Accident Details
On August 26, 2019, about 1644 Pacific daylight time, a Mooney M20C airplane, registration N78988, was substantially damaged when it was involved in an accident near Reno, Nevada. Both passengers were seriously injured, and the pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot Actions and Fuel Management
The pilot reported that before departure, he sumped the fuel tanks, added oil, and departed with the fuel tanks about half full. He determined the fuel level by computing total engine run time since last refueling, as he did not have a dipstick. During the approach, he descended below traffic pattern altitude, turned on the electric fuel boost pump, and switched to the right fuel tank just before entering the right base leg. After turning off the fuel pump, while turning onto final approach, the engine sputtered and lost all power. He switched back to the left tank and turned on the boost pump, then configured for a forced landing. He focused on the airspeed indicator and impacted a fence and the ground, damaging the left wing.
Fuel and Engine Examination
GPS data showed a 35-minute flight, with maximum altitude reached about 20 minutes after departure. An FAA inspector found no fuel smell at the accident site; both wing fuel tanks had ruptured. The aircraft had two 26-gallon integral fuel tanks. The pilot reported 21.6 gallons onboard at departure (9.6 left, 12 right). Postaccident engine run tests showed smooth operation, and about 1 gallon of fuel was found in the engine-driven fuel pump. The propeller blades exhibited damage consistent with impact.
Fuel Gauge and Consumption Analysis
The pilot regularly used fuel quantity gauges, but postaccident examination revealed erroneous indications. Tests showed the right tank gauge indicated near empty with the sender at lowest position; the left tank gauge indicated 6 lbs (no power) and 36 lbs (with power). The senders were sent for examination but tests were inconclusive. The pilot assumed a consumption rate of 10 gph and switched tanks every 30 minutes. He believed the accident was likely fuel exhaustion, as he calculated 1 hour of fuel remaining. He noted possible task saturation from turbulence on the previous flight from Wyoming. A passenger photo before departure showed about 9 gallons left and 12 gallons right. Fuel computations using POH charts indicated about 8.7 gallons in the right and 6.2 in the left at the time of power loss. If the pilot left the selector on one tank for 30 minutes longer than planned, that tank would have been reduced by 5-6 gallons.
Guidance on Fuel Gauges
The FAA's Pilot's Handbook of Aeronautical Knowledge states that fuel gauges are only required to be accurate when reading "empty"; any other reading should be verified. The pilot should visually check fuel levels during preflight inspection.