DIRECT-LIFT DESIGN STRATEGY FOR LONGITUDINAL CONTROL OF HYPERSONIC AIRCRAFT

A longitudinal control design called the G-command, alpha follow-up is described that significantly improves the lag between pitch angle and flight-path angle responses associated with hypersonic flight. The de sign technique relies on classical, successive loop closures to determ ine the control architecture and introduces a direct-lift control stra tegy to design dynamic compensation. This dynamic compensation constra ins and ''washes out'' body-flap input to avoid excessive nap deflecti on and associated heating while providing angle-of-attack control at t he engine inlet. The final design was implemented on a generic hyperso nic aircraft simulation at NASA Dryden and evaluated by a NASA test pi lot familiar with the SR-71. The pilot flew tuning and altitude change maneuvers using the implemented control law and verified the ability to track flight path with ease and precision. Finally, evidence is pre sented that supports a flying qualities metric for longitudinal, hyper sonic flight based on the bandwidth of the flight-path-angle-to-stick- frequency response.