Kevin: As a retired engineer, I agree that you can't eyeball the vertical
c.g. But when you see a picture of a Magni with Greg on board who darn sure
weighs more than 200# and you can roughly eyball a thrust line from an
extended line perpindicular to the prop and that line comes thru Greg higher
than his chest, I'm not going to give you vertical c.g. to the 1 or 2 " but
I would have a hard time believing that the vertical c.g is not going to be
more than a couple of inches below the thrust line. I do agree that CLT
will make a safer ship. I don't agree with all of the emotional shouting
that the non CLT ships were unstable and dangerous. Too many people are
still successfully flying them.
BTW have you ever looked at the accident rate for CFI(G)? I've personally
seen some of the dumbest flying comitted by CFIs. Maybe this is a case if
you can't do teach? I totally agree that if you can find a Good CFI, it is
a whole lot safer and more expedient than self teaching. That said, I
recently flew a 300# single seat helicopter owned by a man who self taught
in the same helo. He could have gotten dual in a R-22, Bell 47, Schweitzer
300, or even a Brantly. Very little of the muscle memory derived from any
of these ships would translate to his tiny ship. A personal friend got his
ticket in a Bell 47 and had he tried to then solo his Safari, his checkout
pilot said he would have crashed. Similar problems were encountered in
training in an RAF then solo your ultralite gyro. I don't have much time in
a two seat gyro, but I did get the controls on the Sparrowhawk prototype and
it didn't fly anything like my Benson. Had I gotten dual in that ship and
then tried to fly my Benson I would have been unlearning a bunch of learned
Sparrowhawk responses.
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478
(760) 408-9747 general and layout cell
(760) 608-1299 technical and advertising cell

www.vkss.com
www.experimentalhelo.com


"Kevin O'Brien" kevin@org-header-is-my-domain-name wrote in message
news:2005042521441716807%kevin@orgheaderismydomain name...
On 2005-04-25 15:37:56 -0400, Peter Wendell
said:

Even a true CLT machine will only be precisely CLT at one specific
load.

Quite true, and as you write it is the size of the moment arm that
makes the difference. The arm on an RAF is over a foot! I would guess
on Dennis-era Air Commands ("classic" to use his term!) it's about six
inches.

In re your discussion with Stu about Magnis, I'd like to state that you
just flat can't eyeball vertical centre of mass. It needs to be
measured.

It *is* possible to design an aircraft with a high thrustline that has
little or no pitch change with application of power (I am told the
SeaStar Amphibian kitplane is one such). Just like it is possible to
design a fixed-wing aiircraft that requires little or no trim change
when adding or subtracting power (the B-17 is one such). In both cases
it is extremely difficult to do, and so it is rare. Most airplanes with
a high thrustline (mostly amphibians and ultralights with high-mounted
engines) exhibit significant pitch change with power. But then, pitch
change can't unload their wings and cause them to flap -- not so a
teetering rotor.

There are lots of folks that have flown many hours in unstable gyros.

Yep. Some instruct in them: basically all the RAF factory guys, plus
guys in their orbit like Dofin Fritts and Jim Logan to name two good
instructors (yes, Dofin got his pee pee whacked and spent a year on the
beach for breaking a rule. I bet he isn't going to break that rule any
more).

There are also too many that didn't make it.

Bingo, Peter.

The fact is that we now know how to build much safer gyros that are
also much easier to fly. And we don't have to give up any speed or
manuverability in the process. So, there is absolutely no reason not to
do it.

Bingo again. See, Peter, Stu, even Dennis: if you GAINED anything from
a high thrust line, you could make a credible argument that the risk
was worth the benefit, that it was a worthwhile compromise. But the
claims made for un-stabbed and non-CLT gyros vice stabbed, CLT ones are
unconvincing.

Combine this with the availability of high quality dual instruction,
and there's no reason that gyros can't acheive a safety record equal
to, or better than, airplanes.

Well, you can lead a horse to water but you can't make him drink. We
are still having guys teach themselves to fly, or almost teach
themselves. Crunch. More troubling, we have had some relatively
low-time, but licenced and well-taught, guys prang, some fatally.
That's part of what worries me -- there's always going to be the guy
who will just go fly, and he is the bane of every CFI/BFI/AFI and
manufacturer's existence.

That syndrome, I think, is why Dennis withheld tail rotor gearboxes (I
believe that was the part) from his helicopter customers until they
could demonstrate training. Both helicopters and gyros can kill you
dead without specific class and category training. (Type-specific is
better if you can).

There are many old timers who followed the Bensen method. The problem
with that is that while the graduated self-instruction method in his
manual seems to work if painstakingly followed, most pilot-wannabees
haven't the patience and self-discipline to follow it. A Bensen B8M of
course had far less energy than the gyros of today -- with its wooden
blades and optimistically-rated 72 HP Mac (more like 40 HP!) it could
just barely kill you (although NTSB records from the period of peak
Bensen popularity shows that it did, frequently).

I have only ever flown Near CLT gyros, but have learned much from those
who learned on machines like yours and who find the current generation
of stable gyros to be superior in every wa

In the end the ASTM subcommittee working on gyro consensus standards
did not require any particular way of meeting the stability standard,
but did set a stability standard and required it to be demonstrated in
flight test. I do not believe an unmodified HTL gyro can pass that test.

--
cheers

-=K=-

Rule #1: Don't hit anything big.