BACK TO BASICS
With so many rc aircraft on the market in both type and number, the beginning rc hobbyist is often overwhelmed by the number of decisions he/she must make regarding what aircraft to buy, as well as how to best operate it. During the course of this blog, we'll delve into some of the issues faced by the new rc operator.
A radio-controlled aircraft is defined as a small flying machine which is controlled remotely by an operator on the ground using a hand-held radio transmitter. The transmitter communicates with a receiver inside the model that sends signals to mechanical relays (servos) and electronic speed controllers, in electric powered planes, which move the control surfaces based on the position of joysticks on the transmitter, thus flying the aircraft. Signals are sent to the plane in the same manner as radio and television broadcasts and they are activated by moving a stick or switch on the transmitter box. Radio signal frequencies are usually measured in kilohertz (kHz), megahertz (MHz) or gigahertz (GHz). The transmitter and receiver in the model must both operate on the same frequency in order to control the plane. The device that determines the frequency utilized by the radio system is called a crystal, and both the transmitter and receiver need a matching crystal to function. Fortunately for the rc operator, crystals are only used in the older MHz radio systems. While radio control systems have operated on designated frequency channels in the MHz range for years, a technology called Spectrum became operational in the early 2000's and is now the dominant radio system. Radio systems using the more recent 2.4GHz frequency band don't require crystals to operate due to a different technology and method of operation, in which random frequencies are applied for each flight, making communication between the rc pilot and the aircraft more secure from outside interference.
Once airborne, the control surfaces of the rc plane come into play. The primary control surfaces of a radio control model plane are the rudder, elevator and ailerons. The most simple rc plane designs fly only by rudder control. The rudder is the movable hinged section at the rear of the vertical stabilizer, which controls the left or right movement of the plane, or yaw. When the rudder is angled to the left, the plane turns to the left and when angled to the right, the aircraft will move in a direction to the right. The elevator is the moving hinged section of the horizontal stabilizer, or tail at the rear of the aircraft. The elevator controls the pitch of the rc model, namely, up, down or level flight. When the elevator is angled upward, the plane will begin to fly upward or fly level with a nose up pitch depending on forward airspeed. When elevators are deflected downwards, the aircraft will begin a dive or descent. If the elevator is held in a level position, the plane will fly level provided it is properly trimmed. The ailerons are hinged moving sections, located at the trailing edge of the wing, frequently positioned toward the outside edge of the wing or wing tip. Ailerons control the roll motion of an aircraft about its longitudinal (fuselage) axis. Ailerons are built in pairs, one left and one right, moving in opposite directions. For example, when the left aileron deflects upwards, the right elevator will simultaneously deflect downward. Ailerons essentially control the roll of an aircraft, left aileron up / right aileron down causes the plane to roll to the left while right aileron up / left aileron down causes the plane to roll to the right. When the elevator is applied upward concurrently with aileron action, the plane will enter into a banked turn in the same direction. Aircraft use this method to turn when they have no rudder control. For an rc plane to be considered fully functional, it must have four dedicated transmitter channels, elevator, throttle, rudder and ailerons, though additional channels may be necessary for functions such as landing gear, lights, bomb bay doors and camera shutters. Helicopters need at least two additional channels over rc planes due to rotor action.
Unless your rc model is a glider, you'll need to consider what type of powerplant is best for your plane. The two most widely used types for rc aircraft are internal combustion engines and electric motors. Internal combustion engines are generically all engines which operate by a fuel source. These sources may include gasoline, glow plug, diesel and turbine. While a glow plug aircraft is sometimes referred to as a nitro powered plane, the difference is only one of name. Internal combustion planes are also often described as gasoline powered aircraft, though they may use a different type of fuel. While there are advantages and disadvantages to each type of power unit, the trend in recent years has favored electric powered rc planes. This is largely due to the development of lithium polymer or LIPO batteries, which come in a gel form and offer near gasoline engine performance. Coupled with the trend in powerplants, the advent of relatively inexpensive ready to fly (RTF) planes over the last two decades has eased entry into radio control aviation for many. In spite of this, a number of hobbyists still prefer gasoline powered planes.
