What is VTOL?
Vertical takeoff and landing (VTOL) aircraft are capable of rising and descending vertically from and to the ground, thus requiring no runway. Some examples are the airship (the modern blimp) and the balloon, which are very inefficient in their forward motion, and the helicopter, which has very limited performance. Convertiplanes are VTOL craft that can fly horizontally with the same effectiveness as a conventional airplane. Their vertical lift during takeoff is provided by a rigid rotor that spins about a vertical axis, by tilted propellers, or, as in some jet VTOL craft, such as the British-built Harrier, by vanes that can direct the engine thrust upward or forward. For more information an in-depth paper entitled Improving Force Flexibility Through V/STOL can be viewed at: http://www.airpower.maxwell.af.mil/airchronicles/aureview/1985/jan-feb/bingham.
