As the power is increased enough to get the helicopter light on the skids, the pilot will begin to receive feedback about whether his control positions are correct. For instance, sliding around on the ground, or pitching and rolling motions may all be signs that the cyclic is not centered. Yawing on the ground is an indication that the pedals are incorrectly set.
You will have to continue to manipulate the controls in order to hold position on the ground during the liftoff. Failure to do so can result in a dynamic rollover situation which can destroy the aircraft. Continue to raise collective until the helicopter transitions into the air. Continue to slowly and smoothly increase collective until the desired hover height is achieved.
As the helicopter leaves the ground, don't be in the habit of pausing at 1/2 inch skid height to get the controls centered before climbing to a normal hover height. Wallowing around at a low skid height is asking to catch a skid on something. Just continue smoothly up to your normal hover height. On the other hand, don't be in the habit of "popping" the helicopter up to a normal hover height. This is a common technique with inexperienced pilots who are trying to get away from the ground. If you are getting your controls centered, there should be no reason to rapidly climb to your hover height, and there are several good reasons not to. The climb to a hover should be slow, and at a steady rate. By going slowly, you have time to identify and correct problems as they occur.
Now increase power a bit, and repeat the exercise.The amount you will have to push the pedals before the helicopter wants to yaw is reduced. The lighter you get, the less you have to push the pedals to yaw, and the narrower the range is where the pedals must be to keep the helicopter straight. If you keep doing this until the helicopter is lifting off, you will be able to judge exactly where the pedals have to be to prevent any yaw during liftoff. Of course, since you are adding more and more engine torque, the centered position will be moving more and more toward the left as you perform the exercize. With practice, you will be able to neutralize pedals without any large yaw forces being placed on the helicopter.
Keep in mind that this is an exercise. As a normal procedure, you don't want to be yawing the aircraft while it is on the ground. This can result in an accident. The trick is to learn how to move the pedals just a little bit, watch for small indications of yaw on the aircraft, and therefore learn exactly where to put the pedals so no yaw takes place. If you have access to a pontoon equipped helicopter, practicing pickups on the water will really teach you to use the anti-torque pedals.
Get the helicopter light on the skids. Push some forward cyclic, and then some rearward cyclic. Feel the helicopter attempt to rock (or slide) forward and backward. Halfway in between is where the cyclic is centered. As you get lighter and lighter, the amount you have to move the cyclic is reduced. As the helicopter is ready to lift off, any movement of the cyclic will cause the helicopter to rock or slide. You have found the center position if you can prevent it from rocking and sliding as the helicopter is ready to pick up.
Now comes the difficult part. All helicopters will want to pitch nose up or down into whatever attitude they want to hover in. This is usually a different attitude from the skids level attitude. If you try to prevent this from occuring, the helicopter will slide forwards or backwards depending on the attitude it wants to hover in. Many things will influence the hover attitude, including the CG of the helicopter. The trick is to figure out which attitude it wants to hover in, given that you are sitting on the ground. Of course, experience will tell you to some degree how a helicopter wants to hover given it's CG, but you should be able to walk up to a strange helicopter and still perform a good liftoff.
The key is to realize that the helicopter will side forward or backward unless it is in the correct pitch attitude. As power is increased, position the cyclic so that the helicopter won't slide. Add more power and notice whether the nose or tail wants to raise. Let the aircraft pitch up or down, but as it does counter the motion with cyclic, just as you do on a slope landing. The idea is not to stop the pitching motion, but to prevent the rotating swashplate (and therefore the main rotor) from pitching with the fuselage. If you have input the correct amount of cyclic, the aircraft has pitched, but still does not want to slide on the ground. Continue adding power, and countering fuselage pitch until the helicopter lifts off. If you do a really good job, you will first feel the front or rear of the aircraft lift off, then one of the remaining skids, and then finally the heel or toe of the remaining skid, all without any sliding around on the ground.
This takes a lot of practice, but will allow you to make very accurate, smooth takeoffs.
Again, the problem is similar to that of the pitch axis. The helicopter in a hover will normally hover one skid lower than the other because of various factors including CG. Your job is to transition from skids on the ground (presumably level) to skids at the hover attitude. You don't know what the hover attitude is yet. So you increase power a bit, and play carefully with lateral cyclic to try and determine where it is centered. You continue to increase power to get light on the skids, and adjust the cyclic to prevent sliding. At some point the helicopter is going to want to roll, and you have to let it, but you do want to counter with opposite cyclic so that the rotating swashplate doesn't roll with the helicopter.
If you do this correctly, the helicopter will roll but not slide, until it is left with one skid in the air, and one skid on the ground, ready to lift off. Continued up collective will cause the final skid to leave the ground with no rolling motion at all, simply a straight up motion. If the helicopter wobbles as it leaves the ground, you didn't have the cyclic centered and you need more practice!
Keep in mind during all this that I'm not advocating sliding around on the ground. That is a very dangerous thing to do. What I am suggesting is that you look for the cues that tell you when the aircraft controls are centered versus displaced. By learning those cues, you can center the controls and perform a perfect takeoff to a hover every time.
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