李斯特城足球會直升機墜毀事故

The Air Accidents Investigation Branch (AAIB) opened an investigation into the accident. Italy's Agenzia Nazionale per la Sicurezza del Volo, representing the state of the manufacturer of the helicopter, and Canada's Transportation Safety Board, representing the state of the manufacturer of the helicopter's engines, provided assistance. Accredited representatives from Poland's State Commission on Aircraft Accidents Investigation and Thailand's Aircraft Accident Investigation Committee also provided assistance. The aircraft's Digital Flight Data Recorder was recovered on 28 October, having been severely damaged in the fire. It was transported to the AAIB's base at Farnborough, Hampshire, for downloading of data contained therein. The wreckage of the helicopter was transported to Farnborough on 2 November.

A coroner's court was created to investigate the official cause of death for the passengers and crew of the helicopter. The investigation reported in the court revealed that there was minimal opportunity for any individuals who survived the initial crash to escape, or anyone to help those trapped.

On 7 November, the European Aviation Safety Agency (EASA) issued an Airworthiness Directive, demanding checks of the tails of all AgustaWestland AW169 and AgustaWestland AW189 helicopters, as a precautionary measure. On 14 November, the AAIB released a Special Bulletin, outlining the progress of the investigation. A loss of yaw control was revealed as the cause of the aircraft crashing, with the reasons for the loss of yaw control not yet determined. The investigation is concentrating on the tail rotor system as a matter of priority. On 30 November, the EASA issued an Emergency Alert Service Bulletin requiring periodic inspection of part of the tail rotor system. This was made mandatory by an Airworthiness Directive issued the same day.

On 6 December 2018, the AAIB published a second Special Bulletin. Investigators revealed that loss of control of the helicopter resulted from the tail rotor actuator control shaft (which controls the pitch of the tail rotor blades) becoming disconnected from the actuator lever mechanism that transmits the pilots' pedal inputs to control the helicopter's yaw. They have also revealed evidence of the normally stationary control shaft being spun by the tail rotor which caused the castellated nut holding the actuator lever in place to friction weld to its carrier, shear off its split pin and rotate off the threaded shaft. The locking nut and pin carrier were found loose in the tail rotor fairing and were bonded together. A duplex bearing that was designed to allow the control shaft to remain stationary (with the rest of the tail rotor assembly rotating around it) have been found to only allow a few degrees of rotation, with the races blocked up by a mix of burnt grease and metallic particles. Work continues to identify the cause of the damage observed to the duplex bearing and to establish its contribution to the failure sequence.}}