Accident Sequence
A multi-engine turbopropeller-powered airplane with a pilot and four passengers departed from a runway. Surveillance video showed that the takeoff and initial climb appeared normal, but the airplane then began to lose airspeed and altitude. It entered a left roll and descended toward the ground. After the airplane went out of sight, a rising plume of smoke was recorded about 1 mile from the departure end of the runway. Shortly after, the camera appeared to shake from wind, and recorded blowing debris and heavy rain on the ramp. Before and during takeoff, the ramp was dry with no rain or noticeable wind. No radio or distress calls were heard from the pilot.
Witnesses saw the airplane’s takeoff and initial climb, describing it as struggling to climb and reporting a steep bank and descent toward the ground. They characterized the weather conditions as stormy and windy, with a weather front passing through. The wreckage was found in heavily wooded terrain adjacent to a factory about 1 mile south of the departure end of runway 18. A post-impact fire consumed most of the airplane.
Examination Findings
Detailed examinations of the airframe, engines, flight controls, and propellers revealed no pre-impact mechanical anomalies that would have precluded normal operations. Both engines and propellers exhibited evidence of rotation at impact, and several large diameter tree branches were found cut consistent with propeller blade strikes, indicating the engines were producing power at impact. A performance study indicated that the airplane climbed to a maximum altitude of about 386 ft above ground level before descending. Review of previous takeoffs from the same runway showed that the airplane’s climb performance during the accident initial climb was diminished, but the reason could not be determined.
Weather Conditions
Review of weather information indicated that the airplane departed about the time a line of extreme intensity precipitation was approaching. Weather reporting equipment at the airport indicated a wind shift associated with this line. A wind shear alert was active in the control tower advising of 15 to 20 kt gains about 1 mile from the runway. Based on observation data, it is likely that during the initial climb, the airplane encountered wind between 20 and 30 kts with direction varying about 50°, from a quartering headwind to a crosswind. After the accident, the wind shifted to a quartering tailwind for the departure runway and increased to 30 to 40 kts. There was no evidence of a microburst or downdraft. The performance study could not conclude why the airplane had diminished performance. Although weather was deteriorating with wind shifts, a weather study determined that the wind shifts likely contributed to, but did not cause the accident.
Pilot Information
The pilot’s autopsy was limited by injury but identified severe coronary artery disease. Within the limits of the autopsy, there was no evidence that a medical event contributed to the accident. Toxicology testing detected a low level of ethanol in cavity blood only, which may have been produced postmortem; it is unlikely that ethanol effects contributed to the accident.
Probable Cause
The official probable cause is the loss of control during initial climb for undetermined reasons, with contributing factor being the sudden wind shifts during the initial climb.