Cessna 172N N733ZN accident near Compton, California

Probable cause

The total loss of engine power on takeoff due to water-contaminated fuel. Contributing to the accident was the inadequately maintained fuel system, which resulted in water entering the fuel tanks through the filler caps.

NTSB analysis

The airplane had not been flown for about 2 months, and due to the long period on the ground, the pilot planned to perform a test flight for the owner. The pilot completed a preflight inspection, which included confirming fuel levels and checking the fuel tanks for contaminants via the drain ports. The left main and nose gear tires were low, so he serviced them with air and then performed a series of engine run-ups, high-speed taxi tests, and takeoff rolls.

The engine lost all power shortly after the first takeoff and the pilot performed a forced landing into a residential area just beyond the airport perimeter.

Postaccident examination revealed significant quantities of water in the fuel system. It had rained during the two-week period leading up to the accident and the airplane had been stored outside. The airplane had only flown for a few hours over the 4 years leading up to the accident and showed significant evidence of corrosion and non-use; the fuel cap gaskets had degraded such that an adequate seal was not possible.

Although the pilot did not find water in the fuel tanks before the flight, examination revealed evidence of long-standing water contamination at the fuel tanks in an area away from the drain port. Given the general poor condition of the airplane and the evidence of water contamination, it is likely that the airplane was not sitting level for significant periods, possibly due to a deflated nose strut in combination with the two low tires. As such, it is likely that water had settled away from the drain ports when the pilot checked for contamination.

Text from the NTSB. Open the NTSB docket for WPR23LA349 for the full record.