Part 1: Soaring for Beginners | Contents | Chapter 2: Getting Started

Chapter 1: An Overview of R/C Soaring

This chapter introduces the concept of radio controlled soaring. R/C soaring is poorly understood outside of the soaring community. This overview should help to clarify what soaring is as a sport and why we do it.

1.1 Flying

Sailplane flying is the ultimate challenge. It is a pure sport, involving just the pilot and the elements. You will be flying your plane at the extremes of visibility, a mile away, at thousands of feet, and in conditions that will later send a chill up your spine. You'll fly in thermals so strong they take your plane out of sight in minutes. You'll have flights where your knees will be shaking twenty minutes after you find out the plane is still OK. You will fly slopes in winds so strong you need ski goggles just to see the airplane. There is little room for error. Unlike our powered brethren, there is no throttle stick to kick in and go around. There's only you and the elements.

At the same time soaring can be the ultimate in relaxation. I've had lazy summer days where the plane just wouldn't come down. I've spent afternoons lying in the grass watching the plane circle itself in a big thermal, with my transmitter laying beside me on the ground. There's nothing like hooking your first big thermal, hitting a perfect landing, completing your first cross country flight or flying your newest plane for the first time. Silent flight is good therapy for the soul.

The people you meet while flying are equally entertaining. You can't imagine how many good people there are in the soaring community. From the local club to the yearly nationals, R/C soaring people are all first rate. At many flying sites the best source of thermals is the hot air rising from the pilots talking. Soaring pilots are a never ending source of tall tales, any of which they will share with the slightest provocation. One of the greatest challenges you will face is to get some flying in between all of the kibitzing.

Flying a radio control plane is not as easy as it looks. For example, a plane coming towards you has its rudder reversed. If you push the stick left, it will turn to your right. It takes some practice to consistently put yourself in the plane's frame of reference, especially when the plane is in a bizarre attitude a long way from you. It will take five or six sessions with an experienced pilot before you can solo. Do not try learning on your own. You will certainly crash the plane on the first flight, and likely destroy your plane after a few flights if you do. If you have an instructor to fly the launches and landings, the life expectancy of your airplane rises dramatically.

Tip 1: Always have an experienced pilot teach you to fly. Learning on your own is a recipe for disaster.

1.2 Types of R/C Soaring

There are two general classes of soaring: thermal and slope. Thermal soaring is generally more popular than slope soaring, primarily because thermal soaring can be done from any football sized field. Each places unique requirements on both the pilot and plane. Many pilots enjoy both thermal and slope flying. There are also significant subclasses in each, based on both contest and sport rules. For example, thermal soaring includes duration, distance, speed, scale model and cross country events, to name just a few. Slope soaring includes duration, slope combat, speed, scale modeling, and much more. All in all, R/C soaring is a very broad sport, enveloping many diverse disciplines.

1.2.1 Thermal Soaring

Thermals are rising bubbles of air caused by the uneven heating of the ground by the sun. Thermals can be found in any terrain, and under any weather conditions, but some conditions and terrain are more likely to produce thermals than others. The plane is launched using a launch system such as a high-start to an altitude of 200-1000 feet, then flown in search of thermals. A plane in a thermal exhibits certain subtle visible signs. With experience, thermal pilots learn to recognize these signs and circle in the thermal to gain altitude and extend flight times. Thermal planes typically have long wingspans, and are flown at great distance in search of lift. For the beginner, thermal flight times are generally only a few minutes, but with practice thermal flights of 20 minutes to well over an hour are not uncommon. Typical thermal competition events include duration, distance, speed, and precision landing.

1.2.2 Slope Soaring

In slope soaring, wind power rather than thermals are used to keep the plane in the air. For slope soaring, you need a suitable hill or slope, with a steady wind blowing up the face. The plane is hand-launched from the edge of the slope, and the wind rising up the slope is used to keep the plane aloft. Finding good slopes with steady wind can be difficult in some areas. Since slope lift is usually much stronger than thermal lift, slope soarers tend to have shorter wings and are designed for quick aerobatic response. Thermal planes can be used for slope soaring, but the reverse is not generally true, since slope soarers are designed to perform in much higher lift conditions. Slope flight times are much longer, in general, than thermal flight times. Slope competitions include duration, speed, aerobatics, and even combat.

1.3 Ten Steps to Successful Soaring

If you are serious about entering the world of soaring, here's ten quick steps to success. All of these subjects will be covered in more detail in the chapters to follow.

