Secrets to Mastering Forward-Slips Upping the Wow Factor with Slipping Show Passes and Landing Setups.

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1 Secrets to Mastering Forward-Slips Upping the Wow Factor with Slipping Show Passes and Landing Setups. By Dave Scott. Owner/Instructor, 1st U.S. R/C Flight School Introduction The ability to slip an airplane has long been a skill that many R/C pilots have wished to learn, and yet despite all that has been written about slips over the years, still, very few R/C pilots can perform a slip, or would even dare to try! The reason is that previous articles have mainly described what comprises a slip, but other than instructions to adjust the controls as needed, none have given specific instructions on how to actually train yourself to do it, until now. There are two types of slips. The first is the wing-low side-slip used to prevent wind drift typically during a crosswind landing. This entails banking the wings slightly into the wind while inputting opposite rudder (cross-controlling) to keep the fuselage aligned with the runway centerline. Akin to balancing a marble on a bowling ball, probably less than 1% of R/C pilots are able to pull off this maneuver. The second type is a forward-slip in which rudder is applied to purposely put the airplane into a skid. At the same time, opposite aileron is applied to bank the wings in the opposite direction of the skid along with some up elevator to offset the turning effect of the rudder and thereby keep the plane tracking in a straight line (figure 1). The skidding forward-slip is typically used to create greater aerodynamic drag in order to reduce airspeed and/or enable a pilot to approach the runway at a steeper angle without building up excess airspeed. However, the author performs forward-slips on nearly every landing, not because I m high or fast, but because it s cool! But the coolest example of a forward-slip is when it s performed the length of the runway by airshow pilots to show off our main sponsor s logo on the top of the wing. A power-on level flight forward-slip, a.k.a., show pass/sponsor pass, also proves to be the easiest way to learn to slip, albeit much higher at first. Normally, slips can be very difficult to perform and beyond the abilities of most R/C flyers. However, this article will reveal the secret to learning how to forward-slip in a matter of minutes, assuming that you re already comfortable with using the rudder throughout your flying, or at a minimum, can routinely sustain a

2 knife-edge. Although, the secret contained in this article may even make it possible for pilots that otherwise don t use the rudder much to be able to slip an airplane. Yet, before we get to that; Slips are typically performed at lower airspeeds, and therefore it is imperative that we review how to recognize when an airplane is approaching a stall for the following reason: A forward-slip entails holding in a lot of rudder while inputting opposite aileron, along with holding up elevator to manage altitude and maintain a straight line. Stalling the airplane while cross-controlling the rudder and aileron and holding in a lot of up elevator is essentially the recipe for a spin. Of course, that s not something you want to have happen anywhere near the ground. Stall Awareness First of all, for a variety of reasons, not the least of which is changing winds, you won t be able to judge whether the plane has enough airspeed merely by looking at it. For example, when flying into a strong headwind, a plane can have plenty of flying speed and yet look too slow, prompting a pilot to unnecessarily add more power and complicate the slip. Conversely, it is not uncommon for pilots to enter a stall/spin and blame it on something other than a stall because in their view the plane had plenty of speed, when in fact it only appeared that way because the plane was flying downwind. Hence, no matter what type of plane you re flying or what the wind is doing, the only true/best way to determine whether the airplane has enough flying speed or is getting close to stalling is by feel. Explained: To enter a stall, the wing must exceed critical angle-of-attack. A stall is therefore often preceded by pulling more and more up elevator, i.e., too much. So, while it is normal to have to hold in some up elevator to keep the airplane on line and control altitude during a forward-slip, if it becomes necessary to keep adding more and more elevator to hold the preferred flight path, the plane is likely getting too slow. At which point you will have to increase the throttle setting to avoid entering a stall. The Secret to Easy Slips And now, the secret to learning forward-slips: As stated earlier, the easiest way to learn to slip is to maintain a power-on constant altitude forward-slip, a.k.a., show pass, but starting higher at first. Next, the reason that so many people fail to learn how to slip is that they have been told to continually adjust the rudder and aileron to vary the slip depending on the circumstances. However, as anyone who routinely slips knows, the secret to executing forward-slips is to pin the rudder stick all the way full and forget about it. For all practical purposes, you are now flying as if the rudder servo had failed at full deflection, and thus have no choice but to fly the plane with the right stick. Specifically, you will need to compensate for the rudder effect by keeping the wings banked in the opposite direction while holding in some up elevator to maintain straight and level flight (figure 2).

