On Wed, 10 Mar 2004 06:06:46 GMT, "John‰]*
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wrote:

In article , Bill
McClain wrote:

And this got me wondering: Does anybody test to see how high up you
can successfully autorotate from? Is there an actual record for this?

Sounds like a self correcting problem. If you are too high to autorotate,
you will very soon be much lower.

Ummm, yeah, I guess so, but...seriously, is it even possible to try
and keep the RPMs up by diving and turning...I guess WITH the
direction of rotor spin...trying to maintain as much inertia in the
mast and blades before they lose so much torque as to be unable to
provide any lift to pull out of the dive and try to flare close to the
ground? I'm pretty much talking through my hat speculating like this;
I don't really know all that much about helicopters (other than that
I'm not all that keen on riding in one).

Believe it or not, the problem is just the opposite.

In a high altitude autorotation the rotor tends to overspeed if you
don't keep an eye on it and a small application of collective pitch is
necessary from time to time to keep it within limits. Turning and
diving are unnecessary.

When I was instructing at Fort Rucker many moons ago we would take
students to 10,000 MSL in a UH-1H and let them play with the
autorotative characteristics. The airspeed for minimum rate of descent
in the UH-1 is 63 knots indicated while the maximum glide distance is
attained at 98 knots. From 10,000 feet the student has lots of time to
vary the airspeed and get a feel for different rates of descent before
a power recovery is required.

We did touchdown autorations every day in the training cycle, but were
limited to six per student per day because they are so intense to a
student that any training benefit beyond that is negligible. On days
when I had three students, I would do eighteen touchdown autorotations
from 1000' to a concrete runway and not think a thing about it.

I used to watch students at Rucker flare and sometimes hit their tail
stingers on the ground after autorotations at tac fields, and one day
I saw an instructor gesticulating wildly at a WOC and grabbing the
controls as the Huey went skidding down a paved strip in a
semi-controlled run-on landing. Another day I saw a near mid-air
between a WOC-flown UH-1 and a Flatiron bird - if they would have hit
they would have landed right on top of the old hospital.

The last autoration I was involved with was due to a fuel-pump fire in
a Huey in Korea, with the end result that we landed on a sandbar in a
river up near the DMZ, nearly hitting some high-tension lines in fog
and drizzle, and spent a long cold winter night waiting for rescue.

John Hairell