Kumaritashvili lost control and slammed into an exposed steel pillar during his last training run at the Whistler Sliding Centre on February 12, hours before the Games' opening ceremony.
His death was the first of a luge athlete in competition since 1975.
"What happened to Nodar has been an unforeseeable fatal accident," said FIL secretary general Svein Romstad.
"After an in-depth analysis we concluded that there was no single reason, but a complex series of inter-related events which led to this tragedy."
The report said Kumaritashvili's run appeared normal going until after exiting curve 15. "At that time Nodar appears to have hung on to the curve too long," it said.
"This resulted in him being sent to the right hand side of the straightaway (going into curve 16) when he steered the sled out of that curve instead of being left of centre on the straightaway which is the preferred positioning going into curve 16.
"Nodar appears to have hit the wall at an exceptional angle that caused the sled to compress rather than break or bounce off. This resulted in the sled serving as a catapult when it decompressed launching him and the sled into the air."
It said the 'catapult effect' of the sled sent the luger over the wall onto the outside of the track.
"Due to the unusual behaviour of the sled at the moment of impact, the sled was inspected by both the police and FIL experts to determine if there were any deficiencies in sled construction," it continued.
The inspection showed the sled met all criteria.
An initial FIL report a day after the crash put the blame on human error by the 21-year-old and the Olympic competitions went ahead, although the starting spot was lowered to reduce the speed of the fast track and a wall was erected to cover the pillars.
The IOC has said it had a moral responsibility but not a legal one, with the federation and organisers responsible for the construction of the track and the staging of competitions.