as deploying retractable landing gear, opening cargo doors, dropping bombs, operating remote cameras, lights, etc. Transmitters are available with as few as 2 channels to as many as 28 channels. The right and left ailerons move in opposite directions. However, aileron control will often use two channels to enable mixing of other functions on the transmitter. For example, when they both move downward they can be used as flaps (flaperons), or when they both move upward, as spoilers (spoilerons). Delta winged aircraft designs commonly lack a separate elevator, its function being mixed with the ailerons and the combined control surfaces being known as elevons. V-tail mixing, needed for such full-scale aircraft designs as the Beechcraft Bonanza, when modeled as RC scale miniatures, is also done in a similar manner as elevons and flaperons. Very small ready to fly RC indoor or indoor/outdoor toy aircraft often have two speed controllers and no servos, in order to cut production costs and lower sale price. There can be one motor for propulsion and one for steering or twin motors with the sum controlling the speed and the difference controlling the turn (yaw). Some .049 glow models use two controls: elevator and rudder with no throttle control. The plane is flown until it runs out of fuel then lands in the fashion of a glider. Turning Turning is generally accomplished by rolling the plane left or right and applying the correct amount of up-elevator ("back pressure"). A three channel RC plane will typically have an elevator and a throttle control, and either an aileron or rudder control but not both. If the plane has ailerons, rolling the wings left or right is accomplished directly by them. If the plane has a rudder instead, it will be designed with a greater amount of Dihedral Effect, which is the tendency for the airplane to roll in response to sideslip angle created by the rudder deflection. Dihedral Effect in model airplane design is usually increased by increasing the Dihedral Angle of the wing (V-bend in the wing). The rudder will yaw the plane so that it has a left or right sideslip, dihedral effect will then cause the plane to roll in the same direction. Many trainers, electric park fliers, and gliders use this technique. A more complex four channel model can have both rudder and ailerons and is usually turned like a full-sized aircraft. That is,