SEA94LA107

While maneuvering in serious icing atmospheric conditions, the fuel/air flow in the throttle body injector became restricted by ice build-up, and the engine lost power. The pilot switched fuel tanks, turned on the auxiliary fuel pump, and cycled the ignition/magneto switch, but did not apply carburetor heat. Being unable to restart the engine, the pilot attempted a forced landing on the unsuitable terrain.

On April 23, 1994, approximately 1000 mountain daylight time (MDT), a Rich RV-4 experimental aircraft, N3344E, impacted the terrain during a forced landing about five miles southwest of Weston, Idaho. The forced landing was initiated by the pilot after a loss of engine power while maneuvering at about 1000 feet above the ground. The personal pleasure flight, which departed Logan-Cache Airport, Logan, Utah, about 0945 MDT, was being operated in visual meteorological conditions at the time of the accident. The private pilot, who was the sole occupant, was not injured, but the aircraft sustained substantial damage. No flight plan had been filed, and there was no report of an ELT activation.

According to the pilot, while he was circling the town of Weston, the engine began to sputter and then lost power. He switched to the other fuel tank, turned on the auxiliary fuel pump, and cycled the ignition/magneto switch, but did not apply carburetor heat. When the engine would not restart, he elected to attempt a forced landing in a nearby field. When he got closer to the field, the pilot discovered that there was a sprinkler system wheel line across the field, and as he attempted to avoid this line during the landing flare, the right wing of the aircraft impacted the ground.

At the time of the accident, the weather observation taken at Logan, Utah, about 15 miles southeast of the accident site, showed a temperature of 45 degrees, and a dew point of 39 degrees. The carburetor icing chart obtained from DOT/FAA/CT- 82/44 shows that, under these atmospheric conditions, there exists the possibility of "serious" carburetor icing at both glide and cruise power settings.

The engine on this aircraft had an Ellison Throttle Body Injector installed in place of its standard carburetor. According to the pilot and the Ellison literature, this installation is susceptible to icing within approximately the same ranges as a standard carburetor, and requires the use of carburetor heat under the same atmospheric conditions.