What happened
On January 11, 2004, a Bell 427 helicopter, registration OK-AHA, operated by ALFA-HELIKOPTER, s.r.o., was performing an emergency medical flight from the Olomouc heliport. The crew was responding to a motor vehicle accident on a highway near Litovel.
During the initial flight phase, the crew encountered deteriorating weather conditions. While flying at an altitude of approximately 50–10/0 m AGL, the aircraft entered an area of reduced visibility. Simultaneously, the crew received word from the ground medical team that fog at the accident site made landing impossible.
In response, the pilot decided to return to Olomouc. The pilot reduced speed to 40 knots and initiated a 180-degree left turn at an altitude of 50 m AGL. During this maneuver, the helicopter entered a layer of ground fog approximately 50 meters thick over a snow-covered field. During the turn, the aircraft's landing skids made contact with the terrain. Following the impact, the pilot performed an intensive maneuver to climb through the fog layer. After verifying that the aircraft systems were functioning normally and checking the crew and landing gear, the pilot proceeded to land on Velký Kosíř hill, which was above the fog layer.
The investigation
The ÚZPLN investigation examined the flight path, meteorological conditions, and the aircraft's technical state. Investigators analyzed the terrain profile and the physics of the turn. Based on the aircraft's speed of 40 knots and the bank angle, the investigators calculated the potential turning radius and time.
Technical inspections confirmed that the Bell 427 was airworthy, with weight and balance within limits, and that the mechanical state of the aircraft did not contribute to the accident. The investigation also noted that the flight path described by the crew did not align with the surrounding terrain profile; specifically, at the stated altitude of 50 m AGL, contact with the ground should not have occurred given the distance and direction of the turn. The investigation concluded that the contact must have occurred because the aircraft was flying at an altitude of less than 33 m AGL, or because the altitude decreased during the maneuver.
Findings
- The primary cause of the accident was a partial loss of spatial orientation.
- This loss of orientation led to a reduction in altitude after the aircraft entered a layer of ground fog over a snow-covered field lacking distinct visual reference points.
- The aircraft sustained damage to the landing skids, the right front lower windscreen, the outside air temperature sensor, the searchlight, and a landing light cover.