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Senna - steering failure?

The report on the accidents during the San Marino Grand Prix weekend at Imola,Italy last year has finally been made public with the Italian investigators concluding that Ayrton Senna's accident was probably the result of a steering failure.

It has taken the investigation - headed by Italian magistrate Maurizio Passarini - nine months to reach this conclusion and the report presented to the court in Bologna last Friday ran to 500 pages. The inquiry involved former F1 driver Emanuele Pirro, ex-Ferrari team boss Roberto Nosetto, and F1 engineers Tommaso Carletti, Mauro Forghieri and Jean-Claude Migeot.

There are no doubts as to the cause of the crash which killed Austrian Roland Ratzenberger. His car went out of control at high speed as the result of a high-speed suspension failure. This occurred because Ratzenberger had gone off the circuit the lap before the crash and failed to pit to check for damage.

But when it comes to Senna's crash, experts are divided over whether the steering was to blame. The data available from the car's telemetry shows that the Williams-Renault hit the wall on the outside of Tamburello Corner at around 130 mph, 12.8 seconds after the car crossed the start-finish line. Everything appeared to be normal until 1.5s before the impact, when the car was traveling at 192 mph. There was then a sudden and unexplained surge within the car's hydraulic system. This was followed immediately by a rapid fall in pressure and then - 0.5s before the impact - by another surge. Other data shows that 1.3s before the impact there were sudden serious vibrations which caused Senna to lift his right foot, reducing the throttle pressure by 40%. This was followed 0.2s later by a complete lift and heavy braking. In the 0.8s before the car reached the wall - 38m from the track - the speed was reduced by over 60 mph.

This evidence - and video evidence which seems to show Senna looking down into the cockpit - suggests that the Brazilian knew something was wrong and the report suggests three possibilities: a puncture; a suspension failure; and a steering failure. Goodyear says that its investigations failed to show any puncture; Williams say there was no suspension failure and Michael Schumacher, who was following Senna closely, saw no evidence of that.

The third hypothesis is steering failure. Photographs from the accident scene show the broken steering column lying beside the car and there is no question that the Williams team had modified the column at Imola because Senna was not happy with the position of the steering wheel. However, the breakage occurred not at one of the new welds on the column but at a position between them and it is this evidence which has led a number of experts to suggest that the breakage occurred during the impact.

The Williams team is now waiting to have the chassis - which has been impounded since the crash - returned to England so that its engineers can conduct their own investigation.

Our sources suggest that there is another possible explanation for the crash: Senna's Williams was running a highly-secret, hydraulically-controlled powersteering system at Imola. The hydraulic system will have been driven by the engine and it is conceivable that the vicious bumps on the inside of Tamburello Corner may have caused a disruption - "a spike" - in the engine revs. This may in turn have caused the hydraulic surges noted by investigators and, as a result, a sudden momentary loss of steering. In such a case the steering column could have been broken after the impact.

It may be that the accident was caused because Senna, under pressure from Schumacher, ran over the Tamburello bumps and, through a serious of circumstances, lost his steering for a vital few moments, until it was too late to avoid hitting the wall.

Such a combination of circumstances can - if you wish - be described as a mechanical failure, it can be described as a driver error, or even because the track was bumpy and the wall was too close to the track.

The best description, however, is probably that the crash was caused by pure bad luck.

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