Trainee pilot's mistake to blame for helicopter crash on White Waltham Airfield approach

A trainee pilot’s mistake caused a helicopter to crash into a field on approach to White Waltham Airfield, an investigator's report has found.

The helicopter, being flown by the trainee and assisted by an instructor, came down beside the M4 near Hurst at around 5pm on February 3.

A report from the Air Accidents Investigations Branch [AAIB] found the crash showed the ‘limitations of human performance’ could not be ‘completely eradicated’.

The Robinson R22 Beta helicopter was beginning its approach to White Waltham Airfield when the trouble began.

Pivoting over the Winnersh Interchange M4 junction, the trainee pilot – who had earlier completed a successful flight in the helicopter – reached for the carburetor heat switch.

But instead, the pilot pressed the fuel mixture switch – coloured bright red and crucial to maintaining steady flight.

As the fuel mixture changed, the engine stuttered and stalled. The helicopter was now dead in the air.

“Realising his mistake, he called that he had ‘pulled the fuel’ at which point the engine rpm [revolutions per minute] was dropping rapidly,” the investigation report said.

Wrestling control away from the trainee, the instructor attempted to right the machine and initiated the helicopter's autorotation function.

The instructor attempted an engine restart but, with the ground rapidly approaching, he had to reassess.

The report said: “With the M4 motorway to his right, and trees and power lines to his left, the only viable option was the ploughed field ahead.

“At this stage there was not enough height left to consider a restart, therefore the instructor concentrated on executing an engine-off landing at the slowest possible forward airspeed.”

As the helicopter collapsed onto the muddy field, the vehicle lurched forward and snapped and bent its rotator blades as the fuselage crumpled over on its side.

The report said: “As the skids touched down, they dug into the soil and the helicopter tipped forward onto its nose before ‘gently’ rolling to the right.

“During the period immediately after ground contact the main rotors struck the rear empennage (tail), which detached from the helicopter and was thrown forward of the wreckage.”

Neither of the pilots were injured in the landing.

The AAIB report said problems with pilots misidentifying the carburetor heat control and fuel mixture control had been identified by the helicopter manufacturer.

‘Inadvertant operation’ of the control had been a risk ‘for many years’, having first been published in 1981, the report said.

A safety notice that said the control knobs were ‘shaped differently’ and the mixture control had a guard and push lock to prevent accidental operation. The investigation report said: “This accident is a reminder that, while risks can be identified and mitigated, the limitations of human performance mean lapses leading to risks maturing cannot be completely eradicated.

“Faced with a challenging, unexpected and time-critical situation, the instructor appropriately prioritised establishing and flying the helicopter in autorotation ahead of attempting a restart.”

It said: “The instructor considered that, had the available touchdown location been on firmer ground the landing would have been completed without damage.”