Rubber-powered models are powered by the stored energy of a twisted elastic material. These range from the simple rubber-band powered toys available in many toy stores, up to the open rubber class, examples of which often use 200 g of rubber in their "motor". Rubber does not produce a constant power output; when fully wound a rubber motor produces its maximum torque, but this drops rapidly at first before 'plateau-ing', finally declining again, after which the propeller stops. Using this initial burst efficiently is vital and automatically variable pitch propellers help here, together with timer-operated changes of wing and tailplane incidence and of rudder setting. At the end of the power run the blades fold back alongside the fuselage to minimize drag during the glide.
The smallest rubber powered model aircraft was built in 1931 by a Philadelphia high school student, called the Flying Flea and was one and a quarter inches long and could remain airborne for approximately one minute.
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