Initial findings published by the Air Accident Investigation Branch (AAIB), who are leading the inquiry into what caused the fatal crash at the Clutha Vaults, said there was nothing to indicate that engine failure had caused the police chopper to plunge into the busy bar.
Nine people were killed, including the pilot and the two police constables on board, when the twin-engined Eurocopter EC135 suddenly dropped out of the sky at around 10.25pm on Friday, November 29.
In its preliminary report, the AAIB said that initial examination of the wreckage "provided no evidence of major mechanical disruption of either engine".
It also said that there was no apparent reason for the rotor blades to have cut out, although investigators say they were definitely not turning at the moment of impact.
The report states: "Initial assessment provided no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine turbine to the main rotor and to the fenestron drive shaft."
The pilot of the helicopter David Traill, 51, and his two passengers - police officers Kirsty Nelis, 36, and Tony Collins, 43 - were killed in the crash as well as six people inside the pub.
The report states that the helicopter had been carrying 95 litres of fuel at the time of the crash, and that radar contact was lost at 10.22pm - just four minutes after the pilot had requested clearance from air traffic control to re-enter the Glasgow Control Zone.
No mayday call was issued before the aircraft went down.
Detective superintendent Robbie Allan, said: "Police Scotland acknowledges the preliminary report by the AAIB. The police investigation is ongoing."
The report comes as Police Scotland confirmed a replacement helicopter has been delivered by Bond Air Services.
Assistant Chief Constable Bernard Higgins said: "Following full technical checks and familiarisation flights on the Eurocopter 135 T2, it is anticipated that the Police Scotland Air Support Unit will shortly be fully operational."
Meanwhile, police confirmed a 33-year-old man was arrested after an investigation into alleged offensive comments made online after the helicopter crash.
He appeared at Glasgow Sheriff Court on Friday and a report will be sent to the procurator fiscal. firstname.lastname@example.org