BDH ultralight helicopter
Carl Grillmair
Howdy
A relative of mine in Germany sent me a newspaper picture of a small
helicopter in built by a Japaneese engineer. The machine had the engine
above the pilot's head, just below the rotor disk. I could see no sign
of an anti-torque mechanism and assume that rotor torque was provided by
tip-ducting, though the newspaper photo cut off the tips of the rotors.
The pilot sat in a minimalist chair with two armrests/consoles,
suspended above a tripod landing gear with plastic wheels. The caption
said the machine would appear at Oshkosh.
Anyone here know anything more about this machine?
Thanks,
Carl
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Carl J. Grillmair Jet Propulsion Laboratory
Mail Stop 183-900
ca...@grandpa.jpl.nasa.gov California Institute of Technology
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John Briggs
Carl Grillmair <ca...@grandpa.jpl.nasa.gov> wrote:
>Howdy
>
> A relative of mine in Germany sent me a newspaper picture of a small
>helicopter in built by a Japaneese engineer. The machine had the engine
>above the pilot's head, just below the rotor disk. I could see no sign
...
>
>Anyone here know anything more about this machine?
This, maybe? But this has contra-rotating rotors. Anyway, I saved it
two years ago off the net:
08/31/95 02:51
From: ro...@gol.com To: ALL
Subj: Ultralight strap-on helicopter Area: rec.aviation.ultralight
I recently posted this message to rec.aviation.rotorcraft but I
thought it might raise some interest here, too.
If you read the series of notes under this title on the ultralight
mail list in February/March of this year you might want to skip down
to the last couple of paragraphs of this posting--I've added some new
stuff there but the first part is a rather lengthy recap. for new
readers.
I was at the Tokyo Aerospace Exhibition last February and saw what
looked like a canvas-webbing chair with a small two-stroke engine on
the back and supporting twin rotors above it. It was billed as a
strap-on helicopter. The two rotors are contrarotating, so torque is
balanced--no need for tail boom/rotor, etc. Pitch is fixed, so
ascent/descent are throttle controlled. I've kept in touch with the
developer and here is a summary first of what I learned then and what
I heard recently after six months of further development. The rotors
were only 3m across (about 10 feet for the metrically challenged) and
close together. As you can imagine, they were completely rigid! They
use some ultrahigh-tech carbon-fiber winding technique and are by far
the most expensive part of this machine. Well, the contrarotating
drive is not cheap, either, and pretty high-tech itself.
The engine then was basically two, horizontally opposed two-cylinder
two-stroke engines running on 25:1 gas:oil mixture. Each had
independent fuel lines and was separately linked to the drive shaft by
a centrifugal clutch arrangement so that either could fail while the
other continued to drive the shaft. The basic engine has quite a long
development history (over 25 years) but is a very high-tech
implementation of the original design, which was created by one of
Japan's top post-war auto-engine designers, a Tokyo University
graduate who has acted as a consultant for much of Japan's post-war
auto industry development. In the two-cylinder version it weighs 2.8kg
and develops 10PS (one PS very nearly equals one HP).
The engine on the current version is not a highly tuned version, so
further tuning could make a bit more power available. It uses THREE
pairs of cylinders, i.e., three essentially independent engines. It
generates 30PS from something under 10kg (22.4lb), and power can be
taken off it at either end. (An aside: that makes it look to me as if
it might be nice for true FAR103 ultralights in either pusher or
dragger configuration.) The developer says it is very fussy over the
oil to be used with the gasoline.
The simple webbing chair has been replaced by a rudimentary kind of
undercarriage. Difficult to explain without a diagram (I'm going to
get some videos of it maybe next week) but when you stand up, you lift
the whole thing including undercarriage off the ground. When you sit
down, the undercarriage bears your weight. This configuration is to
get it classed as a foot-launched device, virtually unrestricted in
Japan, but to allow you to land on the undercarriage wheels if you'd
rather THEY took any landing shock. I would certainly prefer this (!)
The weight of the whole thing is about 55kg (subject to confirmation,
but that's what I recall), so it's well within FAR103.
New in the last six months is not only the extra pair of cylinders,
which allow it to lift a 160kg weight and to provide a controlled
descent when one engine has failed and a "reasonably soft landing"
(whatever that means) when two out of the three have failed. The
"softness" depends on the weight of the pilot... <grin> So 245lb guys
who want to fly an ultralight helicopter should be OK as long as two
of the three engine units are firing.
