It’s the May 1, 1994 And Ayrton Senna has just started the 7th lap in the lead of the San Marino Grand Prix, in Imola. The single-seater is travelling at over 300 km/h when at the entrance to the Tamburello curve the car goes off its trajectory and crashes into the concrete wall. The race against time at the Maggiore hospital in Bologna is useless. At 6:40 pm the famous Brazilian driver – 3 times Formula 1 champion with McLaren – is declared dead. It took a lot 11 years old to ascertain the real cause of Ayrton Senna’s fatal accident. Someone like him could have taken that curve with his eyes closed. Only on May 27, 2005, during the second appeal trial, the Court recognized the cause of the fatal accident steering column failure. It was not the crash itself that killed Senna, but a piece of the right wheel suspension that broke after the impact and lodged right in his helmet. The violent impact left no escape for the Brazilian driver. According to experts and insiders, if the suspension had not taken that absurd trajectory, Senna would have survived the accident probably without any particular consequences.
What caused the accident?
The story of the steering column actually has a background: on the eve of the San Marino Grand Prix, in Imola, Senna he had a modification made to the steering because the car’s cockpit was very narrow, so narrow that when he turned the steering wheel his knuckles rubbed against the body. Which, according to the driver, affected his performance quite a bit. Finally, before that race, the team proposed the solution of lengthen the steering column. So the technicians sawed it in two and inserted an additional piece with a slightly smaller diameter. The breakage of the column occurred precisely at the point where the welding had taken place, made with a less resistant material, as will emerge from the trial.
What Happened on May 1, 1994: The Last Moments Before Impact
The two key elements used as evidence to prove that it was the broken steering column that caused Senna to go off the track are two:
- there telemetry of the car, or the data that the car control units record during a race.
- the video car camera of Senna, where an anomalous movement of the driver on the steering wheel is evident.
Telemetry
From a telemetry (fig.1) you can get a track that is a bit like an electrocardiogram of the car during the race: the main parameters are represented with curves that indicate how fast the car is going, when it brakes, when it accelerates, when it decelerates and so on. Telemetry, during an F1 race, collects data from every single lap. Therefore, it is reset every time you cross the finish line.
In the fig.2 we looked at the telemetry of Ayrton Senna’s 7th lap, in particular the last two seconds that preceded the crash. This graph was used to demonstrate that the cause of the accident was the broken steering column. Let’s see what it says.
We start from 11″, the seconds that have passed since Senna began the seventh lap. Up to 11″ Senna’s race progress is regular. The first line at the top – that blue – it is the line of the speed. At 11” the speed value, while Senna is entering the Tamburello curve, is over 300 km/h. The red line it’s the line of the butterflybasically it’s the accelerator: when the curve is flat and horizontal it means he’s flat on the floor, when it’s vertical it means his foot is off the accelerator. Always at 11” Senna is accelerating regularly, his driving does not present any anomalies. Now let’s examine at the same time the steering data that correspond to the green line and the dark blue line. Precisely the green line indicates the Hydraulic steering pressurethe dark blue indicates the force applied to the steering wheel. To give you an idea of how these lines work: if I apply force to the steering wheel by turning it to the right or to the left, the hydraulic pressure increases. Let’s go a little further to the second 11”3 – so 3 tenths of a second later. Here the telemetry reveals the first anomaly: the butterfly line drops to 50% of its full opening. It means that Ayrton suddenly lifted his foot off the accelerator. The car is decelerating. Why did Senna suddenly lift his foot? If we look the hydraulic pressure of the steering, at 11″3 starts to collapse although the dark blue line indicates that the pilot is still applying force. After two tenths of a second (a 11”5) the butterfly (red line) collapses to zero. Senna has lifted his foot completely off the accelerator. The speed also drops sharply, Senna is braking to reduce the speed, but the car is probably already out of control. A 12”3the control unit is out of order. This is evident from the crazy hydraulic pressure line, a sign that the car is now uncontrollable. The speed at 12”3 it’s not the real one because the sensors are now in a mess. Everything shuts down 12”8 the moment of impact.
The car camera video
To have a complete picture of the dynamics, these telemetry data were synchronized with the race videos, digitized and cleaned by Cineca, the main Italian computing center. In particular, three perspectives were considered: Schumacher’s car camera footagewho at that moment was just behind Senna, the one of the external view of the tambourineAnd Ayrton Senna’s Camera Car. This last perspective proved to be crucial because it shows – right in correspondence with the first telemetry anomaly – an anomalous movement of the steering wheel. The investigations focused on a yellow light button: as Senna starts to travel the tambourine steering to the left, we see that this yellow dot leaves its typical trajectory lowering towards the right in a completely unusual way and signaling the fracture of the steering column. In the last frame, the button is visibly moved by more than 30 millimeters compared to its normal position, highlighting a clear steering problem.
How Formula 1 Scrapped Its Ground
That race weekend had already been marked by another death, that of the driver Ratzenberger, in another terrible accident. And in fact, Senna, who was a character of great human depth and endowed with great human sensitivity, had already appeared visibly tried, so much so that he brought an Austrian flag on board with the promise to wave it at the end of the race. After the death of Ayrton “Magic” Senna, the FIA, the body that organizes the Formula 1 championship, has increasingly placed the safety of the drivers at the center of the competitions. Over the years, changes have been made to the circuits and cars with the addition of carbon fiber survival cells in the single-seaters. New devices have been introduced to raise the protection measures such as HANS, a head and neck support system to reduce the risk of skull base fractures, or like the HALO, inaugurated in 2018, a sort of titanium cage that protects the driver’s head from debris and collisions.
