What happened
On May 22, 2016, an Airbus AS 355 NP helicopter, registration HB-ZOO, was conducting a private sightseeing flight over southern Iceland. The flight, which included the pilot and four passengers, departed from Reykjavík Airport with the intention of flying around Langjökull glacier and returning to Reykjavík.
At approximately 19:38 UTC, while approaching a landing site in the geothermal area near Hengill, the pilot began maneuvering the aircraft at a low altitude of approximately 12–15 meters. During a left turn toward a south-southwest heading, the pilot lost full control of the tail rotor. The aircraft entered a rotation of approximately one and a 1/2 turns, losing altitude and striking the ground. The impact caused an engine fire, though the pilot successfully deployed onboard fire extinguishers and shut off fuel and electrical supplies to mitigate the damage. The crew and passengers were rescued by an Icelandic Coast Guard helicopter approximately 40 minutes later. All five occupants sustained significant injuries, and the aircraft was destroyed.
The investigation
The RNSA investigation examined the aircraft wreckage, weather data, and the pilot's flight experience. Physical examination of the wreckage showed no evidence of mechanical failure in the engines or flight controls prior to the impact. However, investigators noted that the right-side tail rotor pedal was broken due to excessive force applied during the crash.
While the pilot had 1,700 total flight hours, much of that experience was in single-engine helicopters of a similar type, such as the Airbus AS350. The investigation also reviewed meteorological data from the Icelandic Meteorological Office, which indicated winds of approximately 13 knots near the site, with gusts reaching 16–18 knots, contradicting the pilot's estimation of light winds.
Findings
- The pilot's lack of familiarity with the specific handling characteristics of the twin-engine Airbus AS 355 NP compared to single-engine models contributed to the loss of control.
- The pilot likely underestimated the prevailing weather conditions and the impact of wind in the mountainous terrain.
- Loss of tail rotor effectiveness (LTE) was a critical factor; the combination of high power settings, low airspeed, and wind approaching from the right (between 45° and 75° relative to the nose) likely caused aerodynamic interference from the main rotor wake, destabilizing the tail rotor.
- The pilot was not sufficiently assertive in maintaining control of the aircraft during the critical low-altitude maneuver.