LU,
[quote] A vertical vibration may be caused by an out of track blade but I believe that it is most likely caused by the undamped sinusoidal wave that travels down the blade from the tip to the root.
Some helicopters have pendular weights on the
blades or the blade roots as energy absorbers while on the Sikorsky rotor heads they use a Bifiler* System (SP) that absorbs this energy.
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I was under the impression that the Sikorsky Bifiler system was there primarily to reduce LATERAL vibration not vertical as you state.
Can anyone please explain how the Bifiler system works???? <img src="confused.gif" border="0"> <img src="confused.gif" border="0"> <img src="confused.gif" border="0">
"Some days you are the pigeon, some days you are the statue!"
[ 14 January 2002: Message edited by: HeliEng ]</p>