The NR switch should be in HI position when hover flight is greater than or equal to how many feet AGL/AWL?

The NR switch should be in HI position when hover flight is greater than or equal to how many feet AGL/AWL?

• A. 10 ft
• B. 5 ft
• C. 15 ft
• D. 20 ft

Answer: (A)

When you hover, the lift you get from being close to the surface—ground effect—lets you run the rotor at a lower rotor-speed margin. As you rise past that small threshold height, you lose much of that extra lift, so you need a bit more rotor speed headroom to keep the helicopter stable and to prevent rotor speed from sagging under hover loads. The NR switch selects the rotor-speed range, and using the HI position gives you the higher speed range needed to maintain a solid hover once you’re above that threshold. Below the threshold, the ground-effect lift is enough that the lower range is adequate and more efficient.

When you hover, the lift you get from being close to the surface—ground effect—lets you run the rotor at a lower rotor-speed margin. As you rise past that small threshold height, you lose much of that extra lift, so you need a bit more rotor speed headroom to keep the helicopter stable and to prevent rotor speed from sagging under hover loads. The NR switch selects the rotor-speed range, and using the HI position gives you the higher speed range needed to maintain a solid hover once you’re above that threshold. Below the threshold, the ground-effect lift is enough that the lower range is adequate and more efficient.