Interstate S-1B1 N46336 accident near Lititz, Pennsylvania

Probable cause

The pilot’s failure to control the airplane’s pitch attitude, which resulted in an aerodynamic stall during the initial takeoff climb. Contributing to the accident was the pilot’s failure to set the trim in accordance with the pretakeoff checklist and the airplane’s encounter with wake turbulence from a preceding airplane.

NTSB analysis

The airplane departed as the fifth airplane in a formation of six airplanes during an airshow demonstration and was about 75 feet to the trailing right of the preceding airplane during the takeoff and initial climb. The pilot reported that, about 10 feet above ground level (agl), the airplane drifted right of the runway centerline and that he then realigned the airplane with the centerline. About 35 feet agl, he encountered "severe turbulence," and the airplane banked left uncontrollably. He attempted to regain control of the airplane; however, it stalled and subsequently impacted the ground in a nose-low attitude. A left crosswind of about 3 knots existed at the time of the accident. According to Advisory Circular 90-23F, "Aircraft Wake Turbulence," "a crosswind will decrease the lateral movement of the upwind vortex."

Postaccident examination revealed that the pitch trim was set in an almost full nose-up position. The pilot likely did not comply with the before takeoff checklist and confirm that the trim setting was at 0 before takeoff. In addition, the airplane likely encountered wake turbulence from the preceding airplane. The pilot reported no mechanical malfunction or abnormality that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for ERA13LA366 for the full record.