six years, still so many things to learn, but as a former airbus driver, I have to say that Boeing FCOMs dont provide a lot of background information:(
But I am very happy flying that beauty!
Plz correct me if I am wrong:
If the normal and alternate/reserve braking system is inop, I do have the pressure in the Brake Accumulator as final backup, and at the same time the Brake Source Light on captains side is coming up because the pressure for the normal and Alternate/reserve braking system is low, am I right?
Happy landings
Google angle of attack B777 videos, they are awesome and well worth purchasing if you want to improve your knowledge.
VNAV PATH
30th Jun 2015, 16:29
You are correct: that's exactlty the configuration on ground, with no hydraulics at all. That's why it's highly recommanded on preflight to check accumulator pressure on this pressure gauge.
Gents,
many thanks your your support!
@Mutt I will check that info :ok:
Greetings