  • Visit the local soaring club, watch some sailplanes fly and ask for advice from club members.
  • Research and purchase an appropriate trainer sailplane.
  • Purchase a radio with some growth potential in mind.
  • Join the Academy of Model Aeronautics.
  • Joint your local club, and attend the meetings.
  • Clear some space out and build your plane.
  • Have an experienced flier check your progress at several stages as you build your plane.
  • Select an instructor from the local club to help you learn to fly.
  • Fly under the supervision of your instructor until you have soloed your plane in a variety of conditions and attitudes.
  • When you've become a great pilot, take the time to teach someone else to fly!

1.4 Sailplanes

There are four general classes for sailplanes. Sailplanes in class A and B are easier to transport and fly from small fields, but class C and D airplanes have much better performance overall. Most people learn to fly a two-meter airplane, and then build other sailplanes as their skills advance.
  • Class A: Handlaunch - Sailplanes with projected wingspan measuring 1.5 meters or less. These planes are typically very light weight (< 1 lb) and are hand launched like a javelin. Because of their light-weight construction and tiny flight times, handlaunch planes are primarily for intermediate and advanced fliers.
  • Class B: Two Meter - Sailplanes with projected wingspan measuring 2 meters or less. Most beginner sailplanes are two meter ships, because these planes are small, responsive, and have reasonable performance.
  • Class C: Standard - These planes have a projected wingspan of 100" or less. This class was very popular in the 1970's-1980's as it offers a reasonable compromise between the large unlimited class planes and small two-meter planes. Many of the legendary floater designs (Aquila, Sagitta) of the 1970's and 80's were of this size.
  • Class D: Unlimited - Unlimited class sailplanes have projected wingspans over 100". The most popular planes in this class are around 3 meters in size, (10-12 feet). Unlimited class planes have the highest performance, and typically incorporate the most advanced features.

1.4.1 Sailplane Controls

Sailplanes are controlled using anywhere from 2-4 control surfaces. The pilot on the ground uses a small joystick to control these surfaces, and direct the flight of the sailplane from launch to landing. The following controls are most commonly used on sailplanes:
  • Rudder - The rudder controls the left and right (yaw) axis of the airplane. On beginner and intermediate planes, the rudder turns the airplane. On more advanced sailplanes, the rudder is coupled to the ailerons to turn the plane.
  • Elevator - The elevator controls the up and down attitude (pitch) of the airplane. Pulling back on the joystick raises the nose of the airplane, and pushing forward lowers it. On a sailplane, the elevator is used primarily to control airspeed and to coordinate turns.
  • Ailerons - Ailerons are movable surface on the trailing edge of the wing. These surfaces move up and down in an opposite manner (i.e. right side up, left side down) to control the roll angle of the sailplane. They are most often used in coordination with the rudder and elevator to turn the plane.
  • Spoilers - Spoilers are surfaces that extend from the top center of the wing to create turbulence and drag. They are used primarily for precision landings. The typical sailplane has a very shallow glide angle and is difficult to precisely land. Spoilers (and flaps) let you adjust the glide-path for precise spot landings.
  • Flaps - Flaps are movable surfaces on the inner trailing edge of the wing that move together to change the shape of the wing. They are typically extended downward to slow a plane down for landing or thermaling, and reflexed upward for additional speed. Flaps give the advanced pilot more control over the speed and lift characteristics of the wing for better overall performance. In addition, flaps can be extended nearly 90 degrees to act like spoilers for precision landing.

Tip 2: A polyhedral, two channel (rudder, elevator) sailplane like the Gentle Lady is best for beginners!

There are two general sailplane configurations: polyhedral and straight wing. Polyhedral planes have three angles in the wing, that allow them to be turned using only rudder and elevator (two channel) control. The polyhedral angle in the wing provides inherent stability to the plane, making these planes easier to fly. They use only the rudder to turn the plane. Straight wing airplanes have little or no angle in the wings, and instead rely on ailerons coupled with the rudder to turn the plane. These planes usually incorporate rudder, elevator, aileron and flaps for full four channel control. Straight wing airplanes generally perform slightly better on launch and in wind, but are also harder to fly since they do not have the inherent stability of a polyhedral wing. By popular convention, polyhedral planes are affectionately called gas-bags for their slow fight and gentle disposition. Straight-wing and aileron controlled planes are called lead-sleds because they are generally heavier and fly much faster.

