What happened
On 16 July 2020, at approximately 10:33 local time, a privately owned MD 600N helicopter, registration V5-HVD, was conducting a private flight from Grootfontein to Eros Airport. The aircraft was carrying one pilot and three passengers.
While performing an approach into Windhoek along the mountain ridges near Heja Lodge, approximately 6.6 miles from Eros Airport, the aircraft experienced a sudden and immediate loss of engine power. After communicating with the Eros tower for runway 01 clearance, the pilot declared a mayday, after which all radio contact ceased.
In an attempt to manage the emergency, the pilot initiated an autorotation procedure and searched for a suitable landing site while maneuvering between hills to avoid high-voltage power lines. During this maneuver, the pilot lost control of the aircraft, which struck the ground at a shallow angle. The helicopter subsequently tumbled down a ravine and came to rest halfway down a cliff. The impact resulted in the destruction of the aircraft. There were four injuries among the occupants; the pilot and one passenger sustained serious injuries, while the remaining two passengers suffered minor injuries. No fatalities occurred.
The investigation
The investigation into the accident involved the analysis of several critical components and data sources. Because the engine sustained extensive damage, it could not be function tested on-site. Investigators dismantled the Electronic Control Unit (ECU) and sent it to a manufacturer-approved facility in South Africa for data download. Additionally, the Garmin Aera 795 GPS unit was sent to the NTSB facility in the United States to reconstruct the final flight path, including groundspeed and altitude.
To further understand the failure mechanism, ATC audio recordings were also sent to the NTSB laboratory to analyze rotor speed, engine speed, and main rotor transmission speed during the final communications. Several components, including the Generator Control Unit (GCU), Quad Digital Indicator, Dual Analog Indicator, and the Permanent Magnetic Alternator (PMA), were shipped to the manufacturer's laboratories for detailed examination.