Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

B777 Air Demand Pump Inop.

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

B777 Air Demand Pump Inop.

Old 14th Oct 2019, 22:32
  #1 (permalink)  
Thread Starter
 
Join Date: May 2005
Location: Vancouver Island
Posts: 27
B777 Air Demand Pump Inop.

Dispatched with a center hydraulic air demand pump inop., MEL 29-11-03. The procedure required us to power the remaining ADP with the APU bleed for take-off by running the APU bleed and isolating the pump air supply with the L and R bleed isolate valves. After take off the APU was shut down and the bleed isolate valves are returned to their normal open positions.

This makes sense as it allows the remaining pump to provide hydraulic power for the gear retraction and flight controls (I believe primarily the TAC control of the rudder) in the event of an engine failure. What surprised us was that we were not required to re-configure the system for landing, What is different about a single engine go around than an engine out take off?

Any insight greatly appreciated.
Cropduster.
Cropduster is offline  
Old 14th Oct 2019, 23:14
  #2 (permalink)  
 
Join Date: Feb 2002
Location: UK
Age: 56
Posts: 3,206
A guess, less fuel on board so engine power not so critical.
TURIN is offline  
Old 15th Oct 2019, 02:03
  #3 (permalink)  
 
Join Date: Dec 2001
Location: FL, USA
Posts: 2,798
Iím thinking Maximum Landing Weight.
Significantly less then Maximum Take Off Weight.
B2N2 is offline  
Old 15th Oct 2019, 03:39
  #4 (permalink)  
 
Join Date: Sep 2005
Location: home @ 103E
Age: 57
Posts: 80
Raising the gear with hydraulics, lowering it by gravity?
perantau is offline  
Old 15th Oct 2019, 07:40
  #5 (permalink)  
 
Join Date: Jan 2013
Location: Seattle Area
Posts: 263
I'm pretty sure that configuration requirement is driven by critical takeoff rudder response requirements rather than climb performance (gear retraction time).
Dave Therhino is offline  
Old 15th Oct 2019, 08:51
  #6 (permalink)  
 
Join Date: Mar 2002
Location: Here & there
Posts: 820
Originally Posted by Cropduster View Post
What is different about a single engine go around than an engine out take off?
As Dave Therhino said:
I'm pretty sure that configuration requirement is driven by critical takeoff rudder response requirements...
The immediate rudder response in the event of an engine failure during take-off is more critical than the go-around case. The remaining pumps provide sufficient response in the go-around case, without the need to use APU bleed for the operative C system ADP.

BuzzBox is offline  
Old 15th Oct 2019, 11:36
  #7 (permalink)  
Thread Starter
 
Join Date: May 2005
Location: Vancouver Island
Posts: 27
Dave, Buzz Box et all, thank you. There was a lot of head scratching about that on the flight.
Cheers Cropduster.
Cropduster is offline  

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.