1.4.2 Sailplane Pilot Level

Sailplanes designs can also be characterized by pilot level. The advanced competitor generally flies a much more advanced design than the beginner. Pilot skill matters more than plane choice, so don't get too caught up in the plane of the month fashion club. Instead, choose an airplane that challenges your skills, but is appropriate for your current skill level, then fly it until it won't fly anymore. The pilot who is more experienced will generally beat the pilot with the fancier plane. Guidelines for selecting an airplane are included in later chapters, but general characteristics that distinguish beginner, intermediate and advanced planes are introduced here.

Beginner Sailplanes

Beginner sailplanes are designed to be inexpensive, slow, tough, responsive, and very stable. Typically they are two channel (rudder and elevator) planes made of traditional built-up wood construction or Almost- Ready-to-Fly (ARF) foam. Most beginner planes have two meter wings, and may incorporate features like rubber band wing attachments to reduce damage from crashes. True beginner airplanes can be distinguished by their "flat-bottom" airfoils. A flat-bottom airfoil flies at slow speed compared to a more advanced airfoil, making the plane easier for a beginner to fly. If you have never flown before, a beginner plane is a must. Flying an R/C sailplane is much harder than it looks, and crashing a sturdy, slow flying beginner's plane is much better than crashing an expensive, light, fast flying advanced plane.

A revolution in beginner technology took place in 1996-1997 with the introduction of EPP foam thermal and slope trainers. These planes are made of special foam that is wrapped with packing tape to create a nearly indestructible airplane. The technology was originally developed for slope combat airplanes, where opponents intentionally smash their planes together in an attempt to force each other into the ground. These foamies make perfect trainers since they will withstand the heavy punishment an average beginner dishes out. In addition, foamies are easier to build than traditional sailplanes. With a foamie trainer, the beginner will spend a lot more time flying and a lot less time building and repairing - a double advantage!

Intermediate Sailplanes

Intermediate sailplanes are generally moderately expensive, faster, responsive, and slightly less stable. These planes usually have additional controls such as ailerons, flaps or spoilers to accurately control airspeed and altitude for precision competition and landings. The added speed allows these planes to cover a larger area in search of lift, and handle high winds better. Intermediate planes often have stronger, more accurate wood over foam core wings, with carbon fiber reinforcement to allow for more violent zoom launches. The added speed and control of these airplanes allow a pilot who has mastered the basics to expand their skills for better overall performance. Intermediate planes are also the most popular planes for sport flyers who want good performance without investing a bundle.

Advanced Sailplanes

Advanced sailplanes are generally very expensive, fast, unstable, and responsive. These planes are designed for advanced competition, and typically require expensive computer radios to control the plane. A minimum of four channels (rudder, elevator, aileron and flaps) is used with as many as six separate micro-servos. Construction varies from pre-sheeted wood over foam to the most expensive kevlar and fiberglass layered planes. These planes are designed to handle the strongest zoom launch, and are also engineered for speed and distance events. The fast speed and computer control allow these planes to launch higher and search vast distances for lift, as well as achieve blistering speed runs. The features of these advanced planes are only needed for serious competitors with years of experience, but offer the highest performance if used properly.

1.5 Radio Control

Modern radio control systems are truly a miracle in miniaturization. Weighing as little as 4 ounces, these systems let you control your sailplane beyond the point where you can safely see it. Complete radio systems cost anywhere from $60 to well over $1000, but all radios have the following basic components.
  • Transmitter - A transmitter is the system you hold in your hands to fly your sailplane. Most sailplanes transmitters are rectangular, with two joysticks on the front and a long antenna coming out of the top of the box. To fly the plane, the pilot manipulates the controls, which the transmitter then relays to the plane. All modern R/C systems are proportional, which means if you move the joystick a little, the control surface on the plane moves roughly the same amount.
  • Receiver - The receiver is the corresponding controller in the airplane. Receivers are typically small boxes, about the size of a business card and 3/8" to 1/2" deep, with an antenna wire trailing about 24" from it. The receiver intercepts the signal from the transmitter, decodes it, and controls the mechanical servos, which directly push or pull the sailplanes control surfaces.
  • Servos - Servos are small mechanical motors which precisely rotate in response to signals from the receiver. Servos are connected mechanically with pushrods or cables to the control surfaces of the plane. Each plane has from two to six servos. Each servo occupies one "channel" of the radio. The number of channels, and servos, determines how many control surfaces can be controlled. Servos are available in different sizes and power levels for different applications. Standard and micro-sized servos are most commonly used in sailplanes.
  • Batteries - In the airplane, and transmitter are small battery packs which power the transmitter and receiver. Typical rechargeable (NICAD) battery packs are designed to operate anywhere from one to four hours on a single charge. This is typically more than enough for an afternoon of flying. Cheaper radios use standard AA or AAA batteries, which must be replaced after a few afternoon's of flying. It is always better to purchase a system with rechargeable batteries if you can afford it. These batteries can be recharged overnight using a small charger that comes with the system.

