LAX94LA191

The aircraft lost power and collided with rocks short of the runway. The student pilot was unable to regain engine power while turning from the downwind leg to the base leg after realizing his altitude was too low. The airplane's engine stopped running in response to the student pilot's throttle application. The airplane operator suspected the carburetor venturi was iced, choking air flow, and the application of throttle enriched the fuel air mixture to a point where the engine would not run. Examination of the engine did not reveal any evidence of mechanical failure or malfunction. Impact damage precluded the operational testing of the airplane's carburetor heat system. The temperature and dew point at the closest reporting weather observation facility was 68 and 47 degrees respectively. Review of a carburetor icing probability chart revealed that the listed temperature and dew point is in an area of the graph annotated 'moderate icing in cruise power, serious icing with glide power.'

On April 17, 1994, at 0900 hours Pacific daylight time, a Cessna 150M, N9276U, lost power and collided with rocks short of runway 26 of the Redlands Municipal Airport near Mountain Home Village, California. The airplane was being operated by Aero Tech Academy, Redlands, California, as a solo instructional flight. The airplane was substantially damaged, and the student pilot, the sole occupant, received minor injuries. The local flight originated in Redlands, California, about 0830 hours. Visual meteorological conditions prevailed.

The student pilot told the Safety Board that he entered the airport traffic pattern on the crosswind leg about 800 feet above the ground for the purpose of accomplishing a normal landing. On the downwind leg abeam the approach end of the runway, he pulled the carburetor heat on, reduced power to 1,500 rpm engine speed, and extended the wing flaps 10 degrees. As the pilot turned to the base leg, he noticed his altitude was low. He attempted to add power, however, the airplane's engine did not respond. He turned the airplane toward the runway and attempted an engine restart. The engine would not start and the airplane landed short of the runway in a rocky area and nosed over.

Examination of the engine did not reveal any evidence of mechanical failure or malfunction. The magnetos were operationally tested on a test bench and found to be functional.

According to the Federal Aviation Administration (FAA), the operator suspected the carburetor venturi was iced, choking the air flow. The student pilot's application of the throttle enriched the mixture to a point where the engine stopped running and could not be restarted.

The temperature and dew point at the closest reporting weather observation facility was 68 and 47 degrees respectively. Review of a carburetor icing probability chart revealed that the listed temperature and dew point is in an area of the graph annotated "moderate icing in cruise power, serious icing with glide power."