Cessna 172P N65497 accident near Ennis, Texas

Probable cause

A partial loss of engine power for reasons that were undetermined.

NTSB analysis

The flight instructor and pilot observed the engine power decrease about 200 rpm on two occasions while en route. The pilot flew an approach and then a go-around due to excess airspeed during the approach. When the throttle and carburetor heat controls were fully advanced, the engine power only increased to about 2,000 rpm. The flight instructor attempted to increase engine power without success. During the forced landing to a field the airplane hit a tree, which resulted in substantial damage to the right wing.

Examination of the engine revealed normal engine continuity and compression was confirmed on all 4 cylinders. Several hold down studs on the No. 1 cylinder were fractured and their separated pieces were found in the bottom of the cowling. No other anomalies were observed that would have precluded normal engine operation. No impact damage occurred in the vicinity of the engine and investigators could not determine when these studs separated; however, it is unlikely that the separated studs resulted in the slight loss of engine power noted by the pilot and flight instructor.

The weather conditions at the time of the accident were conducive to serious carburetor icing at glide power. The flight instructor recalled pulling the carburetor heat lever out during the approach, therefore, it is unlikely that carburetor icing resulted in the loss of engine power.

Investigators were not able to determine the reason for the loss of engine power.

Text from the NTSB. Open the NTSB docket for CEN22LA230 for the full record.