What happened
On January 12, 2010, a police helicopter crew—consisting of a flight instructor, a pilot, and a systems operator—departed Hannover Airport for a scheduled training flight. The mission was intended to practice tactical standardization maneuvers, including quick stops, hovering out of ground effect, and thermal camera operations, within a designated training area near Wietzenbruch.
During the flight, the instructor took control of the MD 90 and 902 Explorer to demonstrate a contour flight path to the pilot. The instructor flew at approximately tree-top level, heading south, before initiating a steep, high-angle reverse turn to return to the starting point. As the instructor attempted to level the aircraft at a low altitude over snow-covered fields, the helicopter made unexpected contact with the ground.
The impact caused the right skid to break, destroyed the lower forward fuselage, and jammed the directional controls. Snow entered the cockpit, obscuring the crew's vision. After sliding approximately 45 meters, the helicopter briefly regained flight, but entered a roll and yaw instability. The instructor managed to bring the aircraft back into a hover, but it subsequently settled into the snow and tipped onto its right side. The crew successfully shut down the engines and evacuated the wreckage.
The investigation
The BFU investigation focused on the flight maneuvers, the aircraft's mechanical state, and the organizational framework of the police helicopter squadron. Investigators examined the wreckage, which showed significant damage, including a detached rotor head and broken drive shafts. The investigation also reviewed the squadron's Quality Management Manual (QMH), noting that the section regarding training and education was largely incomplete at the time of the accident.
Findings
The immediate causes of the accident were the execution of a high-angle reverse turn with an intended low-level leveling maneuver, an unintended ground impact during the recovery, and environmental conditions—specifically snow-covered terrain and potentially diffuse lighting—that led to a loss of spatial orientation and an error in altitude estimation.
Contributing factors included:
- Inadequate descriptions and specific guidelines for the maneuvers being practiced.
- Insufficient risk assessments for training maneuvers and a lack of established safety margins for low-level flight.
- Organizational deficiencies, including the lack of standardized procedures for police flight operations across different German states.
- Incomplete quality management documentation regarding pilot training and proficiency maintenance.