Use of HDG is limited to greater than how many KIAS?

Use of HDG is limited to greater than how many KIAS?

• A. 30 KIAS
• B. 40 KIAS
• C. 50 KIAS
• D. 60 KIAS

Answer: (B)

HDG mode requires a minimum amount of yaw stability to hold a heading reliably. In a helicopter, especially at low speeds, rotor wash, gyroscopic effects, and rudder/yaw authority become too dominant for the autopilot to manage precisely. To prevent unstable or unsafe heading behavior during hover or slow flight, the system limits the use of HDG to airspeeds above a certain threshold. That threshold is 40 KIAS, so HDG becomes available only when the indicated airspeed is greater than 40 knots.

HDG mode requires a minimum amount of yaw stability to hold a heading reliably. In a helicopter, especially at low speeds, rotor wash, gyroscopic effects, and rudder/yaw authority become too dominant for the autopilot to manage precisely. To prevent unstable or unsafe heading behavior during hover or slow flight, the system limits the use of HDG to airspeeds above a certain threshold. That threshold is 40 KIAS, so HDG becomes available only when the indicated airspeed is greater than 40 knots.