What happened
On March 21, 2013, during a large-scale training exercise for the Federal Police near the Olympic Stadium in Berlin, two helicopters collided on the ground. The formation consisted of three aircraft: an Eurocopter EC155 B and two Eurocopter AS 332 L1 helicopters.
The sequence began when the first aircraft, the EC155 B, landed at a designated area marked by transport buses and ground marshals. As the aircraft approached the landing zone, its rotor wash disturbed a layer of fresh powder snow resting on a frozen surface, creating a significant snow cloud.
The second aircraft, an AS 332 L1, approached the landing zone following a modified flight path to avoid the initial snow cloud. However, the pilot's approach involved a steep descent and a prolonged hover, which generated its own intense snow disturbance. This secondary cloud enveloped the first helicopter already on the ground.
The third aircraft, another AS 332 L1, was also in its landing phase when it encountered the combined snow clouds. The loss of visual references to the ground marshals and the underlying terrain led to a loss of control. The resulting collision between the aircraft caused one fatality and left four persons with serious injuries and five persons with minor injuries. Debris from the wreckage struck nearby areas, causing damage to the ground and vehicles.
The investigation
The BFU investigation focused on the flight profiles, crew coordination, and the environmental conditions at the landing site. Investigators examined cockpit voice recordings, flight data, and video footage of the approach. The investigation scrutinized the organizational procedures of the Federal Police flight group, specifically regarding landing protocols in snowy conditions and communication standards during formation landings. The BFU also reviewed the adequacy of training for "whiteout" and "brownout" conditions and the spacing requirements between aircraft on the ground.
Findings
The investigation established that the primary cause of the accident was the loss of visual references due to a whiteout condition created by the aircraft's own rotor wash. This was driven by several contributing factors:
- The chosen approach profile generated a snow cloud that enveloped the aircraft before touchdown.
- Inadequate crew communication during the approach and landing phases.
- A failure to immediately initiate an aborted landing after losing visual contact with the ground marshal.
- The loss of ground reference caused by the combination of fresh powder snow over a hard, frozen crust.
- Insufficiently defined minimum separation distances between aircraft on the ground.
- Systemic deficiencies in training and standardized procedures for landing in snow or sand.
Safety action
Following the accident, the Federal Police implemented several new procedures for landings in high-disturbance environments. These include the adoption of a "High-Hover Technique," where pilots descend vertically from a high hover to maintain visual contact with the ground. New protocols for crew coordination, decision points, and communication with ground marshals were established. Additionally, a specialized flight simulator training program for whiteout and brownout conditions was developed, alongside annual winter flight briefings for all crews.