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Gyrocopter Speed



 
 
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  #1  
Old March 24th 05, 06:25 AM
Mark
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Default Gyrocopter Speed

I have some basic questions about speeds of gyrocopters.

(Please forgive me if my questions are kind of basic. I'm currently working
on my private pilot for airplanes, with long term goal of getting into
gyros. I have a few hours time in gyros, but not enough yet to know what
I'm talking about.)

Why is there such a wide range of max/cruise speeds for gyros? I notice a
Barnett BRC540 2 place cruises at 110 with a top speed of 138.
An RAF Cruises at 70 with a max of 100.
Most single places seem to cruise between 45 and 80.

Why aren't there more fast single place gyros?

Other than a bigger engine, why can a Barnett go 138 compared to RAF's 100?
What characteristics give it the stability to safely go faster? And why
wouldn't they design those characteristics into other gyros?

If I have a design of a stable gyro that cruises at 50, what would prevent
me from safely adding a bigger engine, re-doing my hang test, and flying at
80 (for example).

If I build a gyro from a kit or plans, when I fly it how can I tell when I'm
going faster than I safely should? (Other than reading designer's specs.)
Do all gyros have a characteristic "feel" when getting to the edge?


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  #2  
Old March 24th 05, 07:01 AM
SHIVER ME TIMBERS
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Mark wrote:

I have some basic questions about speeds of gyrocopters.


Welcome to the group.

With any luck the group's resident expert on gyrocopters will show up
and give you good solid advice on this subject.

Oh Mr. Sandy - Eggo - where are you.
  #3  
Old March 25th 05, 03:13 PM
Stuart & Kathryn Fields
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Mark: Way back in the 60's I had a Benson gyro with a 90hp Mac engine with
a Dwyer wind speed gauge that used a small ball floating in a vertical tube
with the ram air entering the bottom and would push the ball up. The
readings stopped at 85mph but had another few inches of tube above the 85.
I can remember one high speed pass, and I'm not sure that I was really at
full throttle, that stuck the ball all the way at the top of the tube and I
had to take a pipe cleaner to push it back down. Looking at the scale we
estimated at least 105 -115. Maybe more with the ball being stuck. I now
think that I was seriously "Kicking the Bull Dog" and am lucky I didn't
discover a stalling blade or some other aerodynamic entertainment.

--
Stu Fields

"Mark" mark wrote in message ...
I have some basic questions about speeds of gyrocopters.

(Please forgive me if my questions are kind of basic. I'm currently

working
on my private pilot for airplanes, with long term goal of getting into
gyros. I have a few hours time in gyros, but not enough yet to know what
I'm talking about.)

Why is there such a wide range of max/cruise speeds for gyros? I notice a
Barnett BRC540 2 place cruises at 110 with a top speed of 138.
An RAF Cruises at 70 with a max of 100.
Most single places seem to cruise between 45 and 80.

Why aren't there more fast single place gyros?

Other than a bigger engine, why can a Barnett go 138 compared to RAF's

100?
What characteristics give it the stability to safely go faster? And why
wouldn't they design those characteristics into other gyros?

If I have a design of a stable gyro that cruises at 50, what would prevent
me from safely adding a bigger engine, re-doing my hang test, and flying

at
80 (for example).

If I build a gyro from a kit or plans, when I fly it how can I tell when

I'm
going faster than I safely should? (Other than reading designer's specs.)
Do all gyros have a characteristic "feel" when getting to the edge?




  #4  
Old March 31st 05, 05:57 PM
Kevin O'Brien
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Default

On 2005-03-24 01:25:19 -0500, "Mark" mark said:

Why is there such a wide range of max/cruise speeds for gyros? I
notice a Barnett BRC540 2 place cruises at 110 with a top speed of 138.
An RAF Cruises at 70 with a max of 100.


You mean, these are the advertised speeds. Not many Barnett 540s are
flying. There are a number of gyro speed records; I recommend you go to
fai.org and look them up.

Gyro speed is limited by drag. A rotor in autorotation is a draggy
thing. Most gyro fuselages are either designed without any
considerations but function, or are styled without a thought for
aerodynamics. Aero costs money and most gyro firms are in a
hand-to-mouth mode.

Most single places seem to cruise between 45 and 80.

Why aren't there more fast single place gyros?


