Imagine that we drop a Wright Model "B" at its full weight without any power from a certain height. The aircraft will glide for a time but will not be able to keep itself in the air. Imagine that as it drops, the power starts to increase. The plane will continue dropping until there's enough power to keep it aloft. How much power is needed?

In order to keep the airplane flying, the airplane's propulsion system (engine and propellers) has to produce the same amount of power lost in the craft's descent. The Wrights calculated the power requirement of their engines based on the weight of the plane, the thrust of the propellers, and the speed required to move the plane through the air.

In the case of the Vertical Four, the engine's 33.5 horsepower was enough to lift 1245 pounds of aircraft, pilot and passenger at speeds of over 40 miles per hour over distances of over 120 miles!