What happened
On July 5, 2014, a Robinson R44 II, registration LN-OAL, was conducting a commercial reindeer herding operation in the Trollheimen region of Norway. The mission, operated by Midtnorsk Helikopterservice AS, involved moving a herd of reindeer into an enclosure.
While flying westward, the crew identified a small group of animals ahead of the main herd. To manage the movement, the pilot reduced the aircraft's speed to approximately 30 knots and descended to an altitude of about 50 feet above the ground. While flying over a marshy area near a mountain range, the helicopter encountered an unexpected wind gust characterized by a high vertical sink rate. The pilot attempted to compensate using the collective, but the aircraft lacked sufficient power to counteract the downward force. This resulted in the helicopter striking the marsh, followed by a brief bounce before the pilot managed to hover the aircraft on more stable, dry ground.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the aircraft and the operational conditions. Technical inspections of LN-OAL revealed that the landing gear had been bent and the clearance between the tail skid and the ground had been reduced. While the airframe remained intact, repairs were required for a minor deformation in the aft seat structure, and several components, including the rear crosstube, struts, and various fairings, were replaced.
Findings
- The primary cause of the incident was an unexpected downdraft that exceeded the available power of the aircraft at its current mass.
- The aircraft was operating at a high mass of 1,021 kg, which limited its performance margins during low-altitude maneuvers.
- The low-altitude nature of reindeer herding inherently provides small safety margins, which were further compromised by the wind conditions.
- The impact was forceful enough to trigger the emergency locator transmitter (ELT), with an estimated impact force of at least 2.3 G.