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Aerobatics...

So you're tired of flying around in circles...

This is a series of 12 articles written by Russell Knetzger of Milwaukee, Wisconsin. The series is entitled "Aerobatics for Sunday Fliers" and I think is a great series. Why Aerobatics? Well, sooner or later you'll get tired of simply "Boring holes in the Air" and want to do what Russell describes as "puposefull flying". The series originally appeared in the AMA's "National Newsletter". Started by Jim McNeill, It was later Edited and Published by Lou Ward, who "commisioned" this series. She did a fine job. The purpose of the National Newsletter was to glean articles and cartoons from various AMA Club Newsletters, and provide them to Editors of Club Newsletters, so they would have interesting material to include in their monthly Newsletters.

I have divided the subcontent up into smaller blocks, each page dealing with an individual skill or maneuver.
These articles helped me learn a number of maneuvers, and are rather easy to understand.

Here's what you need to know first and foremost...

Sooner or later you'll want to do some basic aerobatics with your R/C model because you'll find it becomes too boring just to fly your model in a level course, aimlessly around the field, flight after flight. Purpose of these articles I have written this series of articles so that the "Sunday sport flyer" can perform aerobatics in a safe and satisfying manner. These lessons are not intended to turn the sport flyer into a competitive "pattern jockey." Rather the practicing of your aerobatics is intended to give you some purposeful flying to do, as Bob Underwood of the St. Louis area prefers to call aerobatics. Also, if you aspire to do some teaching of beginning pilots, being able to control a model through all sorts of unusual positions comes in handy. Even if you don't want to teach, learning some aerobatics gives you the confidence to enjoy your sport flying more, knowing you will be bringing the plane back in one piece each time you go out to the field. If a few of you someday should try your hand at competition, these articles have been constructed in a such a way that you will not have to first unlearn any bad habits. The principles of proper positioning and execution that will be stressed in these lessons should stand you in good stead on the field of competition, if that is where you end up. Description of Aerobatic Maneuvers There are approximately three dozen aerobatic maneuvers commonly performed around the world by radio controlled model model aircraft. The Federation Aeronautique Internationale (FAI) publishes descriptions of how each maneuver is to be performed. The Academy of Model Aeronautics (AMA) incorporates the FAI descriptions, adding a few its own, in its handbook issued every two years to all AMA members. The handbook is entitled Official Model Aircraft Regulations. The drawings and descriptions printed under the section entitled Radio Control Pattern are worth general reading at this point. Planes and construction Some of the three dozen maneuvers listed by FAI and AMA are quite difficult to perform, and require years of practice, as well as the use of special pattern models that are exceptionally well balanced and free of warped flying surfaces or crooked construction. (The word "pattern" refers to the patterns that some aerobatic maneuvers describe in the sky, such as the figure M or the classic figure 8.)Others of these three dozen maneuvers are less difficult, and canbe performed with trainer and sport models. Luckily, unlike full scale aircraft which cannot be flown aerobatically unless specially constructed for that purpose so as to withstand the extra gravitational forces exerted on the airframe, virtually all models are inherently strong enough for aerobatics. This is because the nature of the materials we use and the construction methods in aeromodeling, including on training or sport planes kitted since the early 1970s, makes your model strong enough to tolerate the g-forces generated in the aerobatic maneuvers covered in these lessons. Differences between trainer/sport models and pattern planes The words "trainers and sport models" cover a lot of territory. A really basic trainer on which I prefer a student learn to solo has only three channels (engine, elevator, and rudder) and the main wing uses a flat bottom airfoil. A popular example is the Sig Kadet, or some of Lou Andrews' trainers like the H and A-Ray. However, when it comes to aerobatics, except in the hands of a very experienced pilot, such basic trainers are limited to only a few maneuvers, such as the inside loop, three spins, and the Immelmann turn. The simple addition of ailerons to the flat bottom airfoil trainer will markedly expand its adaptability to aerobatics. The Sig Kadet now offers an aileron option. The use of what I call an "advanced trainer" such as the Goldberg Falcons with semi-symmetrical airfoils, or more especially the Bridi RCM .40 or .60 Trainers or Midwest's Little Stik or Sweet Stik models which employ fully symmetrical airfoils, will allow a truly great variety of aerobatic maneuvers.The main limitation of the flat bottom airfoil is its poor inverted flying ability, and the awkwardness with which it rolls about its longitudinal axis, such as when attempting three horizontal axial rolls. The semi-symmetrical wing also has some difficulty with level inverted flight, but it will do it with heavy application of down elevator. (Remember we are talking about flying upside down.) The fully symmetrical airfoil is ideally suited to aerobatic maneuvers. For that reason it is employed on pattern models, and on full scale aerobatic ships as well such as the Pitts Special or the Christen Eagle (which both happen to be bi-planes). Any sport planes which happen to use the fully symmetrical wing will perform aerobatics markedly better than other sport planes. What prevents advanced trainers and other sport models from performing as well as a pattern plane, even if the fully symmetrical airfoil is used, is the operation of the rudder. A rudder on all trainers and most sport planes is capable of rolling the main wing. this is because of the relative positioning of the main wing and horizontal stabilizer in relation to the engine thrust line, plus other factors which I am not qualified to explain. In fact, on trainers and sport models, if you takeoff having forgotten to plug in your ailerons don't panic. You'll find the rudder controls the plane as well or better than ailerons. On a pattern plane the rudder will "yaw" the the tail of the plane without causing the main wing to roll significantly. (If you forget to plug in your ailerons on a pattern plane, and you then takeoff, you have big troubles.) This rolling versus yawing function of the rudder comes into play on one of the most basic of all aerobatic maneuvers the stall turn. With a yawing rudder, you can get your model to nicely rotate 180 degrees on its yaw axis while in a climbing attitude. But with a trainer or sport model, when you apply rudder to your vertically stalled plane to get it to "wing over" into a descending attitude, you will also get an undesirable rolling of the main wing. This results in the model diving so as to face a direction other than what you want. Also if you attempt knife-edge flight, the moment you apply rudder to keep the nose up, on trainers and sport ships, the main wing will roll out of the knife-edge position.With pattern planes, great experimentation has gone into the designs to achieve a rudder function that will result in nice stall turns, and the holding of extended knife-edge flight. These factors are mentioned only to explain why certain maneuvers are not worth attempting on certain aircraft configurations. There are so many other maneuvers that can still be performed credibly by advanced trainers and sport models that you will not miss these airfoil and rudder related limitations. Should you nevertheless like to build a basic beginning pattern plane that utilizes your .40 engine, and does not entail retractable landing gear, I can make no better recommendation that the Bridi .40 Kaos, or the plane on which it was based, the original .60 Kaos, if you have a .60 sized engine on hand. These Kaos twins fly as easily as the Bridi RCM trainers, or my other favorites, the Midwest Stik series. But the Kaos ships have the advantage of rudder yaw rather than rudder roll. So if you have soloed on a basic trainer, and are debating between the various advanced trainers or sport models, and if you suspect you are going to have an interest in aerobatic flying, try the Bridi .40 or .60 Kaos as your next plane. But for the average sport flyer, your Falcon, Sweet Stik, Cherokee, or Bridi RCM trainer will do just fine. Next lesson let's start flying!