For the true enthusiast, there are a number of ways to construct and assemble an rc plane. Various kits are available on the market, requiring different amounts of assembly, different costs and varying levels of skill and experience. Some kits can be made of all balsa or plywood, while a large number of more recent kits can be built from foam or plastic. Construction of wood kits typically consists of using formers and longerons for the fuselage and spars and ribs for the wing and tail surfaces. Many designs use solid sheets of balsa wood instead of longerons to form the fuselage sides and may also use expanded polystyrene for the wing core covered in a wood veneer, often balsa or obechi. Though rc planes built from these materials are usually heavier, they are also easier to build. Aircraft made from the lightest materials are primarily suitable for indoor flights or areas of low winds. Some of these are made by bringing frames of balsa wood and carbon fiber up through water to pick up thin plastic films, similar to rainbow colored oil films. In recent years craft injection-molded lightweight foam (foamies), sometimes reinforced with carbon-fiber are more compatible for indoor flight, opening new possibilities for hobbyists. Expanded Polypropylene (EPP) foam planes are an improvement over the injection mold foam design due to their flexibility and durability in the event of a crash. Other names for this type of material are AeroCell and Elapor. Since flying models are built under the same principles as real aircraft, construction differs from that of static models. A recent development in rc model designs, is the use of corrugated plastic, marketed as Coroplast. These models are collectively called SPADS, or Simple Plastic Airplane Design. Proponents of the SPAD design emphasize the advantages of ease of construction, durability, and a lower unit price in comparison to balsa models, although the SPAD planes are heavier and often lack the detail of balsa models. However, if an rc hobbyist wants to pursue flight directly, two types of kits are readily available. Ready to fly (RTF) planes come pre-assembled and usually require only wing attachment or other basic assembly. Everything needed is provided including the battery, transmitter and receiver. RTF planes require minimal assembly time and can be prepared for flight within a few minutes. Almost ready to fly (ARF or ARTF) airplanes require final assembly, typically including engine and fuel tank installation (or electric motor, speed controller, and battery), servo and pushrod installation, control surface attachment, landing gear attachment, and sometimes require gluing the left and right wing halves together. The average ARF takes about twenty hours to assemble as opposed to fifty to one-hundred hours for the average wood kit. ARF planes typically only include the airframe and a few accessories, such as pushrods or a
fuel tank. Therefore, the power system ( gas engine, glow engine, electric motor) and any other required accessories, such as radio system components ( transmitter, receiver, battery) must be purchased separately.
Perhaps, the most important issue for the new rc pilot is knowing how to properly fly the aircraft.
The rc aviator of today has a valuable training aid in the form of online flight simulators. Flight simulators allow the hobbyist to make the decisions and go through the motions of flying an rc aircraft without actually flying one. The flight simulator program that runs on your home computer will either have its own transmitter-style controller or or will let you use your own transmitter to power the software. Modern rc flight simulators running on a computer are both an extremely realistic and thorough training program. Depending on your budget, a number of good simulator programs are available, to include AeroFly, RealFlight, Reflex XTR and Phoenix. RC flight sims allow the hobbyist to fly the plane in complete safety while putting the student in situations which increase his/her coordination and reactions. Though there are still differences between operating a simulator and a real rc model, a simulator can give the prospective rc pilot a valuable advantage when they start flying real rc aircraft. Finally, the old fashioned approach of utilizing the services of an rc flight instructor are often the best way for the rc hobbyist to learn how to control the aircraft. While an instructor's guidance won't prevent the occasional accident, they will increase the survival rate of the plane at the end of the day. Instructors allow the student to fly the aircraft, then assume control when difficulty arises. Sometimes crashes do happen when the student transfers control of the aircraft to the instructor. This can be overcome by use of the buddy box system, in which two transmitters are connected by a lead, enabling the instructor to take control in an instant. Instructors also offer insights to the student about characteristics of their aircraft, membership in an rc model club, radio systems and governmental regulation of the hobby. However, the greatest service of an instructor to the rc flight student is offering one-on-one feedback.