We don't disagree, and that's what I've been trying to explain for a long time: The required competency you're talking about is just to change the standard procedure by the Cierva procedure. On this condition alone, a pre-launch higher than 2/3 of the flight rpm becomes beneficial. That's just what you make.
Sorry, Jean Claude, but in these 20+ pages such provisos were missed. We'll test and film our M2 take-offs in 0-wind conditions with differing prerotation RRPMs.
not true
this pre spinner I can pre rotate at 260 ... after this the brakes don't let me go higher (simple cheap cable brakes) bub if I had better brakes I am sure I would go higher,
and this is only an amateur pre spinner built in a very short time ... so 300 rpm have nothing technically exceptionnal
jm-urbani. please note that I was referring to 200 RRPM as the generally recommended technique—not some universal limitation—
Gyros using a U-jointed driveshafts prerotator do not well lend themselves to that technique, because it's hard on the U-joint—thus, they spin to 200 RRPM with a flat disk and then launch while adding aft stick.
....although some U-jointed prerotators are indeed limited to well <300, such the Cavalon (with Rotorhead II) and its max prerotation of 220 RRPM.
Here is a takeoff into 6 gusting to 10 headwind of an AR-1 at Sun N Fun a couple of years back pre-rotating to 200 or so rotor RPM.
Not 300 just 200. You can play these with any gyro all day one up on a 2 seater machine. It's not the spec. Its fake news.
From a standing stop to unstick in about 10 seconds, suggests a stronger headwind. But, accepting your figures, wouldn't the take-off have been even shorter beginning with 300 RRPM? Rhetorically asked, can the U-jointed AR-1 be power-prerotated to 300 RRPM with significant back stick, and, if so would such reduce the service life of the prerotator components (the U-joint in particular)?
We prefer the flexshaft prerotator for reasons already stated, and we've the brakes to hold engine thrust for 300 RRPM. Other firms choose the U-jointed driveshafts. To each their own.
The rest is marketing ploys and show off tricks. Promoting those to be official ways of takeoff procedure or takeoff distance specification is not responsible or safe.
fara, in this thread I've read of no "
promoting" these company test pilot steep climbs (yours included) as "
official ways of takeoff procedure." For the typical owner, it is safest to stay in ground effect after take-off until at least Vx or Vy has been achieved. This completely avoids the H/V danger zone.
OK, back to work; we're wrapping up the M2's final assembly. Engine is "wet" and we're plumbing the fuel system.
Safe flying all!