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767 Hydraulic ADP Question

Posted: Thu May 07, 2020 11:11 pm
by 767333ER
This is for anyone who knows about such things; I have been involved in project for a flight simulator that adds realistic audio for the 767 using the correct logic for all the systems. The ADP has to be about the most complicated to simulate with scripts and sound files since it is so dynamic on this plane. We have found a journal article of all things that has all the information one would need and it says that the ADP in the auto position will run under pressure demand conditions and, in addition, under some other conditions:

1. On ground from flaps selected down to flaps position agree
2. During takeoff from main gear truck switch actuation until flaps are retracted
3. During approach from first flaps extension to spoiler retraction on the ground

https://www.jstor.org/stable/44647773?seq=1

It suggests, but does not explicitly say that in the latter two conditions it will run at "idle" if not under demand which would be gear operation or flaps operation. It says that "idle" is at around 2300 rpm which of course is much lower than what it would run at during demand and I am inclined to believe this article as it does look reliable; however, I have not been able to notice (audibly) this logic, specifically the operation in the latter two conditions when there is no pressure demand between the operation of gear and flaps, on any 767 flight I have been on or in any video I have watched. What I do seem to think I can hear is after the operation of flaps or gear at any point is the relatively downward low frequency sweep it creates when it actually does shut fully off (this is a noise that can he heard over the engines when even at takeoff thrust). Furthermore, according to this it should be operating at some capacity before touchdown and after when the spoilers extend and the brakes come in it just increases to meet demand, so why would it not be audible at all moments before but be so clearly audible once in the runway at a somewhat higher rpm (sometimes it isn't that much higher than "idle"). Is this logic actually correct and the "idle" is just a state that is completely inaudible over the noise of the low thrust and airframe noises or is it not true?

Re: 767 Hydraulic ADP Question

Posted: Fri May 08, 2020 1:15 am
by DL777200LR
If my memory serves me right, with no center electric hydraulic pumps running and the ADP in auto, there is 0 hydraulic pressure with no demand ( ex flap operation) and you can’t hear anything even standing by the ADP exhaust but if the ADP is turned on it is ridiculously loud. The 767-300 AMM states the ADP in auto remains off until system demand exceeds the output of the 2 ACMPs ( center electric pumps)

Re: 767 Hydraulic ADP Question

Posted: Fri May 08, 2020 5:24 pm
by 767333ER
DL777200LR wrote:
If my memory serves me right, with no center electric hydraulic pumps running and the ADP in auto, there is 0 hydraulic pressure with no demand ( ex flap operation) and you can’t hear anything even standing by the ADP exhaust but if the ADP is turned on it is ridiculously loud. The 767-300 AMM states the ADP in auto remains off until system demand exceeds the output of the 2 ACMPs ( center electric pumps)

I can only imagine how loud the new 777 would be with three of those things! So are you saying then that the 767's ADP logic is more simple than what the document I found suggests?

Re: 767 Hydraulic ADP Question

Posted: Sat May 09, 2020 1:04 am
by DL777200LR
767333ER wrote:
DL777200LR wrote:
If my memory serves me right, with no center electric hydraulic pumps running and the ADP in auto, there is 0 hydraulic pressure with no demand ( ex flap operation) and you can’t hear anything even standing by the ADP exhaust but if the ADP is turned on it is ridiculously loud. The 767-300 AMM states the ADP in auto remains off until system demand exceeds the output of the 2 ACMPs ( center electric pumps)

I can only imagine how loud the new 777 would be with three of those things! So are you saying then that the 767's ADP logic is more simple than what the document I found suggests?


According to a 767-300ER Aircraft Maintenance Manual, it is apparently that simple where it remains off until required by demand while in auto mode.

Re: 767 Hydraulic ADP Question

Posted: Sun May 10, 2020 6:25 am
by 767333ER
DL777200LR wrote:
767333ER wrote:
DL777200LR wrote:
If my memory serves me right, with no center electric hydraulic pumps running and the ADP in auto, there is 0 hydraulic pressure with no demand ( ex flap operation) and you can’t hear anything even standing by the ADP exhaust but if the ADP is turned on it is ridiculously loud. The 767-300 AMM states the ADP in auto remains off until system demand exceeds the output of the 2 ACMPs ( center electric pumps)

I can only imagine how loud the new 777 would be with three of those things! So are you saying then that the 767's ADP logic is more simple than what the document I found suggests?


According to a 767-300ER Aircraft Maintenance Manual, it is apparently that simple where it remains off until required by demand while in auto mode.

I see. Thank you!