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rosenbauer2024
Topic Author
Posts: 2
Joined: Mon Jul 02, 2018 9:40 am

Defueling a 737 to tank truck

Fri Oct 05, 2018 8:41 am

Hi, I'm investigating an instance of a fuel truck connected to an Air China Boeing 737-79L, tail number B-5043, CA121/122 route. Air China website says this is probably a 737-800 but I was a bit confused by the 79L. Not an expert myself.

Image

I am trying to determine if the photo above possibly definitively indicates whether the attached hose is fueling or defueling the aircraft.

After researching, it appears this model 737 may defuel there, but I have found mostly information indicating the defuel valve must be engaged, which can only be so if a separate, smaller door towards the engine is open and the lever/valve turned down (preventing the door from closing until disengaged). It appears no such door is open in the photo.

But one comment I read made it sound like the defuel valve or other method can be engaged also somewhere in the control panel near the refuel nozzle under the main door.

So if anyone can please help me understand if the photo indicates whether it is possible to determine if defueling is occurring, I would greatly appreciate it!
 
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Starlionblue
Posts: 19938
Joined: Fri Feb 27, 2004 9:54 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 9:37 am

Can't answer the defueling questions, but 9L is the Air China customer code for Boeing. It is a 700, hence the -7, originally delivered to Air China, hence 9L.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
yeelep
Posts: 766
Joined: Mon Apr 04, 2011 7:53 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 10:59 am

The plane is being fueled, the defuel valve has to be open to defueled. The controls at the fueling panel are used for pressure fueling or transferring fuel between tanks.
 
trijetsonly
Posts: 735
Joined: Tue Jul 21, 2009 10:38 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 11:27 am

Were you trying to find out if China supplies Fuel to North Korea by tankering and defueling passenger planes?

Isn't normal refueling on the left wing? Do the right refuel couplings have a refuel panel?
I only know the 747 where the refuel panel is on the left wing only. The right wind only has an additional refuel coupling for faster fueling.
Happy Landings
 
Dalmd88
Posts: 3131
Joined: Fri Jul 28, 2000 3:19 am

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 12:35 pm

trijetsonly wrote:
Were you trying to find out if China supplies Fuel to North Korea by tankering and defueling passenger planes?

Isn't normal refueling on the left wing? Do the right refuel couplings have a refuel panel?
I only know the 747 where the refuel panel is on the left wing only. The right wind only has an additional refuel coupling for faster fueling.

On the 737 there is only a fuel panel on the right wing. As another has stated the defuel valve is in another panel that is closed in the picture so they are fueling the aircraft.
 
trijetsonly
Posts: 735
Joined: Tue Jul 21, 2009 10:38 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 12:44 pm

Dalmd88 wrote:
trijetsonly wrote:
Were you trying to find out if China supplies Fuel to North Korea by tankering and defueling passenger planes?

Isn't normal refueling on the left wing? Do the right refuel couplings have a refuel panel?
I only know the 747 where the refuel panel is on the left wing only. The right wind only has an additional refuel coupling for faster fueling.

On the 737 there is only a fuel panel on the right wing. As another has stated the defuel valve is in another panel that is closed in the picture so they are fueling the aircraft.


Learn something new every day. Thank you!
Happy Landings
 
stratclub
Posts: 1372
Joined: Fri Jan 05, 2018 10:38 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 5:37 pm

The wording is not quite correct. The defueling valve connects the engine feed manifold to the fueling manifold which allows the aircraft fuel boost pumps to pressurize the fueling manifold.
If a fuel truck is connected to the fueling manifold fuel is pushed back into the fueling truck by using the aircrafts fuel boost pumps.
To transfer fuel you do not connect a fuel truck. You open the defuel valve, open the fueling valve to the tank you want to put fuel into and turn on the aircraft fuel boost pumps for the tank you want to transfer fuel from.

Image

The defueling panel cannot be closed if the defuel valve is in the defuel position.
Image

737 fueling panel
Image
 
Tristarsteve
Posts: 3663
Joined: Tue Nov 22, 2005 11:04 pm

Re: Defueling a 737 to tank truck

Fri Oct 05, 2018 9:08 pm

I only know the 747 where the refuel panel is on the left wing only. The right wind only has an additional refuel coupling for faster fueling.


There is a lot of customer options in fuel connections. The B767 has a refuel panel and two couplings on the left wing, same as B747. It is common to also have a panel on the right wing, but with two couplings and no panel.
The British Airways B767-300 were different. They had a complete fuel panel on the right wing as well. I have never seen another aircraft with a refuel control on both wings. We believe it was a mistake during the ordering of the aircraft, but no-one ever admitted to it. On the BA B767 the left wing panel was in charge. But if you closed the panel, then the right wing panel operated normally. It was very useful at times, but worth the money??
 
