boeing767mech
Posts: 805
Joined: Fri Dec 15, 2000 5:03 pm

757 Fueling Issues

Sat Nov 07, 2009 5:56 pm

Hello out there, my little airline is having issues with fueling our 757's and I was wondering if anyone else's employer is having problems with the 757's.

When fueling the WINGS ONLY, we are having problems with fuel leaking into the center tank sometimes at the rate of 100 pounds a minute. We had manually cycled the center fueling valves to make sure they where closed. This is not a indication problem because after fueling the wings we can pump the fuel out of the center tank, and the level in tank that leaks in goes down as the fuel is pumped

We follow the FIM and measure the shaft on the fueling valve and found it out of limits. One of the aircraft we found the o rings in the center fueling valve completely gone, this airplane was 15 years old, and they where the original valve.

There was an idea that the fueling pressure out of the truck was to high, put after inspection we found that all the trucks where in the limits set by Boeing so it was not a fault of the truck.

So has anyone else out there having this problem?? It seems to be limited to our older aircraft.

David
Never under-estimate the predictably of stupidty
 
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HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: 757 Fueling Issues

Sat Nov 07, 2009 8:19 pm

Seen these problems on older B757s......Our B752SFs have had this issue,the B752PCFs are more reliable,probably due age.

The snags were attributed to leaking Fuel valve & fuel manifold vent valve stuck open on various aircraft,not necessary all three on one aircraft.

regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
futureatp
Posts: 190
Joined: Sun Feb 27, 2000 3:07 pm

RE: 757 Fueling Issues

Thu Nov 19, 2009 12:00 am

ahh yes.....most commonly encountered on "black gauge" Delta 757s. I am not an A&P but do work for an outfit that refuels airliners. I have had several captains tell me the exact reason as to what is happening cant recall as to the specifics.

It is not unusual to open the panel of a RON and find that all but 1500lbs has migrated out of a wing into the center tank. I have had crew members report that they notice it in flight as well.

Not to pick on Delta, but on their older 57's its pretty common(ships 675 and below). So much that if one reads "leaks" on the refueling panel- that could mean 1000lbs of fuel into the center for every 7000lbs fueled into the wings. "Leaks bad" -means be ready to transfer fuel if its a short hop LOL.

Ive joked that I hope DL retains the MX guys who take care of the NW 757 fuel systems as I never have noticed this on a 5500 series NW bird.
 
MX757
Posts: 495
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RE: 757 Fueling Issues

Thu Nov 19, 2009 10:32 am

I checked history on our 757 fleet and came up with the top 3 reasons for fuel migration:

1-DEFUEL VALVES
2-CROSS FEED VALVES
3-BOOST PUMP CHECK VALVES

It was usually leaking O-rings but sometimes the valves were bad.
Is it broke...? Yeah I'll fix it.
 
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HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: 757 Fueling Issues

Fri Nov 20, 2009 8:43 am



Quoting MX757 (Reply 3):
It was usually leaking O-rings but sometimes the valves were bad.

Valve replacement requires tank entry unlike Actuator replacement which is from outside.....takes time as the tank has to be dried & vented for the job.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
Mender
Posts: 248
Joined: Wed Feb 04, 2004 9:36 am

RE: 757 Fueling Issues

Fri Nov 20, 2009 11:51 am

Did replacement of the o rings and adjustment of the fueling valve make any difference?

The fuel manifold drains into the Ctr tank when the pressure is removed. I take it this happens every flight, from every station and it's not simply the bowser driver at a particular base keep letting go of the deadmans handle every few minutes.

If not, this is taking me back around 15 years so my memory is a bit sketchy, I've know the fuel manifold to be cracked before. However I don't think your fuel transfer rate is that bad for this to be the case.

When you reach the pre-selected fuel figure and the fuel valves closes you get a sort of pressure wave inside the manifold for a split second. This can rupture the manifold. As I've not seen this for a very long time I can't remember if we modified our fleet to prevent this or it was just an isolated case.

Whatever, it's still not unusual to find the plastic horseshoe brackets that attach the fuel manifold to the rear bulkhead (wing front spar) of the centre tank to be broken. If the manifold is unsupported for many years then maybe you have a leaky manifold.

Tank entry might be you only way to find out - Enjoy
 
stratosphere
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Joined: Sat Sep 22, 2007 12:45 pm

RE: 757 Fueling Issues

Sat Nov 21, 2009 8:05 pm



Quoting Boeing767mech (Thread starter):
When fueling the WINGS ONLY, we are having problems with fuel leaking into the center tank sometimes at the rate of 100 pounds a minute.

At FedEx virtually ALL the 757's we have acquired so far has had this very problem. Most of the tines it has been problems with the defuel valves and one was a cracked fuel manifold.
 
futureatp
Posts: 190
Joined: Sun Feb 27, 2000 3:07 pm

RE: 757 Fueling Issues

Sat Dec 05, 2009 6:22 pm

Hey I have a supplemental question to add here. On early 757-200 aircraft refuel 100 gallons per minute slower than newer birds. On the refuel panels of these aircraft Boeing says max refueling rate on older birds is 545gpm vs 645gpm at 55psi vs newer ones. Of course all of our equipment is calibrated to 40psi so I never see numbers that high.

My question is: What exactly causes the 100gpm difference? Using United Airlines 757s and air fleets to track manufacturing date I have tracked it down to somewhere in 1992 is when 57s were built to take fuel faster. United Airlines N558UA is the first one in their fleet that takes fuel 100gpm faster(although the refuel panel indicates 545gpm -the slower number).

I have asked several local airline mechanics and no one seems to know the answer. They actually think im nuts because all the replacement part #s are the same.

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