During acceleration, Mach shows at what value, and during deceleration at what value?

During acceleration, Mach shows at what value, and during deceleration at what value?

• A. 0.40 / 0.35
• B. 0.45 / 0.40
• C. 0.46 / 0.41
• D. 0.50 / 0.45

Answer: (B)

Mach readings often exhibit a bit of hysteresis: the display responds at a higher value when you’re speeding up and at a lower value when you’re slowing down. This keeps the indicator from chattering as conditions change. In this context, the indicator tends to show a Mach value around 0.45 during acceleration, and it won’t drop the reading until you drop to about 0.40 Mach during deceleration. That 0.05 Mach difference reflects the built‑in lag/calibration of the system, not a change in the actual speed of sound or the aircraft’s performance. Among the given options, the pair that matches this accelerating-higher threshold and decelerating-lower threshold is the one around 0.45 and 0.40. The other choices imply symmetric thresholds or different offsets that don’t align with the typical hysteresis behavior.

Mach readings often exhibit a bit of hysteresis: the display responds at a higher value when you’re speeding up and at a lower value when you’re slowing down. This keeps the indicator from chattering as conditions change.

In this context, the indicator tends to show a Mach value around 0.45 during acceleration, and it won’t drop the reading until you drop to about 0.40 Mach during deceleration. That 0.05 Mach difference reflects the built‑in lag/calibration of the system, not a change in the actual speed of sound or the aircraft’s performance.

Among the given options, the pair that matches this accelerating-higher threshold and decelerating-lower threshold is the one around 0.45 and 0.40. The other choices imply symmetric thresholds or different offsets that don’t align with the typical hysteresis behavior.