Feedback Control for Penetrating a Downburst

Feedback logic is given that produces satisfactory penetration of an aircraft through a severe downburst. The loglc has two pa ts: (1) A switch that calls for full ttlrottle and tight climb-rate-hold feedback logic when the magnitude of headwind-rate exceeds a threshhold level; this switch stays on until re-set by the pilot after penetration of the downburst. (2) 6 tight climb-rate-hold autopilot, using feedback of pitch-angle to angle-of- attack. After penetration, recovery to steady climbing flight is aided by using feedback of airspeed deviation to throttle. Insights on control strategy are gained from an analysis of energy changes during flight through a downburst. Closed-loop simulations are given for a 727 aircraft penetrating severe downbur.sts on take-off. Boeing's recommendati-on of constant pitch angle was confirmed~an;excellent feedback control strategy. US