Incident Overview
During a Title 14 CFR Part 135 on-demand charter flight, an airline transport pilot attempted a takeoff from a 960-foot-long, rough and uneven gravel airstrip. The pilot and three passengers were on board with baggage. Prior to starting the takeoff, the pilot selected 10 degrees of flaps. During the takeoff roll, as the airplane reached rotation speed, the pilot selected 20 degrees flaps. The pilot reported that the airplane failed to become airborne as it neared the end of the airstrip, prompting an aborted takeoff. Heavy braking was applied, but the aircraft could not be stopped before it went off the airstrip.
Collision and Damage
After leaving the airstrip, the main landing gear wheels collided with a gravel bar. Both main landing gear legs collapsed as a result of the collision. The airplane sustained structural damage to its wings, fuselage, and empennage.
Pilot Report
The pilot noted that there were no preaccident mechanical anomalies with the airplane.