History of Flight
On June 1, 2024, at 1355 Pacific daylight time, a Beech 35-C33A airplane, registration N1259M, sustained substantial damage during an accident near San Diego, California. The pilot and two passengers were not injured. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
The pilot reported that the fuel tanks were filled before departure for the approximately 330-nautical-mile cross-country flight. The fuel selector was initially positioned to the left tank, and the pilot switched to the right tank about 200 nautical miles into the flight. During the landing approach, the pilot did not change the fuel selector position again. The fuel quantity gauges indicated that the right tank contained more fuel than the left during the approach. The auxiliary fuel pump was off, as required by the checklist.
About one mile from the runway on final approach, the pilot fully extended the wing flaps. Shortly thereafter, the engine experienced a partial loss of power and ran roughly. The pilot enriched the mixture but could not restore full power. Determining that the airplane was too low to reach the runway, the pilot executed a forced landing short of the runway. The airplane landed hard, resulting in a nose gear collapse and substantial damage to the left wing.
Aircraft and Fuel System Description
The airplane was a Beech 35-C33A, serial number not specified. Maintenance records were not available; the pilot stated the last annual inspection occurred in March 2024, about 26 flight hours before the accident. The airplane was not equipped with an engine monitor. The pilot estimated that after the flight, the left tank contained 14 gallons usable fuel and the right tank 24 gallons usable.
The fuel system had a total capacity of 80 gallons (74 usable) with rubber fuel cells (bladders) in each wing leading edge. Each filler port featured a visual measuring tab. Fuel flowed from the bladders to a fuel selector (Off, Left, Right positions), then through a strainer, electric auxiliary fuel pump, engine-driven injector pump, metering control unit, fuel manifold, and lines to cylinder nozzles. Excess fuel (about 10 gallons per hour) returned to the selected tank. The system included a check valve, screens at tank outlets and the auxiliary pump inlet, and vent lines terminating on the bottom wing surfaces.
Wreckage and Impact Examination
After recovery, the wings were removed. Fuel system continuity was tested using a small tank of clean fuel connected to the left tank inlet and return. The electric fuel pump was disconnected at the splice. The fuel selector functioned correctly: fuel flowed when selected to the left tank and ceased when moved to right. The fuel strainer screen exhibited areas of corrosion. The throttle and mixture control valve screen was clear.
The fuel manifold was disassembled. The rubber diaphragm was brittle, inflexible, and showed peeling on its upper surface. Numerous rubber flakes were found, but it could not be determined if they would have prohibited venting. The vent hole was unobstructed. The manifold screen was clean but rust-colored; trace rust was present in the manifold cavity. Fuel lines to each cylinder flowed fuel at similar rates when disconnected. Fuel injectors were clear of debris.
Vent system continuity was verified by blowing air. When air was introduced into the left wing vent line, fluid consistent with water was discharged. A water-detecting paste turned deep magenta, confirming water. The right wing vent system produced trace fluid. Corrosion was visible on the bottom of the fuel filler cap and receptacle screens.
Engine examination revealed no external crankcase damage. All six spark plugs showed gray coloration normal for operation. Magneto-to-engine timing was within normal range. Borescope inspection of combustion chambers showed no mechanical damage, foreign object ingestion, detonation, or valve-to-piston contact. Combustion signatures were consistent with normal operation. No oil residue was found in the exhaust system.
With fuel plumbed directly to the left wing root, an engine test run was performed for about five minutes at 1,200 to 1,700 rpm, including a magneto check at 1,700 and 2,000 rpm. The engine operated normally.