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Monday, March 10, 2008

Learning to Hover

A big selling point of helicopters is that you can land in your backyard. Where then would be the best place to learn to hover? An airport with a 12,000' runway and a 7,500' crosswind runway. You want a lot of open space where you're guaranteed not to hit anything. You want somewhere that neighbors won't complain about the noise. You want somewhere with long sight lines to the horizon so that you won't concentrate your gaze in too close. You want somewhere that you can get fuel when you run out. All roads lead to the big airport! Generally the tower and ground controllers will give you permission to practice hovering on whichever runway isn't be used that day and/or over a seldom-used taxiway.

Most instructors will start by giving you one control at a time. You take the antitorque pedals and they handle the cyclic and collective pitch. You practice pedal turns. Then you take the collective while the instructor controls the cyclic and pedals. You go up, you go down. Maybe you land. Then you take the cyclic and the instructor takes the other controls and ... 1 second later the helicopter is oscillating like crazy and you hear "I have the controls" in your headset. Any good instructor will alert you to the fact that you need to be very light on the controls: "you fly with pressures, not movements." The instructor will also tell you that there is a bit of lag between the time that you put in a control input and the time that the helicopter reacts. What most instructors won't tell you is how to deal with these facts.

Here are a few tips for handling the cyclic, which controls forward/back and left/right movement of the helicopter:

  1. Focus your gaze at least 1/2 mile in the distance if the sightlines in your practice area are long enough.
  2. As soon as the helicopter is handed to you it will start to drift to the right. The tail rotor is counterbalancing engine torque but at the same time is pushing the machine to the right. Expect to hold a little bit of left pressure on the cyclic to avoid this translational drift.
  3. Don't put in and hold a control input pressure. Suppose the helicopter is moving forward a bit. You press back on the cyclic and hold that pressure. One second later the helicopter has responded to the initial pressure by arresting its forward creep. One second after that the helicopter has responded to two seconds of continuous pressure by rushing backwards at a frightening clip. If the helo is moving forward, press backwards for a split-second then try to return the cyclic to a neutral position. See if the helicopter stops creeping. If so, great. If not, try another little stab of back pressure. Although every second or two you are doing something with the cyclic, in any given instant you need not be putting in any cyclic input. Nudge the cyclic and then return to center. Nudge and then return.
  4. After an hour or two the instructor might be doing more harm than good in handling the other two controls. Everything is cross-coupled so if he is messing with the collective or the pedals it will require you to take action with the cyclic. It is actually easier to handle all three controls because at least the machine isn't doing completely unpredictable things from your point of view.
  5. Take a break every 20 minutes by practicing takeoffs, trips around the pattern, and approaches to landings.

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