When is flex takeoff not authorized?

• A. Wing and/or cowl anti-ice in use
• B. Runway contaminated with standing water, slush, snow or ice
• C. Warnings of windshear or downdrafts
• D. Anti-skid inoperative

Answer: (A)

Flex takeoff uses a reduced thrust setting based on clean-aircraft performance. It assumes the wings and surfaces are clean and not being heated by anti-ice systems. When wing and/or cowl anti-ice is in use, those surfaces aren’t in a clean, ice-free state, and the actual performance can differ from the assumed calculations. The anti-ice system also introduces additional heat and flow effects that can change thrust and lift in ways that the reduced-thrust assumption doesn’t account for. So, to maintain predictable, safe takeoff performance, flex takeoff isn’t authorized when anti-ice is on.

The other conditions describe scenarios where takeoff with reduced thrust would not be appropriate or would require different handling, but the specific reason flex isn’t authorized here is the presence of anti-ice on the surface.