Uncommanded Fuel Transfer
 

Here is an interesting event that happened the other day. Has anybody heard of or had to deal with such a situation.

"During the climb to cruising altitude after the departure from LGAV, the flight crew identified a slight fuel imbalance.
The associated QRH items were executed in an attempt to rectify the issue, however it was
subsequently identified that there was an uncommanded fuel transfer of 2.6 tons per hour from the
L MAIN tank to the CENTER tank. The flight crew decided to divert to London/Heathrow (EGLL),
UK, and declared a PAN PAN as a precaution. The aircraft landed without further incident.
The operator’s maintenance is currently inspecting the aircraft, and will release it back to service
once the issue is fixed."

That's about 15 gallons per minute if I did my conversion right. That's a pretty big leak - not a leaky coupling o-ring. There are a few things it could be, depending on the airplane model. What model was it? Were they feeding from the center tank at the time or did it start right after center tank runout? The one event I've seen like that was eventually attributed to a center tank pump outlet check valve jammed open at pump shutdown by a piece of debris, allowing some of the output of the main tank pumps on that side to flow backwards through the center tank pump into the center tank

B767 BTW ?

What type aircraft? I have had something like this happen about once a decade on different aircraft, but there's always been an established procedure to deal with it. Not a huge deal as long as you are able to monitor and maintain balance within limits until you land.

Saw a report on this. It was a 767. There wasn't much detail, but fuel transferred via the refueling system, which was inoperative in some way and was supposed to be in a configuration dictated by the MEL. Either a valve failure or a valve locked wrong led to the transfer - the report wasn't clear. It was verified and fixed readily by maintenance.

I know this thread is a bit old, but I learned more about the cause of the event. The airplane was dispatched with refuel valves locked open in both the main and center tanks, allowing fuel transfer. Boeing subsequently put out a multi-operator message advising operators not to dispatch the airplane with refuel valves locked open.

Here is another one via Google Translate:

"N718SK, an MHI RH Aviation CRJ-700 operated by SkyWest Airlines as SKW9898,
was on a flight under instrument flight rules from the international airport of
Montreal/Pierre Elliott Trudeau International, QC (CYUL) to Chicago O'Hare, US
(KORD). Immediately after takeoff, the message R MAIN/SCAV Ejector Caution is
appeared on the Engine Indication and Crew Alerting System (EICAS) and
the crew noted that fuel was being transferred from the left tank to the right one. During
climb en route, at 15,000 feet and approximately 32 nm west of CYUL, the message from
fuel imbalance appeared and the flight crew declared an emergency due to
a fuel imbalance issue and requested a return to CYUL. The crew followed
the emergency checklist (QRH) and the imbalance seemed to come from the system
automatic fuel transfer. At the beginning of the descent, the imbalance remained stable
to about 1200 pounds and reduced at lower altitudes. The crew had no problem
control or performance and the aircraft landed safely at 18:13z with the services of
rescue and firefighting aircraft (SLIA) on alert. There were no injuries."