ERA16LA111 · Cessna 152

The engine's valves were adjusted the week before the flight to remedy engine performance issues that would typically begin between 10 and 45 minutes in flight. The private pilot performed a full preflight check with no anomalies noted. He then departed, orbited the airport for about 45 minutes, and continued flying over the airport. No engine issues were noted until about 1 hour 5 minutes after takeoff, when the engine began to run roughly. The pilot entered the traffic pattern, but, while operating with the mixture control full rich and the engine at 2,250 rpm with normal oil temperature and pressure, the engine went to idle and did not respond to throttle input. Unable to reach the intended runway, the pilot initiated a descent for a forced landing to a road but, while descending, collided with a utility pole and then impacted the ground hard.

Examination of the engine revealed no evidence of preimpact mechanical failures or malfunctions that would have precluded normal operation. Although a blockage of the left fuel vent line was noted several months after the accident, the airplane was equipped with vented fuel caps, which would have mitigated the issue had it existed at the time of the accident. In addition, although the magnetos were improperly timed, this would have been detectable by the pilot before takeoff and likely did not contribute to the reported loss of engine power. Further, although the weather conditions were favorable for the formation of serious carburetor icing at glide power, the pilot was not operating in that regime when the loss of engine power occurred. Therefore, the reason for the loss of engine power could not be determined based on the available evidence.

Verbatim NTSB analysis and probable cause from the NTSB dataset