Proprotor Short-Haul Aircraft-STOL and VTOL

Abstract

This Paper examines the characteristics of a series of aircraft for the short-haul market. The low disk-loading propeller/rotor is applied to a prdpeller-STOL (short takeoff and landing) transport, a fan jet-STOL transport, a tilt rotor-VTOL (vertical takeoff and landing) transport, and a fan jet-VTOL transport. The resulting aircraft concepts have an efficient low-speed, lift-propulsion system, and can operate with low noise and air pollution from metropolitan V/STOL airports. This paper concentrates on the first two STOL configurations. For low and medium disk-loading STOL aircraft, the gimbal propeller Has important operational advantages compared to the rigid propeller. At takeoff, longitudinal cyclic pitch can be used to produce an upward force to reduce tail download requirements. For takeoff and landing in severe crosswinds, significant side force can be produced by means of lateral cyclic pitch. In cruise, the gimbal propellers give a significantly better ride than rigid propellers. In the approach, longitudinal cyclic pitch can control glide-slope height precisely. A STOL transport with a cruise speed of 400-500 knots (wing loading near 75 psf) could use the deflected slip-stream concept and medium disk-loading (30 psf), folding propeller/rotors (Frontispiece). Propulsion-system power requirements in both the cruise and low-speed mode would be supplied by convertible fan-shaft engines. This Paper shows the power balance between a twin fan-jet cruise requirement of 475 kt and an engine-out critical maneuver requirement at 60 knots.