A Study of Direct Lift Control to Improve Maneuverability in the Transonic Region.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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Current fighter aircraft have shown undesirable properties of dynamic maneuverability in the transonic region. A direct lift control system was designed to decrease pitch rate overshoot, eliminate normal acceleration reversal, and speed lift build up. The system used leading edge slats as the direct lift device due to the availability of transonic flight test data from a McDonnell-Douglas project. The slats had significant steady state benefits, as well as providing a suitable direct lift surface. The closed loop system was designed around a fly-by-wire primary flight control system, and used a linear blend of pitch rate and pilot acceleration feedback. This permitted investigation of handling qualities criteria in the manner of the newly proposed criterion. Digital computer solution provided extensive root locus analysis to determine stability and set optimum gains. The results were verified by a three-degree-of-freedom analog simulation. The problem was evaluated at five flight conditions covering a wide range of dynamic pressures. It was found that direct lift control gave significant transient improvement in load factor build up, reduced pitch rate overshoot, and permitted precise tracking capability in the transonic region. Author
- Attack and Fighter Aircraft
- Fluid Mechanics