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Phillip
July 21st 03, 09:21 AM
Would a gyro with a swashplate ( just for pitch control) fly any different
(better,worse) than using a tilt type rotor head? Just more complex?

Also, I've seen some photos of early kit helicopters that appear to have
just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
wish? Does a helicopter need to have collective pitch for anything other
than auto-rotaion?

Silly questions, but it's a late night. :)

Phillip
July 22nd 03, 12:52 AM
"Rhodesst" > wrote in message
...
> >Power adjustments. Wally
>
> Power adjustments? I don't see the difference a swashplate over a tilt
head
> for cyclic control would make to a gyros rotor system. Care to explain
> further?
>
> OTOH, I think that sport gyros today use the tilt rotor hub because it's a
very
> simple design, and it works very well. No swashplate and associated
linkages,
> not to mention the fact that there's no need for individual feathering
hinges
> on the rotor blades themselves. Much less to go wrong and/or maintain.
>
> JMO,
> Fly Safe,
> Steve R.

The K.I.S.S. formula at it's best.

So why not on a helicopter? (Like those old kits I mentioned). I'm assuming
because you'd lose auto-rotation?

Phil Miller
July 22nd 03, 01:43 AM
On Mon, 21 Jul 2003 01:21:13 -0700, "Phillip" > wrote:

>Would a gyro with a swashplate ( just for pitch control) fly any different
>(better,worse) than using a tilt type rotor head? Just more complex?

Just more complex. The net effect would be the same. Increase the angle
of attack 90 degrees before desired disc upward movement, decrease AoA
90 degrees before. Gyroscopic precession then makes the desire movement
happen.

>Also, I've seen some photos of early kit helicopters that appear to have
>just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
>wish? Does a helicopter need to have collective pitch for anything other
>than auto-rotaion?

Helicopter collective increase/decreases pitch angle of all blades
collectively and thereby increases/decreases lift. Pull collective up,
go up. lower collective, go down. It's a bit more complex than that, but
I'll leave that to the experts here.

>Silly questions, but it's a late night. :)


Phil
--
Definitions of a pilot - No. 1

The average pilot, despite the sometimes swaggering exterior,
is very much capable of such feelings as love, affection,
intimacy and caring.
These feelings just don't involve anybody else.
US Navy Times

Stan Gosnell
July 22nd 03, 02:08 AM
"Phillip" > wrote in
:

> Also, I've seen some photos of early kit helicopters that
> appear to have just a tilting head (no way to auto-rotate
> ?). Isn't this a bit of a death wish? Does a helicopter
> need to have collective pitch for anything other than
> auto-rotaion?

Helicopters depend on collective pitch for control of power -
they have no other way to fly. Without collective pitch, you
can't get off the ground, or change power, or get back on the
ground in one piece.

--
Regards,

Stan

Guy Alcala
July 22nd 03, 03:02 AM
Stan Gosnell wrote:

> "Phillip" > wrote in
> :
>
> > Also, I've seen some photos of early kit helicopters that
> > appear to have just a tilting head (no way to auto-rotate
> > ?). Isn't this a bit of a death wish? Does a helicopter
> > need to have collective pitch for anything other than
> > auto-rotaion?
>
> Helicopters depend on collective pitch for control of power -
> they have no other way to fly. Without collective pitch, you
> can't get off the ground, or change power, or get back on the
> ground in one piece.

IIRC, at least the first Piasecki helo and maybe the first Hiller
lacked collective pitch. Lift was controlled by the throttle
(which controlled the engine and thus rotor rpm), and they seemed
to have flown just fine. There are clearly advantages to the
collective system as later models all included it, but it's not
as if a helo has to have one to fly.

Guy

Phillip
July 22nd 03, 03:55 AM
"Guy Alcala" > wrote in message
. ..
> Stan Gosnell wrote:
>
> > "Phillip" > wrote in
> > :
> >
> > > Also, I've seen some photos of early kit helicopters that
> > > appear to have just a tilting head (no way to auto-rotate
> > > ?). Isn't this a bit of a death wish? Does a helicopter
> > > need to have collective pitch for anything other than
> > > auto-rotaion?
> >
> > Helicopters depend on collective pitch for control of power -
> > they have no other way to fly. Without collective pitch, you
> > can't get off the ground, or change power, or get back on the
> > ground in one piece.
>
> IIRC, at least the first Piasecki helo and maybe the first Hiller
> lacked collective pitch. Lift was controlled by the throttle
> (which controlled the engine and thus rotor rpm), and they seemed
> to have flown just fine. There are clearly advantages to the
> collective system as later models all included it, but it's not
> as if a helo has to have one to fly.
>
> Guy
>

I guess what I wondered was , other than a need to auto-rotate, a tilt
system would work on a helicopter the same as a gyro? Yes I know
auto-rotation is needed...I'm just wounding if the concept is the same. :)

That's what these kits mentioned (it's been a long time), you added power
to go up, remove power to come down...seems simple enough. Don't think I'd
like the idea of no collective control for auto-rotation.

Phil Miller
July 22nd 03, 04:09 AM
On Tue, 22 Jul 2003 10:43:27 +1000, Phil Miller
> wrote:

>On Mon, 21 Jul 2003 01:21:13 -0700, "Phillip" > wrote:
>
>>Would a gyro with a swashplate ( just for pitch control) fly any different
>>(better,worse) than using a tilt type rotor head? Just more complex?
>
>Just more complex. The net effect would be the same. Increase the angle
>of attack 90 degrees before desired disc upward movement, decrease AoA
>90 degrees before. Gyroscopic precession then makes the desire movement
^^^^^^
>happen.

