CEN22LA230

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.

On June 2, 2022, about 1803 central daylight time, a Cessna 172P, N65497, was substantially damaged when it was involved in an accident near Ennis, Texas. The flight instructor and pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. While enroute to the Ennis Municipal Airport (F41), the flight instructor reported that the engine power decreased about 200 rpm on two occasions. The pilot flew an approach to Runway 16 at F41 and executed a go-around due to excess airspeed. When the throttle and carburetor heat controls were advanced to the full forward position, the engine power only increased to about 2,000 rpm. The flight instructor adjusted the mixture control and reapplied carburetor heat in an attempt to increase engine power, but the power decreased, and the flight instructor executed a forced landing to a field. During the landing roll, the flight instructor turned right to avoid cows and the airplane impacted a tree, which resulted in substantial damage to the right wing. The postaccident examination of the engine revealed normal engine continuity and no anomalies were observed with the carburetor. Four 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 All spark plugs had signatures consistent with normal engine operation when compared to a Champion Check-a-plug chart. The weather conditions at the time of the accident were conducive to serious carburetor icing at glide power.