FAN-IN-WING AIRCRAFT HANDLING QUALITIES
The XV-5 was a proof-of-concept lift-fan aircraft and thus employed a completely "manual” powered-lift flight control system. The lack of an integrated powered-lift system required the pilot to manually control the aircraft flight-path through independent manipulation of stick, engine power, thrust vector angle and collective lift. This lack of an integrated powered-lift management system (and in particular, the conversion controls) was responsible for most of the adverse handling qualities of the aircraft. An advanced digital flyby-wire control system must provide level one handling qualities, especially for integrated powered-lift management.
CONVERSION SYSTEM DESIGN
The manually operated conversion system was the most exacting, interesting and potentially hazardous flight operation associated with the XV-5. This type of "bang-bang” conversion system should not be considered for the SSTOVLF. Ideally, the conversion should consist of a fully reversible and continuously controllable process. That is, the pilot must be able to continuously control the conversion process. Good examples are the XV-15 Tilt Rotor, the X-22A and the AV-8 Harrier. Furthermore, the conversion of the SSTOVLF with an advanced digital flight control system should be fully decoupled so that the pilot would not have to compensate for lift, attitude or speed changes. The conversion controller should be a single lever or beeper-switch that is safety-interlocked against inadvertent actuation. The conversion airspeed limit corridor must be wide enough to allow for operational flexibility and compensate for single-pilot operation where mission demands can compete for pilot attention.