Woops. After.

>>Also, I've seen some photos of early kit helicopters that appear to have
>>just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
>>wish? Does a helicopter need to have collective pitch for anything other
>>than auto-rotaion?
>
>Helicopter collective increase/decreases pitch angle of all blades
>collectively and thereby increases/decreases lift. Pull collective up,
>go up. lower collective, go down. It's a bit more complex than that, but
>I'll leave that to the experts here.
>
>>Silly questions, but it's a late night. :)
>
>
>Phil


Phil
--
"Me fail english? That's unpossible!"
Ralph Wiggum

Paul Baechler
July 22nd 03, 11:07 PM
In article >,
"Phillip" > wrote:

>"Rhodesst" > wrote in message
...
>> >Power adjustments. Wally
>>
>> Power adjustments? I don't see the difference a swashplate over a tilt
>head
>> for cyclic control would make to a gyros rotor system. Care to explain
>> further?
>>
>> OTOH, I think that sport gyros today use the tilt rotor hub because it's a
>very
>> simple design, and it works very well. No swashplate and associated
>linkages,
>> not to mention the fact that there's no need for individual feathering
>hinges
>> on the rotor blades themselves. Much less to go wrong and/or maintain.
>>
>> JMO,
>> Fly Safe,
>> Steve R.
>
>The K.I.S.S. formula at it's best.
>
>So why not on a helicopter? (Like those old kits I mentioned). I'm assuming
>because you'd lose auto-rotation?

The basic principle of autogyro flight is auto-rotation. What you'd lose
is a simple, practical way of controlling powered flight.

--
Paul Baechler

Phillip
July 23rd 03, 07:41 AM
"Bart" > wrote in message
...
> Phillip wrote:
> >
>
> > I guess what I wondered was , other than a need to auto-rotate, a tilt
> > system would work on a helicopter the same as a gyro? Yes I know
> > auto-rotation is needed...I'm just wounding if the concept is the same.
:)
> >
> > That's what these kits mentioned (it's been a long time), you added
power
> > to go up, remove power to come down...seems simple enough. Don't think
I'd
> > like the idea of no collective control for auto-rotation.
>
> No, a helicopter can not operate without a swashplate. Without the
swashplate
> you'd just be able to go up and down. I'll probably draw some heat here
for
> this,
> but autogyros have more in common with airplanes than they do helicopters.
> The aerodynamics are really different.
>
> In horizontal flight, a helicopter is constantly changing the pitch of
> each main rotor blade independently as it travels around in the circuit.
> The advancing blade has negative relative pitch, and the retreating blade
> has hugely positive relative pitch. Horizontal thrust is not derived by
> tilting the mast.
>
> The swashplate is controlled by the cyclic and collective together. The
two
> flight controls are "mixed together" to move the swashplate. The
collective
> moves the pitch of all blades equally, the cyclic tilts the swashplate to
> cause the pitch changes to be become "cyclical".
>
>
> Bart

I see those brothers (Nolan ?? ) built a coaxial with no swash plate....but
also no auto-rotation. twin engine though. How do they get away with it? I
guess the twin rotors would cancel all those bad things out.

This is one of the kits I saw.

http://www.airscooter.com

No swashplates, no collective, NO AUTOROTATION (scary) two engines I think.

Phil Miller
July 25th 03, 01:22 PM
On Fri, 25 Jul 2003 11:57:53 GMT, Terry Spragg >
wrote:

>For the simplest possible reason:
>
>An auto gyro is always flown in autorotation, with fixed plade
>pitch set for 'gliding'. If you apply torque to an auto rotor,
>you do not get lift, you get propelled groundward.

G'day Terry,

Are you saying that autogyro's have negative pitch on their rotor
blades? If so, you are wrong.

If that's not what your saying, I apologise. I have misunderstood your
meaning. Could you please explain this statement?

Cheers,


Phil
--
Pfft...english! Who needs that? I'm never going to England.
Homer J. Simpson

Rhodesst
July 25th 03, 02:28 PM
>On Fri, 25 Jul 2003 11:57:53 GMT, Terry Spragg >
>wrote:
>
>>For the simplest possible reason:
>>
>>An auto gyro is always flown in autorotation, with fixed plade
>>pitch set for 'gliding'. If you apply torque to an auto rotor,
>>you do not get lift, you get propelled groundward.
>
>G'day Terry,
>
>Are you saying that autogyro's have negative pitch on their rotor
>blades? If so, you are wrong.
>
>If that's not what your saying, I apologise. I have misunderstood your
>meaning. Could you please explain this statement?
>
>Cheers,
>
>
>Phil

I was wondering about that myself!

Fly Safe,
Steve R.

Phil Miller
July 27th 03, 08:30 AM
On 25 Jul 2003 13:28:55 GMT, (Rhodesst) wrote:

>>On Fri, 25 Jul 2003 11:57:53 GMT, Terry Spragg >
>>wrote:
>>
>>>For the simplest possible reason:
>>>
>>>An auto gyro is always flown in autorotation, with fixed plade
>>>pitch set for 'gliding'. If you apply torque to an auto rotor,
>>>you do not get lift, you get propelled groundward.
>>
>>G'day Terry,
>>
>>Are you saying that autogyro's have negative pitch on their rotor
>>blades? If so, you are wrong.
>>
>>If that's not what your saying, I apologise. I have misunderstood your
>>meaning. Could you please explain this statement?
>>
>>Cheers,
>>
>>
>>Phil
>
>I was wondering about that myself!

