Date: Thu, 28 Apr 2005 22:29:14 -0400
To: WSFA members <WSFAlist at WSFA.org>
From: "Mike B." <omni at omniphile.com>
Subject: [WSFA] Re: Alternative reality v SF
Reply-To: WSFA members <WSFAlist at WSFA.org>

At 08:43 PM 4/28/05 -0400, Ted White wrote:

>> barrier twice on every revolution anyway.  The "X-wing" design is another
>> way to have both vertical takeoff and high speed level flight...basically
>> you stop the helicopter blades once you are up and moving, and lock them in
>> a "X" shape so they act as fixed wings.  Don't know if they've actually
>> built one of these yet or not.
>
>Sounds like an old autogyro, although I believe its unpowered overhead
>blades freewheeled.

The X-wing isn't an autogyro.  It's a helicopter (powered variable pitch
blades with the usual vertical takeoff, hover and fly in any direction
abilities) that can convert in flight to a fixed wing aircraft that just
happens to have two forward swept and two rear swept wings mounted above
the fuselage.  Looks like they did build a prototype:

http://avia.russian.ee/vertigo/sik_x-wing-r.html
http://www.fotosearch.com/CRT132/005615wm/

Some discussion about it here, with some more pics of other designs:

http://forums.x-plane.org/lofiversion/index.php/t12039.html

An Autogyro isn't a helicopter, though it looks like one if you don't
inspect it too closely.  The rotor is generally not powered, though some
have a small motor to spin the blades up to decrease takeoff run or
temporarily connect the thrust motor to the rotors to pre-spin them or do a
"jump" takeoff (really small ones, like the Bensen Gyrocopter, are often
spun up by the pilot's hand giving them a push).  The rotors are spun in
flight by the airflow through the "disk" resulting from forward motion, and
once moving provide lift.  There's generally a pusher prop, though some
have a tractor arrangement, to provide the forward motion.

Autogyros can have really short takeoff and landing runs, even vertical
takeoff in some models, but they can't hover and most can't takeoff
vertically.  A typical run for a single-seat small model might be 20'-50',
where a similar size airplane might need 200' or more even for a STOL
design.  They do suffer from the same speed limitations as helicopters
though...which isn't an issue for the small personal type where the pilot
is basically sitting in a bucket seat bolted to an aluminum 2x4.  45-90mph
is plenty fast enough for that!  ;-)

Theory of operation, history and some pics are here:

http://www.jefflewis.net/autogyros.html

-- Mike B.
--
A clean desk is a sign of a cluttered desk drawer.