Wanted: 2-33 left wing

"One immediate problem I see is that friction in the rotor axis would
tend to make the fuselage counter-rotate, and that would have to be
countered somehow. A secondary rotor out on the boom is what real
helicopters use, but that would be cheating in a glider model.

Johan Larson, mad-scientist wannabe"

Wait. You need to study helicopters. The tail rotor is called an
anti-torque device and is there to counteract the torque of the main rotor.
If someone shoots the tail rotor off, or the mechanism fails, you simply
reduce the throttle to zero (and drop the collective). It is called
autorotation. Once you go into autorotation, the main rotor continues to
turn, you are a heli-glider - and there is no torque developed by the engine
so the tail rotor is not necessary for anti-rotation. Of course there is a
minor problem in that the change in pitch of the tail rotor determines which
direction the helicopter is facing, but that is a minor detail.

If you are not careful hovering during certain wind conditions, you may end
up in an uncontrolled spin. At that point, you simply throttle the engine
down, try to put it down level, shut the fuel supply off and then try to
explain to the insurance company that it was not your fault. As soon as the
throttle is shut down, you stop spinning - or so the book says. I have not
tried it yet.

Colin

At 16:42 22 March 2006, wrote:

With that in mind, it should be possible to
design a helicopter that has no engine at all, but
is designed to come
down as slowly as possible.

Now, correct me if I'm wrong, (and I havent read the
previous listings either) but is that not what a Gyrocopter
basically is? I know it has a pusher engine, but there
is no engine driving the main rotor (apart from take
off I believe, to get the rotor moving)

So, presumably, once in the air, the blades turn as
a helicopter that is autorotating does. Just need to
have some high efficiency small Nimbus 4 'rotors' and
there you go...hover in the core of the thermal and
go up like a rocket!

Regards,

Someone who doesnt know what hes talking about (so
please enlighten me!)

Jono Richards wrote:
At 16:42 22 March 2006, wrote:

With that in mind, it should be possible to
design a helicopter that has no engine at all, but
is designed to come
down as slowly as possible.

Now, correct me if I'm wrong, (and I havent read the
previous listings either) but is that not what a Gyrocopter
basically is? I know it has a pusher engine, but there
is no engine driving the main rotor (apart from take
off I believe, to get the rotor moving)

So, presumably, once in the air, the blades turn as
a helicopter that is autorotating does. Just need to
have some high efficiency small Nimbus 4 'rotors' and
there you go...hover in the core of the thermal and
go up like a rocket!

Regards,

Someone who doesnt know what hes talking about (so
please enlighten me!)




I think your right and you beat me to it in replying. Tell you what,
I'll ask Ken Wallace at the weekend as he's a member of my aero club
[Shipdham in Norfolk] [Ken Wallace, auto gyro guru ala little nelly from
the James Bond film, grandson of Barnes Wallace etc ]and see if he
thinks its a winner.

The Bensen Gyroglider ? Any left flying ? Any one
flown one off-tow ?

Ian

COLIN LAMB wrote:
"One immediate problem I see is that friction in the rotor axis would
tend to make the fuselage counter-rotate, and that would have to be
countered somehow. A secondary rotor out on the boom is what real
helicopters use, but that would be cheating in a glider model.

Johan Larson, mad-scientist wannabe"

Wait. You need to study helicopters. The tail rotor is called an
anti-torque device and is there to counteract the torque of the main rotor.
If someone shoots the tail rotor off, or the mechanism fails, you simply
reduce the throttle to zero (and drop the collective). It is called
autorotation. Once you go into autorotation, the main rotor continues to
turn, you are a heli-glider - and there is no torque developed by the engine
so the tail rotor is not necessary for anti-rotation. Of course there is a
minor problem in that the change in pitch of the tail rotor determines which
direction the helicopter is facing, but that is a minor detail.

If you are not careful hovering during certain wind conditions, you may end
up in an uncontrolled spin. At that point, you simply throttle the engine
down, try to put it down level, shut the fuel supply off and then try to
explain to the insurance company that it was not your fault. As soon as the
throttle is shut down, you stop spinning - or so the book says. I have not
tried it yet.

