The 16 April, Matra brought its 640 to the Sarthe circuit. Henri Pescarolo took it to the track to warm up the engine... but disaster struck a few miles down the Mulsanne straight : the car took off, and was pulverised - miraculously Pescarolo was pulled out alive - although he was severely burned.
According to what Pescarolo has later reported, the bodywork/wings in the front were flexing too much at high speeds, which suddenly allowed for the air to enter under the car, lifting it from the track.
French engineer Patrick Bourdon who had Robert Choulet as instructor during his final engineering training in 1970, has supplied me with Robert Choulet's view on the accident:
Apparently Robert Choulet was (at the time) very annoyed with Henri Pescarolo, whom he regarded as having destroyed 'his' car, by taking it to full-throttle, rather than progressively building up speed.
Choulet's explanation for the accident was that not the front of the car, but simply the top of the doors was flexing, turning them into small airfoils, which produced sufficient lift to remove what was left of the traction - hereby causing the crash. According to Choulet, had only Pescarolo followed his instruction to build up speed progressively, the fault would have been detected, and eradicated, and the accident would never have happened.
It doesn't change too much of the story though, - the car was able to
do so high speeds than the smallest aerodynamic problems could have fatal
consequences. - something on the car flexed a little too much, causing
havoc with the aerodynamic properties, and thereby the crash.
It was new to me however, that de relationship between Henri Pescarolo and Robert Choulet should have taken such a downturn. Obviously Henri must have felt "let down" by the engineeres/designers. The 640 was not rebuilt, and the project was forgotten.