Oh Dear, sorry Hal I wasn't trying to make you in to fish food.

I obviously totally failed to explain how angle of attack constantly changes on an autogyro.

I notice that you state that your rotor disc has a fixed angle of attack........I would prefer to use the term ' aft rake ' as it is the tilt back of the rotor shaft that gives you what you are describing. Even that angle of attack is not fixed, what about when you are flying very slowly at a high nose angle ???? Is the angle of attack not greater now ?

This is what I think you are getting me all confused with, I am talking about changes in angle of attack of the individual blades as they rotate whereas I think you are talking about the rotors as if they are a solid disc fixed to the fuselage like a wing. This is why I said to throw away the book on fixed wing aerodynamics, as the terminology for rotary wing is very specific to prevent just this type of confusion with angle of attack.

You mentioned that the air/water is not moving. It IS moving RELATIVE to your hand/the rotor blade. Makes no difference whether your blade is moving forward or if the air is moving due to it being a windy day, the effects are exactly the same which is why the term 'relative' is used.

On a fixed wing everything relates to line of flight because everything is facing the line of flight, on a gyro is the retreating blade facing the line of flight ? If the craft is moving forward at 20 knots and the tip speed velocity of the retreating blade is 70 knots how can you say that its angle of attack is fixed to the crafts direction ? The airflow for that blade is 50 knots in the opposite direction that the gyro is flying.

Picture that retreating blade, right now it is moving through the air at 50 knots in the opposite direction the gyro is flying( blade tip velocity minus gyro forward speed ). Right now its angle of attack is the angle between its chordline and its plane of rotation. As this blade is retreating and articulated it would be flapping down, this flapping down would cause the airflow to hit the blade more on the underneath than straight ahead....hey presto the blade has increased its angle of attack by flapping curing dysymmetry of lift .

If you hold your model in the breeze and don't let the rotors spin then the retreating blade aerodynamics are the same as for a fixed wing and the above does not apply. You have to forget everything ever written about fixed wing aerodynamics for a rotating wing, as line of flight is only 1 component of many that set the rules for what is going on with how airflow relates to the blades.

Phew !

Watch out for them sharks

Sean