Primary finding
Probable cause
The pilot's failure to maintain adequate separation during a formation flight, which resulted in an encounter with wake turbulence, an aerodynamic stall, and collision with terrain.
Investigator assessment
Analysis narrative
The pilot reported that, while flying in formation inbound for landing, during the base leg to final approach turn, the airplane in front of his slowed down too much and he had to maneuver to give the airplane room to land. During the maneuver, the accident airplane encountered the preceding airplane’s wake turbulence and subsequently entered a spin at about 100 ft above ground level. The pilot was able to recover from the spin and collided with the ground hard in a wings level attitude. The wings and fuselage were substantially damaged. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.