Take a look at the tractor Little Wing. That holds a number of speed
and distance records. It is plansbuilt, although you can purchase the
frame tack- or finish-welded.

Other than a bigger engine, why can a Barnett go 138 compared to RAF's 100?


Well, with who-knows-how-many Barnetts flying, I would like to see
proof it does go that fast before accepting the number.

IMHO an RAF at high speed -- which is around 100 -- is in a hazardous
flight regime.

What characteristics give it the stability to safely go faster?


Gyro stability is a very large can of worms, largely because one large
maker believes it's all voodoo or myth, and not a matter of science. So
forgive me if I don't go there.

And why wouldn't they design those characteristics into other gyros?


If you want speed, you don't want a gyro. It's just that simple.

If I have a design of a stable gyro that cruises at 50, what would
prevent me from safely adding a bigger engine, re-doing my hang test,
and flying at 80 (for example).


Engine is only part of your powerplant. There's the propeller. A lot of
guys got killed because Rotaxes replaced Macs as powerplants. And they
could drive a longer prop, but the prop wouldn't clear the runway. So
the whole engine was moved up. or the gearbox flipped. Raising the
thrustline relative to the vCG, and resulting in PPO (bunt over). This
is normally an unsurvivable mode.

Everything you change in a gyro affects all the other components in a
system as well as the system as a whole, and often (unless you have a
bunch of knowledge and experience, and sometimes still even then!) in
unexpected ways.

For more on gyros read:

(1) FAA's Rotorcraft Flying Handbook, including all the helicopter
stuff at the beginning (the gyro stuff assumed you understood the helo
stuff). Available for free on the FAA website as a .pdf, or for money
from the GPO and booksellers in the dead-trees edition. (google
"Rotorcraft Flying Handbook" site:faa.gov to find the .pdf).

(2) www.rotaryforum.com, which is a web based rotorcraft forum with a
strong gyro bias. There is a little bit of good information on the PRA
website www.pra.org and will soon be more (the site is being redone).

cheers

-=K=-

Rule #1: Don't hit anything big.

  #5  
Old March 31st 05, 10:42 PM
Steve R.
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"Kevin O'Brien" kevin@org-header-is-my-domain-name wrote in message
news:2005033111575992791%kevin@orgheaderismydomain name...
On 2005-03-24 01:25:19 -0500, "Mark" mark said:


If you want speed, you don't want a gyro. It's just that simple.


Or any rotorcraft for that matter. Sure, some helicopters are much faster
but none (or at least, very few) of them are really close to even the
average general aviation fixed wing and certainly no contest for "many" of
the experiemental fixed wing kits around.

Fly Safe,
Steve R.


  #6  
Old April 1st 05, 05:58 AM
Steve R.
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"The OTHER Kevin in San Diego" skiddz "AT" adelphia "DOT" net wrote in
message news

You mean I can't screw holes in the sky as fast as a Lancair??


Well, maybe once! :-D

Fly Safe,
Steve R.


  #7  
Old April 5th 05, 08:18 AM
Kensandyeggo
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Default


Mark wrote:
I have some basic questions about speeds of gyrocopters.

(Please forgive me if my questions are kind of basic. I'm currently

working
on my private pilot for airplanes, with long term goal of getting

into
gyros. I have a few hours time in gyros, but not enough yet to know

what
I'm talking about.)

Why is there such a wide range of max/cruise speeds for gyros? I

notice a
Barnett BRC540 2 place cruises at 110 with a top speed of 138.
An RAF Cruises at 70 with a max of 100.
Most single places seem to cruise between 45 and 80.

Why aren't there more fast single place gyros?

Other than a bigger engine, why can a Barnett go 138 compared to

RAF's 100?
What characteristics give it the stability to safely go faster? And

why
wouldn't they design those characteristics into other gyros?

If I have a design of a stable gyro that cruises at 50, what would

prevent
me from safely adding a bigger engine, re-doing my hang test, and

flying at
80 (for example).

If I build a gyro from a kit or plans, when I fly it how can I tell

when I'm
going faster than I safely should? (Other than reading designer's

specs.)
Do all gyros have a characteristic "feel" when getting to the edge?


  #8  
Old April 5th 05, 08:20 AM
Kensandyeggo
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Posts: n/a
Default


Mark wrote:
I have some basic questions about speeds of gyrocopters.