No reply from Terry? Oh well...I guess we'll have to remain ignorant,
Steve.

Cheers,

Phil
--
Women vs Aircraft

Aircraft don't object to a preflight inspection.
Aircraft come with manuals to explain their operation.
Aircraft have strict weight and balance limits.
Aircraft don't come with in-laws.
Aircraft don't care about how many other aircraft you have flown.
Aircraft and pilots both arrive at the same time.
Aircraft don't mind if you look at other aircraft.
Aircraft don't mind if you buy aircraft magazines.
Aircraft expect to be tied down.
Aircraft don't comment on your piloting skills.
Aircraft don't try and make you crash and burn.
Aircraft don't whine unless something is really wrong.
When aircraft go quiet, it's a bad thing.
May 2001 Pacific Flyer Magazine

PW
August 1st 03, 12:27 AM
"Rod Buck" > wrote in message
...
> In message >, Terry Spragg
> > writes
> >
> >An auto gyro is always flown in autorotation, with fixed plade
> >pitch set for 'gliding'. If you apply torque to an auto rotor,
> >you do not get lift, you get propelled groundward.
>
> Alas, not true - an autorotating rotor does NOT normally have negative
> blade pitch - it has positive pitch of 1-3 degrees, and therefore
> generates lift by rotation.
>
> Therefore, if you powered it by a torque from the hub, it would lift off
> perfectly well.
>
> It would NOT try to screw it's way into the ground, as it would if the
> blade pitch was neggy.
>
>
> Pitcairn gyros used jumpstart, where the blades are spun up to well
> above normal RPM, in zero pitch, then the usual autorotational pitch of
> 1-3 degrees is applied (either by collective or by delta-three hinges,
> which increase the pitch angle when hub torque disappears.)
>
> You must, of course, declutch the hub drive as soon as you increase
> pitch and take off - with no tail rotor or other countertorque means,
> you'd spin real fine....
>
>
> The delta-3 hinge is a ferocious beast - once you get above flight rpm,
> you MUST take off, there is no way out - bit like lighting those Shuttle
> SRB's - it's not a question of whether you go or not, it's just which
> direction....
>
> As soon as you declutch the motor, or reduce motor RPM, the hinges
> increase the pitch, and off you go.....
>
> The gyro leaps 1-200 ft in the air, and then the prop drive provides
> forward motion to start normal autorotational gyro flight - the rotor
> pitch is NOT reduced again to do this - it stays at the normal 1-3 deg.
>
>
> >If you apply
> >power, you are flying a helicopter, which must have some manual
> >control over pitch if both powered flight and autorotation is to
> >be possible.
>
> Wrong again, friend.
>
> It's perfectly possible to have a helo with a fixed pitch rotor, set to
> the small positive angle for autorotation, and alter lift by changing
> engine power, and thus rpm. (You can then use head gimbal as in gyro to
> alter pitch cyclically for directional control).
>
> (The rotor rpm would be quite a bit higher than normal for the same
> lift)
>
> However, the rotor momentum (flywheel effect) makes the control
> extremely sluggish and impractical, compared to collective pitch
> control.
>
> However, one safety improvement would be that, as the rotor is always in
> the low-angle suitable for autorotation, if the engine quits, a
> freewheel device in the rotor drive chain would ensure you entered auto
> painlessly.
>
> --
> Rod Buck

Rod,

You just answered soooo many of my questions. THANK YOU! Would you mind
if we talked a bit via e-mail?

Again, thanks

Phil Williamson
Oregon City, Or.

Rod Buck
August 1st 03, 11:22 AM
In message >, Charlie+
> writes
>On Wed, 30 Jul 2003 21:06:07 +0100, Rod Buck >
>wrote as underneath my scribble :
>
>Rod, as a matter of interest have you personally done one of these
>takeoff jumps? Sounds exciting/scary!

Not done it personally - seen it in the flesh once, and on film lots of
times. Scared me sh*tless to WATCH it - never mind fly it!

>Presumably the change over to propdrive is immediate on initiation so
>there is some element of forward drive from the start of the leap?

Yup, dead right. My impression is that there is some sort of changeover
mechanism, whereby the motor drives either the rotor hub, to spin-up the
rotor to well above flight RPM, or the normal propeller to provide
inflight thrust as in a normal gyro.

So, when you get up to 150% flight RPM, you pull the lever, the hub is
declutched, and the prop engaged....

>Is the direction of the leap unpredictable / local wind etc causing
>major imbalances?
>Also is there some drop in initial altitude until full gyro level
>flight and control can be achieved? if so - how much swoop do you
>estimate?
>Charlie+
>
From what I've seen, you obviously line the gyro's nose into wind, (and
as in all aviation, a decent wind helps no end).

Got to be careful to get the cyclic central, so the thing leaps up
vertically (but with some forward thrust from the prop during the leap,
so the leap is actually forward, even if the rotor is horizontal)

Then, at the top of the leap, the rotor must be angled back to the
normal gyro angle to ensure upward airflow through the rotor (and drag
to balance the prop thrust) as you move into wind.

Where there is a wind of, say, 15mph or more, I saw no evidence of drop
or swoop at the top of the leap - it just flew off.

In nil-wind, I would anticipate there must be some drop, maybe 50ft.
Depends on the engine thrust, and how quickly it accelerates the gyro to
normal forward flightspeed. This is why a wind prevents drop, of course.
A 15mph wind means you've got at least 20mph airspeed at the top of the
leap - you must gain at least 5mph forward speed in the leap if the prop
is running.

