Which item includes a Mach number in its limit description?

Which item includes a Mach number in its limit description?

• A. Vb (10,000 ft and above)
• B. Vwindow
• C. Vle
• D. Vfe 1

Answer: (A)

Mach numbers show up in speed limits when altitude makes compressibility effects and aerodynamic margins the controlling factor. At higher altitudes, pilots and charts switch to Mach to keep speeds within safe limits as airspeed indicators can be less representative of actual dynamic pressure. In this item, the limit for Vb at 10,000 ft and above is described using a Mach value, so it’s the one that includes Mach in its limit description. The other limits—Vwindow, Vle, and Vfe 1—are expressed in knots and pertain to mechanical or configuration constraints (window operation, landing gear, and flap settings), which don’t use Mach in their limit descriptions.

Mach numbers show up in speed limits when altitude makes compressibility effects and aerodynamic margins the controlling factor. At higher altitudes, pilots and charts switch to Mach to keep speeds within safe limits as airspeed indicators can be less representative of actual dynamic pressure.

In this item, the limit for Vb at 10,000 ft and above is described using a Mach value, so it’s the one that includes Mach in its limit description. The other limits—Vwindow, Vle, and Vfe 1—are expressed in knots and pertain to mechanical or configuration constraints (window operation, landing gear, and flap settings), which don’t use Mach in their limit descriptions.