The need of stick force stability for attitude-stabilized aircraft. Part II

Abstract

A description is given of flight tests related to the effect of various levels of (artificial) positive stick force stability on the longitudinal controllability in the landing approach of an attitudestabilized aircraft. Approach performance and pilot commentary of 60 ILS/VASIS approaches flown with a twin-engined jet transport have been analyzed. The aircraft was operated at a speed corresponding to the bottom of the thrust required versus speed curve. Feedback of a signal proportional to the difference between the actual and the reference airspeed was used to generate (artificial) stick force stability. For the intermediate gradient of positive stick force stability investigated (approximately 1 lb per 6 knots), a modest reduction of airspeed deviation on the approach has been measured; pilot effort and glide path tracking performance did not differ from those in the case of neutral stick force stability. For a high gradient of positive stick force stability (approximately 2.8 lbs per 6 knots) a marked increase in pilot effort and serious degradation of glide path control performance have been measured.