This is enough to maintain level flight.

--
Rod Buck

Rod Buck
August 1st 03, 11:30 AM
In message >, writes
>You lost me there. :) I was talking about the use of a tilt rotor (with a
>fixed pitch) on a helicopter. Other than losing auto-rotation, what is the
>downside? I know losing auto-rotation IS a big deal. I saw a coaxial kit
>that uses a tiltrotor (no swashplate, no collective...no auto-rotation) But
>they have two engines. Seems like dropping all the extra hardware for pitch
>control (they use engine speed to control lift) would be a good thing.


Look, you can alter the lift force of a rotor by two methods. Either you
keep the same rotor rpm, and alter the pitch angle of the blades, OR you
keep the blade angle the same, and alter the rotor RPM.

Or, of course, a combination of the two.

The problem is that, without collective pitch control, you can only vary
the lift force by increasing or decreasing rotor rpm, ie by altering
engine power.

This is very slow to act, due to rotor inertia (flywheel effect) and
means that control is extremely sluggish and imprecise compared to
collective pitch control, where the rotor speed is constant, but the
attack angle of the blades is changed instantly.

You do NOT need a collective-pitch control to change from powered flight
to autorotation - you could just set the blades to autorotation angle to
start with, and then vary power to increase lift - then, if the engine
quit, the freewheel device in the drive chain would let the blades
outspeed the engine, and you'd enter autorotation automatically.

The confusion you are having is, I think, because you (and several
others) think that the blades have to be at positive pitch for powered
flight, and altered to negative pitch (nose-down to the plane of the
rotor disk) for autos. THIS IS INCORRECT.

Blades autorotate perfectly well with a small positive pitch angle -
normally about 1-3 degrees (depends on the airfoil used)



--
Rod Buck

Ken Sandyeggo
August 2nd 03, 06:02 AM
Let me jump in here a little. I got to ride with John Potter at
Paducah, KY last winter in an Air & Space. The prop is constantly
engaged. There is no transition from the engine powering the rotor
and then switching to the prop after the jump in this craft. The
Lycoming turns the prop just like any other prop in a pusher
configuration. The rotor is engaged via a multi-belt driven geared
transmission. The rotor spins up to somewhere over 300 rpm (while
depitched)if my memory isn't letting me too far down. The tires alone
keep the gyro from counter-rotating. One wheel was on a piece of ice
during one of the spinups and John had to move it onto a dry patch.

Once the proper rotor rpm was reached, John reached to the panel and
pressed a button. The blades instantly repitched and we shot straight
up like a rocket. I'm sure that the transmission disengages
simultaneously. The ship reaches maybe 30-40 feet and smoothly
transitions into forward flight and a climb mode. There is no loss of
altitude during the transition. Now I suppose someone could screw it
up and not have enough throttle on during the jump start, but the
engine rpm seemed to up there some to get the blades going, and the
jump happens very quickly. As I recall, full throttle is applied as
soon as she jumps. It's a very, very fast sequence. You're at the
top of that jump before you can blink.

We took off on the runway and then from the tarmac perpendicular to
the wind, and there didn't seem to be any problems.....no more than a
plane taking off in a crosswind. I felt no yawing or unsteadiness
from the crosswind jump and never experienced any dropping.

Now I'm going strictly by memory on the mechanics, but I believe I
have the basics correct.

Ken J. - Sandy Eggo



Rod Buck > wrote in message >...
> In message >, Charlie+
> > writes
> >On Wed, 30 Jul 2003 21:06:07 +0100, Rod Buck >
> >wrote as underneath my scribble :
> >
> >Rod, as a matter of interest have you personally done one of these
> >takeoff jumps? Sounds exciting/scary!
>
> Not done it personally - seen it in the flesh once, and on film lots of
> times. Scared me sh*tless to WATCH it - never mind fly it!
>
> >Presumably the change over to propdrive is immediate on initiation so
> >there is some element of forward drive from the start of the leap?
>
> Yup, dead right. My impression is that there is some sort of changeover
> mechanism, whereby the motor drives either the rotor hub, to spin-up the
> rotor to well above flight RPM, or the normal propeller to provide
> inflight thrust as in a normal gyro.
>
> So, when you get up to 150% flight RPM, you pull the lever, the hub is
> declutched, and the prop engaged....
>
> >Is the direction of the leap unpredictable / local wind etc causing
> >major imbalances?
> >Also is there some drop in initial altitude until full gyro level
> >flight and control can be achieved? if so - how much swoop do you
> >estimate?
> >Charlie+
> >
> From what I've seen, you obviously line the gyro's nose into wind, (and
> as in all aviation, a decent wind helps no end).
>
> Got to be careful to get the cyclic central, so the thing leaps up
> vertically (but with some forward thrust from the prop during the leap,
> so the leap is actually forward, even if the rotor is horizontal)
>
> Then, at the top of the leap, the rotor must be angled back to the
> normal gyro angle to ensure upward airflow through the rotor (and drag
> to balance the prop thrust) as you move into wind.
>
> Where there is a wind of, say, 15mph or more, I saw no evidence of drop
> or swoop at the top of the leap - it just flew off.
>
> In nil-wind, I would anticipate there must be some drop, maybe 50ft.
> Depends on the engine thrust, and how quickly it accelerates the gyro to
> normal forward flightspeed. This is why a wind prevents drop, of course.
> A 15mph wind means you've got at least 20mph airspeed at the top of the
> leap - you must gain at least 5mph forward speed in the leap if the prop
> is running.
>
> This is enough to maintain level flight.

