"Nick" wrote in message
...

"Steve L." wrote in message
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Negative collective? .....ROTFLMFAO! Boy I dont think I have that
option
on mine.

What is the pitch range on this helicopter?......anyone?......I 'fly' RC,
but it'd be interesting to know that negative pitch as not
possible.....does
that go for all full size helis?

I know of only one big helicopter that ever had negative pitch (-3°). It
is a military American one; can't recall the type.
The reason for that is that it should be able to do a very quick
vertical descent while hovering just over tree tops.

For all other helicopters it were pretty useless but would cost a lot
because the control rigging would need far more travel.

There is no civilian helo with negative pitch, not even 0°. The minimum
pitch might be as high as +4°.

Thanks for the reply. But what happens during autorotation to keep the
headspeed up? ......headspeed will surely decay very quickly at +4degrees?

I fly RC helicopters too and have "very" limited experience in the full size
counterparts. What most RCer's don't understand is that you don't need
negative pitch to autorotate. What RCer's refer to as "negative" collective
is simply an measurement of blade incidence. It has nothing to do with the
rotor blades aerodynamic angle of attack (AOA). Nick, even if you're
running your model with a -5 at full down setup, the blades are still flying
a positive AOA in the auto at that setting. Granted, it'll be dropping like
a rock in that mode but the blades are still seeing a positive AOA. I've
played around with autos on my RC birds and, with a bit of a breeze, have
made sustained autorotative approaches and a safe landing with the
collective as high as +3 degrees. Granted, I wasn't carrying a lot of rotor
rpm on the descent so the collective "pull" at the bottom was a bit critical
but it's definitely doable.

The full size birds, as Steve L pointed out, rarely if ever go into the
negative incidence range. First, because the simply don't need to and more
importantly, because they are "much" more critical about maintaining a
specific rotor rpm. If they dropped into a negatie incidence range, they'd
overspeed the rotor with obvious results. The big guys simply can't stand
the rpm swings that our models do in their stride.

FWIW!
Fly Safe,
Steve R.