Aeronca 11AC N85893 accident near Ishpeming, Michigan

Probable cause

The pilot's failure to maintain airspeed following a loss of engine power due to carburetor icing while turning from base to final at a low altitude, which resulted in the airplane's wing exceeding its critical angle of attack and a subsequent aerodynamic stall.

NTSB analysis

During a personal local flight, the private pilot made a low pass in the airplane over the runway and turned left to enter the traffic pattern for landing. A witness stated that the airplane "looked mushy" when it made its left crosswind turn. Another witness reported that the airplane appeared to enter a "close-in" traffic pattern at an estimated altitude of 100 to 150 ft above ground level. He further stated that the airplane's airspeed seemed slower than normal. He stopped watching the airplane until he heard a change in its engine noise. When he looked back, the airplane was in a left bank turning from the base leg to final approach, and the engine stopped producing power. The airplane immediately went into a left spiral and turned about 360° before impacting the ground. The accident site was located about 1,200 ft from the approach end of the runway near the runway centerline. A postaccident examination of the airframe and engine did not reveal any evidence of a mechanical malfunction or failure that would have precluded normal operation.

Although the airplane's calculated weight at the time of the accident was about 6 pounds over its maximum gross weight, this likely was not a factor in the accident as it would not have significantly increased the airplane's stall speed. A carburetor icing probability chart indicated a probability of serious icing at glide power at the temperature and dew point reported at the time of the accident. Given that no mechanical reason for the loss of engine power was identified, it is likely that the loss of engine power was due to carburetor icing. Following the loss of engine power, the pilot likely failed to maintain adequate airspeed, resulting in the airplane's wing exceeding its critical angle-of-attack and a subsequent aerodynamic stall.

Text from the NTSB. Open the NTSB docket for CEN16FA269 for the full record.