In SNECMA Magazine April 2003, the Coléoptère and its final fate is discribed. About the
crash the folowing is said:
"On that day, Auguste Morel lifted off on his ninth flight, which was to turn into the
almost tragic crash. “Everything happened very quickly,” recalls Michel Bonin. “Along
with Pierre Drouot (the second airframe mechanic), we rolled back the gantry, and
the Coléoptère lifted off. It stabilized, then started a quick descent. We thought it was
going to recover, but it began to fall too quickly and started to oscillate and rotate to
horizontal. We heard the engine scream with the effort. At the last minute, Auguste Morel
was able to eject.” Roger Mouton was on the scene as well:
“I was near the radio truck, and Auguste Morel ejected about 30 meters away from
me. I ran to him at once, but he was badly hurt. We wondered what could have gone
wrong.” One theory at the time was a jammed throttle, preventing the pilot from
using full throttle during takeoff."
All other reports mentioned this oscillation, too, which I think , wouldn't be started by
the downwash from a heli, but by problems with engine response.