What happened
On 11 October 2023, an AW169 helicopter, registration G-KSSC, was operating as a Helicopter Emergency Medical Service (HEMS) asset to attend an incident in Maidstone, Kent. Upon arrival, the crew identified a suitable landing area at a cricket pitch near Bearsted Common, approximately 80 m from the primary emergency responders.
The crew performed an airborne survey of the site, selecting an approach track designed to avoid residential properties and a cricket pavilion. During the final approach, the pilot noticed two members of the public near the edge of the cricket square. To mitigate the risk to these individuals, the pilot halted the descent at approximately 160 ft agl and adjusted the aiming point further into the field.
As the aircraft established a hover at roughly 40 ft agl, the rotor downwash caused ground covers on the pitch to roll from their positions. Following the landing and engine shutdown, the crew discovered that a bystander had been struck in the leg by one of the moving covers, resulting in a minor injury. The individual was subsequently treated by a paramedic and transported to the hospital.
The investigation
The investigation established that the ground covers in question were mounted on wheels and equipped with brakes; however, these brakes had not been engaged, allowing the covers to move easily under the force of the air.
Analysis of the aircraft's performance indicated that the downwash from an AW169 at maximum takeoff weight can reach velocities of approximately 46 kph. While the crew had attempted to manage the risk by adjusting their approach and height, the force of the air was sufficient to displace the unsecured equipment.
Findings
- The primary cause of the injury was the displacement of unsecured ground covers by rotor downwash.
- The wheel brakes on the cricket pitch covers had not been applied, making them susceptible to movement.
- Although the pilot took active measures to avoid pedestrians by adjusting the approach path and descent height, the downwash effect persisted at the landing altitude.
Safety action
Following the incident, the operator updated its Operations Manual by issuing a Flying Staff Instruction (FSI). This update provides pilots with enhanced guidance regarding downwash awareness and provides links to industry resources for further study.