What device is used to limit blade flap at low rpm or when the rotor is stopped?

What device is used to limit blade flap at low rpm or when the rotor is stopped?

• A. Static Stop
• B. Dynamic Stop
• C. Rotor Lock
• D. Pitch Stop

Answer: (A)

The main idea is that blade flap is the up-and-down motion of the rotor blade about its hinge. When the rotor is turning slowly or not turning at all, wind and gravity can cause the blade to flap quite a bit. A static stop is a fixed mechanical limit built into the hub or blade root that stops this flap from moving beyond a safe amount. It’s specifically designed for low rotor speeds or a stopped rotor, so it’s the device that best prevents excessive flap when the rotor isn’t yet producing lift. The other devices aren’t meant for this purpose: a pitch stop limits how far the blade can change pitch (angle of attack) rather than lateral flap; a rotor lock is used to keep the rotor from turning when parked; and a dynamic stop isn’t the standard term used to describe flap limiting at low speeds.

The main idea is that blade flap is the up-and-down motion of the rotor blade about its hinge. When the rotor is turning slowly or not turning at all, wind and gravity can cause the blade to flap quite a bit. A static stop is a fixed mechanical limit built into the hub or blade root that stops this flap from moving beyond a safe amount. It’s specifically designed for low rotor speeds or a stopped rotor, so it’s the device that best prevents excessive flap when the rotor isn’t yet producing lift.

The other devices aren’t meant for this purpose: a pitch stop limits how far the blade can change pitch (angle of attack) rather than lateral flap; a rotor lock is used to keep the rotor from turning when parked; and a dynamic stop isn’t the standard term used to describe flap limiting at low speeds.