That doesn't sound quite right. With the engine shut down, and the main
rotor spinning freely, there should still be some friction between the
rotor shaft and whatever mechanism attaches it to the fuselage. This
friction would be slowing down the rotor, and by action-reaction
causing the fuselage to rotate in the direction of the rotor. And if
there's no tail rotor, there isn't really anything to stop this
rotation of the fuselage.

I'm a bit surprised this isn't mentioned in the book, but at a guess,
the force is low enough compared to engine-torque to be dismissed in a
powered aircraft, since it is only relevant in a rarely-encountered
emergency situation. But in a glider-variant, it could well be
significant.

wrote:
That doesn't sound quite right. With the engine shut down, and the main
rotor spinning freely, there should still be some friction between the
rotor shaft and whatever mechanism attaches it to the fuselage. This
friction would be slowing down the rotor, and by action-reaction
causing the fuselage to rotate in the direction of the rotor. And if
there's no tail rotor, there isn't really anything to stop this
rotation of the fuselage.

Autogyros always have relatively large vertical stabilizers, I assume
this provides enough directional stability at normal airspeeds to
overcome the friction of the rotor bearings. The vertical stab(s) may
provide enough drag to prevent spinning at zero horizontal airspeed, but
I doubt real autogyros can be trimmed to fly that way for more than a
moment or two, even with the engine off.

Marc

That doesn't sound quite right. With the engine shut down, and the main
rotor spinning freely, there should still be some friction between the
rotor shaft and whatever mechanism attaches it to the fuselage. This
friction would be slowing down the rotor, and by action-reaction
causing the fuselage to rotate in the direction of the rotor. And if
there's no tail rotor, there isn't really anything to stop this
rotation of the fuselage.

I'm a bit surprised this isn't mentioned in the book, but at a guess,
the force is low enough compared to engine-torque to be dismissed in a
powered aircraft, since it is only relevant in a rarely-encountered
emergency situation. But in a glider-variant, it could well be
significant.

Well, the main rotor bearing in a small helicopter costs over $30,000 and
has a limited lifespan. They are good, low friction berings and need to be
so to avoid heat buildup.

I understand physics, but your basic premise is based upon friction. If
there is slight friction, then the mass itself of the fuselage would tend to
keep it in place - plus the small angled vertical fin. That provides all of
the stability necessary until you start powering the main rotor.

In any event, there are helicopter pilots who have had their tail rotor jam
or be completely shot off and they are still alive to tell you about it.
Maybe you should tell them why they should have spun to their death. And
neither the pilot operator's handbook nor the FAA helicopter mentions that
the helicopter will go into a death spin if the tail rotor fails.

By the way, I calculated that the Schweizer 300C has about a 2.5 to 1 glide
ratio according to the factory specifications, but could never reach that.
I was always under 2 to , but it may simply be poor gliding technique.

Colin

Ian Cant wrote:
The Bensen Gyroglider ? Any left flying ? Any one
flown one off-tow ?

Ian





When I visited the Udvar-Hazy division of the National Air and Space
Museum a couple of months ago I saw a W.W.II vintage, unpowered, folding
gyroplane designed to be carried aboard a U-boat and launched tethered
to the ship as an reconnaissance vehicle. I have a snap shot, but,
alas, it can't be posted here. If interested send me an e-mail and I'll
send you a copy.

Al

"When I visited the Udvar-Hazy division of the National Air and Space
Museum a couple of months ago I saw a W.W.II vintage, unpowered, folding
gyroplane designed to be carried aboard a U-boat and launched tethered
to the ship as an reconnaissance vehicle. I have a snap shot, but,
alas, it can't be posted here. If interested send me an e-mail and I'll
send you a copy."

These gyroplanes were not used very long as there was a flaw. If the pilot
saw and reported an enemy nearby, the submarine would release the gyroplane
and submerge. If they got in a hurry, they would submerge without
releasing. The entire project lasted only a few months if I recall.

I wonder if an allied pilot got credit for shooting down a tethered
gyroplane. The secret was probably to buzz the submarine and cause it to
release the gyroplane, then shoot down the gliding gyroplane - after all it
is an aircraft.

Colin

Actually, Bensen developed several Gryogliders. The first was the B6 in
1953. They were designed to be towed by a car to 150 feet or so, and
then released. He also developed a version on floats that was towed by
a boat.