Investigators reveal cause of Leicester City helicopter crash

A pin that came loose in the tail rotor control mechanism caused the catastrophic helicopter crash which killed Leicester City owner Vichai Srivaddhanaprabha and four others.

The Thai billionaire, two members of his staff, Nusara Suknamai and Kaveporn Punpare, pilot Eric Swaffer and another passenger, Izabela Roza Lechowicz, all lost their lives on Saturday October 27.

Khun Vichai's aircraft, a £6.7million 2016 Augusta AW169, spiralled out of control shortly after take off.

The helicopter came down in a car park near the stadium just over an hour after Leicester had drawn 1-1 against West Ham United in the Premier League, erupting into flames.

According to the Air Accidents Investigation Branch, the pin linking the pilot's pedals with the tail rotor blades became disconnected.

[PHOTO: COURTESY]

The eight-page report concluded the failure of the rotor caused the helicopter to violently veer to the right which led to it crashing in a fireball and being completely destroyed.

The evidence gathered to date shows that the loss of control of the helicopter resulted from the tail rotor actuator control shaft becoming disconnected from the actuator lever mechanism," declared the special report. from the AAIB.

"Disconnection of the control shaft from the lever prevented the feedback mechanism for the tail rotor actuator from operating and the tail rotor actuator from responding to yaw control inputs.

"Loss of the feedback mechanism rendered the yaw stops ineffective, allowing the tail rotor actuator to continue changing the pitch of the tail rotor blades until they reached the physical limit of their travel. This resulted in an uncontrollable right yaw.

[PHOTO: COURTESY]

"Sufficient force and torque had been applied to the castellated nut on the actuator end of the control shaft to friction weld it to the pin carrier and to shear the installed split pin.

"The observed condition of the duplex bearing and the increased torque load on the castellated nut that remained on the spider end of the shaft is consistent with rotation of the tail rotor actuator control shaft.

"Whilst the shaft was rotating and a yaw control input was applied, the shaft “unscrewed” from the nut, disconnecting the shaft from the actuator lever mechanism, and causing the nut to become welded to the pin carrier."

The report adds that burnt-on grease was discovered on a key part of the control system at the crash site.

It states: “The control shaft, the locking nut and pin carrier, and the duplex bearing/sliding unit assembly were removed from the wreckage and inspected in detail.

“The locking nut on the bearing end of the control shaft was found to have a torque load significantly higher than the required assembly value.

“The inner races of the bearing could only be rotated a few degrees in either direction by hand.

“There was a build-up of black grease inside the slider unit around the inboard face of the duplex bearing.

“The section of the control shaft adjacent to this bearing face showed evidence of burnt-on grease and was discoloured along its length.”

Footage of the incident appeared to show sections of the tail rotor falling away in mid-air, with the aircraft reaching an altitude of approximately 430ft before plummeting to the ground.

Freelance photographer Ryan Brown, who was covering the game, witnessed the incident occur and told BBC Radio Leicester: "The engine stopped and I turned round and it made a bit of a whirring noise, like a grinding noise.

"The helicopter just went silent, I turned round and it was just spinning, out of control. And then there was a big bang and then [a] big fireball."

Safety checks were ordered on helicopters of a similar design to the AugustaWestland AW169 in light of the tragedy.

The European Aviation Safety Agency (EASA) issued the Airworthiness Directive focusing on the tail rotor of the helicopter and on November 30 mandated repetitive inspections "of the castellated nut that secures the tail rotor actuator control shaft to the actuator lever mechanism, and the tail rotor duplex bearing."

Foxes keeper Kasper Schmeichel was among the witnesses to the tragedy, which devastated the footballing world and led to an outpouring of tributes from fans and clubs across the country.

As a close friend of Srivaddhanaprabha and the last player to see him alive, Schmeichel has felt the impact of the crash as much as anyone.

Schmeichel said: “I was on the pitch, I waved him off, I saw it all happen.

"It was something that will stay with me, unfortunately.

“It is not a nice memory but the club have been great and everybody has received the support they needed. I spoke to somebody.”

Leicester captain Wes Morgan stated in the immediate aftermath of the crash: "Absolutely heartbroken and devastated regarding the news of our chairman. A man that was loved and adored by everyone here at lcfc."

Players and staff travelled to Bangkok for his funeral in early November, while son Aiyawatt, known affectionately as ‘Top’, has since announced that the club will erect a statue of Khun Vichai at the King Power stadium.

The investigation into the initiating cause and exact sequence of the failure continues, with the AAIB marking it as a priority.