No defects were identified during a mechanical inspection of a helicopter the day before it crashed in Broome, killing a well-known West Australian pilot and a 12-year-old girl.
The finding is made in a preliminary report by the Australian Transport Safety Bureau into the July 4 crash which killed prominent businessman Troy Thomas, 40, and 12-year-old Amber, whose family has requested her surname not be published.
Mr Thomas's daughter Mia and teacher's aide Maddy Down, 24, were also seriously injured.
The group had been setting off on a scenic flight on the Robinson R44 helicopter from an industrial property when it broke apart and fell to the ground.
Witnesses described hearing a bang as the helicopter reached about 55 feet (17 metres) .
Preliminary investigations revealed Mr Thomas and another pilot had reported feeling unusual vibrations through the tail rotor pedals several days earlier - a sensation Mr Thomas likened to having his feet tapped by spoons.
A report published on Wednesday reveals the helicopter was inspected the day before the crash by a maintenance engineer and no defects were found.
The dynamic balance of the tail rotor was also found to be within limits, and when a maintenance pilot started the helicopter, they could not feel any vibration.
A test flight was not undertaken because of the confined nature of the yard and concerns with securing the site.
Mr Thomas was told about the findings and instructed to conduct a check flight.
ATSB transport safety director Mike Walker said the R44 pilot's handbook advised that a change in the sound or vibration of a helicopter could indicate an impending critical failure.
"It is not clear whether the pilot experienced any vibrations through the pedals at the time of the accident flight," Dr Walker said.
"Nevertheless, the ATSB urges any R44 pilot who experiences unusual vibrations through the tail rotor pedals to land as soon as possible and follow the advice in the pilot's operating handbook."
Investigations are continuing, including further analysis of CCTV footage.
Several major components of the R44 have been taken to the ATSB's technical facilities in Canberra for further analysis.
A 3D X-ray of the tail rotor gearbox found no evidence of internal damage.
"The ATSB will continue to extensively examine and analyse the recovered components as it seeks to determine the contributing factors behind the in-flight break-up," Dr Walker said.
Australian Associated Press