Stephen Austin
August 3rd 03, 10:21 AM
>Let me jump in here a little. I got to ride with John Potter at
>Paducah, KY last winter in an Air & Space.

I think the key word there is winter. Low density altitude is key.

>Once the proper rotor rpm was reached, John reached to the panel and
>pressed a button.

Hmm, well, the button on the panel is to engage the prerotator clutch. If
you'll remember, once that button is pushed the throttle is increased so the
engine is about 1500 RPM. At that point you begin pumping the hydraulic lever
to engage the clutch. You slowly pump the handle to maintain continous
pressure while at the same time working the throttle to maintain 800 RPM. It
is very much like engaging the clutch on an Enstrom. Once rotor RPM and engine
RPM marry the handle is quickly pumped until the engage button on the panel
pops out. This indicates the system is fully engaged. From then the RPM is
increased to 370 RPM.

>The blades instantly repitched and we shot straight
>up like a rocket. I'm sure that the transmission disengages
>simultaneously.

The blades are depitched by pushing a button on the top of the throttle. Hehe,
it all happens so quickly that it is easy to lose track of what happens when.
That's why the depitch button is on the throttle. It would take too long to
push a button on the panel and then have to bring your hand back to the
throttle.

> The ship reaches maybe 30-40 feet and smoothly
>transitions into forward flight and a climb mode. There is no loss of
>altitude during the transition.

Winter had a lot to do with that. Jump takeoff is unlikely above a 2000' DA.
No doubt pilot skill, gross weight, wind, etc. play a major part. But I do
know that when I've flown the 18A it was in the summer. Max jump height was
about fifteen feet and after the jump we sunk to about five feet before we got
ahead of the power curve and established a climb. I do remember also that if,
after the jump, the aircraft settles to the ground, power must be reduced and
the sequence started all over again.

BTW, for a jump, the rotor is spun to 370 RPM. Operating RPM green arc is from
200-320 RPM. It's all a bit tricky but quickly becomes second nature.
Regardless the 18A is a great flying ship.


Stephen Austin
Austin Ag Aviation
Charleston, Missouri

Stephen Austin
August 3rd 03, 10:24 AM
>
>The only problem with the A&S was a severe limitation on the operation at
>the local field because of noise restrictions - it sure was a loud bird.

Hmm, at Farrington Airpark? I think someone was pulling your leg. I've never
heard of any noise restrictions there. It's kind of in the boondocks anyway.
And, for that matter, there is a stock car track about one hundred yards from
the strip (the strip actually began life as a drag strip until Don bought it).
Anyway all those cars are one heck of a lot louder than an 18A.


Stephen Austin
Austin Ag Aviation
Charleston, Missouri

Michael Pilla
August 3rd 03, 01:54 PM
"Stephen Austin" > wrote in message
...
> >
> >The only problem with the A&S was a severe limitation on the operation at
> >the local field because of noise restrictions - it sure was a loud bird.
>
> Hmm, at Farrington Airpark? I think someone was pulling your leg. I've
never
> heard of any noise restrictions there. It's kind of in the boondocks
anyway.
> And, for that matter, there is a stock car track about one hundred yards
from
> the strip (the strip actually began life as a drag strip until Don bought
it).
> Anyway all those cars are one heck of a lot louder than an 18A.
>
>
> Stephen Austin
> Austin Ag Aviation
> Charleston, Missouri

Nope. My A&S 18A lesson was in NJ, but I forget the town. Even though the
airstrip was in the Western (less populated portion of the state - rural,
actually), the local residents were the highly paid, city-commuter types
(NYC) and, apparently both vocal and influential. The 18A clearly was
louder than the other planes (typical spam can range, plus a goodly amount
of low-powered Cubs, Champs, etc.) - it definitely stood out during ops.

Michael Pilla

Stephen Austin
August 3rd 03, 05:24 PM
>NJ, but I forget the town. Even though the
>airstrip was in the Western (less populated portion of the state - rural,
>actually), the local residents were the highly paid, city-commuter types
>(NYC) and, apparently both vocal and influential. The 18A clearly was
>louder than the other planes (typical spam can range, plus a goodly amount
>of low-powered Cubs, Champs, etc.) - it definitely stood out during ops.
>
>Michael Pilla
>
>
>
>
>
>
>

Man, don't you hate that? Was it one of those deals where the airport was
there long before any of the homes?


