Clark 1000 N9018R accident near Warehouse Point, Connecticut

Probable cause

The pilot’s failure to maintain adequate airspeed during the initial climb after takeoff, which resulted in the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall. Contributing to the accident was the pilot's decision to conduct the takeoff from a grass runway rather than a paved surface, and his decision to continue the takeoff after the airplane traveled into taller vegetation, which significantly increased the distance required to clear trees at the end of the runway.

NTSB analysis

The private pilot was taking off in the single-seat, single-engine biplane. A witness described that, during the takeoff roll on the mowed grass beside the paved runway, the airplane veered left into taller grass, but the pilot continued the takeoff toward tall trees. After becoming airborne, the airplane's pitch attitude was "much too severe," and it appeared to "run out of energy" as the wings rocked back and forth. The airplane settled onto the ground in tall weeds off the departure end of the runway, nosed over, and came to rest inverted. A video of the flight depicted a flight profile consistent with that described by the witness. Smooth, continuous engine sounds were heard well into the airplane's descent.

The pilot's decision to depart from the grass runway rather than the paved runway increased the overall takeoff distance required, a distance which increased even more when the airplane traveled into taller vegetation during the takeoff roll. Rather than aborting the takeoff, the pilot chose to continue, and the airplane became airborne at a point from which it could not maintain a climb over the trees at the end of the runway. The pilot responded by increasing the airplane's pitch attitude, resulting in an exceedance of its critical angle of attack and an aerodynamic stall.

Text from the NTSB. Open the NTSB docket for ERA15LA365 for the full record.