Rotorque:
Excellent Thread.
To put it simply, If you think about a lateral vibration or a shuffle, most noticable in the hover, it is generally caused by a weight imbalance in the rotor system. A simple addition of weight or reduction generally will cure this.
A vertical vabration or hump, is generally caused by the way the blades fly or the tracking (which is not to say that the blades have to be in track to be smooth). In a multi-bladed system, you may experience what is known as a 3 per or 5 per rotation vibration. this is usually remedied by either a trim tab adjustment or pitch rod adjustment but may also require a weight adjustment. Most companies use the 8500 vibration analysis equipment and if all adjustments recommended are followed, then you will usually end up with a pretty smooth machine.
Another consideration is whether the Vib is a medium freq (MRH) or a high freq (TR). these vibs can usually be quite distinct and the solution arrived at by any competent crew.
Well that's my two cents worth.
Cheers, OffshoreIgor
