Mid-air collision between training aircraft near Waddesdon

Casualties unknown • Near Waddesdon, Buckinghamshire, GB

A Cessna 152 and a Guimbal Cabri G2 helicopter collided in mid-air during training flights in Buckinghamshire, resulting in four fatalities.

What happened

On 17 November 2017, a Cessna 152, registration G-WACG, and a Guimbal Cabri G2 helicopter, registration G-JAMM, collided in Class G airspace near Waddesdon, Buckinghamshire. Both aircraft were engaged in training operations and were not receiving air traffic control services at the time of the impact.

G-WACG departed Wycombe Air Park, climbing to 4,000 ft before initiating a steady descent. Simultaneously, G-JAMM departed the same airfield, climbing to approximately 1,500 ft. Radar data indicates that the flight paths of the two aircraft converged. The Cessna 152 was descending from a higher altitude and was positioned behind and above the helicopter. The collision occurred at approximately 12:01 UTC, causing the destruction of both aircraft and the four fatalities on board.

The investigation

The AAIB investigation utilized NATS radar data and ADS-B recordings to reconstruct the flight paths. The investigation examined the wreckage, which was located within the grounds of the Waddes．den Estate. Analysis of the Cessna 152 wreckage revealed that the helicopter's rotor blades struck the aircraft's right wing and subsequently severed the elevator control cables, leading to the loss of the empennage. The Guimbal Cabri G2 sustained severe damage, including the loss of a main rotor blade, which rendered the helicopter uncontrollable.

Investigators also assessed the visibility limitations for both crews. For the occupants of G-WACG, the helicopter was positioned in a blind spot beneath the aircraft's nose. For the crew of G-JAMM, the engine and gearbox structure significantly restricted rearward visibility. Furthermore, the helicopter's grey rotor blades provided low visual conspicuity against the ground.

Findings

  • The primary cause of the collision was the inability of the pilots to see and avoid each other due to the geometry of the flight paths and the inherent limitations of the visual scanning method.
  • The aircraft were operating in uncontrolled airspace without compatible Electronic Conspicuity (EC) aids that could have alerted the pilots to each other's presence.
  • The descending aircraft was following a similar track to the helicopter, which limited the opportunity for detection.
  • The helicopter's rotor blade color scheme did not provide sufficient visual enhancement to aid detection from above.

Probable cause

The collision occurred because the flight paths of the two aircraft converged in a manner that placed the helicopter in the blind spot of the descending Cessna, and the lack of compatible electronic conspicuity devices prevented the pilots from detecting the conflict through non-visual means.

Frequently asked questions

What happened in the 2017-11-17 Cessna 152 and Guimbal Cabri G2 accident near Near Waddesdon, Buckinghamshire, GB?

A Cessna 152 and a Guimbal Cabri G2 helicopter collided in mid-air during training flights in Buckinghamshire, resulting in four fatalities.

What aircraft was involved and where did it happen?

The accident on 2017-11-17 involved a Cessna 152 and Guimbal Cabri G2, registration G-WACG and G-JAMM , at Near Waddesdon, Buckinghamshire, GB.

What was the probable cause of the accident?

The collision occurred because the flight paths of the two aircraft converged in a manner that placed the helicopter in the blind spot of the descending Cessna, and the lack of compatible electronic conspicuity devices prevented the pilots from detecting the conflict through non-visual means.

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