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Autorotation

Autorotation is in my opinion is the most exciting and useful basic maneuver. The main objective of an autorotation maneuver is to bring a helicopter to a safe landing without power from engine. Autorotation could save some damage from what might end up with a costly crash, especially with a flame out engine and tail rotor drive failure during flight.

To setup a helicopter to learn autorotation, you have to setup the throttle hold collective pitch curve and the tail. The collective pitch at throttle hold position should be setup with around -3 degrees collective pitch at full down throttle stick, the max available collective pitch at the max throttle stick, and linear collective pitch output all through the range. The throttle position should be at a point to achieve a reliable idle without the clutch engaged. As to the tail, if your helicopter have an autorotation clutch equipped, set it up so that the tail will not be driven during autorotation, as a driven tail will does more harm then help for a beginner to learn autorotation. Finally, if you have a heading lock gyro, set the gyro up so that during autorotation the gyro will be at normal mode, not heading lock mode.

Basically, an autorotation maneuver is comprised of four parts - entry, steady decent, flare and landing. The entry phase will determine where the helicopter will land. The steady decent will allow you to maneuver the helicopter to a point of landing. The flare slows the helicopter's descent rate and forward speed. The landing will put your helicopter to land at safe grounds.

It is best to learn autorotation when there is moderate wind present. Choose a big piece of flat land without any obstruction would greatly enhance the chance of safe landing. Let the helicopter climb to an altitude you are comfortable with and bring it to a position just downwind of your location. At this point slowly lower the collective to full down and keep in that position to make the engine cut to idle. Use the cyclic to keep the helicopter level and still keep some forward speed. You do not want the nose pointed up or down at this moment cause the helicopter would either stall or pick up too much forward speed, and both would hinder the decent of the helicopter to its desired position. You'll loose tail rotor control because it isn't driven during autorotation but as long as the helicopter have forward speed this will not be a problem. Work the cyclic so that the helicopter reaches an altitude of around 20 feet and 50 feet directly from where you are standing (We call this position the "bail out point"), simply power back up and transition to a hover. Don't worry about the throttle hold switch at this point. All you want to do is get used to controlling the model in the descent. Play with this for a while until you could start to get comfortable with it.

After that, lower the collective and flip the hold switch. Now the pitch would be more sensitive than what you have in hovering mode. Fly the machine down to the altitude of around 20 feet, turn off throttle hold and transition to the hover. The tail would wag once the throttle hold switch is turn off, so be prepared for a sudden change of orientation of the helicopter. Repeat this process until you get completely comfortable with the feeling of the collective pitch at throttle hold position. As you get more proficient doing this, try to lower the altitude and pull the helicopter closer than the bail out point.

When you get to the point that you're doing a power recovery to hover at 3 to 5 feet, then simply leave throttle hold active and feather the collective in to cushion the landing. You will have done your first full down auto and you'll find that it's no big deal other than being a great deal of fun. While going through this process, you'll be learning about those three phases. This will give you a bit more inertia to play with when it's time to increase collective for the landing. Smoothness helps a lot in this maneuver so try not to be jerky with it. The higher the wind is the less you'll need to flare to zero out your ground speed. That's one of the reasons it's easier to auto with a bit of wind. In calm conditions, you'll have to flare relatively hard and you won't have the additional lift provided by the breeze to cushion the touchdown. Go slow and work up to it. If you do the process right, the first power off landing will be a no brainer. If you actually experience a power failure while in flight, it is very important to bottom the collective NOW!

The rotor rpm will start to slow immediately and that natural 1 to 2 second delay that occurs while we're saying "Oh Sh**!" to ourselves is long enough to get you in trouble so be quick about dropping the collective. The quicker you can get the airflow reversed and coming up through the rotor from below, the greater you chance of doing a successful auto or at least minimizing the damage. That's another point, there are airspeed/altitude combinations that you probably won't be able to do a successful auto from. If you're going to pile it is anyway (say from a servo or ball link failure), flipping the hold switch and allowing the rotor rpm to slow as much as possible before impact can help minimize the damage. The slower the rotor is turning on impact and the fact that there is no power being applied to the rotor will make a big difference in your repair bill. One last thing, engine failures aren't the only thing you'll need to know how to autorotate for. If you have a tail rotor drive failure, that requires an auto too. Basically, the tail controls the torque reaction from the engine. If the tail fails, you can't control the torque and thus can't control the helicopter. The only way to regain control is to get rid of the torque and that means killing the engine and now you're back to doing an autorotation. Here again, it's important to be quick. That fuselage can spool up faster than you'd ever believe after the tail blades quit spinning.

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