Stephen Austin
Austin Ag Aviation
Charleston, Missouri

Ken Sandyeggo
August 3rd 03, 05:43 PM
(Stephen Austin) wrote in message >...
> >Let me jump in here a little. I got to ride with John Potter at
> >Paducah, KY last winter in an Air & Space.
>
> I think the key word there is winter. Low density altitude is key.
>
> >Once the proper rotor rpm was reached, John reached to the panel and
> >pressed a button.
>
> Hmm, well, the button on the panel is to engage the prerotator clutch. If
> you'll remember, once that button is pushed the throttle is increased so the
> engine is about 1500 RPM. At that point you begin pumping the hydraulic lever
> to engage the clutch. You slowly pump the handle to maintain continous
> pressure while at the same time working the throttle to maintain 800 RPM. It
> is very much like engaging the clutch on an Enstrom. Once rotor RPM and engine
> RPM marry the handle is quickly pumped until the engage button on the panel
> pops out. This indicates the system is fully engaged. From then the RPM is
> increased to 370 RPM.
>
> >The blades instantly repitched and we shot straight
> >up like a rocket. I'm sure that the transmission disengages
> >simultaneously.
>
> The blades are depitched by pushing a button on the top of the throttle. Hehe,
> it all happens so quickly that it is easy to lose track of what happens when.
> That's why the depitch button is on the throttle. It would take too long to
> push a button on the panel and then have to bring your hand back to the
> throttle.
>
> > The ship reaches maybe 30-40 feet and smoothly
> >transitions into forward flight and a climb mode. There is no loss of
> >altitude during the transition.
>
> Winter had a lot to do with that. Jump takeoff is unlikely above a 2000' DA.
> No doubt pilot skill, gross weight, wind, etc. play a major part. But I do
> know that when I've flown the 18A it was in the summer. Max jump height was
> about fifteen feet and after the jump we sunk to about five feet before we got
> ahead of the power curve and established a climb. I do remember also that if,
> after the jump, the aircraft settles to the ground, power must be reduced and
> the sequence started all over again.
>
> BTW, for a jump, the rotor is spun to 370 RPM. Operating RPM green arc is from
> 200-320 RPM. It's all a bit tricky but quickly becomes second nature.
> Regardless the 18A is a great flying ship.
>
>
> Stephen Austin
> Austin Ag Aviation
> Charleston, Missouri

Hi Steve,

Thanks for the technical straightening out. It does happen quickly
and you're right, I missed a lot of it. It is a kick to ride in. It
was the middle of winter....I think the temp was in the low 20s. I'm
sure the jump wouldn't be as impressive on a hot day at some altitude.

John is still restoring them at about 2-3 per year and you can buy one
ready to go in like-new condition......I'm going to guess here
again.....around a 100 thou if I recall the number John gave me. I'm
thinking it was either a little more or a little less. Short-term
memory must be going.

Ken J. - Sandy Eggo

Michael Pilla
August 3rd 03, 08:04 PM
"Stephen Austin" > wrote in message
...
> >NJ, but I forget the town. Even though the
> >airstrip was in the Western (less populated portion of the state - rural,
> >actually), the local residents were the highly paid, city-commuter types
> >(NYC) and, apparently both vocal and influential. The 18A clearly was
> >louder than the other planes (typical spam can range, plus a goodly
amount
> >of low-powered Cubs, Champs, etc.) - it definitely stood out during ops.
> >
> >Michael Pilla

> Man, don't you hate that? Was it one of those deals where the airport was
> there long before any of the homes?
>
>
> Stephen Austin
> Austin Ag Aviation
> Charleston, Missouri

Of course. But, of course, that is irrelevant to those who move, later.
Even Steve Forbes, of Forbes magazine, fought the improvements at a small
airport that was near his property even though, years earlier, the airport
owners supported Forbes when he wanted to have an exemption to zoning
ordinances. The record was clear: airport owners supported him, he
vociferously opposed their improvements. Result: Forbes: 2, Somerset
Airport, 0.

Michael Pilla

Terry Spragg
August 4th 03, 03:36 AM
Rod Buck wrote:
>
> In message >, writes
> >You lost me there. :) I was talking about the use of a tilt rotor (with a
> >fixed pitch) on a helicopter. Other than losing auto-rotation, what is the
> >downside? I know losing auto-rotation IS a big deal. I saw a coaxial kit
> >that uses a tiltrotor (no swashplate, no collective...no auto-rotation) But
> >they have two engines. Seems like dropping all the extra hardware for pitch
> >control (they use engine speed to control lift) would be a good thing.
>
> Look, you can alter the lift force of a rotor by two methods. Either you
> keep the same rotor rpm, and alter the pitch angle of the blades, OR you
> keep the blade angle the same, and alter the rotor RPM.
>
> Or, of course, a combination of the two.
>
> The problem is that, without collective pitch control, you can only vary
> the lift force by increasing or decreasing rotor rpm, ie by altering
> engine power.
>
> This is very slow to act, due to rotor inertia (flywheel effect) and
> means that control is extremely sluggish and imprecise compared to
> collective pitch control, where the rotor speed is constant, but the
> attack angle of the blades is changed instantly.
>
> You do NOT need a collective-pitch control to change from powered flight
> to autorotation - you could just set the blades to autorotation angle to
> start with, and then vary power to increase lift - then, if the engine
> quit, the freewheel device in the drive chain would let the blades
> outspeed the engine, and you'd enter autorotation automatically.
>
> The confusion you are having is, I think, because you (and several
> others) think that the blades have to be at positive pitch for powered
> flight, and altered to negative pitch (nose-down to the plane of the
> rotor disk) for autos. THIS IS INCORRECT.
>
> Blades autorotate perfectly well with a small positive pitch angle -
> normally about 1-3 degrees (depends on the airfoil used)
>
> --
> Rod Buck


Well...

You also change the flight path. The blades need to see an
updraught to absorb power to spin, to generate lift somehow.

The change in direction of the airflow between a nose down
attitude under power in a helo and a nose up, direction slightly
down for autorotation makes the mechanical aoa at the hub
different from the aoa of the airflow on the rotor.

I cannot claim any authority for this beyond personal
experimentation, and my conjecture, apparantly widely debated if
not misunderstood, seems in at least a common sense way to be
true.

A small toy illustrates a point which becomes intuitive. A stick
twirled between the palms with rotor blades attached ascends
until the energy stored on the rotor is consumed. The toy begins
to descend rapidly. The rotor reverses and spins up. The descent
slows dramatically.

