Secrets to snap rolls

Inside and outside snap rolls can add great excitement to your flying while opening up a whole new world of maneuver possibilities. Outside, or “negative,” snap rolls are accomplished by applying full (normal rate) down-elevator while at the same time cross-controlling the rudder and aileron. How does this work? The ailerons produce the same direction of rotation whether the snap is inside or outside; however, during an outside snap, the rudder causes the tail to rotate in the opposite direction in which the rudder is applied. Because of this, the rudder must be input opposite the aileron to achieve the same rotation as the aileron during an outside snap roll.

Here’s an example. During a right out-side snap roll, full-forward elevator is used to cause the wing to exceed the plane’s critical (negative) angle of attack and stall. At the same time, aileron and rudder rotate the airplane clockwise to the right. A close examination will show that left rudder actually moves the tail clockwise during a right outside snap. Just remember to cross-control the aileron and rudder inputs when performing an outside snap roll.

The direction in which you apply aileron determines whether it is a left or right snap. During initial training when you’re remembering the stick positions for each, it helps to think of a left outside snap as a “meter snap,” with both sticks applied toward the traditional top center location of the transmitter’s battery meter. A right outside snap is an “outside corners” snap. Note that if your model is greatly overpowered, you may want to snap at a lower throttle setting, especially when the airplane is descending.

Most airplanes outside snap-roll better to the right (with left rudder and help from the propeller slipstream). Many people also find that right snaps are more comfortable because their fingers don’t have to stretch as far. Stopping a snap is accomplished by simply neutralizing the controls. Keep in mind that the snap will continue a bit farther in the split second that it takes you to neutralize the controls and for the airflow to reattach to the wing. Therefore, you’ll need to start neutralizing the controls a split second before you actually want the snap to stop.

FLYING AN OUTSIDE AVALANCHE

Whereas the typical stunt pilot often seeks stimulus through taking risks and buying new equipment, the proficient aerobatic pilot energizes his flying by introducing variations and rearranging maneuver components to come up with new maneuvers. One example is adding an outside snap roll to the top of an outside loop to perform an outside avalanche.

After establishing a parallel line with the wings perfectly level, an outside avalanche is performed by pushing into an outside loop and then inputting an outside snap roll at the top of the loop. The snap is stopped with the wings perfectly level (upright), and then the plane is pushed through to complete the outside loop. At this point, students of precision aerobatics should emphasize their use of left rudder during the first half of the loop to correct any negative P-factor and prevent sideways drift prior to the snap. Keep in mind that most of the problems people experience with this maneuver are due to performing a poor loop because the pilot is thinking ahead about the snap. Consequently, the snap usually ends up magniflying the deviations that originated during the loop. On the other hand, a pilot can get away with a less than stellar snap when the loop that led up to snap was tracking truly vertical.

Snapping to an “Attitude”Correctly stopping whole-number snap rolls (1 or 2) is obvious, however, stopping fractional snap rolls such as 1/4 requires an awareness of which attitude the plane needs to be in when the snaps are completed.

In other words, since there is little time to count fractions of snaps, you instead snap the airplane to a predetermined attitude. For example: when a 1/2 outside snap rolls are performed from an upright attitude on top of an outside loop, you must stop the snaps with the airplane inverted (setting the stage for a pull into the back side of the loop).

Another option is to perform the first half of the loop inside (pulling), execute 1/2 snaps, and push into the back side of the loop. In this version, the airplane would approach the top of the loop inverted, and the pilot would snap the airplane to the upright attitude prior to pushing to complete the loop.

Because the airplane travels some distance throughout the snap, it’s important to initiate the snap a little before the top of the loop to center the snap overall across the top of the loop, i.e., 1:00.

A double outside snap at the top of a loop is another variant of the avalanche. Because the double snap offers more time to anticipate when to neutralize the con- trols with the wings level, most pilots find that the double snap avalanche is easier than a single. Keep in mind that the double snap will take longer to complete and must therefore be initiated a little earlier than where you start a single snap to keep the snaps centered over the top of the loop, e.g., 1:30.

Initiate an outside loop with the wings level. As the airspeed decreases, add left rudder to correct for negative P-factor and maintain a precise vertical track during the first half of the loop.

Another awesome avalanche variant is accomplished by performing a half snap rolls at the top of a loop and, to the awe of those who are able to discern what happened, completing the loop with the airplane in a reverse attitude to what it was at the start. Note that the 1/2 snap avalanche is easier when the first half of the loop is performed to the “outside” if things get a little out of line, the corrections will be easier to make during the conventional pull-out loop finish. This maneuver is called an “outside-inside avalanche,” referring to the first and second 1/2 loops.

Many of the challenges that advancing aerobatic pilots experience are not due to their ability to master the finer points of the maneuvers, but are the result of focusing so much on the advanced components that they neglect the fundamentals. How comfortable you are inputting the snaps on top of loops will reflect how well you flew the first part of the loop, and whether the wings are level when entering the back side of the loop after the snaps. During your initial training, I recommend that you briefly pause at neutral after the snap to reduce the tendency to botch the snap as a result of rushing to enter the back side of the loop. No doubt, these maneuvers present some great flying challenges, but the rewards of learning them are some of the greatest that can be had in the sport. Happy flying!

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Take off with a Snap

If you are aspiring to become a better aerobatic pilot, no doubt you’re constantly searching to add excitement and variety to your flying. After all, the best aerobatic pilots are skilled when it comes to combining certain elements from one maneuver with elements from another. This month, I would like to combine the snap roll with a takeoff, so you can get attention on your flight right from the start! Before we get into a deep discussion about this eye-catching aerobatic move, we will begin by taking a look at your aircraft and how it is set up with respect to dual rates and exponential settings. Now, let’s get down to business!

