Narrative:

The flight was a combined day VFR and night VFR cross country to satisfy the requirements of part 61 for the commercial multi engine rating. The fuel consumption rate expected for the flight was based on experience as 14 gph (for both engines). The fuel capacity on the main tanks is 36 gallons per side; permitting five hours of flight with no reserve. The training flight was planned to last four hours; with landings and takeoff's at airports enroute. On the last leg; 3.4 hours into our planned four hour flight; we leveled off at 8;500 MSL twenty miles from the airport. We experienced a yaw to the left and a loss of power on the left engine. We immediately turned back towards the departure airport; and contacted approach control; received a squawk code and instructions to enter a right downwind. After feathering the left engine we were able to maintain our altitude in VMC. Our route of flight to the airport over flew the interstate. The northbound lane was our alternate if the right engine quit. We landed with the left engine feathered and taxied to the ramp.the plane was serviced with 65.5 gallons of 100LL. Elapsed time on the hobbs meter for the flight up to that point was four hours. The placarded fuel capacity is 36 gallons. The right tank required 34.5 gallons to fill it to capacity; thus the left tank required 31 gallons. Upon returning to home base; a flight of 0.7 hours; the plane was serviced with fuel and required 13 gallons to fill. Our actual fuel burn was 18.5 gph; compared with a prediction of 14 gph; a difference of 32%. Engines are lycoming O-320s. My assumption on the fuel burn was based on flight in the local area; training with maneuvers; multiple landings; simulated engine failures; power off stalls. This cross country flight was my first experience with an extended cruise regime of flight. My lack of experience was a factor in this event. The flight included landings at the half way point; where fuel was readily available. The fuel gauges are never relied upon as they are notoriously inaccurate. The elapsed time from the hobbs meter provided my estimate of fuel consumption. The fuel gauges are always inaccurate in the old airplanes I fly so they are routinely disregarded. The most accurate fuel gauges is your wrist watch; which I did not disregard. How accurate is your estimate of your rate of fuel consumption and how much are you willing to bet on it? What is the real capacity of your fuel tanks and how much are you willing to bet on that?

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Original NASA ASRS Text

Title: A PA23 experienced fuel exhaustion followed by a successful engine shutdown and landing. Fuel tank capacity was found to be less than placarded. Fuel consumption per hour planning was in question.

Narrative: The flight was a combined day VFR and night VFR cross country to satisfy the requirements of Part 61 for the commercial multi engine rating. The fuel consumption rate expected for the flight was based on experience as 14 GPH (for both engines). The fuel capacity on the main tanks is 36 gallons per side; permitting five hours of flight with no reserve. The training flight was planned to last four hours; with landings and takeoff's at airports enroute. On the last leg; 3.4 hours into our planned four hour flight; we leveled off at 8;500 MSL twenty miles from the airport. We experienced a yaw to the left and a loss of power on the left engine. We immediately turned back towards the departure airport; and contacted Approach Control; received a squawk code and instructions to enter a right downwind. After feathering the left engine we were able to maintain our altitude in VMC. Our route of flight to the airport over flew the interstate. The northbound lane was our alternate if the right engine quit. We landed with the left engine feathered and taxied to the ramp.The plane was serviced with 65.5 gallons of 100LL. Elapsed time on the Hobbs meter for the flight up to that point was four hours. The placarded fuel capacity is 36 gallons. The right tank required 34.5 gallons to fill it to capacity; thus the left tank required 31 gallons. Upon returning to home base; a flight of 0.7 hours; the plane was serviced with fuel and required 13 gallons to fill. Our actual fuel burn was 18.5 GPH; compared with a prediction of 14 GPH; a difference of 32%. Engines are Lycoming O-320s. My assumption on the fuel burn was based on flight in the local area; training with maneuvers; multiple landings; simulated engine failures; power off stalls. This cross country flight was my first experience with an extended cruise regime of flight. My lack of experience was a factor in this event. The flight included landings at the half way point; where fuel was readily available. The fuel gauges are never relied upon as they are notoriously inaccurate. The elapsed time from the Hobbs meter provided my estimate of fuel consumption. The fuel gauges are always inaccurate in the old airplanes I fly so they are routinely disregarded. The most accurate fuel gauges is your wrist watch; which I did not disregard. How accurate is your estimate of your rate of fuel consumption and how much are you willing to bet on it? What is the real capacity of your fuel tanks and how much are you willing to bet on that?

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.