Cessna 170A N170TW accident near Palmetto, Florida

Probable cause

The pilot's failure to use the proper hand propping procedures, resulting in a runaway airplane.

NTSB analysis

The pilot and passenger were on a cross-country flight when the pilot noticed that the battery was no longer charging. After landing, the pilot decided to save battery power for the return flight by hand propping the airplane. He briefed the passenger for the hand start procedure, but did not realize the throttle was in the full throttle position. Upon starting, the engine went to full power. The pilot was unable to reenter the airplane before it made two tight left circles on the ramp and collided with an open hangar and the airplane inside.

Federal Aviation Administration Pilot's Handbook of Aeronautical Knowledge FAA-8037-3a contains a section titled, "Hand Propping", which indicates to never allow a person unfamiliar with the controls to occupy the pilot's seat when hand propping. The section also indicates that an additional precaution includes placement of chalks in front of the main tires or if not feasible, the airplane's tail may be securely tied.

Text from the NTSB. Open the NTSB docket for GAA15CA008 for the full record.