Boeing767mech From United States of America, joined Dec 2000, 992 posts, RR: 3 Posted (3 years 6 months 2 weeks 3 days 11 hours ago) and read 3876 times:
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.
Futureatp From United States of America, joined Feb 2000, 211 posts, RR: 0 Reply 2, posted (3 years 6 months 6 days 5 hours ago) and read 3286 times:
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.
Mender From United Kingdom, joined Feb 2004, 224 posts, RR: 0 Reply 5, posted (3 years 6 months 4 days 17 hours ago) and read 3068 times:
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
Futureatp From United States of America, joined Feb 2000, 211 posts, RR: 0 Reply 7, posted (3 years 5 months 2 weeks 5 days 11 hours ago) and read 2435 times:
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.