Narrative:

I was to depart tiw for fca on a pilot service flight to pick up the owners of the aircraft from vacation. The WX was VFR but I filed an IFR flight plan to clear some clouds covering the cascade mountains en route. After topping off the tanks prior to departure, I found that the fuel quantity indicators showed all 4 tanks 1/2 to 3/4 full. Because of this I paid no respect to those gauges the rest of the flight. Based on the performance figures in the poh, I calculated that the 5 hour trip would require 151 gals. The aircraft carries only 137 gals, so at fca I put in the minimum 30 gals to get us back to tiw with the 30 min fuel reserve. 80 mi east of tiw the fuel gauges began to show empty but I paid them no mind and trusted my calculations. 8 NM east of tiw we experienced 2 short power interruptions once on each engine in a descending turn. After landing at tiw I found that the aircraft had only 7 gals of fuel remaining in all 4 tanks. For an aircraft that burns just over 30 gph that equates to about 10 mins of reserve, much less than I had planned. Those power interruptions could only have been to an interruption in the fuel flow due to the low fuel status and the turn or ingestion of some sediment in the bottom of the tanks. The cause of this incident was the inaccuracy of the fuel consumption charts in the poh at cruise and the lack of any climb fuel consumption data at all. Contributing to this incident was my decision to put in the minimum amount of fuel required at fca instead of the maximum. This decision was made after concerns about the full load of passenger and baggage and the high density altitude. I knew that full fuel would have placed the aircraft a few hundred pounds over gross weight. Another contributing factor was my complete disregard for the fuel gauges as they neared empty. This was due to the historically inaccurate nature of aviation fuel quantity indicators in GA. The key here is not to trust fuel gauges unless they read empty. After flying other aircraft near their performance envelope and finding the poh data right on the money, I placed too much faith in the performance data of this much older aircraft/poh when I had never flown it near its performance envelope before.

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Original NASA ASRS Text

Title: FLYING AN UNFAMILIAR ACFT THE RPTR FINDS HE HAS ALMOST NO FUEL REMAINING ON ARR AT DEST. QUANTITY INDICATIONS WAS IN DOUBT FROM THE BEGINNING OF THE OP.

Narrative: I WAS TO DEPART TIW FOR FCA ON A PLT SVC FLT TO PICK UP THE OWNERS OF THE ACFT FROM VACATION. THE WX WAS VFR BUT I FILED AN IFR FLT PLAN TO CLR SOME CLOUDS COVERING THE CASCADE MOUNTAINS ENRTE. AFTER TOPPING OFF THE TANKS PRIOR TO DEP, I FOUND THAT THE FUEL QUANTITY INDICATORS SHOWED ALL 4 TANKS 1/2 TO 3/4 FULL. BECAUSE OF THIS I PAID NO RESPECT TO THOSE GAUGES THE REST OF THE FLT. BASED ON THE PERFORMANCE FIGURES IN THE POH, I CALCULATED THAT THE 5 HR TRIP WOULD REQUIRE 151 GALS. THE ACFT CARRIES ONLY 137 GALS, SO AT FCA I PUT IN THE MINIMUM 30 GALS TO GET US BACK TO TIW WITH THE 30 MIN FUEL RESERVE. 80 MI E OF TIW THE FUEL GAUGES BEGAN TO SHOW EMPTY BUT I PAID THEM NO MIND AND TRUSTED MY CALCULATIONS. 8 NM E OF TIW WE EXPERIENCED 2 SHORT PWR INTERRUPTIONS ONCE ON EACH ENG IN A DSNDING TURN. AFTER LNDG AT TIW I FOUND THAT THE ACFT HAD ONLY 7 GALS OF FUEL REMAINING IN ALL 4 TANKS. FOR AN ACFT THAT BURNS JUST OVER 30 GPH THAT EQUATES TO ABOUT 10 MINS OF RESERVE, MUCH LESS THAN I HAD PLANNED. THOSE PWR INTERRUPTIONS COULD ONLY HAVE BEEN TO AN INTERRUPTION IN THE FUEL FLOW DUE TO THE LOW FUEL STATUS AND THE TURN OR INGESTION OF SOME SEDIMENT IN THE BOTTOM OF THE TANKS. THE CAUSE OF THIS INCIDENT WAS THE INACCURACY OF THE FUEL CONSUMPTION CHARTS IN THE POH AT CRUISE AND THE LACK OF ANY CLB FUEL CONSUMPTION DATA AT ALL. CONTRIBUTING TO THIS INCIDENT WAS MY DECISION TO PUT IN THE MINIMUM AMOUNT OF FUEL REQUIRED AT FCA INSTEAD OF THE MAXIMUM. THIS DECISION WAS MADE AFTER CONCERNS ABOUT THE FULL LOAD OF PAX AND BAGGAGE AND THE HIGH DENSITY ALT. I KNEW THAT FULL FUEL WOULD HAVE PLACED THE ACFT A FEW HUNDRED POUNDS OVER GROSS WT. ANOTHER CONTRIBUTING FACTOR WAS MY COMPLETE DISREGARD FOR THE FUEL GAUGES AS THEY NEARED EMPTY. THIS WAS DUE TO THE HISTORICALLY INACCURATE NATURE OF AVIATION FUEL QUANTITY INDICATORS IN GA. THE KEY HERE IS NOT TO TRUST FUEL GAUGES UNLESS THEY READ EMPTY. AFTER FLYING OTHER ACFT NEAR THEIR PERFORMANCE ENVELOPE AND FINDING THE POH DATA RIGHT ON THE MONEY, I PLACED TOO MUCH FAITH IN THE PERFORMANCE DATA OF THIS MUCH OLDER ACFT/POH WHEN I HAD NEVER FLOWN IT NEAR ITS PERFORMANCE ENVELOPE BEFORE.

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.