(Please forgive me if my questions are kind of basic. I'm currently

working
on my private pilot for airplanes, with long term goal of getting

into
gyros. I have a few hours time in gyros, but not enough yet to know

what
I'm talking about.)

Why is there such a wide range of max/cruise speeds for gyros? I

notice a
Barnett BRC540 2 place cruises at 110 with a top speed of 138.
An RAF Cruises at 70 with a max of 100.
Most single places seem to cruise between 45 and 80.

Why aren't there more fast single place gyros?

Other than a bigger engine, why can a Barnett go 138 compared to

RAF's 100?
What characteristics give it the stability to safely go faster? And

why
wouldn't they design those characteristics into other gyros?


Kevin O. answered everything perfectly. 138 in a gyro? I'd have to
see that. A McCulloch J-2 with a 180 horse Lyc only cruises at around
80, despire the old brochure claims of 95.

If I have a design of a stable gyro that cruises at 50, what would

prevent
me from safely adding a bigger engine, re-doing my hang test, and

flying at
80 (for example).

If I build a gyro from a kit or plans, when I fly it how can I tell

when I'm
going faster than I safely should? (Other than reading designer's

specs.)
Do all gyros have a characteristic "feel" when getting to the edge?


  #9  
Old April 5th 05, 08:23 AM
SHIVER ME TIMBERS
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Posts: n/a
Default

Kensandyeggo wrote:

Nothing that I could see.

------------------------------------------------------------------------

Long time no hear from Mr. Eggo.

Was kinda wondering what you were up to these past few months.

I kinda dropped out of the newsgroup scene for a while but I'm back,
just kinda lurking and enjoying Kevins stories about the day in the
life of a helicopter pilot trainee.

So are you and the bottomless pit still doing your burger runs to the
outlying areas.... or what.?????

Curious minds always want to know.
  #10  
Old April 5th 05, 05:39 PM
Kevin O'Brien
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Default

On 2005-04-05 03:20:13 -0400, "Kensandyeggo" said:

Kevin O. answered everything perfectly. 138 in a gyro? I'd have to
see that. A McCulloch J-2 with a 180 horse Lyc only cruises at around
80, despire the old brochure claims of 95.


And not to pile on, but Carter Aviation Technologies claimed that their
CCTD would be good for 400 kt (I believe) on a six-cylinder auto motor.
The 3.8 six has been replaced by a 5.7 eight making ~380 HP and they
are flying at about 160 mph -- not knots.

They will go faster, I am sure. But I don't see 400. And they get speed
by unloading and slowing the rotor, and flying on lift from the wings.
The concept of the CCTD is to use the rotor not as the principal
lifting surface but as the mother of all low-speed lift-enhancing
devices on what's functionally a fixed-wing in cruise.

An experienced gyro entrepreneur is claiming 150 for a new design of
his, to be introduced next week. I believe that RAF claims 100 for the
RAF 2000 GTX SE. That's as credible as the fourteen year olds who write
into Road and Track about their imaginary Ferraris.

Gyro designers and marketing operations used to be mostly on the
up-and-up. Then came Dennis Fetters and the first Air Command (I have
to stress that the current Air Command is a whole different operation,
that makes a safe gyro and as far as I know sells it honestly).
Dennis's gyro had the best specs in the industry, thanks to Dennis's
skills.

Skills at typing press relases and performance charts....

Unfortunately, when his numbers got loose in the wild, people believed
them. "Gee, why would I buy a gyro that cruises at 65 when this Air
Command goes 110?" That set off an arms race of spiraling, bogus
performance claims. For other gyro makers, none of whom ever got rich
at this thing, it was "lie or die." I think many of them don't even
KNOW what the true performance numbers of their sheenry is.
(I can only think of one gyro manufacturer that has actually
instrumented a test aircraft the way, well, professionals do). Not
meaning to dampen anyone's ardour for gyros, they're great fun and safe
as houses with a little training and judgment (some are safer than
others to be sure). Just trying to get things onto a factual basis. I
would not trust the Barnett 138 nor the RAF 100 (RAF's can go that
fast, but it is not IMHO in a safe flight regime at that point).

cheers

-=K=-

Rule #1: Don't hit anything big.

 




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