What happened
On October 13, 2018, an Italian-registered Pipistrel Alpha Electro departed from Drachten airfield, heading toward Stadskanaal airfield. During the arrival phase, as the pilot joined the aerodrome traffic circuit and transitioned from the downwind leg to the base leg, the aircraft experienced a sudden loss of altitude. The aircraft impacted the ground, and a post-impact fire ensued. The pilot, who was the sole occupant, was fatally injured, and the aircraft was destroyed.
The investigation
The Dutch Safety Board investigated the circumstances of the crash to determine the cause of the sudden descent. The inquiry focused on the aircraft's flight configuration, technical systems, and the pilot's handling of the aircraft. The investigation specifically examined the role of the electric propulsion system and the aircraft's battery performance, as well as the aerodynamic characteristics of the aircraft's wing configuration during the approach.
Findings
Technical analysis of the batteries revealed that they did not contribute to the accident. Instead, the investigation determined that the primary cause was a low airspeed situation that brought the aircraft close to its stall speed. This led to a stall and a subsequent incipient spin from which the pilot was unable to recover.
Several contributing factors were identified, including the aircraft's specific landing configuration of +25° flaps on the base leg and the use of full-wing span flaperons. Additionally, the investigation noted the lack of a stall warning system and the pilot's limited experience and training specifically with the Pipistrel Alpha Electro model.