Narrative:

This leg was to oak. The aircraft had 2 MEL's; 'leading edge transit light on' and '#2 generator inoperative.' the MEL's caused some restrs. The leading edge transit light restr us to .65 mach/300 KTS. The #2 generator inoperative restr us to FL350 or below because we had to use the APU generator for the bus. Everything was normal until about 30 mins into the flight. At that time the #2 aft fuel boost failed. We followed the QRH guidance and turned off the switch. At this time the boost pump failure did not impact our operations so we continued on. Lights came on all over the cockpit because the APU shut down. While I was sorting out the system failures caused by 1 bus operation; the flight attendants were ringing us because it was now dark in the cabin. After running the QRH checklists; I realized that we now had no fuel boost pumps on the right main tank because part of the load shedding was to de-power the #2 forward boost pump. Combined with the earlier failure of the #2 aft boost pump and our altitude of FL320; we now faced the possibility of #2 engine flameout. The QRH for loss of both boost pumps on 1 side calls for a descent to FL300 or below to prevent flameout or loss of thrust. I instructed first officer to begin a descent to FL300 and I called ZOA to request an immediate descent to FL280. Center said to stand by. I informed him that we must descend now because of loss of fuel boost pumps. He said that FL280 was not available but FL300 was. I said FL300 would be fine. He cleared us to FL300. The problem was by the time the controller said; 'cleared to FL300 we had already descended approximately 500 ft and were slowly descending through FL315. I feel that I made the decision to start an immediate descent a little too soon. We should have waited until cleared by center to start down. I could even have opened the fuel xfeed for a few mins without getting too much of a fuel imbal. (This procedure is not mentioned in the QRH). So I should have either stayed at FL320 until cleared lower; or declare an emergency before starting down. This error was compounded by an 11 hour duty day and over 7 hours of flight time; a very busy malfunction with lots of lights and QRH reading. Supplemental information from acn 701239: after clearing our flight path visually and with TCAS; the captain told me to go ahead and start descending as he briefly informed ATC of our aircraft condition. During our descent passing approximately FL310; ATC cleared us to descend to FL300. We leveled off at FL300 and proceeded on our planned route and landed uneventfully. We should have told ATC about our aircraft problem on the initial request for a descent and ATC could have vectored the aircraft in front of and below us appropriately to allow us to descend.

Google
 

Original NASA ASRS Text

Title: B737-300 FLT CREW HAS ELECTRIC FUEL PUMP PROBS DURING CRUISE AND DSNDS WITHOUT CLRNC.

Narrative: THIS LEG WAS TO OAK. THE ACFT HAD 2 MEL'S; 'LEADING EDGE TRANSIT LIGHT ON' AND '#2 GENERATOR INOP.' THE MEL'S CAUSED SOME RESTRS. THE LEADING EDGE TRANSIT LIGHT RESTR US TO .65 MACH/300 KTS. THE #2 GENERATOR INOP RESTR US TO FL350 OR BELOW BECAUSE WE HAD TO USE THE APU GENERATOR FOR THE BUS. EVERYTHING WAS NORMAL UNTIL ABOUT 30 MINS INTO THE FLT. AT THAT TIME THE #2 AFT FUEL BOOST FAILED. WE FOLLOWED THE QRH GUIDANCE AND TURNED OFF THE SWITCH. AT THIS TIME THE BOOST PUMP FAILURE DID NOT IMPACT OUR OPS SO WE CONTINUED ON. LIGHTS CAME ON ALL OVER THE COCKPIT BECAUSE THE APU SHUT DOWN. WHILE I WAS SORTING OUT THE SYS FAILURES CAUSED BY 1 BUS OP; THE FLT ATTENDANTS WERE RINGING US BECAUSE IT WAS NOW DARK IN THE CABIN. AFTER RUNNING THE QRH CHKLISTS; I REALIZED THAT WE NOW HAD NO FUEL BOOST PUMPS ON THE R MAIN TANK BECAUSE PART OF THE LOAD SHEDDING WAS TO DE-POWER THE #2 FORWARD BOOST PUMP. COMBINED WITH THE EARLIER FAILURE OF THE #2 AFT BOOST PUMP AND OUR ALT OF FL320; WE NOW FACED THE POSSIBILITY OF #2 ENG FLAMEOUT. THE QRH FOR LOSS OF BOTH BOOST PUMPS ON 1 SIDE CALLS FOR A DSCNT TO FL300 OR BELOW TO PREVENT FLAMEOUT OR LOSS OF THRUST. I INSTRUCTED FO TO BEGIN A DSCNT TO FL300 AND I CALLED ZOA TO REQUEST AN IMMEDIATE DSCNT TO FL280. CTR SAID TO STAND BY. I INFORMED HIM THAT WE MUST DSND NOW BECAUSE OF LOSS OF FUEL BOOST PUMPS. HE SAID THAT FL280 WAS NOT AVAILABLE BUT FL300 WAS. I SAID FL300 WOULD BE FINE. HE CLRED US TO FL300. THE PROB WAS BY THE TIME THE CTLR SAID; 'CLRED TO FL300 WE HAD ALREADY DSNDED APPROX 500 FT AND WERE SLOWLY DSNDING THROUGH FL315. I FEEL THAT I MADE THE DECISION TO START AN IMMEDIATE DSCNT A LITTLE TOO SOON. WE SHOULD HAVE WAITED UNTIL CLRED BY CTR TO START DOWN. I COULD EVEN HAVE OPENED THE FUEL XFEED FOR A FEW MINS WITHOUT GETTING TOO MUCH OF A FUEL IMBAL. (THIS PROC IS NOT MENTIONED IN THE QRH). SO I SHOULD HAVE EITHER STAYED AT FL320 UNTIL CLRED LOWER; OR DECLARE AN EMER BEFORE STARTING DOWN. THIS ERROR WAS COMPOUNDED BY AN 11 HR DUTY DAY AND OVER 7 HRS OF FLT TIME; A VERY BUSY MALFUNCTION WITH LOTS OF LIGHTS AND QRH READING. SUPPLEMENTAL INFO FROM ACN 701239: AFTER CLRING OUR FLT PATH VISUALLY AND WITH TCAS; THE CAPT TOLD ME TO GO AHEAD AND START DSNDING AS HE BRIEFLY INFORMED ATC OF OUR ACFT CONDITION. DURING OUR DSCNT PASSING APPROX FL310; ATC CLRED US TO DSND TO FL300. WE LEVELED OFF AT FL300 AND PROCEEDED ON OUR PLANNED RTE AND LANDED UNEVENTFULLY. WE SHOULD HAVE TOLD ATC ABOUT OUR ACFT PROB ON THE INITIAL REQUEST FOR A DSCNT AND ATC COULD HAVE VECTORED THE ACFT IN FRONT OF AND BELOW US APPROPRIATELY TO ALLOW US TO DSND.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.