PPRuNe Forums

Go Back   PPRuNe Forums > Flight Deck Forums > Tech Log
Forgotten your Username/Password?

Tech Log The very best in practical technical discussion on the web


Reply
 
Thread Tools
Old 19th Sep 2008, 13:13   #1 (permalink)
 
Join Date: Jul 2006
Location: Norway
Age: 31
Posts: 124
737-800 Hydraulics

Hello

Our FCOM states that the electric hydraulic pumps should be switched on in sequence 1 - 2, and switched off in sequence 2 - 1, to minimise the transfer of hydraulic fluid between system A and B.
It isn't a problem operationally from what I've heard, but a procedure we utilise to not create an increased workload on the tech staff.
My guess is that there has to be a check valve somewhere in one of the hydraulic systems, but I haven't figured out which one.

Does anyone here know which system?

All inputs are welcome
KristianNorway is offline   Reply
Old 19th Sep 2008, 15:28   #2 (permalink)
 
Join Date: Dec 2000
Location: very close to STN!!
Age: 59
Posts: 519
never seen that--

i've been on 737's since the early 90's, 100,200,300,400,500 and now the 800 and i have never seen that in any books i have been given.

must be a company added change and someone in your company should know.
stator vane is offline   Reply
Old 19th Sep 2008, 18:27   #3 (permalink)
 
Join Date: Jul 2006
Location: Norway
Age: 31
Posts: 124
Yes.. I got the impression this was company - specific. One wouldn't find it in the FCTM.

I'll try our tech staff, but if anyone knows about the procedure please let me know.

I would appreciate it
KristianNorway is offline   Reply
Old 19th Sep 2008, 18:35   #4 (permalink)
 
Join Date: Jul 2000
Location: My views - Not my employer!
Posts: 697
Brake shuttle valve (between main/alternate brakes)?

Ok, I am a classic driver
Cough is offline   Reply
Old 20th Sep 2008, 07:57   #5 (permalink)
 
Join Date: Jan 2002
Location: Brisbane, Australia
Posts: 964
Yeah...

with the brakes,
if you set the park brake with system B, then secure sys B,
turn on sys A, and release the park brake, there will be a small transfer of hydraulic fluid, or vice versa!

The same effect will be had with the reversers, since they can be operated open with a 'normal' hydraulic system, depending on the side, and closed with the standby system.

But these are things one would do intentionally, not something done unintentionally!

In response to your Q, I don't know of any otherway to transfer fluid from one hyd sys to another, on the 737NG.

Think of your current procedure when being pushed/towed without the steering disconnect pin in place, don't you toggle the system A pumps off and on, without changing the on status of system B!

Cheers...FD...
Flight Detent is offline   Reply
Old 21st Sep 2008, 11:48   #6 (permalink)
 
Join Date: Jul 2006
Location: Norway
Age: 31
Posts: 124
Hello

Thanks Cough and FD.

Cough was right. I spoke to one of our techs who said the initial thought was to limit fluid transfer via the brake shuttle valve.

On the other hand the applicability of the procedure is questionable since the unpressurized system pressure must drop below 1500 psi before the brake shuttle valve shifts hydraulic source.
KristianNorway is offline   Reply
Old 21st Sep 2008, 14:15   #7 (permalink)
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,401
Yer can always rely on Capt 'S' Hydraulics
BOAC is online now   Reply
Reply
 
 
 


Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 12:29.


vBulletin® v3.8.7, Copyright ©2000-2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
1996-2012 The Professional Pilots Rumour Network