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 What All That Stuff Means On The Radio Box
 WHAT ALL THAT STUFF MEANS ON THE RADIO BOX You are out looking for your first radio, an upgrade radio, you are reading ads and boxes and there are all these terms you don't understand. Something about mixing. Do you need that? Maybe, maybe not, but it would be good if you understood the terms. Here is a short discussion on surface/channel mixes. This occurs when more than one control surface is moved by a single input from your radio. I will only touch a few, but you will get the idea. I invite others to clarify or correct my comments and add where these mixes, or others, are used. First, there are three primary control surfaces: Elevator - Pitch or attitude control - nose up and down - usually part of the tail Rudder - Yaw control - nose left and right - usually part of the tail. On a plane without ailerons, the rudder can work with dihedral in the wings to roll the plane to effect turns. Aileron - Roll Control - usually on the trailing edge and outer aspect of the wings, though ailerons can extend the full length of the wings in aerobatic planes. There are two secondary control surfaces, usually used in landing. Flaps - These are a moveable part of the trailing edge of the wing that you lower to slow a plane while adding lift to the wing and lowering the stall speed. Spoilers - Typically used in landing gliders or sailplanes, these are on the top of the wing. When these are raised, they reduce, or spoil the lift of the wing in that area. They can help slow a plane down and raise the stall speed of the plane causing it to descend from lack of wing lift. These can also be helpful in getting sailplanes out of strong thermals. BASIC SURFACE MIXES These two use two surfaces that are coordinated to create the function that are typically performed by separate surfaces. When we move two of these surfaces together we call that surface mixing. V-Tail mix - comes from the fact that on a V-tail plane, you do not have a separate elevator and rudder. The two V surfaces are mixed to perform these functions. If you hit up elevator, both move up. If you hit right rudder AT THE SAME TIME as up elevator, the tail surfaces move some more moving the nose to the right as it moves up. So you have mixed the rudder in with the elevator input. V-tail mixing. For this reason, the surfaces on a v-tail plane are called ruddervators; rudder/elevators Elevon or Delta Mixing - Typically used on a flying wing, like the Zagis, delta wing, like my Electrajet. They combine the function of elevator for pitch, and ailerons for roll. This is elevator/aileron mixing. The surfaces are referred to as elevons when they are used in this way and are usually located at the back of the plane. Many of the newer non-computer radios include v-tail and elevon mixing whereas it used to require a computer radio, or the addition of a special mixing device in the electronics package. Many of the low cost RTF 3 channel planes incorporate mixing in their design. For example the Aerobird uses V-tail mixing. The F27 Stryker uses elevon mixing. ADVANCED SURFACE MIXES Note that none of these mixes are required to fly a plane using a computer radio you can coordinate all types of combinations for different effects. Some can be turned on during the flight. Flip a switch and you will get a different behavior from the control surfaces for the same stick input. I will use the convention of master/slave where one surface gets the input and the other follows. For example, aileron/rudder would imply that you input aileron control and the rudder follows without you touching the rudder stick. While you can do this manually, some of these mixes would be would be very hard to do by hand, and some can ONLY be done from a computer radio. Many of these mixes require radios with 6-8 channels and some require the radio be able to address 4 servos in the wings independently, a feature of higher end radios. Aileron/rudder mix - Coordinated Turn - On power planes and on sailplanes, it is normal to add rudder to aileron input. This is called a coordinated turn and is common to do manually on non-computer radios, but computer radios can be set up to do this automatically. This results in a smoother, more efficient turn. Flapperons - Ailerons can act as flaps, used if you don't have flaps, for landing control. These are known as flapperons which is a change in assignment of the surface from aileron behavior to flap behavior. This requires two servos for the ailerons. Flapperons - flaps act like ailerons. Found this idea being used on a R/E Differential Spoilers - You can take spoilers, at the top of the wings, and tie them to the aileron function. Now you have your spoilers at different heights causing a roll effect. Not as effective as ailerons, but it could enhance the roll of a plane that does not have ailerons. To do this your spoilers require two servos instead of one and they must be controlled from separate channels. This would require at least a 5 channel radio.. Elevator/flaps - snap flaps - This is used in aerobatics or racing to effect very very fast turns or very tight loops. When you pull elevator, the elevator goes up and the flaps go down causing a change in pitch AND an increase in lift in the wing. The plane will turn very tightly. Careful, this can lead to a stall if you don't have enough speed but in the typical application, this is done at high speeds, or in planes that have very powerful motors. Aileron/flaps - You can add the flaps to the ailerons so that the flaps move with, and coordinate with the ailerons The flaps become extensions of the ailerons for more control surface movement. This takes 4 wing servos, and they must each be controlled from a separate channel on your radio. This requires at least a 6 channel computer radio. Only more advanced radios can do this. Likewise, the ailerons can be made to follow the flaps to multiply the effect of lowering flaps. This requires a minimum of three servos, two on the ailerons and one on the flaps. Ailevator - on aerobatic or pattern planes they will split the elevator so that two servos operate each half. Normally they move together to create the normal elevator motion. However when you enable the ailervator mix, the elevator halves will move with input from the ailerons causing the plane to roll much more quickly. This requires the two elevator servos to be controlled from separate channels on the radio. Typically this requires a 7 or 8 channel radio. Snap Roll - this is a mix that actually moves surfaces during a roll to create a highly coordinated and highly repeatable type of aerobatic maneuver. Ailerons and rudder will be controlled. Elevator is likely to be programmed in as well. I have never used this one, but it sounds cool! Camber Changing Trailing Edge - Typically used on sailplanes, they use a mix where the ailerons and flaps move together, typically not from one of the sticks, but from a switch or dial. By moving them slightly up or down, perhaps 1/16", you change the shape of the wing while it is flying. By lowering the flaps and ailerons together you create a more under cambered wing which generates more lift, but typically more drag. If you move them up slightly, then it is called reflex. A minimum of three wing servos is needed to do this. I don't know if this is used on power planes. Crow, Butterfly or Airbrakes - Commonly used on sailplanes, this is a breaking mix used to quickly slow the plane, often in contest flying where you need a very precise landing. Both ailerons go up while the flaps go down. Often there is some elevator mixed in to keep the plane level. This would take at least a 6 channel radio that can take the coordination of as many as 6 servos controlled by one stick, lever, dial or switch. Flight Conditions - Essentially this moves surfaces to a new trim position based on some flight situation. It could be take-off or landing, or it could be some point in an aerobatic routine. It might be a sailplane circling in a thermal. Whatever it is, it establishes a new trim point for the surfaces when there is no stick input. On my gliders, on winch launching, I flip launch mode or launch condition and the ailerons droop 15% and the flaps droop 25% to give me more lift during launch. Imagine the fun you can have changing between different launch modes, or moving from launch to standard flight mode to several enhanced flight modes, to a camber change to 3 different landing modes. Well, this is one of the values of computer radios. Not all computer radios can do all of these mixes and there are other mixes not mentioned here. However when you read the spec sheets, they will usually list Airplane Mixes, perhaps Sailplane Mixes and some also do Helicopter Mixes. You will also hear about mode 1 and mode 2. In North America, Mode 2 is the standard. Developed by Geistware of Indiana© ., 1999. |
