A148

DESIGN: AeroVantage - PropRotor

Consider Using Gimbaled Rotors: This might become a separate page under the 'Hub' heading.

Reasons.

The collective could be by a mechanism similar to that which is proposed for DESIGN: AeroVantage ~ PropRotor - Hub - 2x4 Layout.

On a scale version, such as a UAV, rotor speed change may be a substitute for collective.

The longitudinal cyclic already exists in the pivoting portion of the transition mechanism.

The lateral cyclic is the only significant addition. See; AeroVantage ~ Trim, Stability & Control - Stability

The rotational inertia of the rotors should be relatively low since the motor's weight is concentrated at the center. In fact, the negation of the swashplate and actuators etc. from the rotor's mass will also help.

The longitudinal and lateral rotation will result in controllability being slower than that of the swashplate, but gyros should handle the stability concern.

A scale model might serve as a fast and cheap prototype for initial development and evaluation. Build a RC flying-wing and add propellers, plus transition and gimbal servos?

Coaxial Proprotor:

Patent:

5,381,986, Wingtip mounted, counter-rotating proprotor for tilt wing aircraft. Jan 17 1995, McDonnell Douglas Helicopter Co. Have hard copy.

Wild Idea:

Mission Selectable Blades:

Have two sets of quick change PropRotor blades. The removable blades will assist in storage, particularly if the wings are removable or foldable.
The primary reason is that one set of blade is optimized for cruise (high speed or long distance) and the other set is optimized for hover (high lift and long loiter time). The electronic control (computer controller) would be selectable for either of two programs; one to suit each of the blade sets.
This would be for the AeroVantage, but it could be applicable to any PropRotor type of craft.

Positive Pitch of the PropRotors during Cruise:

Would it make sense to give the fore and the aft proprotors a positive pitch at an angle up to the pitch of the main wings?
This is not just one or more tractor or one or more pusher propellers, which would create an unbalanced moment about the lateral axis of the craft.
A pitch of only a few degrees should provide more to the lift then it removes from the propulsion. Ref Stepniewski's consideration of a slight forward angle on the mast of his Intermeshing-ABC.

Active Blade Twist: (ABT)

It appears that active blade could be an advantage during descent and autorotation.

Post by Dennis Fetters in the thread 'Pros and Cons of Counter-rotating Coaxial Propellers on a Gyrocopter':

Hear the Wa Wa Wa..... Two props, two bladed. You need one to be a three bladed and the other one to be two or four bladed.

Also, you need to spread the props apart about 10" for a 55" diameter setup, or you create a high-pressure zone between the blades as they approach, killing efficiency, and to reduce vibration. This will not be a concern.

By the time you do it all right, the weight offsets any performance gained. Just like a ducted fan. Good ideas, but to make them work makes them so heavy you gain nothing.

Last Revised: September 6, 2009

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