[headline: Ground School: Hover Training, Part 1]
[subhead: Become a successful heli pilot by learning to hover]
[author: Dave Scott]
[graphics by the author]
[sidebar in text file]
Dave Scott is a full-scale aerobatics competitor and airshow pilot, and has worked in the development of several full-scale aircraft. He founded 1st U.S. R/C Flight School and has professionally trained more than 1,500 RC pilots of all skill levels. His groundbreaking flight training manuals and articles feature the accelerated airplane and helicopter training techniques that he’s developed during his 14,000 hours of instructing experience.
More information about Dave’s flight school and manuals can be found at www.rcflightschool.com.[dingbat]
As the saying goes, some of the most rewarding activities are often the most challenging, and learning to fly helicopters often fits into that category. Indeed, merely hovering a helicopter has been compared to trying to balance a marble on top of a bowling ball, so those who become successful heli pilots have something to be proud of.
Although the new generation of entry-level, fixed-pitch helicopters have never been easier to fly, flying more agile collective-pitch (adjustable) helis is a skill that requires a lot of practice. The practice cannot be haphazard or pilots risk developing improper habits that will impair learning and future success.
The following instructions, combined with simulator practice, are aimed at helping new helicopter pilots learn to hover with greater efficiency and fewer mistakes.
The Simulator Advantage
Much of the challenge of flying helicopters stems from the fact that a pilot often has to manipulate all four primary controls at the same time (compared with an average airplane pilot who uses only two controls most of the time). Training on a simulator allows a heli pilot to learn the controls independently before combining them.
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 with a simulator, flying a highly stable, fixed-pitch aircraft will seem like child’s play.
I’ll forgo discussing entry-level coaxial helis, not only because they are so inherently stable that they almost fly themselves, but because the control techniques required to fly them are in many ways contrary to the techniques used to fly more agile, single-rotor helis. Specifically, coaxial helis typically require you to hold in inputs to maneuver them, which is a habit to avoid when hovering single-rotor helis.
Thanks to modern helicopter software and design, a typical entry-level, single-rotor heli is nearly as stable as a coaxial heli, but features enough agility to allow control techniques closer to those used to fly collective-pitch helicopters. Whether hovering a fixed-pitch, single-rotor heli or a more agile, collective-pitch heli, one can expect to use similar control techniques.
The biggest difference flying entry-level, fixed-pitch helis, including quadcopters, is that they are 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 will not return to upright on their own. Deviations will tend to grow worse unless the pilot immediately corrects them.
Collective-pitch helicopters require more control inputs to fly and there’s less margin for error if overcontrolled. Conversely, entry-level, fixed-pitch helis don’t require as many corrections and consequently allow more time to react, thereby making them the better choice for rookie pilots (Figure 1).
Ground School 101
Unlike an airplane that moves in the direction it’s pointed, as a rule, a collective-pitch helicopter’s movement is determined by which way the main rotor disk is tilted, regardless of where it’s pointing.
For 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 is to dropping.
The left “collective” control stick is used to control height by changing throttle/rotor rpm 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.
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 how the controls are listed in the transmitter menu.
Takeoff and Hover Techniques
To keep the heli from moving around before liftoff, you’ll need to smoothly “spool up” the rotor rpm to the point where the heli appears light on the skids. Steadily advance the throttle further to lift off. Spooling up in stages should prevent the rotor torque from jerking the heli around, making it easier to enter a stable hover.
During a stationary hover, the right control stick is used to correct unwanted left, 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 toward working the throttle to take off and control altitude.
You may run into experienced heli pilots who put much 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 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 overcontrolling. 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 because that would make controlling the size of the bumps difficult. Instead, a bump is a controlled in-out input that creates 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 need. Novice pilots are best served by trying to keep all their bumps tiny and operate by the rule that if one bump isn’t enough, you can always apply another.
When flying more maneuverable collective-pitch helis, don’t get lulled into thinking that you’ve found the “sweet spot” and can pause at neutral, because before you finish that thought, the helicopter will likely have already started moving. As a rule, if a deviation is corrected late, it’ll take a larger input to correct it, thus increasing the potential for overcontrolling.
Helicopter pilots need to keep their fingers nimble or moving while hovering in order to be ready to respond to the moment’s needs. In other words, continuing to input tiny adjustments, rather than waiting until after the deviation is obvious to respond, helps to reduce the likelihood of overcontrolling.
There are differing opinions about whether it is best to look at the rotor disk or the helicopter’s body while hovering. The fact is, it’s a combination of both, but mostly it’s the body.
The problem with trying to detect deviations by looking strictly 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. 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 (Figure 3).
During a stationary hover, use the rudder 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 simulator, 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 okay 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. Crashing out of a hover usually doesn’t occur because the nose is 10° off heading. Crashes occur when a pilot is so focused on correcting yaw that he or she neglects to return the heli to level or stop it from moving!
For various reasons, helicopters are prone to rising and sinking while hovering and therefore require frequent throttle adjustments to maintain the same height. On average, slightly more than half throttle is required to hover, thus, if a throttle adjustment remains above or below that setting for any length of time, the heli will end up climbing or descending.
In order to maintain the same height during hover, the proper response to rising and sinking is to briefly bump or nudge the throttle more or less to stop the trend and then return to slightly above half throttle (or to whatever throttle position your heli best hovers). If it turns out that the initial bump of throttle isn’t enough, you can always bump the throttle again and/or learn to change the size of the bump depending on the severity of the rise or sink.
In the same way that bumping the right stick enables more precise flight control, briefly bumping the throttle will enable you to stop unwanted altitude changes without affecting a climb or descent in the other direction (Figure 4).
Anyone who can maintain a stationary hover can also land the helicopter. Gradually lower the heli and establish a stationary hover a few inches above the ground. Because of the ground-effect phenomena, the helicopter will tend to descend more slowly as it gets close to the ground. This sometimes causes novice pilots to feel as though they must reduce the power further, only to experience a sudden drop and hard landing.
Practice gently nudging the throttle to lower the heli an inch at a time until it touches down. Furthermore, don’t ever allow the heli to touch down if it’s moving sideways, forward, or rearward, because doing so in the real world would likely result in the heli tipping over and the rotor blades striking the ground.
Although it’s only on a simulator, reinforce good habits by not letting the heli touch down unless it’s vertical.
There’s no shortage of people telling pilots what the helicopter is supposed to do, but not many can explain how. Consequently, most fliers hold on to the narrow view that only practice makes perfect. The million dollar question is, “practice what?”
In the absence of any plan for success, it becomes more difficult to maintain the motivation to overcome challenges when learning. On the other hand, those who increase their odds of success by understanding the proper techniques beforehand are more motivated to continue putting forth the effort.
Now that the control techniques required to hover are understood, next time we’ll apply the timeless crawl-walk-run approach to learning to fly in order to produce maximum results in the shortest amount of time possible. Good luck!
1st U.S. R/C Flight School