What happened
On 2 July 2022, an Agusta AW1 and69, registration G-KSST, was operating an emergency services flight in Epsom, Surrey. After attending a local incident, the crew was re-tasked and prepared for departure from an urban landing site. The departure procedure involved a variable takeoff decision point, where the helicopter climbed backwards to an altitude of 200 ft before transitioning into forward flight.
As the aircraft transitioned to forward flight, the rotor downwash impacted a nearby residential garden. The force of the air displaced various items, including cardboard packaging and a heavy patio umbrella. The umbrella was lifted from its stand and struck a person in the garden in the face, resulting in a minor injury consisting of a significant cut. The umbrella subsequently became embedded in the wall of the house. Two other individuals present in the garden were unhurt.
The investigation
The investigation examined the flight data and the physical characteristics of the aircraft's rotor system. The Agusta AW169 has a rotor diameter of 12.12 m, and at the time of the incident, the aircraft was operating at a weight of 4,272 kg. Calculations determined that the downwash velocity at the rotor head was approximately 44 kph (27 mph), with maximum velocity typically occurring between 1.5 and 2 rotor diameters below the aircraft.
Investigators analyzed the impact of the local geography on the airflow. While the helicopter was at an altitude of 200 ft, which should have resulted in dissipated downwash, the investigation considered how the physical layout of the area—such as houses, fences, and hedges—might have influenced the air movement.
Findings
- The helicopter was performing a specific takeoff procedure that required climbing backwards toward a residential area.
- The transition to forward flight coincided with the downwash affecting the garden.
- Local geographical features may have funneled or accelerated the downwash, increasing its impact on objects in the garden despite the aircraft's altitude.
- The movement of the patio umbrella was the direct cause of the facial injury to the resident.