What is the primary function of Bifilar Vibration Absorbers?

• A. Absorb vibrations and stresses
• B. Increase blade pitch range
• C. Provide anti-torque
• D. Reduce weight

Answer: (A)

The key idea is that a Bifilar Vibration Absorber acts as a tuned damper to taken out specific blade vibration modes, thereby protecting the blade and surrounding structure from fatigue. It does this by adding a secondary mass–spring system that moves in opposition to the blade’s vibration at a targeted frequency. When the rotor hits that vibration, the absorber absorbs energy and reduces the amplitude, lowering the cyclic stresses transmitted through the blade, hub, and other components. This is why the primary function is to absorb vibrations and the stresses they cause. It doesn’t change how the blade pitches, it isn’t an anti-torque device, and it adds some weight rather than reducing it.