Thursday, August 10, 2017
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Heli Training Forward Flight Procedure Turns

Heli Training - Forward Flight Procedure Turns.qxdThis month, 1st U.S. RC Flight School’s progressive helicopter training series is aimed at helping new heli pilots learn forward flight procedure turns with greater efficiency and fewer mistakes.
As always, it’s presumed that these lessons will be practiced on a simulator prior to flying in the real world, and the control techniques described apply primarily to flying collective (adjustable) pitch helicopters, with the understanding that if a person can fly a more agile collective pitch heli in a sim, flying a highly stable fixed pitch heli will seem like child’s play in the real world. Also, in the interest of simplifying the text, all the control applications will be described using the customary airplane terms aileron, elevator, and rudder.

GROUND SCHOOL
The first turn that every heli pilot learns is a pirouette using the rudder to point the nose in different directions while hovering. These turns are usually limited to 90 or 180- degrees so they are over with before needing very many adjustments. Executing a forward flight 180-degree procedure turn using the aileron to bank the heli and holding in rudder and elevator to carve around the
turn is much more intricate and requires techniques very different from those used to hover (figure 1). First of all understand that the rudder is held in throughout a procedure turn and
that the amount largely determines how wide or tight the turn will be. Thus, proficient pilots commit to holding a small rudder input when they intend to perform wider turns, or a slightly larger rudder input when they intend to perform tighter turns. The bank angle also goes hand in hand with the rudder input. For example, holding a small rudder input requires a shallower bank (smaller aileron input) to gently carve around the turn without skidding, whereas a slightly larger rudder input requires a steeper bank to cleanly carve around the turn. The bank angle then determines how prone the heli is to losing altitude and thus how much elevator is required to keep the turn level, i.e., the steeper the bank, the more inclined the heli is to dropping, and thus the more elevator you’ll need to pull to keep the turn level, and vice-versa. Altogether, the first step is to establish moderate to high speed forward flight. The procedure turn is then initiated by coordinating small amounts of rudder and aileron, followed by pulling elevator.

Figure 1
Figure 1

The rudder is held in and adjusted to the turn level. The turn is then completed by removing the rudder and elevator and applying opposite aileron to return to level. One of the great things about turning helicopters is that there’s none of the usual confusion that novice airplane pilots encounter trying to determine which direction to apply the aileron to return to level; Since helicopters require you to hold in the rudder and sometimes aileron throughout the turn, when it comes time to level out, all a helicopter pilot has to do is go “opposite”.
FINER POINTS
In order to cleanly carve around the turn without skidding, pilots must learn to fine tune the amount of rudder they’re holding and/or fine tune the bank angle (figure 2). 

For example, when the nose of the heli points to the outside of the turn (not enough rudder relative to the bank angle), the solution is to add more rudder and/or shallow the bank angle. Or, when the heli skids into the turn (too much rudder relative to the bank angle), the solution is to lessen the rudder and/or steepen the

Figure 2
Figure 2

bank. There’s no magic solution for quickly learning to coordinate these inputs.

Depending on the setup and other factors, it takes practice to develop this skill. However, a good understanding going into your sim practice will put you well ahead of the curve. While all procedure turns require some elevator, slower speed turns rely more on power adjustments to maintain level flight, whereas higher speed turns rely primarily on using the elevator to correct altitude changes. Bottom line: correct altitude changes during a turn with elevator, but if  attempts to arrest a descent with the elevator don’t produce immediate results, add more power. If you pull too much elevator during a turn and cause the heli to lose forward momentum, you’ll have to push forward elevator to lower the nose and reestablish forward movement while adding power to prevent a loss of altitude.

 Note: It’s very easy to forget to hold in the rudder when making other adjustments during the turn. If this occurs, the tail rotor gyro will prevent the nose from turning and cause the heli to enter a sideways skid and back-slide into the

Figure 2
Figure 2

ground if the rudder isn’t reapplied in time. Thus, you must make it a priority to continue holding in the rudder throughout the entire turn. In fact, if you’re going to make a mistake while turning, it would be better to input slightly too much rudder and end up hastening the finish of the turn versus dealing with the awkward perspective of the heli pointing away from the turn when not enough rudder is used (figure 3). On a related note: The solution whenever you lose orientation is often to add more rudder in order to alter the heli and achieve a clearer perspective.

 

 

 

 

Figure 3
Figure 3

 

PRECISION TURNS
A slightly more intricate turn technique used by competition pilots to achieve a more axial entry into the turn consists of sequencing the bank input first, then applying and holding in the rudder and elevator. In other words, the rudder and elevator are delayed until the bank has been established (figure 4).

A precise exit of the turn is similarly accomplished by neutralizing the rudder and elevator when the nose points exactly where you intend to fly, and then applying aileron only to achieve an axial rollout to level. Keep in mind that precision turn entries and exits typically require higher entry speeds in order to generate the

Figure 4 A more axial entry into high speed turns is accomplished by first applying aileron to “set the bank” and then applying rudder and elevator to carve around the turn and keep it level. Precise exits are accomplished by neutralizing the rudder and elevator when the nose points exactly where you intend to fly, and then applying aileron only to achieve an axial rollout to level.
Figure 4 A more axial entry into high speed turns is accomplished by first applying aileron to
“set the bank” and then applying rudder and elevator to carve around the turn andkeep it level. Precise exits are accomplished by neutralizing the rudder and elevatorwhen the nose points exactly where you intend to fly, and then applying aileron only
to achieve an axial rollout to level.

inertia needed to execute the steps without losing altitude.

REAL WORLD TRANSITION
Modern flight simulators are so realistic that it won’t take long to achieve the same level of success in the real world that you achieved flying the sim, assuming your heli is setup correctly and you pace yourself. Your odds of success can be further improved by initially flying only in calm conditions. Despite the optimistic claims of the manufacturers, flying entry level fixed pitch helis in even the slightest wind is very risky and should be avoided. Collective pitch helis handle wind much better, but it’s still recommended that you avoid flying in wind until you get a few dozen successful flights under your belt. When you do decide to fly in wind, be ready to make considerably more adjustments (especially throttle) compared to flying in calm conditions. For example, you’ll have to be ready to apply more power when transitioning from upwind to downwind or the turns will drop (figure 5). As a rule, anytime a deviation is corrected late, it will take a larger input to correct it, thus increasing the potential for over-controlling. Therefore, keep your fingers moving when flying in wind in order to be ready to respond to the needs of the moment, i.e., don’t ever 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 have already started moving.

Figure 5
Figure 5

CONCLUSION

In some ways the sterile world of the simulator tends to make flying a little easier than it is in the real world, however, even the best resolution in a sim is not as good as the real world, so seeing the heli in the sim is more challenging. Since vision plays such an important roll in heli flying, you can take confidence from knowing that if you can do it in the simulator, you will probably find real world flying to be a little easier simply because you can see better. Good luck! 

 

 

 

By Dave Scott Instructor, 1st U.S. RC Flight School

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