Yes, we have done the prop balancing thing but it hasn't stopped this particiular type of vibration. Normal prop imbalance can be felt through the control column and is during all phrases of flight.
The vibration I'm speaking of seems to start at lower altitudes and only at high IAS, like 238 to 250kts with normally little or no TQ. In fact the other day I was flying another aircraft in the fleet, where the vibiration started at 240kts with 36-40% TQ. The vibrations were felt all through the aircraft. By advancing the PL slightly, the (inc TQ) the vibration disappears. So don't believe this issue is one of balance.
Any more thoughts?
