Accident Overview
On September 20, 2023, about 0830 Pacific daylight time, a Cessna 172N, registration N733ZN, was substantially damaged in an accident near Compton, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 flight.
Preflight and Preparations
The airplane had not flown for about two months, prompting the pilot to perform a return-to-service test flight for the owner. He conducted a preflight inspection, visually checking fuel quantity through filler cap openings and cross-checking with fuel gauges, observing between 7 and 10 gallons per side. He checked wing tank fuel drains and found no water. Noting low left main and nose gear tires, he taxied to the fuel island to service them with air. He planned a long engine run-up and high-speed taxi runs.
Engine Run-Up and Takeoff
The run-up lasted 15 to 20 minutes, during which the engine ran rough on the right magneto. The pilot advanced the throttle fully and leaned the mixture, resolving the roughness. He then performed high-speed taxi runs and, on the third attempt, decided to continue with a flight. After reaching about 50 to 100 feet above ground level, the engine momentarily lost power, followed shortly by a complete loss of power.
Forced Landing and Damage
The pilot executed a forced landing straight ahead, striking a parked vehicle. The left wing and forward fuselage sustained substantial damage. The left fuel tank was breached and leaked fuel. A sheriff's deputy checked the right fuel tank through the filler neck and observed fuel at a depth of 3 inches; however, the nose gear assembly had folded aft and detached, leaving the airplane in a nose-down attitude when the measurement was taken.
Postaccident Examination
Examination revealed evidence of long-term non-use, including corrosion within the engine compartment and on airframe skin surfaces, as well as mold-like deposits on cabin upholstery and plastic facias. A complete fuel system examination showed the fuel strainer contained about one-quarter blue fuel and three-quarters water. The carburetor bowl drained 75 milliliters of fuel and 25 milliliters of water. Approximately 10 milliliters of water was found in the right fuel tank, with globules still present. Internal tank inspection showed corrosion-like discoloration at the tank roots and forward areas. Both fuel cap rubber gaskets were degraded, brittle, and cracked, failing to provide a firm seal; the left cap gasket was completely severed by a crack.
Maintenance History and Service Bulletin
An annual inspection was completed on July 15, 2023, after which 20 gallons of fuel was added. At the time of the accident, the airplane had accrued only 1.7 flight hours since that inspection. The previous annual inspection occurred in November 2019, with just 2 hours flown in the intervening four years. Cessna Service Bulletin SEB 92-26 revision 1, which provides a modification for additional fuel drains to assist in detecting and removing water or other contaminants, had not been applied to the accident airplane. While Cessna stated compliance was mandatory, FAA regulations do not require adherence to service bulletins for Part 91 operations.
Environmental Factors
The airplane was stored outside, and rain showers had passed through the area during the two-week period before the accident. Accident damage prevented an assessment of the nose gear strut assembly to confirm if it had been adequately serviced.