According to Andy Mellor, vice president of the FIA's Safety Commission, the severity of such an impact was "as if you drop the car 48 metres to the ground without a crumple zone".
OBITUARY - Jules Bianchi: 1989-2015
The latest data comes from the FIA's new World Accident Database (WADB) that sources information from racing accidents all over the world, and has been designed to help improve safety.
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The details from the findings of Bianchi's crash nine months ago in Suzuka have been released by German publication Auto Motor und Sport.
GPS data shows Bianchi lost control of his Marussia in the wet conditions at 132mph before colliding with the 6.8-tonne recovery crane that was removing Adrian Sutil's stricken Sauber just 2.61 seconds later at a speed of 78mph and an angle of 55 degrees.
The car was deflected four metres in a longitudinal direction, and two metres to the side.
It was initially thought, via g-sensors in the earplugs, Bianchi's impact was at 92g, but it is now understood these slipped out at a crucial moment.
Fresh calculations have determined the actual impact was 254g.
Mellor added: "The problem was the Marussia partly dipped below the stem of the crane and was therefore pressed from above against the bottom of the crane.
"That worked like a brake, with an abrupt deceleration. In this process we had the contact between the helmet and the crane. We had never seen something like this before."
Safety Commission head Peter Wright believes it was incumbent on the FIA to investigate Bianchi's accident in full to gain insight for future crash prevention.
"It is still often the case some accidents must first occur in order to learn from it - Bianchi is the best example," said Wright.
"This was a scenario we could not have previously imagined. That's why it was very important to really investigate this accident to the smallest detail.
"We have never invested so much time and effort in an analysis."
Wright denies, however, a closed cockpit - as has been suggested - could have aided Bianchi's cause.
"The car would have been stopped by the roof, and although the head would not have hit the crane, it would have hit the roof with the same result," said Wright.
Suggested to Mellor recovery cranes could be better protected, he claims "six layers of tyres" would have to be attached, and described this as "not acceptable".
The FIA's main response to the accident has been the introduction of the virtual safety car system to slow down all cars on track when a incident is occurring, such as a recovery vehicle removing a car.
Bianchi died last Friday after a nine-month fight for his life, with his funeral taking place at Cathedral Sainte Reparate in his home city of Nice on Tuesday.
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