1.5.1 Radio Channels and Frequencies

Radios generally have a fixed frequency, also called a channel assigned to them. Different radios are on different channels, allowing more than one plane to fly simultaneously. In the United States, 50 channels, numbered 11-60, are allocated by the FCC in the 72MHz frequency range for model aircraft use. For most radio systems, you specify the channel when you purchase the radio system, and will use than channel as long as you own the radio. For most radio systems, you must send the transmitter to the manufacturer to change the channel. Some advanced computer radios let you change channels by purchasing an additional transmitter module and receiver crystals, but these systems generally are very expensive. If you are going to purchase a new radio, it is a good idea to check with your local sailplane club first. Many clubs keep lists of frequencies for each member, and can tell you which channels are open for use. Obtaining your own channel is always best, since you don't want to have to take turns with someone else on the same channel when you fly.

Note that in the US, laws governing radio control changed in 1991 from wide band systems to narrow band. All systems manufactured since 1991 are designed for the new 50 channel narrow band frequencies. You should, however, avoid using any pre-1991 radio control system unless it has been upgraded to the 1991 standard. The pre-1991 systems use the same frequency band, but each channel in the old band occupies several channels in the new band. If you use an old system, you could potentially shoot down several of your friends who are using nearby narrow band channels. Most 1991 compatible systems are identified by a gold sticker on the receiver.

Clearly, if two pilots are flying on the same channel, the result will be disaster. At most club flying sites, and all competitions a simple method is used to control frequencies so two pilots do not conflict. If only a few pilots are at the field, simply cross checking with the other pilots to determine conflicts may be sufficient. If a large number of pilots are flying, clothes pins labeled with each channel number are used. The rule is simple, if you don't have the clothes pin with your channel number clipped to your transmitter, you can't turn the radio on. At very large contests, transmitters are actually impounded in a central area, and released to the pilot only when it is the pilot's turn to fly.

Interference can also be a problem if you are flying alone. Someone could be flying planes at a field nearby, and still cause trouble for you. Its a good idea to know which fields are within a few miles of your chosen flight zone. As extra insurance, I always turn the receiver on for a minute or two before turning my transmitter on at unknown sites. If the controls start moving or seem excessively noisy, I will stop and try to find the source of the problem. Its better to lose an hour of flying than lose an airplane.

1.5.2 Radio Control Types

There are four general types of aircraft radios. They vary in functionality from the simplest two channel radio to the most expensive computer radio. A brief description of the four types follows:
  • Two Channel Systems - Two channel radios are very inexpensive, priced at less than $100 for a complete system. Unfortunately, most two channel systems have two control sticks, one per channel. Typically the rudder control is on the right joystick, and the elevator is on the left. This type of system is very difficult to learn and control because you need to use and coordinate both hands to fly. Slightly more expensive four channel radios have both rudder and elevator on a single joystick on the right side, making it much easier for the pilot to control. Also two channel systems rarely come with rechargeable batteries, meaning you must constantly buy new batteries. For a few dollars more, an inexpensive four channel system is a better buy.
  • Four Channel Radios - Simple four channel radio systems are available for less than $150 and are a great investment for the beginner. Four channel systems offer the standard two stick control system, rechargeable batteries and three servos. A four channel system of this type can be used to control beginner to intermediate planes easily, and can even be used on some advanced sailplanes. For a beginning or intermediate pilot, this type of system offers the most bang for the buck.
  • Mixing/Computer Radios - Basic computer and electronic mixing radios offer many of the same features. The most important of these is the ability to electronically mix two radio channels together. For example, when the pilot extends spoilers or flaps, it tends to pitch the airplane either up or down. Using a mixing radio, the elevator can be mixed with the flaps or spoilers to automatically compensate so the plane does not change pitch. Another example is V-tail mixing, where a V-tailed airplane needs mixing of the two control surfaces to provide separate pitch and yaw control. Rather than mechanically link the two channels, a mixing radio can mix them electronically. The limitation of these radios is that mixing is typically allowed only on preset channels and in preset configurations. They offer a reasonable compromise for intermediate pilots who need mixing features but don't want to spend the extra money for a sailplane programmable computer radio. Typical prices for new systems are in the $200- $250 range.
  • Sailplane Programmable Radios - The most capable and most expensive radios have dedicated sailplane functions, including programmable mixing. These radios directly support many of the most common sailplane functions, and also have programmable mixing functions to allow any channel to be mixed to any other. This gives the pilot the most flexibility since any function can be assigned to any switch or control. In addition, each control and mixer is electronically adjustable, allowing the radio to be tailored to precisely trim the airplane. Typically these transmitters can store three or more plane configurations in memory, letting you switch between them at will. Naturally, these are the most expensive radios to purchase, but you can often find used systems at a discount price, making them very attractive. Fully programmable sailplane radios cost $400- $1000, but used transmitters are available for as little as $150.