FIRST THINGS FIRSTMany aerobatic airplanes today are advertised as being “3D-capable,” and they have very large control surfaces so that they can perform maneuvers while in a stalled condition. However, having large control surfaces and a lot of control surface deflection is not needed for any maneuver that isn’t considered “3D” and, with respect to this month’s move, a lot of control deflection is not needed. The goal is to perform a precise 1½ positive snap on takeoff’nice, crisp and clean!

If you usually read my columns, you are aware of the fact that I prefer to use flight modes, with my dual and/or triple rates on one switch. This means that my aileron, elevator and rudder rates are on one switch. To perform the combo maneuver of the month, I prefer to use two flight modes. On my lowest rate, I have about 15 degrees of aileron, 12 degrees of elevator and 35 degrees of rudder deflection with 20-, 25- and 50-percent exponential, respectively. On my second rate, I have about 30 degrees of aileron, 25 degrees of elevator and 32 degrees of rudder deflection and 45-percent exponential on all of these surfaces. Keep in mind that values differ from airplane to airplane.

When I perform any takeoff and landing, I am always on my low rate settings. Where I perform a stunt like a snap roll only feet from the ground, I switch to my mid rate settings right before the snap roll and switch back to my low rate setting when the snap roll is completed. While everyone has different personal preferences, this is the setup that has worked best for me as I do not want my aircraft to be sensitive while flying on low rates.

No matter what size aircraft you are flying, whether it is a small park flyer or giant-scale, always take advantage of flight modes and adjust each rate as needed to cater to your liking. For example, once flying, if you move the aileron stick to its maximum and the roll rate of the aircraft is slow, increase the dual rate for that given rate. Similarly, if you feel that the airplane is too quick to respond around neutral but the endpoint value is great (the dual rate value), increase the amount of exponential you are using. Do this test on all control surfaces.

OVERVIEW OF A 1 ½ POSITIVE SNAP ON TAKEOFFBefore attempting the 1½ positive snap

on takeoff, you should be proficient with performing positive snap rolls in general. When you execute this move, you must be in complete control and exit the maneuver at a safe altitude. Do not drop altitude throughout the snap roll as this can be fatal when you’re only feet from the ground!

Depending on the power to weight ratio of your aircraft, your throttle percentage may differ slightly. On most of my models, I prefer to apply almost maximum power throughout the takeoff roll and then decrease power slightly once the airplane breaks ground. Then I pitch the airplane up slightly by pulling back on the elevator control stick and apply the same direction rudder and aileron. I’ll release elevator to unload the airplane and ensure that it does not drop any altitude through the rotation. Then, once inverted and after 1 ½ snaps have been performed, I’ll release aileron and rudder input and apply a touch of down-elevator to sustain level inverted flight. While this may sound simple, there are a lot of different elements that need to be perfected.

FOUR STEPS TO SUCCESSLet’s divide this stunt into four steps. In this example, we will take off from left to right. Always take off into the wind. If a strong crosswind exists, take off in a direction that is favorable.

Step 1. While on low rates, add about 80-percent throttle and apply rudder input as needed to keep the airplane travelling straight down the runway. With tail-drag-gers, you’ll need to hold some up-elevator and slowly release elevator input as the airplane is nearing the liftoff speed. Then, pull back ever so slightly on the elevator control stick until the airplane is in the air.

Step 2. Once you are about 15 feet in altitude, flip to your mid rate and come back slightly on power if the airplane’s speed is too fast. Pull back slightly on elevator input and apply the same direction aileron and rudder to initiate the snap roll. In this case, we will perform the snap roll to the left, so we will need left aileron and left rudder. Sometimes, people are confused by the control inputs needed in performing snap rolls. When performing a positive snap roll, up-elevator is needed along with the same direction of aileron and rudder input. When performing a negative snap roll, down-elevator is needed in addition to opposite direction rudder and aileron. It is critical to time this portion of the maneuver so that the airplane will precisely execute 1½ rotations and exit inverted.

Step 3. Throughout the 1½ rotation, apply throttle (if needed) to keep the airspeed up. Once the airplane nears the 1½ rotation point, you’ll need to neutralize aileron and rudder so that the airplane stops the rotation precisely where desired. This step may take some time to perfect, so altitude and familiarity is key. After all, this maneuver should only be done on takeoff if you are confident in your ability to execute snap rolls on demand in a precise fashion.

Step 4. Since 1½ positive snap rolls have just been performed, you will now only have to apply down-elevator, as needed, to sustain your altitude. Once you are familiar with how to perform this maneuver, you can pull the throttle back to drop airspeed slightly and descend in altitude so that you are just inches off the ground while inverted!

I have just described the perfect scenario where little to no wind is present. If a severe crosswind exists, I recommend that you perform the snap roll into the wind. For example, if we are taking off from left to right and there is a strong wind blowing in, I would snap to the left so that the airplane snaps away from you. Heavy winds may cause the airplane to drift throughout stalled maneuvers like the snap.

Now you have the keys to fly the 1½ positive snap on takeoff with utmost pizzazz. I must admit, this maneuver is very exciting to both watch and perform, but it is demanding on your flight skills. Do not attempt this maneuver until you are fully capable of precisely executing snap rolls without any loss in altitude. Until next time, safe flying and always remember to have fun!

BY JOHN GLEZELLIS; ILLUSTRATION BY FX MODELS

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