As the saying goes, some of the most rewarding activities are also often the most challenging, and learning to fly helicopters certainly fits into that category. Indeed, merely hovering a helicopter has been compared to trying to balance a marble on top of a bowling ball. Therefore, those who become successful heli pilots really have something to be proud of.
While the new generation of entry level fixed pitch helicopters have never been easier to fly, flying more agile collective (adjustable) pitch helis is a skill that requires a lot of practice, but the practice cannot be haphazard or else pilots risk developing improper habits that will impair learning and future success. The following instruction, combined with simulator practice, is aimed at helping new heli pilots learn to hover with greater efficiency and have far fewer mistakes in the real world.
Dave Scott is a full-scale aerobatic competitor, airshow pilot and has worked in the development of several full-scale aircraft. He founded 1st U.S. RC Flight School and has professionally trained more than 1500 RC pilots of all skill levels. His ground breaking 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 his books and flight school can be found at www.rcflightschool.com.
THE SIM 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 to the average airplane pilot that 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.
Note: We’ll forgo discussing entry-level “coaxial” helis because they are so inherently stable that they almost fly themselves, but mostly 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 inputs to get them to maneuver, which is a habit to be avoided when hovering collective pitch helis. Thanks to modern heli software and design, the 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 more maneuverable collective pitch helicopters. Thus, 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 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. Entry level fixed pitch helis on the other hand don’t require as many corrections and consequently allow more time to react, thereby making them the better choice for rookie pilots to start with in the real world.
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 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-percent 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. 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.
Small brief aileron & elevator bumps are the primary type of control input used to correct deviations during a stationary hover. To avoid over-controlling, it is better to correct a deviation with multiple small bumps than trying to correct with a single large bump or holding the correction in.
Tip: 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 the 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 over-controlling. Therefore, helicopter pilots need to keep their fingers nimble or moving while hovering in order to be ready to respond to the needs of the moment. In other words, continuing to input tiny adjustments, rather than waiting until after the deviation is obvious to respond, helps to reduce the chances of you over-controlling.
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.
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 above 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 whatever throttle position your heli hovers at). 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.
Anyone who can maintain a stationary hover can also land the heli: First, gradually lower the heli and establish a stationary hover a few inches above the ground. Due to the phenomena known as ground effect, the helicopter will tend to descend more slowly when it gets close to the ground, which sometimes causes novice pilots to feel like they must reduce the power further, only to experience a sudden drop and hard landing. Instead, 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. So, even though it’s just a simulator, reinforce good habits by not letting the heli touchdown unless it’s vertical.
There’s no shortage of people telling pilots what the heli is supposed to do, but not many can explain how. Consequently, most flyers 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.
Words by Dave Scott, Instructor, 1st U.S. RC Flight School