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DL_Mech
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Re: Defueling a 737 to tank truck

Sat Oct 06, 2018 2:04 am

Tristarsteve wrote:
The British Airways B767-300 were different. They had a complete fuel panel on the right wing as well. I have never seen another aircraft with a refuel control on both wings.


Maybe to match their 757s with the refueling panel on the Right Wing? Boeing used to do all kinds of custom installations for customers. Our 757s had manual landing gear door release handles similar to the 767.
This plane is built to withstand anything... except a bad pilot.
 
DL777200LR
Posts: 150
Joined: Fri Nov 20, 2015 12:15 am

Re: Defueling a 737 to tank truck

Sat Oct 06, 2018 7:43 am

stratclub wrote:
The wording is not quite correct. The defueling valve connects the engine feed manifold to the fueling manifold which allows the aircraft fuel boost pumps to pressurize the fueling manifold.
If a fuel truck is connected to the fueling manifold fuel is pushed back into the fueling truck by using the aircrafts fuel boost pumps.
To transfer fuel you do not connect a fuel truck. You open the defuel valve, open the fueling valve to the tank you want to put fuel into and turn on the aircraft fuel boost pumps for the tank you want to transfer fuel from.

Image

The defueling panel cannot be closed if the defuel valve is in the defuel position.
Image

737 fueling panel
Image



Unless you cut off half the handle, which I have heard a story that someone actually did once lol.
Last edited by DL777200LR on Sat Oct 06, 2018 7:53 am, edited 2 times in total.
Nothing better than the sound of a 77W GE90-115B on engine start.
 
DL777200LR
Posts: 150
Joined: Fri Nov 20, 2015 12:15 am

Re: Defueling a 737 to tank truck

Sat Oct 06, 2018 7:47 am

Tristarsteve wrote:
I only know the 747 where the refuel panel is on the left wing only. The right wind only has an additional refuel coupling for faster fueling.


There is a lot of customer options in fuel connections. The B767 has a refuel panel and two couplings on the left wing, same as B747. It is common to also have a panel on the right wing, but with two couplings and no panel.
The British Airways B767-300 were different. They had a complete fuel panel on the right wing as well. I have never seen another aircraft with a refuel control on both wings. We believe it was a mistake during the ordering of the aircraft, but no-one ever admitted to it. On the BA B767 the left wing panel was in charge. But if you closed the panel, then the right wing panel operated normally. It was very useful at times, but worth the money??



DL 777s have complete fueling panels on both wings but the left is still the master fueling panel. Only the left panel will work if both are open at the same time. Pretty sure not many airlines actually take this option.
Nothing better than the sound of a 77W GE90-115B on engine start.
 
Dalmd88
Posts: 3131
Joined: Fri Jul 28, 2000 3:19 am

Re: Defueling a 737 to tank truck

Sat Oct 06, 2018 1:01 pm

DL777200LR wrote:
stratclub wrote:
The wording is not quite correct. The defueling valve connects the engine feed manifold to the fueling manifold which allows the aircraft fuel boost pumps to pressurize the fueling manifold.
If a fuel truck is connected to the fueling manifold fuel is pushed back into the fueling truck by using the aircrafts fuel boost pumps.
To transfer fuel you do not connect a fuel truck. You open the defuel valve, open the fueling valve to the tank you want to put fuel into and turn on the aircraft fuel boost pumps for the tank you want to transfer fuel from.

Image

The defueling panel cannot be closed if the defuel valve is in the defuel position.
Image

737 fueling panel
Image



Unless you cut off half the handle, which I have heard a story that someone actually did once lol.

I've had to change the handle a few times on a C check because it had been modified so the door could close. Never understood why someone would go to the trouble of cutting it.
 
stratclub
Posts: 1372
Joined: Fri Jan 05, 2018 10:38 pm

Re: Defueling a 737 to tank truck

Sat Oct 06, 2018 5:15 pm

If you make something idiot proof, nature just comes up with a better idiot. It is possible that Darwin has a hand in these type of things.
 
rosenbauer2024
Topic Author
Posts: 2
Joined: Mon Jul 02, 2018 9:40 am

Re: Defueling a 737 to tank truck

Mon Oct 08, 2018 12:43 am

Thank you all for the help. So it appears the defuel valve door being closed at least means there can be no clear indication in the photo of defueling occurring, despite the possibility a handle was cut (which seems unlikely but in a case such as this where doing so would help get away with illegal activity, it is at least plausible).

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