Narrative:

I am writing this letter in explanation of the emergency; which occurred during a flight from ZZZZ to ZZZ. The flight was a reposition to pick up a client from ZZZ and return him to ZZZZ. As a result of a fuel miscalculation made by myself; the aircraft started to run out of fuel on the midfield right downwind position for runway 10. At the first indication that the aircraft was encountering fuel starvation; I immediately commenced a descending right turn into runway 10 and notified the control tower of my situation. I was immediately cleared to land; and did so without incident. I landed approximately halfway down the runway; and exited at taxiway foxtrot. During the turnoff onto taxiway F; the right engine quit running. At this point; I was completely clear of all runways; and shut the aircraft down. When the fire trucks showed up; I told them what happened. I walked to the FBO and had them re-fuel the aircraft. To the best of my knowledge; the origin of the fuel miscalculation that I made was during a flight to and from ZZZZ1 on the day prior. I departed ZZZZ with full inboard tanks (108 gallons) and 10 gallons in the outboard tanks. During the return trip from ZZZZ1 to ZZZZ; there was apparently much more fuel in the outboards than I thought; for I completed the majority of the return flight on the outboards. As a result of this; the inboard tanks consumed much less fuel than I had originally planned for. When I carried the numbers over in our tech log the next day; I started that days flights with 45 gallons on the inboard tanks and 0 on the outboards; (I had run the outboards dry on the return trip the night before) which is slightly over one hours' worth of fuel. After a flight to and from ZZZZ2; I departed ZZZZ at XA10 local time to ZZZ. Based on the chart our company uses for fuel consumption on the navajos; I departed ZZZ with 25 gallons of fuel; which should have yielded 38 minutes of flight time for the approximate 10-15 flight. When making fuel calculations with this table; it is my personal habit to err on the side of caution; and I often make it a point to add several gallons to whatever number is given so that there is a bit of a 'cushion.' although the numbers on paper indicate that the aircraft had 25 gallons of fuel; I was certain that there was a bit more. As a result of this; I was quite alarmed when both engines started to sputter on the midfield downwind leg. As a result of this; I made it a point to review the fuel logs for all flights made several days prior; and have come to the conclusion that the error was made sometime during this period. In the end; the lesson learned here is that fuel gauges and tech logs can be grossly inaccurate. Always assume you have less fuel than you think and plan accordingly. Especially in light piston aircraft (where the gauges are not annually calibrated) if you cannot physically see or touch fuel in the tanks; you must assume you are in trouble.

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Original NASA ASRS Text

Title: A PA-31 landed as fuel exhaustion was occurring after several flights during a time period when usage was estimated but not visually verified.

Narrative: I am writing this letter in explanation of the emergency; which occurred during a flight from ZZZZ to ZZZ. The flight was a reposition to pick up a client from ZZZ and return him to ZZZZ. As a result of a fuel miscalculation made by myself; the aircraft started to run out of fuel on the midfield right downwind position for Runway 10. At the first indication that the aircraft was encountering fuel starvation; I immediately commenced a descending right turn into Runway 10 and notified the Control Tower of my situation. I was immediately cleared to land; and did so without incident. I landed approximately halfway down the runway; and exited at Taxiway Foxtrot. During the turnoff onto Taxiway F; the right engine quit running. At this point; I was completely clear of all runways; and shut the aircraft down. When the fire trucks showed up; I told them what happened. I walked to the FBO and had them re-fuel the aircraft. To the best of my knowledge; the origin of the fuel miscalculation that I made was during a flight to and from ZZZZ1 on the day prior. I departed ZZZZ with full inboard tanks (108 gallons) and 10 gallons in the outboard tanks. During the return trip from ZZZZ1 to ZZZZ; there was apparently much more fuel in the outboards than I thought; for I completed the majority of the return flight on the outboards. As a result of this; the inboard tanks consumed much less fuel than I had originally planned for. When I carried the numbers over in our tech log the next day; I started that days flights with 45 gallons on the inboard tanks and 0 on the outboards; (I had run the outboards dry on the return trip the night before) which is slightly over one hours' worth of fuel. After a flight to and from ZZZZ2; I departed ZZZZ at XA10 local time to ZZZ. Based on the chart our company uses for fuel consumption on the Navajos; I departed ZZZ with 25 gallons of fuel; which should have yielded 38 minutes of flight time for the approximate 10-15 flight. When making fuel calculations with this table; it is my personal habit to err on the side of caution; and I often make it a point to add several gallons to whatever number is given so that there is a bit of a 'cushion.' Although the numbers on paper indicate that the aircraft had 25 gallons of fuel; I was certain that there was a bit more. As a result of this; I was quite alarmed when both engines started to sputter on the midfield downwind leg. As a result of this; I made it a point to review the fuel logs for all flights made several days prior; and have come to the conclusion that the error was made sometime during this period. In the end; the lesson learned here is that fuel gauges and tech logs can be grossly inaccurate. ALWAYS assume you have less fuel than you think and plan accordingly. Especially in light piston aircraft (where the gauges are not annually calibrated) if you cannot physically see or touch fuel in the tanks; you must assume you are in trouble.

Data retrieved from NASA's ASRS site as of April 2012 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.