What happened
The incident involved N3447R, which collided with a hangar following an attempt by the pilot to manually rotate the propeller. The aircraft was unoccupied and had not been chocked at the time of the event. The pilot reported that the aircraft's battery was insufficient to crank the engine past the compression stroke. Consequently, the pilot exited the cockpit to pull the propeller through top dead center. Upon successfully starting the engine, the pilot attempted to re-enter the aircraft but slipped. During this process, the unoccupied aircraft began to taxi and ultimately struck a hangar.
The investigation
The investigation focused on the mechanical state of the aircraft and the actions taken by the pilot. It was determined that the battery was too weak to turn the engine past the compression stroke. The pilot's decision to manually rotate the propeller led to the engine starting unexpectedly while he was outside the aircraft.
Findings
Contributing factors included the weak battery condition and the failure to chock the aircraft before attempting manual rotation. The pilot's slip prevented him from controlling the aircraft immediately upon startup, leading to the collision with the hangar.