Keith W

The gyroscopic forces on the blades when changing changing axes is minimal as it is
done over a relative long period of time. In contrast a propeller  changes axes
in an airplane at about 60 degrees per second during a stall or spin. The tilt
rotor does 90 degrees change in 20 or 30 seconds.

Perhaps a small electric motor could be added to orient the blades in an impending
crash.

It is not just that it flies 100 MPH faster. It flies much much higher and much much further
than any helicopter.

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

"No discussion on the controversial V22 tilt rotor would be complete without a discussion
on Vortex Ring State or VRS for short. An issue has been made about the V22 Osprey's 47
degree blade twist and how it affects the Vortex Ring State. 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.

The V22 can roll over if one rotor stalls and the opposite side rotor does not stall.
Special landing techniques have been devised to overcome the problem namely by limiting
the decent rate to 1000 FPM.

What the V22 Osprey critics don't realize is an off the shelf variable twist rotor
blade such as we are proposing above is already on the market and has been proved
to work. Namely the IVO. Thousands have been sold over the past ten years.

Contact IVO and see if they will build a variable twist rotor for your needs.
http://www.ivoprop.com/ if I were Bell/Boeing I would be looking long and hard at
this option for the V22 rotors.

We are not affected to the same extent as the V22 is to VRS as we have only
one rotor axis. However blade twist negatively affects the efficiency of the
rotor in the vertical take off mode. Never the less Boeing is working on their
own system of variable blade twist. Here is a graphic that gives some
estimated performance improvements."

I believe for every proplem there is an answer. Just like the Wright brothers.

-- 
Paul Lamar ...No rotor no motor.

Paul,
Looks like Keith has a strong opinion on the subject and that's OK, he might
be right with some issues, however I believe that with small aircraft, some
of the prop strike issues can be overcome with longer landing gear.
I find all points of view interesting, it's all grist for the mill.
George (down under)




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