Turbulence Penetration Speed is defined as the lower of which two values?

• A. 260 KIAS/.70M whichever is lower
• B. 280 KIAS/.75M, whichever lower
• C. 300 KIAS/.80M whichever lower
• D. 320 KIAS/.85M whichever lower

Answer: (B)

Turbulence penetration speed is the speed you fly through rough air to limit structural loads. It is defined as the lower of two limits: 280 KIAS and Mach 0.75, whichever results in the lower airspeed. This ensures you stay within safe limits whether you’re operating at low speeds where indicated airspeed matters or at higher altitudes where Mach limits become the controlling factor.

In practice, you compare the indicated airspeed corresponding to Mach 0.75 at your altitude with 280 KIAS, and use the lesser of the two. This helps prevent excessive dynamic pressure in turbulence and avoids exceeding the aircraft’s structural or compressibility limits.

The other options propose different pairs, but the standard guidance used for turbulence penetration is the lower of 280 KIAS or Mach 0.75.