What happened
On 7 April 2016, a McDonnell-Douglas MD-500E helicopter, registration N60EP, was conducting a local flight near Suwałki, Poland, to capture aerial photographs of new company facilities. The flight, operated by Salag Sp. z o.o., involved the pilot and one passenger.
After taking off from a nearby helipad, the pilot climbed to an altitude of approximately 40 meters to begin a hover for photography. During this hover, the aircraft experienced a sudden and violent loss of control. The tailboom abruptly lowered, and the helicopter entered a right yaw accompanied by a left bank angle. The aircraft completed two full turns around its vertical axis before striking the ground approximately 230 meters from the takeoff site. The impact caused the main rotor blades to undergo a characteristic "tulip" deformation due to a stall. The helicopter was destroyed, and both the pilot and the passenger sustained serious injuries.
The investigation
The PKBWL investigation examined the wreckage, the aircraft's maintenance history, and the pilot's qualifications. Investigators reviewed the functionality of the transmission system, including the interconnect shaft and clutches, finding no irregularities or evidence of improper maintenance. While the right-hand flight controls had been removed for the passenger's convenience and the cockpit control cover was missing, the commission determined these factors did not contribute to the crash. Technical analysis confirmed the engine was operating at maximum power and the control system remained functional until the tailboom broke upon impact.
Findings
- The primary cause of the accident was a main rotor stall triggered by the pilot's excessive reaction to a thermal gust.
- The presence of thermal gusts acted as a contributing factor to the occurrence.
- The aircraft was properly maintained, and the pilot was fully qualified and rested.
- The pilot and passenger were wearing seatbelts, which aided their survival during the impact.