The apparent wind on the blades must be at a + aoa to
autorotate, even if the aoa at the reversed hub wrt the shaft may
be -, and the airflow presents a greater + to the reversed blade
with as much - mechanical aoa as it was + rotating in the
ascending phase, spinning it up by energising it, and with
increase in apparent airspeed of the rotor the aoa becomes less +
in regard to the flightpath of the blade arounds the hub, while
being - to the airflow around the craft. Autorotation is a
delicate balance, yes? One must fly the collective carefully to
do autos. It is a skill I cannot claim.

The airflow changes from downward to upward on the rotor blades
of the toy. If the hub rotation does not reverse, the +
mechanical aoa of a powered nose up gyro becomes - wrt the
airflow in the retreating blade, the flight path becomes
downward, wrt apparent airflow to the craft now nose down wrt
horizon, but still + in one sense, and - in another. In
autorotation, part of the rotor's flightpath must be - aoa wrt
the aparrent airflow on the blade.

Watch the toy fly again. Meditate some more. Grok the universe.
Be one with gravity.

Is it possible to explain this in some other way? I can't seem to
express it well. Perhaps a cartoon video is available somewhere?

This is possibly a flawed intuit, and I cannot yet grasp it all.
I am not a rotorhead, but have watched many autorotations from
the tower at a helo flight school, complete with commentary from
those "3 dimensional thinkers" that direct the traffic. As a
control tower radio tech, I have had some "unofficial" flight
training, er, perhaps I should say unofficial experience in fixed
wing and rotor, and understand aerodynamics to an extent in model
design and flight.

If I claim to be a little perlexed, at least you must respect my
honesty. In autorotation flight, part of the rotor disk must be
in - air aoa, yes or no?

--
Terry K - My email address is MY PROPERTY, and is protected by
copyright legislation. Permission to reproduce it is
specifically denied for mass mailing and unrequested
solicitations. Reproduction or conveyance for any unauthorised
purpose is THEFT and PLAGIARISM. Abuse is Invasion of privacy
and harassment. Abusers may be prosecuted. -This notice footer
released to public domain. Spamspoof salad by spamchock -
SofDevCo

Phil Miller
August 4th 03, 04:00 AM
On Mon, 04 Aug 2003 02:36:31 GMT, Terry Spragg >
wrote:

>If I claim to be a little perlexed, at least you must respect my
>honesty. In autorotation flight, part of the rotor disk must be
>in - air aoa, yes or no?

G'day Terry,

I am going to read your post in full again offline, but let me answer
this bit quickly.

There is no need for any part of the aerofoil to be in -ve AoA. It is
not blown around like a toy fan. Have a look at this page
http://www.copters.com/aero/autorotation.html

See in figure 2-89 that because of the upward inflow the lift vector is
tilted forward? The portion of lift in the forward direction acts to
pull the blade forward (or around).

Hope this helps. I'll reread your post and send some more later, if
required.

Cheers,


Phil
--
Pfft...english! Who needs that? I'm never going to England.
Homer J. Simpson

Rhodesst
August 4th 03, 11:41 PM
>There is no need for any part of the aerofoil to be in -ve AoA. It is
>not blown around like a toy fan. Have a look at this page
>http://www.copters.com/aero/autorotation.html

Hi Phil,

Great link! Turns out I understood this stuff better than I thought I did.
I've read plenty about the physics, just never seen it laid out this well in
pictures. Thanks for posting it.

Fly Safe,
Steve R.

Phil Miller
August 5th 03, 12:37 AM
On 04 Aug 2003 22:41:43 GMT, (Rhodesst) wrote:

>>There is no need for any part of the aerofoil to be in -ve AoA. It is
>>not blown around like a toy fan. Have a look at this page
>>http://www.copters.com/aero/autorotation.html
>
>Hi Phil,
>
>Great link! Turns out I understood this stuff better than I thought I did.
>I've read plenty about the physics, just never seen it laid out this well in
>pictures. Thanks for posting it.

No probs, Steve.

Google is a wonderful tool. I typed in "autorotation" and that was one
of the first ones listed. :-)

Phil
--
I am so smart...S.M.R.T.
Homer J. Simpson

Phil Miller
August 5th 03, 12:50 AM
On Mon, 04 Aug 2003 02:36:31 GMT, Terry Spragg >
wrote:

>Well...

G'day Terry,

Did the page I pointed you to help at all?

>You also change the flight path.

Yeah.

>The blades need to see an updraught

Yep.

>to absorb power to spin, to generate lift somehow.

Not sure what this means?

>The change in direction of the airflow between a nose down
>attitude under power in a helo and a nose up, direction slightly
>down for autorotation makes the mechanical aoa at the hub
>different from the aoa of the airflow on the rotor.

Not sure what you mean by mechanical AoA at the hub, but the AoA of the
blades increases (more +ve), for the same pitch angle, with an upward
flowing airstream.

>I cannot claim any authority for this beyond personal
>experimentation, and my conjecture, apparantly widely debated if
>not misunderstood, seems in at least a common sense way to be
>true.
>
>A small toy illustrates a point which becomes intuitive. A stick
>twirled between the palms with rotor blades attached ascends
>until the energy stored on the rotor is consumed. The toy begins
>to descend rapidly. The rotor reverses and spins up. The descent
>slows dramatically.

ISTR from childhood playing with this type of device, but I don't
remember them reversing direction of rotation during flight. They would
descend as rpm decreased. Are you just doing a thought experiment and
extending the flight?

