Amateur-built SKYSTAR KTFOX CLSC 4 N90KF accident near Mountain Rest, South Carolina

Probable cause

A partial loss of engine power due to carburetor icing. Contributing to the accident was the engine’s lack of carburetor heat.

NTSB analysis

The pilot reported that, while maneuvering at low altitude surveying fields in his experimental, amateur-built airplane, the engine stopped producing power about 600 ft above ground level (agl) and the propeller continued to windmill. He selected a field for a forced landing site, established the best glide speed, and turned on the electric fuel pump, which restored some power to the engine for about 10 seconds. He stated that when he realized that the airplane would not make it to the selected field, he reduced the throttle to idle and performed a forced landing into trees.

Postaccident examination of the engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation; however, the engine was not equipped with carburetor heat as recommended in the engine installation manual.

The weather conditions at the time of the accident were conducive to the formation of serious carburetor icing at cruise power engine power settings. Thus, it is likely that carburetor ice formed and subsequently resulted in the partial loss of engine power during the climb from the low pass over the field. Had carburetor heat been installed on the engine and been used during these low approaches, the ice accumulation likely would have been prevented.

Text from the NTSB. Open the NTSB docket for ERA21LA192 for the full record.