High-altitude autorotations?

Not terribly military, I know, but...the local TV channel's news
helicopter (a Bell Jet Ranger) and its pilot appeared in a commercial
in which the stated ceiling was 22,000 feet. I remarked to my
aircraftwise 8-year-old, "Twenty-two thousand feet? I wouldn't do
that!" When Joshua asked why, I explained about the difference
between helicopters and airplanes when it comes to gliding and
dead-stick landings.

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?

Bill McClain wrote:

Not terribly military, I know, but...the local TV channel's news
helicopter (a Bell Jet Ranger) and its pilot appeared in a commercial
in which the stated ceiling was 22,000 feet. I remarked to my
aircraftwise 8-year-old, "Twenty-two thousand feet? I wouldn't do
that!" When Joshua asked why, I explained about the difference
between helicopters and airplanes when it comes to gliding and
dead-stick landings.

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.

Bob McKellar

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).

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.
************************************************** **********************
http://travel.howstuffworks.com/helicopter.htm

What is autorotation?

Autorotation is a condition where the main rotor is allowed to spin
faster than the engine driving it. How is that achieved? It is actually
quite simple.
All helicopters are fitted with a free wheeling unit between the engine
and the main rotor, usually in the transmission. This free wheeling
unit can come in different forms but one of the most popular is the
sprag clutch. The free wheeling unit will allow the engine to drive the
rotors but not allow the rotors to turn the engine. When the engine/s
fail the main rotor will still have a considerable amount of inertia
and will still want to turn under its own force and through the
aerodynamic force of the air through which it is flying. The free
wheeling unit is designed in such a way to allow the main rotor to now
rotate of its own free will regardless of engine speed. This principle
is the same reason that if you are in your car and you push your clutch
in, or put it into neutral while the car is still moving, the car will
coast along under it's own force. This occurs regardless of what you do
to the accelerator pedal.


Controlled Descent ?

The next question you are probably asking yourself is: "Does the pilot
retain control of the helicopter?" The answer is yes. The pilot will
still have complete control of his descent and his flight controls. The
majority of helicopters are designed with a hydraulic pump mounted on
the main transmission. As the rotor will still be turning the
transmission, the pilot will still have hydraulically assisted flight
controls. The pilot will be able to control his descent speed and main
rotor RPM with his collective control stick. He will be able to control
his main rotor RPM by increasing the collective pitch, which will
increase drag on the rotor blades and thereby slow the main rotor. If
he needs to increase his rotor RPM, he can decrease his collective
pitch therefore decreasing drag.
The pilot will usually be able to find a suitable area for a safe
landing by normal manipulation of his cyclic control stick and his
directional, or tail rotor pedals.
Larger helicopters will usually have a generator mounted on the
transmission that will still provide electrical power for flight and
communication systems.


What happens to Torque Effect ?

Torque effect is the aircraft's tendency to rotate in the opposite
direction to the main rotor due to Newton's third law "Every action has
an equal and opposite reaction". This is the reason why we need a tail
rotor or some other form of anti-torque control. The question at hand
is what happens to torque effect during autorotation? Well torque
effect is directly proportional to the amount of force driving the main
rotor, so when when the engine fails the amount of force driving the
main rotor instantaneously decreases and therefore the torque effect
decreases. This being the case the fuselage of the helicopter will tend
to rotate due to the sudden lack of torque effect. The pilot will
therefore have to immediately manipulate his directional pedals to
overcome this problem and retain control of his aircraft.

Conclusion

So in conclusion if your helicopter's engine/s should fail it is not
just possible, but quite easy for the pilot to retain control and land
safely and gently. This is the reason I believe that helicopters are
far safer and more fun to fly in than fixed wing aircraft. A fixed wing
aircraft will always need forward speed to safely land, with or without
an engine operating. A helicopter can be made to land with zero forward
speed whether the engine is operating or not.

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

"John Hairell" wrote in message
...
On Wed, 10 Mar 2004 06:06:46 GMT, "John?]
"
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

John, you might be able to answer a question I have regarding autorotations.
My late brother experienced exactly one serious mishap in a helo (outside
getting shot down once in Vietnam and having various small arms rounds zing
through the cabin on other occasions). It involved an autorotation in a
Schweizer 300C (read as Hughes 300/TH-55). He was checking out a cop from
the (unnamed big city) police department, which had recently purchased a
couple of 300C's for law enforcement work. Apparently the cop, who was also
a part-time ARNG Cobra pilot, had come through flight school during the
post-TH-55 days. During the autorotation, the guy apparently treated the
300C like it was a Cobra, which I gather is a bad thing to do, and when my
brother tried to take back over the guy froze up and fought the
controls--resulting in a hard landing and rolling the aircraft onto its side
(he compounded that by stomping all over my brother, who was left on the
lower side, in his haste to depart the now-stationary aircraft). Any idea
what the guy could have done that led to my brother trying to take control?
And FYI--the accident investigation cleared my brother in the incident, so I
gather that his side of the story was the way it happened.

Thanks.

Brooks

John‰] wrote:

much interesting info snipped



Controlled Descent ?

The next question you are probably asking yourself is: "Does the pilot
retain control of the helicopter?" The answer is yes. The pilot will
still have complete control of his descent and his flight controls. The
majority of helicopters are designed with a hydraulic pump mounted on
the main transmission.

Is this how the anti-torque rotor is driven in the event of powerplant
failure?

"Bill McClain" wrote in message
m...
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

Yes.

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).

Any altitude the coptor is controllable at can be autorotated from.
During the decent the rotor is spun by the vertical air flow, storing
some of the energy in the form of rotation inertia in the rotor system.
Instead of the rotor pushing the air down, the air pushes the rotor around.
Doing this slows the helicopter some, but not enough to save you.
What saves you is that near the ground the pilot can take the energy
back out of the rotor system -by changing the blade pitch- to generate
lift and gently set you on the ground. Now obviously you don't want
to wait too long to do this but you also don't want to do it too soon
and not have enough stored energy in the system to reach the ground
gently. If you are really high when the flair is done, when you fall
again you can put the energy back into the system and do it all over.


The trick is not to flair too early, unless it's *really* early.

In article ,
(John‰]*
Boulet's return to earth becomes the longest autorotation in helicopter
history.
And resulted in the dirtiest underpants on record.

Did Igor work out all this stuff early on, or did it evolve with each
new generation of helos? I mean, were the VS 300 and R4 capable of
controlled autorotation, etc.?

Yes sir....

We certainly owe a lot to Uncle Igor. BTW, I haven't seen anyone include the
actual definition of an autorotation in this thread:

Autorotation, (n)., a method of keeping the pilot's hands and feet busy as he
plummets to his death.

v/r
Gordon
====(A+C====
USN SAR

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