rcfs
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From: Shawano,
WI, USA
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Much of the challenge flying helicopters stems from the fact that a pilot often has to manipulate all four primary controls at the same time (compare the average airplane pilot uses only two controls most of the time). Fortunately, training on a simulator allows a heli pilot to learn the controls independently before putting them all together.
This article focuses primarily on the control techniques required to fly more agile collective pitch helicopters, with the understanding that if a person can fly a collective pitch heli in a sim, flying a highly stable fixed pitch will seem like child’s play in the real world.
The biggest difference flying an entry level fixed pitch heli is that it’s designed to return to upright flight when the pilot neutralizes the controls. The tradeoff for the increased agility of collective pitch helis is that they are less stable and thus will not return to upright on their own, rather, deviations will tend to grow worse unless immediately corrected by the pilot. Consequently, collective pitch helicopters require more control inputs to fly and there’s less margin for error if over-controlled.
Ground School 101
Unlike an airplane that moves in the direction it’s pointed, as a rule, a helicopter’s movement is determined by which way the main rotor disk is tilted irrespective of where it’s pointing. Example: Pulling the right “cyclic” control stick to tilt the heli’s nose up causes the heli to move backward and tilting the nose down causes it to move forward. Tilting the rotor disk to the right causes the heli to move to the right, and vice-versa. The amount of tilt is determined by the size and duration of the control inputs. The steeper the tilt, the more rapidly the heli will move in that direction and the more prone it also is to dropping. The left “collective” control stick is used to control height by changing throttle/rotor rpms along with changing the angle/pitch of the main rotor blades to increase and decrease lift. Moving the left control stick left and right varies the tail rotor to control yaw (where the nose is pointed). As a rule, when the left stick is neutral, a good heading-hold tail rotor gyro will continue to keep the nose pointing in the same direction. Note: It is customary to use the airplane term “aileron” to describe bank and roll control, “elevator” to describe tilting the heli forward and backward, and “rudder” to describe yaw. This is also how the controls are listed in the transmitter menu.
Takeoff & Hover Technique
To keep the heli from moving around prior to lift off, you’ll need to smoothly “spool up” the rotor rpm’s to the point where the heli appears light on the skids. Then steadily advance the throttle further to lift off. Spooling up in stages should prevent the rotor torque from jerking the heli around and thus make it easier to enter a stable hover.
During a stationary hover, the right control stick is used to correct unwanted left and right, forward and backward movements while the rudder is used to keep the nose pointing in the same direction. Thanks to the stabilizing effect of a heading-hold gyro, most of the attention given to the left stick at this point will be directed at working the throttle to take off and control altitude.
You may run into experienced heli pilots who put a lot of emphasis on the left stick tail rotor control because they use it as much as the right while maneuvering and performing aerobatics. However, 90% of the control inputs made during a stationary hover are brief bumps of aileron and elevator with the right stick.
Once airborne, the name of the game is to keep all your control inputs small and brief. The problem with making a large input or holding one in is that it often requires another large input to compensate, thus increasing the risk of over-controlling. Consequently, deviations during hover need to be corrected with small brief bumps of aileron and elevator (figure 2). It’s important not to jerk the stick since that would make controlling the size of the bumps difficult; instead, a bump is a controlled in-out input that affects a slight heli response as long as the input is small. Excluding aerobatics, experienced pilots vary the size of their bumps; very very small, very small, and small, depending on how large of a correction they’re looking for. Novice pilots are best served to try to keep all their bumps “tiny” and operate by the rule that if one bump isn’t enough, you can always apply another.
There are differing opinions about whether it is best to look at the rotor disk or the body of the helicopter while hovering. The fact is it’s a combination of both, but mostly it’s the body. The problem with trying to detect deviations strictly looking at the rotor disk is that often by the time the pilot sees the disk tilting, the heli has already started drifting. Furthermore, a helicopter can be moving even when the rotor disk is level, or remain stationary when the rotor disk is banked into the wind for example. Therefore, watching the rotor disk to determine what corrections to make doesn’t always work. That is why proficient pilots primarily watch the body or the “heli as a whole”.
During a stationary hover, the rudder is used to keep the body of the helicopter pointing in the same direction. If your heli features a quality heading-hold gyro or you’re flying in the ideal world of a sim, there will only be an occasional need to use the rudder to realign the nose. If the deviations are corrected early, small nudges of rudder should straighten it out. If the deviation is larger, thanks to the stabilizing effect of the tail rotor gyro, it’s ok to hold in the rudder as long as you need to.
Whenever things start becoming hectic, focus on using the right stick to level the rotor disk and reestablish a stationary hover, then use the rudder to correct the body. Understand, crashing out of a hover usually doesn’t occur because the nose is 10 degrees off heading, crashes occur when a pilot is so focused on correcting yaw that he neglects to return the heli to level or stop it from moving.
Taken from 1st U.S. R/C Flight School's Heli Flight Training manual
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