It was not possible for the pilot to recover from the tail rotor failure on the helicopter that crashed and killed Leicester City soccer club owner Vichai Srivaddhanaprabha in 2018, Britain's aviation accident investigator reported on Wednesday.
Pilot Eric Swaffer, his partner Izabela Roza Lechowicz and two members of Vichai's staff, Nusara Suknamai and Kaveporn Punpare, were also killed in the crash shortly after takeoff outside the King Power Stadium in the central English city of Leicester following a Premier League match.
Britain's Air Accidents Investigation Branch (AAIB) said that the helicopter was yawing uncontrollably and descending rapidly at a low altitude near buildings at night after the tail rotor failed. The tail rotor counteracts the torque of a helicopter's main rotor to ensure the aircraft does not spin out of control.
"The investigation found that, in the prevailing circumstances, the loss of yaw control was irrecoverable," it said in its final report on the crash.
Nevertheless, the pilot managed to land softly enough for four of the five people on board to survive the impact, according to post-mortem examinations.
"Their reported injuries would, however, have prevented them from being able to escape from the helicopter without external assistance, given the position in which it came to rest," AAIB said.
The helicopter was on its left side and its fuel tanks were damaged, resulting in a major leak that ignited quickly, according to the report.
Police officers arrived within a minute of the crash but were unable to break the helicopter's windscreen with their batons and other handheld equipment as the aircraft burned, AAIB said. The fire killed those onboard, the report said.
The investigators found that problems with the bearing in the tail rotor of the Leonardo LDOF.MI AW169 helicopter began a sequence of failures leading to the crash.
Italy's Leonardo has since issued 16 service bulletins for the model, including additional inspection requirements, the report said.
Litigation specialists Stewarts, which represents the families of Vichai, Swaffer and Lechowicz, said the report showed there was nothing the pilot could have done to prevent the crash.
Stewarts said litigation had already begun in Italy against Leonardo on behalf of the families of Swaffer and Lechowicz and Vichai's family was considering legal recourse against the manufacturer.
"I am deeply saddened by the course of events," Vichai's son, Aiyawatt, said in a statement. "Almost five years after my father's passing, this report provides concerning evidence against Leonardo."
Leonardo did not respond immediately to a request for comment outside normal business hours.
The AAIB report said the European Union Aviation Safety Agency (EASA) had also published nine airworthiness directives for Leonardo's AW169 and AW189 models.
The final report also offered eight more recommendations to EASA, including changes to its certification requirements and the way it assesses and mitigates against potential catastrophic failures.
EASA could not be reached immediately for comment outside normal business hours.