The Flight Corridor


You saw in the descriptions a lot of emphasis on centering the maneuver in front of you, and positioning the flight path parallel to the flying field. these of course are important factors that judges use during competition in scoring maneuvers. Was it perfectly centered? Did the plane fly perfectly parallel to the runway? But since these articles are aimed at the noncompetitive sport flyer, let's discuss why proper positioning is still important. The reason for a proper flight path Proper positioning of aerobatic maneuvers by the sport flyer has to do with preventing disorientation. There is no quicker way to crash your model than to practice aerial maneuvers in all sorts of cockeyed positions relative to yourself. I have seen pilots do loops viewed head on; I have seen Immelmanns done directly overhead; and I have seen maneuvers with the plane swooping dangerously toward the pilot and other people assembled at the flight line. All of these positions can quickly lead to disorientation and to panic. Once you are controlling your plane in a state of panic, the outcome is likely to be a crash.
The Proper Flight Path
The proper position for a model aircraft performing an aerobatic maneuver is on a flight path running parallel to the flight line, exactly up or down wind, and out about 300 feet from yourself. The proper location within that overall flight path to execute the maneuver is directly opposite, centered on yourself. An entry and exit altitude of 100 to 200 feet is suggested. At some fields where obstructions or rules do not permit your adjusting the flight path to be exactly into the wind, you may have to forego practicing many of your aerobatic maneuvers on days of noticeable crosswinds. It takes considerable practice to learn to fly a maneuver crosswind without the plane blowing in on you, or drifting way out. So let's leave that complication for the competition pilots. You as a sport flyer, practice your maneuvers without crosswinds. Practicing the aerobatic flight path: the split S turn Keeping a plane flying level and relatively parallel to the flight line requires mastery of two skills: trimming and the split S turn. I won't spend much time on trimming because you should by now know how to set your trim controls to achieve straight and level flight. However it is surprising how many times I have assumed the controls of another pilot's plane, only to find it wanting to sink and to roll. The other pilot was instinctively holding up in his elevator stick, and also holding some aileron correction to overcome the roll without being conscious of either of these corrections. Unfortunately, when the other pilot would attempt some simple maneuver, these out of trim conditions would complicate his efforts, resulting in a bad maneuver and perplexity on his part. So get your plane trimmed into straight and level flight. You must be relaxed as you enter or exit a maneuver, and you can't achieve these moments of relaxation if you are not able to let the plane fly itself for awhile.