Narrative:

The fuel system was changed from a wet wing having a 66 gallon capacity to a bladder arrangement having a 55 gallon capacity. Further; the dimensions are different and the 'dip stick' is not yet calibrated to measure the fuel in each tank. The fuel injector servo was overhauled after having a throttle malfunction. Departed with what appeared to be full fuel in right tank and partial (approximately 3/4 full) in left tank. Trip took 1.5 hours with fuel computer showing 18.8 gallons used. The 18.8 gallons appeared correct; given the normal fuel burn and the actual read-out. All fuel was used from the right tank. The right tank was not visualized. Prior to departing on the next leg; 10 gallons was added to the right tank. I calculated that there was 18.7 gallons in the right tank. The level observed in the right tank appeared correct; but inexperience with the new bladder did not allow accurate measurement. Departed on right tank and at approximately 1 hour into the flight; the engine slowed; then surged and then lost power. I was 5 miles from an airport in VMC at 5000 ft. I immediately turned to the airport; declared an emergency and then started to troubleshoot. My first thought was the throttle system based upon the surge and the recent maintenance. I took me awhile before trying to switch fuel tanks. When I did switch tanks (approximately 800 ft AGL on a short base leg); the throttle was approximately 1/2 closed. This caused the engine to re-start; but there was a large pitch change; which startled me. I retarded the throttle and continued to glide to the landing. The actual approach and landing were without incident. The right fuel tank appeared to be dry and no fuel could be sumped. The first issue may be the 'appearance' of the tank being full based upon the different shape; etc. Contributing to this is the fact that the 'dip stick' measuring tool is not yet calibrated. The second issue may be the inaccurate fuel computer; either the gallons per minute function or the total fuel consumed on a trip. The third issue and the main cause is my practice of always flying on the right tank for 1.5 hours before switching tanks. I desire to switch tanks as few times as possible on a trip. I always try to have the left wind heavier to compensate a right turning tendency cause by mis-rigging or an autopilot turning tendency. If this practice is continued; it must be done on a full tank (27.5 gallons). With the reduced total fuel capacity. I need to be more precise with the actual fuel in the tanks. I use to have a large margin. I need to calibrate the on board fuel computer and the 'dip stick.'

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Original NASA ASRS Text

Title: A change from a wet wing to a bladder fuel tank causes a Mooney pilot to misjudge fuel quantity prior to departure. When the right tank runs dry the reporter assumed a fuel injector problem had reoccurred and set up for an emergency landing. Fuel selector was moved to another tank on final and engine started but reporter continued to landing.

Narrative: The fuel system was changed from a wet wing having a 66 gallon capacity to a bladder arrangement having a 55 gallon capacity. Further; the dimensions are different and the 'dip stick' is not yet calibrated to measure the fuel in each tank. The fuel injector servo was overhauled after having a throttle malfunction. Departed with what appeared to be full fuel in right tank and partial (approximately 3/4 full) in left tank. Trip took 1.5 hours with fuel computer showing 18.8 gallons used. The 18.8 gallons appeared correct; given the normal fuel burn and the actual read-out. All fuel was used from the right tank. The right tank was not visualized. Prior to departing on the next leg; 10 gallons was added to the right tank. I calculated that there was 18.7 gallons in the right tank. The level observed in the right tank appeared correct; but inexperience with the new bladder did not allow accurate measurement. Departed on right tank and at approximately 1 hour into the flight; the engine slowed; then surged and then lost power. I was 5 miles from an airport in VMC at 5000 FT. I immediately turned to the airport; declared an emergency and then started to troubleshoot. My first thought was the throttle system based upon the surge and the recent maintenance. I took me awhile before trying to switch fuel tanks. When I did switch tanks (approximately 800 FT AGL on a short base leg); the throttle was approximately 1/2 closed. This caused the engine to re-start; but there was a large pitch change; which startled me. I retarded the throttle and continued to glide to the landing. The actual approach and landing were without incident. The right fuel tank appeared to be dry and no fuel could be sumped. The first issue may be the 'appearance' of the tank being full based upon the different shape; etc. Contributing to this is the fact that the 'dip stick' measuring tool is not yet calibrated. The second issue may be the inaccurate fuel computer; either the gallons per minute function or the total fuel consumed on a trip. The third issue and the main cause is my practice of always flying on the right tank for 1.5 hours before switching tanks. I desire to switch tanks as few times as possible on a trip. I always try to have the left wind heavier to compensate a right turning tendency cause by mis-rigging or an autopilot turning tendency. If this practice is continued; it must be done on a full tank (27.5 gallons). With the reduced total fuel capacity. I need to be more precise with the actual fuel in the tanks. I use to have a large margin. I need to calibrate the on board fuel computer and the 'dip stick.'

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.