I'm not trying to misrepresent anything. I'm trying to work out the complex physics that goes on at rotor stall. I can find nothing in my text books about it and I am trying to put together the bits of the puzzle.
I think we can probably all agree that the rotor stalls due to the angle of attack becoming too large.
Here are 3 extracts taken from Norman Baileys book. I hope he will not mind me using them. He knows who I am.
Cyclic input alters the plane of rotation. NOT the angle of attack. (Bailey, principles of flight, p40).
forget the red herring of cyclic affecting pitch. do not confuse pitch with angle of attack. forward cyclic will not increase angle of attack on retreating blade
When the disc is flared, a componant of the horizontal airflow will now be opposing the induced flow. The change in direction of the airflow relative to the blade will INCREASE the angle of attack and therefore an increase in total rotor thrust. (Bailey, principles of flight, P100).
It is with this in mind that I suggest that a flare will push the disc towards a stall. If this is true, the converse must be true.
...At the same time, section D at the root becomes stalled and the extra drag generated causes a reduction in the size of the autorotative area and a rpm decrease. (Bailey, p50)
There is a diagram on page 51 which shows the stalled area of the blade is larger on the retreating blade than on the advancing blade.
It is with this in mind that I make my assumption of left roll as stall approaches.
Last edited by Gaseous; 8th Jan 2005 at 21:19.