This article is more than 1 year old

This article is more than 1 year old

The helicopter crash in which the Leicester City football club owner, Vichai Srivaddhanaprabha, and four other people were killed appears to have been caused by the failure of a part in the tail rotor that linked it to the pilot’s controls, investigators have found.

Safety agencies have now ordered owners of similar Agusta helicopters to check parts within the rotor, after a second special bulletin released by the Air Accident Investigation Board (AAIB) confirmed mechanical failure had been detected.

Leicester City helicopter crash investigators focus on tail rotor Read more

Investigators in Farnborough are still examining wreckage to fully understand the sequence of events that led to the helicopter making an uncontrolled turn to the right, contrary to the pilot’s pedal commands, before it spun and crashed.

The report focuses on a “castellated nut” that secures the control shaft in the tail rotor.

An inspection found parts of the mechanism had become disconnected. With the pilot’s pedal commands rendered ineffective, and the system failing, the pitch of the helicopter’s tail rotor blades “reached the physical limit of their travel”, investigators said.

A preliminary AAIB report in November used black box data that showed the aircraft “yawed to the right” when the pedal should have sent it left.

The helicopter, an AgustaWestland AW169, had made four successful flights on 27 October before its last ascent from the pitch of Leicester’s King Power stadium after the match.

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Footage of the last flight suggested that sections of the tail rotor may have fallen off in mid-air. The aircraft reached a height of 430ft before spinning down and crashing almost upright on concrete steps beside the stadium’s car park, and was rapidly engulfed in flames.

The five occupants: Vichai and his guests Nursara Suknamai and Kaveporn Punpare, along with the pilot Eric Swaffer and another passenger, Izabela Roza Lechowicz, died at the scene. The tragedy was widely marked in Leicester and the footballing world, in recognition of the fairytale transformation of the football club bought by Vichai in 2010 into unlikely Premier League champions in 2016.

The European Aviation Safety Agency ordered precautionary safety checks on the tail rotors of all Agusta AW169s and AW189s, manufactured by the Italian aerospace company Leonardo, after the crash, but last week issued mandatory instructions for “repetitive checks” of the suspect nut and bearing.

The investigation is likely to conclude in the second half of 2019.