a VERY close call....who'd be deck crew?

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°.

"Steve L." wrote in message
news
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?

"Nick" wrote in message
...

"Steve L." wrote in message
news
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.

I didn't measure it, but from the look of it the blade pitch at the tip of
the main rotor of my jetranger when its at 90 degrees to the right (the
most negative pitch point) and the collective full down is roughly 0
degrees, it might even be a shade negative.

Bart


"The OTHER Kevin in San Diego" skiddz "AT" adelphia "DOT" net wrote in
message ...
On Sat, 24 Feb 2007 15:06:40 -0800, Steve L. wrote:


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.

A&P buddy of mine who was in the Marines told me the CH-53 can do
about -3 degrees collective. Not sure of the reasoning behind it..

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°.

The negative twist in the blades might get parts of the blade into
negative pitch in an auto (or even a rapid power descent) but I don't
know if the AoA ever goes negative...

B4RT wrote:
I didn't measure it, but from the look of it the blade pitch at the tip of
the main rotor of my jetranger when its at 90 degrees to the right (the
most negative pitch point) and the collective full down is roughly 0
degrees, it might even be a shade negative.

Was that with the cyclic neutral? If so, it would
be interesting to have someone in the ship apply
full down collective and full back cyclic while
you looked at it.

Don W.

"The OTHER Kevin in San Diego" skiddz "AT" adelphia "DOT" net wrote in
message ...
On Wed, 28 Feb 2007 13:15:15 -0500, "B4RT"
wrote:

I didn't measure it, but from the look of it the blade pitch at the tip of
the main rotor of my jetranger when its at 90 degrees to the right (the
most negative pitch point) and the collective full down is roughly 0
degrees, it might even be a shade negative.

Hey Bart,

Any idea where I can get my hands on an old Bell 206 collective
assembly? Specifically the collective lever and end "box"...
Preferrably something that's been removed from service and is of no
use to anyone any longer..

I don't really know.

It would probably be easier to find a Huey collective, its not a life
limited part on the Jetranger so the only place to find one would be a
boneyard. Surplus military parts are all over from what I hear.

Bart