Well, wikipedia has THIS to say about the flight
https://fr.wikipedia.org/wiki/SNCASE_SE.1010
Le samedi
1er octobre 1949 vers 14h00, le prototype décolle de Marignane pour son 34e vol comportant deux essais. Le second essai consiste à couper deux des moteurs
14R sur une aile, et à pousser les deux autres à fond. Le
gouvernail se bloque et l'avion part dans une
vrille à plat. Les deux moteurs coupés refusent de redémarrer, et moins de 20 secondes plus tard l'avion s'écrase dans des vignes près de
Carcès,
Var3.
Wow. Some words about the 14R engines: they were 1600 hp radials from before WWII (MB-157 and many others) , brought back from the grave after WWII... and that engine was a complete disaster. In the end France took an Hercules licence from Bristol to replace that piece of junk. The Noratlas for example switched from 14R to Hercules after the prototype phase.
It was a bit like the RR Vulture for the British or the J-40 for US Navy jets. Whatever aircraft got that engine, was doomed. So were the unfortunate pilots.
In that peculiar flight, the SE-1010 was to fly on two engines at full power, and cut the other two engines on the other wing (!!!!). Lecarme hated the aircraft, he felt the tail could "blank" and then the aircraft would go into a flat spin, and a non recoverable with that. hence his desire for a thorough wind tunnel testing.
And well, the flight testing was insane, considering how shitty the 14R were, plus the stall risk warned by Lecarme... And guess what happened ?
- the vertical tail blanked out
- the aircraft went into a deep spin (how surprising !)
- the crew abandonned the suicidal test, hence they tried to restart the two engines they had cut (and save their lives)
- the 14R being... the 14R, the two engines stubbornely refused to restart
- the aircraft fell like a brick led into a vineyard, killing everyone onboard
Geez, what a stupid waste of lives, aircraft and money. As stupid as the Cormoran crash, or the loss of Kostia Rozanoff on a demo flight of the Mystère IVB, barely missing a tribune packed full with French and British aviation heavyweights and politicians, among them Duncan Sandys (for you fellow british whatifers outraged by the 1957 white paper: that day of April 1954 poor Rozanoff missed the politicians stand by only a hair breadth)