Also new is the, er, rudder. The original idea was to gently brake one
of the rotors, unbalancing the torque as to rotate the craft. This is
too slap-bang. The thing spins like a top without much control over
the eventual direction it points. The idea now is to have a vertical
tail fin attached to the back of the "chair" in the downdraft from the
rotors. Slight angling of a control surface on the fin performs nicely
to change direction.
Control is by handlebars hanging from the rotor assembly. Pull back to
move forward, push forward to move backwards. OK, the guy knows that's
counter-intuitive but he says flying this thing is so unlike anything
else he's ever flown (and that's a lot, including helicopters,
gyrocopters and various fixed wing) that habits don't seem to get
carried over to it. Others with less variety of experience might feel
differently. (I didn't find many habits carried over from a de
Havilland Tiger Moth to a Paraplane.)
Max non-redline revs are 8,500, and the thing lifts strongly at
anything above 6,500rpm (could require higher for someone heavier than
the slightly built Japanese test pilot). There is an automatic
idle-advance function so that if an inexperienced pilot throttles
right back he or she won't drop out of the sky. This is set at
6,000rpm--a gentle sink--and there is, of course, manual overide so
you can lose height quickly if you really, really want to.
There is a ballistic parachute attached to the tail fin which at the
moment unfortunately means that if it deploys, you're going to be
hitting the earth face down. There is also a rotor brake that goes
into action immediately after the parachute has deployed, and one
thing the developers are considering is making the tail assembly
hinged so that it and/or the parachute lines can pass through the now
stationary rotors and enable a parachute landing in proper seated
position with the undercarriage taking any shock. I just hope they get
the safety interlocks between parachute deployment and rotor brake
right!
He greatly disappointed me by saying they would probably sell this in
the US before attempting to sell it in Japan, which is where I am.
He's had over 100 people wanting to buy one (one 747 captain wanted to
buy a set of four, one each for his entire family including two
kids--he said it would be cheaper than buying a four-seater helicopter
and give them independent mobility into the bargain), but many of them
are saying crazy things like "Yeah, I could take off from my back
garden and be at the golf club in less than an hour" neglecting the
fact that this would involve flight over cities. And Japanese cities,
in case you didn't know, are very, very closely built up (try finding
a park or open site big enough to land in? you'd have to be very
lucky!). Must say it had occured to me that it would be a lot more
fun--and faster--than my own one-and-a-half-hour's commute into
central Tokyo. But at least *I* know that's impractical!
On the other hand he has concerns that people in the U.S. wouldn't
believe his warnings about the need for specific types/grades of oil
for the two-stroke mixture and might experiment with disastrous
results. How about it, readers? The mean-time between overhauls on the
engine is conservatively set at 300 hours but he thinks this might be
increased to 500 by the time they are selling these things.
Next week I'm dropping by the office with my daughter to see some
video footage and maybe help with making an edited version to send
people who show interest, so if you have any questions and I get them
either via this newsgroup or E-mail, I'll ask'em. Replies will go to
the group, not individually (I have a business to run).
I have no personal financial interest in this project, and I know very
little more than I've posted here. I do know it's not going to be
cheap. How about list price of 30,000 US dollars? <gulp> However, it
really excites me and I'm determined to be a customer. Anybody else
interested?
Roger
Roger D. Williams
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History Will Absolve Me
John Briggs (jebr...@goodnet.com Phoenix, Arizona, USA)
Jim
> I have no personal financial interest in this project, and I know very
> little more than I've posted here. I do know it's not going to be
> cheap. How about list price of 30,000 US dollars? <gulp> However, it
> really excites me and I'm determined to be a customer. Anybody else
> interested?
>
> Roger
Great post Roger, and very interesting. That $30,000. price tag will
guarantee total failure in the USA if it ever gets here. Its a good idea
though.
Just an opinion mindya
Jim
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Just an opinion mindya
Now a Tailwind owner...YES!!!
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Gerald Lopez
: A relative of mine in Germany sent me a newspaper picture of a small
: helicopter in built by a Japaneese engineer.
thanks for starting this thread Carl and for those who followed up too.
I saw the german newspaper article in question and was also intrigued.
I wanted to find a URL for you guys but was unable to. What I can tell
you is that the japanese pilot in the pic was wearing a HUGE smile!
gerry