Narrative:

Flying in marginal VFR, opted to return to anc IFR from naken intersection on V319. While still in VFR PNF noticed fuel low level caution light illuminate temporarily. Aircraft was burning both engines from aft tank. Time and fuel burn agreed with quantity on fuel gauge, 650 pounds, which is well above point where fuel low level caution light should come on (75 pounds). After some discussion crew decided warning light was in error, continued to burn out of aft tank and initiated climb from naked intersection along V319 from 2500 to 10000 ft. At 9000 ft crew noticed left engine fuel flow dropping and loss of power on that engine. Action: left engine power lever idle, propeller feathered, fuel tank selector switched moved from both (engines) after to norm, and standby boost emergency switches were engaged. Engine regained power west/O further action, and flight continued to destination with no further incident. At no time did booster pump failure caution light illuminate. A mechanical irregularity report was filed with FAA by maintenance departure. The result was: the motive line check valve strainer was partially blocked, restricting flow to collector tank, allowing more fuel to exit collector tank then ejector system could provide a maximum climb power, x-feed valve set to aft tank. Failure of #1 booster pump and concurrent failure of the automatic change-over system in the associated tank may result in an engine flame-out, especially at high altitudes. Under these circumstances the booster pump caution lights for the affected tank will not illuminate. (Note: this was a seaplane and it is not uncommon to have 1 booster pump go off-line due to dampness in the electronic circuitry; they usually come back on-line when they dry off.) fuel xfer failure: if during level flight a fuel low level caution light illuminates and the related fuel quantity indicator denotes contents of approximately 330#, a fuel xfer failure can be assumed to have occurred. Fuel xfer will continue by gravity feed, and flight may continue; however, sustained climb and descent attitudes must be made with caution. The problem, restriction of fuel to the engine, was correctly analyzed by the crew and rectified effectively; however, I will never climb in xfeed again. I believe a more thorough knowledge of the fuel system would have prevented that, and perhaps more lights would have flashed upstairs when the caution low fuel level light illuminated, even though we knew, in fact, that there was plenty of fuel in that tank.

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Original NASA ASRS Text

Title: SMT CLIMBING WHILE IN A CROSSFEED CONFIGN LOSES POWER TO 1 ENGINE WHICH IS RESTORED BY A RESELECTION OF FUEL SOURCE.

Narrative: FLYING IN MARGINAL VFR, OPTED TO RETURN TO ANC IFR FROM NAKEN INTXN ON V319. WHILE STILL IN VFR PNF NOTICED FUEL LOW LEVEL CAUTION LIGHT ILLUMINATE TEMPORARILY. ACFT WAS BURNING BOTH ENGS FROM AFT TANK. TIME AND FUEL BURN AGREED WITH QUANTITY ON FUEL GAUGE, 650 LBS, WHICH IS WELL ABOVE POINT WHERE FUEL LOW LEVEL CAUTION LIGHT SHOULD COME ON (75 LBS). AFTER SOME DISCUSSION CREW DECIDED WARNING LIGHT WAS IN ERROR, CONTINUED TO BURN OUT OF AFT TANK AND INITIATED CLB FROM NAKED INTXN ALONG V319 FROM 2500 TO 10000 FT. AT 9000 FT CREW NOTICED LEFT ENG FUEL FLOW DROPPING AND LOSS OF PWR ON THAT ENG. ACTION: LEFT ENG PWR LEVER IDLE, PROP FEATHERED, FUEL TANK SELECTOR SWITCHED MOVED FROM BOTH (ENGS) AFTER TO NORM, AND STANDBY BOOST EMER SWITCHES WERE ENGAGED. ENG REGAINED PWR W/O FURTHER ACTION, AND FLT CONTINUED TO DEST WITH NO FURTHER INCIDENT. AT NO TIME DID BOOSTER PUMP FAILURE CAUTION LIGHT ILLUMINATE. A MECHANICAL IRREGULARITY RPT WAS FILED WITH FAA BY MAINT DEP. THE RESULT WAS: THE MOTIVE LINE CHK VALVE STRAINER WAS PARTIALLY BLOCKED, RESTRICTING FLOW TO COLLECTOR TANK, ALLOWING MORE FUEL TO EXIT COLLECTOR TANK THEN EJECTOR SYS COULD PROVIDE A MAX CLB PWR, X-FEED VALVE SET TO AFT TANK. FAILURE OF #1 BOOSTER PUMP AND CONCURRENT FAILURE OF THE AUTOMATIC CHANGE-OVER SYS IN THE ASSOCIATED TANK MAY RESULT IN AN ENG FLAME-OUT, ESPECIALLY AT HIGH ALTS. UNDER THESE CIRCUMSTANCES THE BOOSTER PUMP CAUTION LIGHTS FOR THE AFFECTED TANK WILL NOT ILLUMINATE. (NOTE: THIS WAS A SEAPLANE AND IT IS NOT UNCOMMON TO HAVE 1 BOOSTER PUMP GO OFF-LINE DUE TO DAMPNESS IN THE ELECTRONIC CIRCUITRY; THEY USUALLY COME BACK ON-LINE WHEN THEY DRY OFF.) FUEL XFER FAILURE: IF DURING LEVEL FLT A FUEL LOW LEVEL CAUTION LIGHT ILLUMINATES AND THE RELATED FUEL QUANTITY INDICATOR DENOTES CONTENTS OF APPROX 330#, A FUEL XFER FAILURE CAN BE ASSUMED TO HAVE OCCURRED. FUEL XFER WILL CONTINUE BY GRAVITY FEED, AND FLT MAY CONTINUE; HOWEVER, SUSTAINED CLB AND DSNT ATTITUDES MUST BE MADE WITH CAUTION. THE PROB, RESTRICTION OF FUEL TO THE ENG, WAS CORRECTLY ANALYZED BY THE CREW AND RECTIFIED EFFECTIVELY; HOWEVER, I WILL NEVER CLB IN XFEED AGAIN. I BELIEVE A MORE THOROUGH KNOWLEDGE OF THE FUEL SYS WOULD HAVE PREVENTED THAT, AND PERHAPS MORE LIGHTS WOULD HAVE FLASHED UPSTAIRS WHEN THE CAUTION LOW FUEL LEVEL LIGHT ILLUMINATED, EVEN THOUGH WE KNEW, IN FACT, THAT THERE WAS PLENTY OF FUEL IN THAT TANK.

Data retrieved from NASA's ASRS site as of July 2007 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.