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SkyShoe65
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Joined: Wed Dec 30, 2020 4:45 pm

B767-300 Jettison Rate

Wed Dec 30, 2020 5:25 pm

Hello.
There are recent AD's regarding CWT tank explosion concerns on cargo aircraft as well as passenger.
My question is related to an alternate solution in lieu of the NGS.
I am working on an analysis to show no adverse effect between an alternate Ignition Mitigation Means and the Fuel Jettison System

Literature that I found indicates the Jettison system is capable of 140,000 lb/hr fuel flow.
Digging through IPC's I see that the Jettison Override pump is the Hamiltion Sundstrand 5009656
This has a rated flow of 35,000 lbs/hr in Jettison mode; where both the override pump and jettison pump operate together.
Both these pumps units are in a single pump housing. (For normal engine feed operations from the CWT, only the override pump runs.)

So you have a left wing and right wing jettison system, each with a pump that delivers 35,000 lb/min
So the total system should only flow 70,000 lb/hr?
How do you get to 140,000 lb/hr as listed in other aircraft documentation? What am I missing?
Do the Boost pumps also participate in Jettison flow?
Any explanation would be appreciated. Thanks.
 
Qantas744er
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Joined: Sat Jun 04, 2005 4:36 am

Re: B767-300 Jettison Rate

Wed Dec 30, 2020 7:21 pm

On the 767-300ER the total jettison rate (override/jettison pumps operating together) is 2,645 lbs/minute or 158,732 lbs/hour.

There are two dual pump units. Each pump within the dual pump units has a jettison rate of 39,683 lbs/hour (x 4 pumps total gives you 158,732 lbs/hour during jettison).
 
arcticcruiser
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Re: B767-300 Jettison Rate

Wed Dec 30, 2020 10:25 pm

And there are B767-300ERs out there with a single jettison pump each side. And also ones without fuel jettison capability at all. Welcome to the wonderful world of Boeing options.
 
Lpbri
Posts: 289
Joined: Tue Sep 27, 2016 7:18 pm

Re: B767-300 Jettison Rate

Thu Dec 31, 2020 12:14 am

In my training materials, for later build 300-ERs, the 2 center tank override pumps are used to jettison fuel. They each have an output of 25,000 lbs/hr. I see no mention of “dual pump units”.
 
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SkyShoe65
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Joined: Wed Dec 30, 2020 4:45 pm

Re: B767-300 Jettison Rate

Mon Jan 04, 2021 1:25 pm

Thanks.
Can you point me to a technical source for the numbers you provided?
Acceptable data to the FAA as the rules for substantiation go.
The rates I see are from the Hamilton Sundstrand CMM, and they conflict with what you are telling me.
It says the pump rate is 25,000 for the override pump, and 35,000 when both override and Jettison pump are operating together.
Perhaps I am looking at the wrong pump?
 
stratclub
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Joined: Fri Jan 05, 2018 10:38 pm

Re: B767-300 Jettison Rate

Mon Jan 18, 2021 9:50 am

I may be mistaken, but aren't the Override Jettison pumps the same pump? My recollection of the 787 seems to remember that to be true. IIRC, the main tanks and the center wing Override/Jettison pumps are all turned on and the center wing fuel is burned first because the O/J pumps have a higher pressure than the main tank pumps. I'm thinking the 767 works the same way.
 
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747classic
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Re: B767-300 Jettison Rate

Mon Jan 18, 2021 12:38 pm

AFAIK the correct Boeing name is"override / jettison pump ", this kind of pump is used on several Boeing types.

Image

Original uploaded by Avsoft, see : https://www.avsoft.com/product/boeing-b ... -diagrams/

The dual pump, as installed in later built 767-300 aircraft,* works in single mode when CW fuel is used during normal ops. This "single"override mode provides a higher pressure than the boost pumps, installed in the wing tanks. So the CW fuel is used first, there after the boost pumps take over and the wing tanks are used, (if the CW tank is empty, the override jetison pumps stops operating)

If selecting " jettison on" at the over head panel, the dual pumps will work together in jettison mode (higher rate) and the jettison tranfer vlv's will open, pressurizing the jettison manifold. Selection of the RED Left and/or Right nozzle will actually start the fuel dumping by opening one (in case of a wing fire) or both jettison nozzle vlv's.

767-300 fuel panel at overhead panel
Image

Original uploaded by Ken Hoke at twitter, see : https://twitter.com/AeroSavvy/status/834075911792254977

* , see : http://www.boeing.com/assets/pdf/commer ... eldump.pdf
 
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747classic
Posts: 4038
Joined: Sat Aug 15, 2009 9:13 am

Re: B767-300 Jettison Rate

Mon Jan 18, 2021 1:51 pm

Important addition : On the 767 only CW tank fuel can be jettisoned ! (too late for editing above )

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