AUTOROTATION
So you want to learn to shoot autorotation! Great! It’s amazing how something
so simple can be so much fun and also be so intimidating to learn.
Lets start with the helicopter set-up. The helicopter for are example will have the normal pitch settings at a -2 degrees to a +8 degrees and will hover at + 5 degrees of pitch. For the most part the helicopter will do autorotation's at a -4 degrees to a +8 degrees. You need the extra negative pitch so that on a decent you can keep the blades spinning. This -4 degrees is just an initial starting point, we will adjust the pitch later, but this will keep you out of trouble at first. You should also use blades that are weighted. The heavier the blades the better they auto rotate. I personally like to set the top end pitch at 2 more degrees than what the engine will handle. I do this because I like the pitch to come in a little bit earlier so I don’t have to go to the farthest reaches of the throttle stick. You do not want to much because at the last part of the auto you will go back up in the air to soon with out any head speed. This will probably make more sense later. When I set up some one else’s helicopter so they can learn to do autorotation's I also drop the pitch setting at hover to +4 degrees on the hold pitch curve setting. This lets the helicopter come down a little when they hit the hold switch. Beginners have a habit of hesitating on the throttle right after hitting the switch and this can cause the head speed to drop before they come down on the throttle. By dropping the setting to +4 the helicopter will start to descend as soon as they hit the hold switch. Next if your radio has a tail rotor offset for hold you will want to set this for some left tail rotor, or actually your taking the right tail rotor out. This is because when your hovering you need a certain amount of right rudder to hold the nose straight. When you hit the hold switch and disconnect the engine you do not need this right tail rotor any more and so the tail rotor offset will take the tail rotor back to a “0” degree setting, or the amount that will keep the nose straight when you hit the hold switch.
PART #1: HOVERING AUTOROTATION
So now were ready to start. I have people learn in four parts. The first part is to do some hovering auto’s. This is when you have your helicopter in a hover, about 1ft to start. Then you hit the hold switch and let the heli fall. This will help you learn the feel of hitting the switch. You will want to start out low and move to an altitude of about shoulder level. The higher you get the more you will have to learn to apply pitch as the helicopter gets closer to the ground. This will teach you to move the throttle stick. Get used to doing these.
PART #2: POWER ON APPROACHES
Next is something you should already be familiar with. Doing power on approaches. The most important part of the auto, besides surviving is the set up of the auto. You will want to try to hit the same spot in the sky. After you do you one approach you can adjust accordingly so you can end up in the same spot. When you first learn to do autorotation's or approaches you want to end up past your self so that you are back behind the helicopter... just like when you learned to hover. This will take some of the scare factor out. On a day with a light wind, which is the type of day you want to do your first autorotation, you will want to be out at a 45 degree angle. Up 40 feet, out 40 feet, up 100 feet, out 100 feet. The more the wind the more you will be up verses out, i.e.: up 100 feet, out 40 feet. The less the wind the farther you will be out verses up, i.e.: Out 100 feet, up 40 feet. What I have the student do is go up and turn with tail rotor, start moving forward. By moving forward slightly will guarantee that the nose of the helicopter is pointing down. One of the worst things you can do is have the tail low. This will reduce the head speed much quicker. Right after you get moving you will want to come down on the throttle stick. You want to do this because when you do the autorotation, you want to come down on the collective first, then hit the THROTTLE HOLD SWITCH. If you have to much forward speed you will come down to fast and over fly your self. If you do not have enough forward speed you will end up short of your self. Do these to about 20 feet high then bail out at head level. Your only learning to set up the auto and the look of the decent. The angle the helicopter will come down will be like this. You will start out with a “nose low” attitude and then end up with the nose a little bit high. This happens because you will use the aft cyclic or back elevator to stop your forward flight. You use the pitch to stop the decent and help with the stopping of the forward speed.
PART #3: USING THE HOLD SWITCH
Now you will want to keep doing the descents you have been practicing but at a much higher altitude. The higher the better. Do a few power on approaches like what you practiced in PART #2. Once you familiar with the higher altitude, you will want to start hitting the hold switch, and MAKE SURE YOU COME DOWN ON THE THROTTLE STICK FIRST! Let the helicopter fall about 20 feet or so and then turn the hold switch off, finish the descent, then do another one. Get use to this and let the helicopter come down farther each time.
PART #4: PUTTING IT ALL TOGETHER!
Well the biggest thing is getting the nerve to do this. You have done the approaches, you have done the hovering auto’s, all that’s left is to get the nerve and go for it. Make sure you do it with some wind, this make’s it easier and will give you that extra lift you need. At first try to fly long so you will be behind the helicopter when it comes down to the ground. This will give you that hovering auto feel that you learn earlier, but don’t concentrate on this, concentrate on the helicopter and give it what it needs and make it do what you want it to do. All an autorotation is, is the power on descents and landings that you practiced earlier. Also at the bottom of the auto you will want to push forward on the cyclic to level the helicopter just before touch down. This will lessen the likely hood of a boom strike. If the tail boom is low and the back of the blade disk is low and pulling down, what happens is the helicopter will hit the ground and flatten out, pushing the tail boom up as the blades are still trying to go down in the back and you will end up with a boom strike if you hit hard enough. On that subject, make sure your main blades are tighter also. Start the flare about 15 foot above your head level. This is where you have to be careful and rely on your decent practice. If you flare too soon, you will run out of head speed for the last part of the autorotation. However if you flare too late, you will hit the ground. On the way down you can vary the amount of flyby by dropping the nose of the helicopter, but the fall speed will pick up. Or you can lengthen the autorotation by raising the nose slightly and floating the helicopter down.
After you learn these you will find that they are very simple to do, and are allot of fun. It will amaze you how something so simple can be so much fun. Especially when you try to hit the center of a 18 inch pad.
Good luck!
HB