I received the following e-mail from Jim Ryan about autorotations and the required pitch angles to make them work.
Hope winter is treating you well – what am I saying? Of COURSE winter is treating you well! Durned Floridians.
I’ve set a task to myself to really master autos this year, and which will in part take a rethink on how I have my Multiplex Evo radio set up. That said, a couple of years ago you did an OUTSTANDING primer on training for autos, and I can’t seem to find the article. Do you happen to know what issue it was in?
On a related topic, it seems to me that one should use more and more negative collective in throttle hold the smaller the heli is in order to keep head speed up. Is this your practice? Do you have recommended setup guidelines for 600, 500 and 450 size helis?
Jim – the article on autos you mentioned can be found in the August 2012 issue of Model Airplane News.
As for the negative pitch, the amount you need is controlled by several factors such as desired rate of descent, pitch angle of the nose (level, nose down, etc.), weight and airfoil shape of the blades, how much drag is on the rotor system (such as to drive the tail rotor), etc. You also want to set the max negative pitch to a couple degrees past optimum so you have an increased rate of descent if you overshoot your landing spot. I would start with a max of minus 5 degrees and see if that to maintain rotor speed with a little extra negative if needed.
Thanks for your e-mail, and let me know how this works for you.