The high power to weight ratio of the Mazda Wankel rotary engine and low
fuel
consumption compared to a small turbo prop engine combined with carbon
fiber
construction has made practical scaling down old vertical take off
aircraft
designs that did not enter production in the 1960's. Certain very
fortuitous
things happen when you are able to take off vertically. The first thing
that
happens is; it is no longer necessary to have a lot of wing area to take
off
and land. Wings are heavy as the bending load on the wing spar is high. A
lot
of weight can be taken out of the wing as the span and wing area are
limited
to only enough to keep the vehicle airborne at high speed. The cost of the
aircraft compared to conventional aircraft is reduced due to less raw
material
required. Read carbon fiber.


This class of aircraft has a bright future. Man has dreamed of taking off
from
his back yard and flying someplace at high speed for a long time. Tilt
rotor VTOL
has made that dream come true. In my opinion the tilt rotor will replace
the
helicopter and take some conventional aircraft sales. This will be due to
a higher
cruise speed at a the same fuel burn. The helicopter will go the way of
the Dodo
bird IMHO. It won't happen overnight of course. It will take many years.

No discussion on the controversial V22 tilt rotor would be complete
without a
discussion on Vortex Ring State or VRS for short. A big deal has been made
about
the V22 Osprey's 47 degree blade twist and how it affects the Vortex Ring
State.
The V22 can roll over if one blade stalls and the opposite  blade does not
stall.
Special landing techniques have been devised to overcome the problem
namely by
limiting the decent rate to 1000 FPM. We are not affected to the same
extent as
the V22 is to VRS as we have only one rotor axis. However fixed blade
twist
negatively affects the efficiency of the rotor in the vertical take off
mode.

Unlike a helicopter, high blade twist is necessary in a tilt rotor to get
good
propeller efficiency at high speed. This high twist can cause blade stall
in
the vertical landing mode. I also suspect it affects the ability of the
V22 to
auto rotate. What the V22 Osprey critics don't realize is an off the shelf
variable twist propeller blade is already on the market and has been
proved
to work. Namely the IVO. Thousands have been sold over the past ten years.

http://www.ivoprop.com/

The tip of the rotor needs only change from about 30 degrees at 300 MPH to
10 degrees at takeoff. This is achieved by the stiff six foot long carbon
fiber torque tube.

The root needs to change from about 70 degrees at 300 MPH to about 10
degrees
at takeoff. This amount of twisting is done over a rotor length of about
six feet.
Glass fiber is used for the blade proper because it has a low modulus of
elasticity
and twists easily. Glass fiber is used for the hub for the same reasons.

http://www.rotaryeng.net/VTOL.html

The picture of the damaged IVO has nothing to do with a prop failure.
It merely shows what the inside construction of the IVO looks like. It
shows the
stiff 4130 steel torque tube. The crash was caused by something else.


Alex please pass this on to your buddy Ivo and set up a meeting for you
and me.
--
Paul Lamar ...No rotor no motor.

I usually stay out of these conversations; however, I thought I'd throw in
my two cents regarding the demise of helicopter in favor of the tilt rotor
aircraft.

First, I think that if they can get a reliable tilt rotor aircraft into
regular production, especially one capable of carrying significant numbers
of passengers, it will represent one of the more major advances in recent
aviation history.

Having said this, I question the conclusion that the helicopter will
eventually vanish into oblivion.

The two aircraft really aren't designed for the same mission.

The helicopter is basically used for two types of missions, one for which
it is well suited and another less so.  The first is for working for
extended periods of time in a relaltively limited area.  Logging is one
classic example.  The other, EMS and short range transportation is really
not its forte'.  Nobody reasonable has ever claimed a helicopter's strenth
is cross country flights.

The tilt rotor, on the other hand, targets missions that load up, take off
vetically, reach their destination quickly, and then land vertically.  It
really isn't designed to hover around for extended periods of time.

Hence, I believe they will coexist, each doing what they do best.

George Lazik


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