Three different modulation methods are used to encode your radio signals. These are, in increasing order of price, Amplitude Modulation (AM), Frequency Modulation (FM), and Pulse Code Modulation (PCM). AM and FM are essentially the same methods used in AM and FM car radios, but on a different R/C frequency. The vast majority of radios in use today are FM, as FM is reliable and relatively inexpensive. FM radios are less susceptible to noise and interference than their AM counterparts. In addition, most FM receivers are dual filtered, adding an additional layer of noise suppression. PCM radios offer even better noise rejection that FM, but at a significantly higher price. Unless you are flying a very expensive (> $1000) airplane, you will find that FM offers very good noise rejection and range at a reasonable price, making it the radio system of choice for most pilots.

1.6 Launching

There are six generally accepted methods for getting your plane into the air. For slope soaring the plane is hand-launched from the top of the slope. For thermal soaring, the plane is usually towed into the air using a towhook on the bottom of the airplane under the wing. Each method will be covered in detail in later sections of the book, but a brief summary is included here.
  • Hand Launch - Hand launching is simply giving your airplane a good solid heave to achieve flying speed. This method is used primarily for slope and hand-launched (class A) gliders, but you can hand launch larger planes to test the trim and provide landing practice.
  • High-Start - A high start is nothing more than a really big rubber band. A standard high-start consists of 100 feet of surgical tubing and 200-400 feet of nylon or monofilament string. One end is staked down, the rubber is stretched 50-100 yards, and the towhook of the airplane is connected to the other end. The high-start pulls the plane up to a height of 200-400 feet, and a small parachute returns the high-start to the ground.
  • Electric Winch - A winch is an electric version of a high-start. Rather than rubber, an old Ford starter motor is used to launch the plane. The winch sits in front of the pilot, and is connected with nylon or monofilament line through a pulley as much as 1000 feet away and back to the airplane. The pilot controls the speed of the winch using a foot or hand switch by pulsing the motor. The main advantage of the winch is faster pulling speed and the ability to control launch speed. Generally a winch will launch a plane much higher than a high-start, with launch altitudes of 500-1000 feet possible.
  • Motor Assist - Sailplanes can be equipped with small gas or electric motors. Though sailplane purists will scoff at you, this is a good method for achieving excellent thermal altitude. Electric sailplanes are generally more accepted than gas because they are quiet. The main disadvantage of motors is their weight. Batteries and gas engines are heavy, and this hurts your thermaling performance. Tiny, 60" 400-speed thermal planes have caught on in some parts of the country because they are inexpensive, and small enough to throw in the trunk. Since you can fly a small electric from most any field in minutes, they are very popular for lunch break and after work flying.
  • Hand Tow - If you have an athletic friend or child, you can hand-tow your plane. This method has gained dramatically in popularity in recent years because of a new international thermal competition called F3J, which specified hand tow launches. The specified towing equipment is 150 meters of monofilament or nylon line. You can achieve spectacular launches using hand-tow of 500-800 feet, and the equipment is extremely cheap.
  • Aero-tow - Aero-tow uses a radio controlled powered aircraft to tow the sailplane into the air. This method is most popular for scale sailplanes since it duplicates the majesty of full-scale aero-tow. This method is the most demanding in terms of equipment, since the powered plane must be of sufficient size and power, and both planes must be equipped with releasable towhook. It is also very demanding for both pilots since the tow must be made at the correct speed and attitude to avoid a variety of possible problems. Still, for the scale purist, aero-tow is the ultimate launch!

Part 1: Soaring for Beginners | Contents | Chapter 2: Getting Started

Copyright 1997-1998 Bradley J. Smith
All Rights Reserved