To: Rotorque
The way you describe it, the Alpha Angle must have something to do with the bending moment on the shaft or, the overturning moment imparted from the rotor to the fuselage caused by the very strong couple between the head and the shaft. You also indicated that the ability to read this Alpha Angle Indicator was very important especially when you were on the ground.
The Cheyenne H-56 rigid rotor had such a strong couple that the cyclic was locked out while you were on the ground. If the cyclic could be moved on the ground you could roll the helicopter over. I think it was unlocked by a squat switch on the landing gear. To maneuver on the ground you would use the propeller on the tail for forward motion and the tail rotor for ground directional control or, you would have to hover taxi to get from one spot to an other.
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The Cat