3 Constant Altitude Forward-Slip, a.k.a., Show Pass: Set the throttle between 1/4 and 1/2. Pin the rudder over full while simultaneously holding in and adjusting opposite aileron and up elevator to maintain straight and level flight (with the top of the plane facing the spectators). Moderate the throttle if necessary to achieve the ideal bank angle between degrees (more speed = more bank. Less speed = less bank). If it becomes necessary to keep adding more elevator to maintain altitude (the plane is too slow), add more throttle. Note: This maneuver is much easier to learn when the plane is banked toward you and performed on low rates with no more than 30 degrees of rudder deflection. You could try it on high rates, but your plane will tend to become squirrely and the maneuver will end up looking more like a knife-edge. While knife edges are cool, they re not nearly as distinctive as a degree banked skidding forward-slip. The average amount of throttle required to perform a show pass (constant altitude) forward-slip will vary with each airplane. As a rule, the faster the airplane is flying, the more you ll have to bank the wings to keep the plane from turning and/or climbing due to the increased rudder authority. If too fast, the maneuver essentially becomes a knife edge. Conversely, only a moderate bank is required at slower airspeeds. At first, I suggest you err on the safe side and use approximately half throttle. Then, as your proficiency and confidence increases, use slightly less power each time until you achieve the sweet spot with the wings banked between degrees. All that said, it still comes down to adjusting the bank and elevator to maintain a straight line, irrespective of what the bank angle is. For example, if you asked me how much bank I typically end up with, I couldn t tell you. That s because I m not paying much attention to the wings, but am concentrating on adjusting the aileron and elevator to maintain the path I want to fly. However, if it starts looking too much like a knife edge, I ll reduce the throttle a bit more. Note that as you start using lower power settings, you will find it necessary to hold larger amounts of up elevator to maintain altitude. Thus, prior to trying to slow down your slips, it would be smart to take the

4 airplane up high, enter a forward-slip, and gradually reduce the power until you have to add so much up elevator to maintain level flight that you put the airplane into a stall. Then keep repeating this exercise until you have a good idea of how much elevator it takes to force a stall. Descending Forward-Slip on Approach Once you re proficient at maintaining constant altitude forward-slips, you ll be ready to start practicing descending forward-slips in preparation for those times when you need to induce a steeper landing approach or to scrub off excess airspeed (figure 3). The execution is no different than the previous show pass slip, except the throttle will be closed and you will allow the plane to descend while you adjust the aileron and elevator to track the runway centerline. Start higher at first and practice several descending slips, holding each slip a little closer to the ground before going around. When ready to land, smoothly remove the slip inputs when it looks like the eventual touchdown will be near the front of the runway. Forward-Slip Landing Approach: To bleed off excess altitude approaching the runway without building up excess speed, idle the motor and pin the rudder over full while simultaneously holding in and adjusting opposite aileron and up elevator to track the runway centerline. It s a common mistake to advise pilots to vary the rudder during forward-slips to control the airspeed and angle of the descent. However, that is not how the pros do it (i.e., those who make everything they do look easy). Expert pilots typically don t vary the degree of slip, but simply hold the full rudder slip longer or take it out earlier depending on the need. For example: If the airplane is quite high, we ll just keep the slip in longer until the plane is closer to the ground. If the plane is just a tad high, the slip would be taken out earlier when the plane intercepts the proper glide path. Yes, you could, and eventually probably will, vary the slip angle during approaches, but it takes a lot more effort. It s also the leading cause of loss of control or close calls for those learning to slip due to the preoccupation with varying the rudder causing pilots to neglect the all important right control stick.

5 One last important point must be made; As a rule, the only time an expert pilot would need to use a forward-slip, outside of showing off, is during a dead-stick landing. E.g., we ll approach slightly higher or faster than normal to ensure reaching the runway, and then use a slip to scrub off the extra altitude/speed. While it might disappoint some of you to hear this, if you re looking forward to using forward-slips to counter your tendency to approach the runway too high and too fast, you ve got the cart before the horse. Frankly, if you had the skill to perform a successful forward-slip, you wouldn t be landing high and/or fast in the first place! Hence, it s a great tool to have in your skill set for those occasions when it s needed, but if your approaches are regularly too high and/or fast, you first need to determine what is fundamentally wrong with your landing setups (See my article: Finding the Optimum Final Approach Speed). Like everything else, forward-slips can be broken down in even more detail, and there are even more scenarios in which forward slips can be used, but as a result of your preparation and the skills you learn practicing what s been covered here, you ll have the foundation required to successfully take on any additional challenges. Good luck!