Disconnected cockpit pedals caused the helicopter crashed that killed the Thai billionaire owner of Leicester City football club and four others on October 28, a British investigation found on Thursday.
The death of Vichai Srivaddhanaprabha shocked global sport and left the small city in the heart of England in mourning two years after their improbable first and only championship season.
The helicopter, decorated the blue and white colours of the team, spun out of control on takeoff moments after it cleared the stadium's roof.
Vichai attended most Leicester home matches, landing and taking off from the centre of the pitch.
Britain's Air Accident Investigation Branch (AAIB) said a series of cockpit pedals had somehow become disconnected from the rotor on the helicopter's tail.
"The loss of control of the helicopter resulted from the tail rotor actuator control shaft becoming disconnected from the actuator lever mechanism," the eight-page AAIB report said.
The helicopter began to spin uncontrollably to the right as a result.
The AAIB said it was treating a further probe into what caused the pedals to disconnect "as a priority".
Europe's aviation safety authorities have ordered mandatory checks on the type of helicopter involved, finding no other problems to date.