B747-400 QRH: "HYD CONTROL 1,4"
Thread Starter
Joined: Nov 2008
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From: Europe
B747-400 QRH: "HYD CONTROL 1,4"
Good evening everybody.
In the B747-400 QRH I find the "HYD CONTROL 1,4" NNC.
Why is there no such checklist/advisory message for system 2 and 3?
I've tried to search for an answer to this question but without results, so this might be a no brainier for everyone else.
The only reason I might find is that demand pumps 1 and 4 are commanded ON when selector is in AUTO and trailing flaps are in transit or extended past "1". System 1 and 4 have some quite demanding tasks during takeoff and landing and loss of system pressure is maybe more critical.
Do anybody have some insight in this logic?
Best regards,
Bluescan
In the B747-400 QRH I find the "HYD CONTROL 1,4" NNC.
Why is there no such checklist/advisory message for system 2 and 3?
I've tried to search for an answer to this question but without results, so this might be a no brainier for everyone else.
The only reason I might find is that demand pumps 1 and 4 are commanded ON when selector is in AUTO and trailing flaps are in transit or extended past "1". System 1 and 4 have some quite demanding tasks during takeoff and landing and loss of system pressure is maybe more critical.
Do anybody have some insight in this logic?
Best regards,
Bluescan
Joined: Jun 2001
Aviation Qualifications: ATPL
Posts: 1,186
Likes: 59
From: OZ
It seems pretty straight forward to me. The QRH action is to turn the ADP(s) manually on to potentially avoid slow operation if the control fault is affecting the demand pump sensing. If it is another control fault, no harm done.
Think about the missed approach certification requirements for one.
Think about the missed approach certification requirements for one.
Joined: Jun 2001
Posts: 452
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From: In da north country
NSEU,
AFAIK, All -400's have 4 ADP's. ( alt.demand pump) However, #2&3 ADP's can be either electric or pneumatic depending on the original operator. All -400's have the #4 system w/ an electric Aux pump and some operators also have the #1 system with an electric aux pump.
AFAIK, All -400's have 4 ADP's. ( alt.demand pump) However, #2&3 ADP's can be either electric or pneumatic depending on the original operator. All -400's have the #4 system w/ an electric Aux pump and some operators also have the #1 system with an electric aux pump.
Joined: Jun 2001
Posts: 452
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From: In da north country
Sometimes it does; as on the classic.
The -400 can have either electric or air driven Demand pumps. United elected to go with all four powered by pneumatics. All the ones I have flown, Ex Malaysian, ex JAL, ex ANA, ex cargolux, have electrically powered demand pumps. That seems to be the Boeing norm.
The -400 can have either electric or air driven Demand pumps. United elected to go with all four powered by pneumatics. All the ones I have flown, Ex Malaysian, ex JAL, ex ANA, ex cargolux, have electrically powered demand pumps. That seems to be the Boeing norm.
Joined: Feb 2004
Posts: 1,410
Likes: 36
From: Australia
I believe Korean Air Lines also has 4 ADPs (air-driven pumps).
Sorry for the confusion... I've never heard of the expression "Alt Demand Pump". Aux perhaps.
The Air Driven Pumps on the inboards are normally associated with PW engines, so I assumed the extra hydraulic flow was for the reversers. Extra demand was given as a reason for the message inclusion, hence my question.
Cheers
Sorry for the confusion... I've never heard of the expression "Alt Demand Pump". Aux perhaps.
The Air Driven Pumps on the inboards are normally associated with PW engines, so I assumed the extra hydraulic flow was for the reversers. Extra demand was given as a reason for the message inclusion, hence my question.
Cheers
Joined: May 2000
Posts: 3,203
Likes: 2
From: Seattle
Our PW-engined 744s still have Air-driven Demand Pumps on 1 & 4, Electric-driven Demand Pumps on 2 & 3, as well as Engine-driven Hydraulic Pumps on all 4.
Last edited by Intruder; 20th July 2016 at 21:18.
Joined: Feb 2004
Posts: 1,410
Likes: 36
From: Australia
Originally Posted by Willit Run
And to further confuse things; some operators, (JAL birds) have electric AUX pumps on #1 and #4
Joined: Oct 1999
Posts: 206
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From: Up there
The ultimate gold standard of 744 is
AUX (ACMP) on 1 & 4 (Towing - body gear steering, brakes)
ADP on 1 & 4
ACMP on 2 & 3
The most basic, cheaper, maintain parts commonality with the "classic" is/was
AUX (ACMP) on 4 (brakes)
ADP on 1,2,3 & 4.
Boeing used* to let you customise (added expense to Boeing) however those days are over and the gold standard it is 👍
*Unless you're POTUS, military or just insanely loaded.
The -8.
AUX (ACMP) on 1 & 4 (Towing - body gear steering, brakes)
ADP on 1 & 4
ACMP on 2 & 3
AUX (ACMP) on 1 & 4 (Towing - body gear steering, brakes)
ADP on 1 & 4
ACMP on 2 & 3
The most basic, cheaper, maintain parts commonality with the "classic" is/was
AUX (ACMP) on 4 (brakes)
ADP on 1,2,3 & 4.
Boeing used* to let you customise (added expense to Boeing) however those days are over and the gold standard it is 👍
*Unless you're POTUS, military or just insanely loaded.
The -8.
AUX (ACMP) on 1 & 4 (Towing - body gear steering, brakes)
ADP on 1 & 4
ACMP on 2 & 3
