We have been chasing a vibration from the first few hours on our Legacy IO-550 with stock compression and a Hartzell 3 blade.  I don’t have easy access to the prop model but it is the standard Hartzell supplied by Lancair for the IO-550. 

Our vibration varies in magnitude with power setting and air speed.  It is most noticeable with control stick shake but also could be felt on the dust cover.   I went thru an exhaustive series of finding engine/cowl contact points, questioning gear doors, rechecking control surfaces, two prop balances and an engine rebuild (cracked case).  I thought it was almost fixed several times since it was not easily replicated.  Then it would come back, sometimes very slightly, other times worse. 

Actually, this is a relief to know what the likely problem is after 5 years and 400 hours of chasing a fix.  We just booked a Southwest round trip to OSH.  I really don’t want to be the next statistic.  Thanks Bob and Ed.

Steve