When both MCDR and MCRIT are active, sweepback changes in which way?

• A. Increases
• B. Decreases
• C. No change
• D. Unpredictable

Answer: (A)

Sweepback is used to manage Mach effects in the transonic regime. When both MCDR (drag rise related to Mach) and MCRIT (critical Mach number) are active, the control logic increases wing sweep to push the onset of transonic drag to higher speeds and to reduce wave drag. By sweeping the wings back more, the flow over the wing stays subsonic longer, raising the critical Mach and improving high-speed performance. Decreasing sweep would worsen transonic drag characteristics, and there’s no basis for unpredictability when these two indicators are driving a coordinated adjustment.