An overheated power controller resulted in the loss of power to the electric motor on a Pipistrel Alpha Electro aircraft that had to make an emergency landing during a flight in Norway on Aug. 14, 2019, according to an accident report published today by the Norwegian Safety Investigation Authority (NSIA). The aircraft lost all propulsive power on approach to Arendal Gullknapp Airport, forcing the pilot to make an emergency landing in a lake with no resulting injuries to the two people on board.
The investigation concluded that the overheating in the power controller resulted from insufficient coolant having been added during a recent replacement of the aircraft’s single electric motor. The NSIA team said that a lack of clarity in Pipistrel’s maintenance manual for the aircraft contributed to this error.
The report included several recommendations based on lessons learned from the incident. It said that Pipistrel should revise the flight manual to make it clearer to pilots how to regain electrical power after an inflight failure, as well as give clearer instructions as to how to replenish coolant levels. It further recommended that the flight manual should include more information about the minimum altitude for safely deploying the Alpha Electro’s all-aircraft recovery parachute.
Pipistrel confirmed it was involved in the NSIA investigation and a spokeswoman explained that it has, "in the interest of drawing unbiased and safety-improving conclusions, provided full support while respecting international standards and recommended practices of ICAO Annex 13." The Slovenian company is working on designs for several other electric- and hydrogen-powered aircraft.