To: cullcov
Vertical bounce is quite common on Bell helicopters due to the fact that when the blades are in line with the longitudinal centerline the blades have minimal lift and for an instant the fuselage drops and when the blades leave that position they start to lift and the fuselage rises again. This also causes the blades to flex and generate a traveling wave down the blades. In many Bell blades they incorporate a weight that is internal of the blade and is positioned at the nodal point of the wave thus canceling the wave before it reaches the head and the fuselage. That is why Bell invented the NodaMatic Suspension system. Now the fuselage is highly stable with no more vertical bounce but the driveline including the gearbox is being beaten to death.
------------------
The Cat