>The apparent wind on the blades must be at a + aoa to
>autorotate,

Yeah.

>even if the aoa at the reversed hub wrt the shaft may
>be -,

Do you mean the *pitch* is -ve because the rotor is now turning in
reverse?

>and the airflow presents a greater + to the reversed blade
>with as much - mechanical aoa as it was + rotating in the
>ascending phase, spinning it up by energising it, and with
>increase in apparent airspeed of the rotor the aoa becomes less +
>in regard to the flightpath of the blade arounds the hub, while
>being - to the airflow around the craft.

No. I lost it completely there. Are you saying that although the toy,
now spinning in reverse, seems to have a -ve pitch, it actually has a
+ve AoA because it is descending?

>Autorotation is a delicate balance, yes?
>One must fly the collective carefully to do autos.

As I understand it (and I never got that far in my (limited) experience
in helicopters), it's a matter of engine failure...collective to minimum
ASAP...leave it there until the correct height above the ground...pull
collective to flare. It's not a matter of adjusting the collective
during the auto. I stand ready to be corrected by those in the know.

As for gyroplanes, they will happily autorotate all day without any
means to vary the pitch collectively at all.

>It is a skill I cannot claim.
>
>The airflow changes from downward to upward on the rotor blades
>of the toy. If the hub rotation does not reverse, the +
>mechanical aoa of a powered nose up gyro becomes - wrt the
>airflow in the retreating blade,

No. And this is where you are striking trouble, I suspect. The AoA on
the retreating blade does not go -ve. In fact, if anything, the
retreating blade has a higher angle of attack than the advancing blade
(but that is another discussion). the rotor disk is tilted back, yes,
but the blade is doing several hundred miles per hour. The apparent wind
is several hundred miles per hour *in the direction of travel* (plus a
downward component). The direction of the craft has an influence, but
not as significant as I think you think.

>the flight path becomes
>downward, wrt apparent airflow to the craft now nose down wrt
>horizon, but still + in one sense, and - in another. In
>autorotation, part of the rotor's flightpath must be - aoa wrt
>the aparrent airflow on the blade.

I don't see what you mean. Unless you are thinking that the airflow
caused by craft movement is the apparent airflow. In an aeroplane this
would be the case, but an aeroplane's wings are not doing several
hundred miles an hour and creating their own apparent airflow.

>Watch the toy fly again. Meditate some more. Grok the universe.
>Be one with gravity.

Ooom...OOooommm...

>Is it possible to explain this in some other way? I can't seem to
>express it well. Perhaps a cartoon video is available somewhere?
>
>This is possibly a flawed intuit, and I cannot yet grasp it all.
>I am not a rotorhead, but have watched many autorotations from
>the tower at a helo flight school, complete with commentary from
>those "3 dimensional thinkers" that direct the traffic. As a
>control tower radio tech, I have had some "unofficial" flight
>training, er, perhaps I should say unofficial experience in fixed
>wing and rotor, and understand aerodynamics to an extent in model
>design and flight.
>
>If I claim to be a little perlexed, at least you must respect my
>honesty. In autorotation flight, part of the rotor disk must be
>in - air aoa, yes or no?

My vote? No.

Cheers,

Phil
--
Definitions of a pilot - No. 1

The average pilot, despite the sometimes swaggering exterior,
is very much capable of such feelings as love, affection,
intimacy and caring.
These feelings just don't involve anybody else.
US Navy Times

Rhodesst
August 5th 03, 05:43 AM
>>The change in direction of the airflow between a nose down
>>attitude under power in a helo and a nose up, direction slightly
>>down for autorotation makes the mechanical aoa at the hub
>>different from the aoa of the airflow on the rotor.
>
>Not sure what you mean by mechanical AoA at the hub, but the AoA of the
>blades increases (more +ve), for the same pitch angle, with an upward
>flowing airstream.

I think what they're refering to when they say "mechanical AoA" is blade
incidence.

Fixed wing aircraft generally have their wings set a some positive incidence
relative to the long axis (longitudinal) of the fuselage. The main reason for
this, as I understand it, is so the fuse will fly in a level attitude at cruise
while allowing the wing to fly at a positive AoA to produce the lift needed to
maintain flight. This positive incidence is fixed and cannot be changed or
adjusted by the pilot.

Helicopters, OTOH, adjust the incidence of their rotor blades through
collective and cyclic commands. In this case, the incidence is a measurement
of the angle of the rotor blade cord line relative to an imaginary line running
perpendicular (90 degrees to) the rotor mast. While changing the incidence of
the main rotor blades (through collective and cyclic commands) will change the
aerodynamic AoA, they are not the same thing. For example, if you could lower
the collective to a negative "incidence" (I'm not sure if full size helicopters
do this, I know that RC models do), the rotor blades would still be seeing a
positive AoA while in flight due to the steep descent angle.

FWIW,
Fly SAfe,
Steve R.

Phil Miller
August 5th 03, 08:11 AM
On 05 Aug 2003 04:43:37 GMT, (Rhodesst) wrote:

I wrote:

>>Not sure what you mean by mechanical AoA at the hub, but the AoA of the
>>blades increases (more +ve), for the same pitch angle, with an upward
>>flowing airstream.
>
>I think what they're refering to when they say "mechanical AoA" is blade
>incidence.

Yeah, I think you're right. Pitch angle (or angle of incidence).


Phil
--
Pfft...english! Who needs that? I'm never going to England.
Homer J. Simpson

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