What is Vb at 10,000 ft and above?

What is Vb at 10,000 ft and above?

• A. 130
• B. 270 / .76M (lowest)
• C. 250
• D. 160

Answer: (B)

At higher altitudes, published speed limits are shown with two values: an indicated airspeed and a Mach number, and you must use the lower of the two. This is because as the air gets thinner, Mach becomes the controlling factor, so the limiting speed is the smaller value to ensure you don’t exceed structural or performance limits. So, for this speed at 10,000 feet and above, you see 270 knots or Mach 0.76, with a note that the lower value applies. In practice, that means you would not exceed the speed corresponding to the lower of those two limits; the Mach limit (.76) tends to be the controlling one at altitude, so you must stay at or below Mach 0.76 (or the equivalent 270 knots IAS, whichever is the lower). The other numbers are not the altitude-limited value shown.

At higher altitudes, published speed limits are shown with two values: an indicated airspeed and a Mach number, and you must use the lower of the two. This is because as the air gets thinner, Mach becomes the controlling factor, so the limiting speed is the smaller value to ensure you don’t exceed structural or performance limits.

So, for this speed at 10,000 feet and above, you see 270 knots or Mach 0.76, with a note that the lower value applies. In practice, that means you would not exceed the speed corresponding to the lower of those two limits; the Mach limit (.76) tends to be the controlling one at altitude, so you must stay at or below Mach 0.76 (or the equivalent 270 knots IAS, whichever is the lower). The other numbers are not the altitude-limited value shown.