What happened
On October 13, 2007, at approximately 09:05 UTC, a powered ultralight glider, an MW 155 with registration OK-DZG 03, was performing a training flight at Šumperk airport (LKSU). The crew consisted of an instructor and a student performing circuit training. After the instructor completed a solo test flight, the two-seat aircraft took off with the student on board.
Shortly after liftoff, at an altitude of approximately 30 meters, the aircraft began to visibly yaw to one side, followed by a loss of altitude. The aircraft then entered a series of oscillations, eventually resulting in a roll and a subsequent impact with the ground on runway 36. The impact triggered an immediate fire. While the instructor managed to extricate himself from the wreckage, the student had to be rescued by bystanders after the fire was partially suppressed. Both crew members later succumbed to their injuries; the student died from polytrauma, and the instructor died 14 days later due to complications from inhalation burns.
The investigation
The ÚZPLN investigation examined the flight conditions, the mechanical state of the aircraft, and the control dynamics of the MW 155. The investigation confirmed that the aircraft was airworthy, possessed a valid technical certificate, and the crew members were fully qualified and medically fit for the flight. Meteorological data indicated a wind from 360 degrees at 5 m/s, which was within permissible limits for training but potentially contributed to turbulence.
Investigators also analyzed the physical ergonomics of the aircraft's cockpit. It was noted that the instructor, seated in the rear seat, has limited leverage over the control stick compared to the pilot in the front seat. This configuration limits the instructor's ability to apply corrective forces to the control linkage.
Findings
- The primary cause of the accident was pilot error by the student, specifically improper control inputs that induced uncommanded oscillations.
- The instructor was unable to counteract these oscillations due to the reduced mechanical advantage caused by his position in the rear seat.
- Orographic turbulence caused by the 5 m/s wind may have contributed to the initial instability of the aircraft.
- The aircraft was destroyed by the impact and subsequent fire.