What happened
On 25 December 2002, a Bolkow BO 105DBS-4, registration G-ESAM, was operating as an air ambulance near Epping (Theydon Bois), Essex. The crew had been dispatched to attend a road traffic accident on the B172, a road bordered by tall trees. To reach the scene, the pilot performed a high hover and maneuvered the aircraft between two small trees to land vertically on the road.
After approximately 30 minutes, a patient was loaded onto the aircraft for hospital transfer. During the departure, the pilot initiated a high hover and began moving the aircraft backwards along the road. A crewman, positioned at the open port door, provided guidance. As the aircraft moved back over the initial trees to transition toward a clear area, the main rotors struck an overhanging branch from a large tree located on the southern side of the road. The impact caused a vibration and a vertical bounce, leading the pilot to land the aircraft back on the road and shut down the engines. There were no injuries to the three crew members or the single passenger on board.
The investigation
Investigators examined the aircraft and found damage to the trailing edge of one main rotor blade and a bent trim tab on a second blade. The investigation focused on the pilot's departure technique and situational awareness. It was noted that the pilot had unintentionally applied a helipad departure procedure—which involves a deliberate rearward movement during the climb—rather than a standard vertical lift into a high hover.
Findings
- The pilot experienced a loss of spatial awareness following a 35-minute period with the engines running on the road.
- The crew's attention was focused on navigating the small trees on the northern side of the road.
- The pilot was unaware of the overhanging branch located behind the aircraft due to the position of the large tree's branches being obscured from the cockpit.
- The pilot had subconsciously adopted a rearward-moving departure profile typically used for helipads, which placed the aircraft in close proximity to the tree.