B767 ENG SPOOL-DOWN DURING CLB WHILE FUEL XFEED OP WAS IN PROGRESS.

Narrative

SHORTLY AFTER TKOF; PASSING THROUGH FL270; THE CAPT ASKED ME TO BAL THE WING TANKS; AS WE HAD ABOUT A 700 LB SPLIT. TURNED OFF THE R MAIN PUMPS AS I INITIALLY PERCEIVED THIS TO BE THE LOW SIDE. SEVERAL SECONDS LATER; I REALIZED THAT THE L SIDE WAS LOW AND I TURNED THE R SIDE BACK ON AND TURNED THE L SIDE OFF. AT NO TIME DID I OPEN THE XFEED. ALMOST IMMEDIATELY CAPT RPTED A LOSS OF THRUST ON THE R ENG FOLLOWED IMMEDIATELY BY 'WE HAVE LOST BOTH ENGS.' I IMMEDIATELY TURNED THE L MAIN FUEL PUMPS ON AND STARTED THE QRC FOR LOSS OF BOTH ENGS. BEFORE FINISHING THE QRC; THE CAPT RPTED THAT HE HAD BOTH ENGS BACK. I DECLARED AN EMER UPON DISCUSSION WITH THE CAPT. WE DECIDED ON ZZZ AS A DIVERT DUE TO ITS PROX AND LONG RWY LENGTH. WE BEGAN A SLOW DSCNT WHILE WORKING THROUGH THE QRC AND IRREGULAR EEC ITEMS. WE RETURNED THE EEC'S TO THEIR PRIMARY MODE AND ALL EICAS INDICATIONS RETURNED TO NORMAL. UPON RECEIVING CLRNC; WE LANDED IN ZZZ. WE DECIDED ON A HVY LNDG BECAUSE WE DID NOT KNOW THE EXACT CAUSE OF THE ENG MALFUNCTION. WE ALSO BELIEVED THAT IT COULD HAPPEN AGAIN WITHOUT WARNING. I FEEL THAT THIS INCIDENT WAS CAUSED BY FUEL STARVATION TO THE ENGS WHILE THE PUMPS WERE OFF. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAID THE ENGS ROLLED BACK TO APPROX 40% N2 AND THAT BOTH GENERATORS DROPPED OFF LINE. THE TOTAL TIME; DETERMINED FROM THE FLT RECORDER FROM FUEL BOOST PUMP SWITCHING BEING TURNED OFF TO ENG ROLLBACK; WAS APPROX 14 SECONDS. THE ACFT WAS TEST FLOWN AND THE CONDITION WAS REPEATED ON THE TEST FLT. IT WAS FOUND THAT THE ENGS WOULD SUCTION FEED; IF IT WAS BEGUN AROUND 10000 FT; RIGHT ON UP TO THE SVC CEILING OF THE ACFT. IF; HOWEVER; IT WAS BEGUN AT HIGHER ALTS ENG SPOOL-DOWN OCCURRED. THE ACFT WAS RECENTLY FUELED AND IT IS BELIEVED THAT AERATION AND FUEL CAVITATION WERE CONTRIBUTING FACTORS. THE MEL HAS SINCE BEEN CHANGED TO REQUIRE ALL TANK PUMPS BE OPERABLE FOR DISPATCH. THE RPTR IS CONCERNED THAT HIS TRAINING AND ACFT MANUALS INDICATE THAT THE ENG FUEL PUMPS WILL SUCTION FEED WITHOUT FUEL TANK BOOST PUMPS.