A DUAL-FAN VTOL AIRCRAFT USING OPPOSED LATERAL TILTING FOR PITCH CONTROL

The hover pitch-stability and control response of a dual-fan VTOL aircraft employing opposed lateral tilting (OLT) of its fans – which induces gyroscopic and fan-torque pitching moments to act on the aircraft - are predicted using analytical methods. Actual response times, control loads, and other relevant data are estimated for a full-scale aircraft by hypothetically incorporating OLT into the Doak VZ-4 VTOL aircraft of the 1960’s. It was found that severe gyroscopic loads on the tilting devices occurred not from the actual tilting per se but from the resulting pitching of the aircraft – just as for the fan mountings of conventional aircraft. These loads can be reduced to acceptable values while maintaining good aircraft response times by using fans having relatively low mass moment of inertias, and laterally tilting them at a high rate – much higher than the pitch rate of the aircraft.