Blade replacement uses which principle: weight-moment equality?

Blade replacement uses which principle: weight-moment equality?

• A. Replace blade with one having the same weight
• B. Replace blade with one having the same distance from axis
• C. Replace blade with one having the same thickness
• D. Replace blade with one having the same weight-moment

Answer: (D)

Maintaining balance hinges on matching the mass distribution about the rotor axis. The weight moment is the blade’s weight times its distance from that axis, and this moment is what creates or cancels unbalance as the rotor spins. Replacing a blade with one that has the same weight moment keeps the rotor’s dynamic balance the same, so centrifugal loads, vibrations, and natural frequencies stay consistent with the original setup. If you only match weight, you could still alter balance if the radial position differs. If you only match the distance from the axis, the mass might differ and shift the overall moment. If you only match thickness, that doesn’t guarantee the mass or its distribution about the axis. Hence, weight moment matching is the criterion that preserves the rotor’s balance most reliably.

Maintaining balance hinges on matching the mass distribution about the rotor axis. The weight moment is the blade’s weight times its distance from that axis, and this moment is what creates or cancels unbalance as the rotor spins. Replacing a blade with one that has the same weight moment keeps the rotor’s dynamic balance the same, so centrifugal loads, vibrations, and natural frequencies stay consistent with the original setup.

If you only match weight, you could still alter balance if the radial position differs. If you only match the distance from the axis, the mass might differ and shift the overall moment. If you only match thickness, that doesn’t guarantee the mass or its distribution about the axis. Hence, weight moment matching is the criterion that preserves the rotor’s balance most reliably.