Cessna 172 N9556H accident near Lancaster, Ohio

Probable cause

A partial loss of engine power due to the formation of carburetor ice.

NTSB analysis

The pilot departed and remained in the airport traffic pattern. While on the downwind leg, he applied carburetor heat then reduced power to 2,000 rpm. Abeam the approach end of the runway, he reduced power further, then turned onto the base leg, where he recognized that the engine had lost power. After turning onto final approach and realizing that the airplane would not reach the runway, he performed an off-airport landing in a field, resulting in nose-over and substantial damage to the left wing, fuselage, and aft empennage.

Postaccident examination of the engine revealed no evidence of preimpact failure or malfunction of the powertrain, ignition, air induction, exhaust, or carburetor heat systems. Although there was fuel contamination (particulates) found in the carburetor and airframe fuel strainer, and fibrous material inside the carburetor inlet screen, the amount and location of the contamination likely existed at the time of takeoff and the pilot did not report a loss of engine power until being at a reduced power setting on the base leg of the airport traffic pattern. Reported weather conditions were conducive to the formation of carburetor icing at glide and cruise power. Although the pilot reported that he applied carburetor heat before reducing engine power while on the downwind leg of the traffic pattern, it is likely that the ice accumulated to the degree that the carburetor heat was insufficient at the partial power setting to melt the ice that had accrued, resulting in a partial loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA22LA309 for the full record.