On the Wednesday following the weekend after having fixed the ignition system problem, we decided to test the new control system at different rotor RPMs with the aircraft anchored to the ground in our test pit.

At 300 RPM, the control stick of the new control system with the new rotor (version #4, without dogleg) could be moved in a circular pattern hitting the forward, right side, aft, and left side stops in less than 2 seconds.

At 350 RPM, some control stick shake was noticed when the control stick was moved in the same manner as above.

At 400 RPM, the rotor produced a surprisingly severe stick shake. Inspection of a video taken of the rotor head indicated a rotor blade weave. A blade weave seemed impossible due to all the previous rotor blade tests. Careful inspection of the control cables revealed essentially no slop or deadband.

Due to the stabilizing effect of the dog leg design of the previous rotors (versions #2 & #3) and the friction caused by the hydraulic control system (24 sliding seals) and the viscous damping caused by the fluid flow through the tubes, any blade weave tendencies in the rotor blades were masked. Once the dogleg was removed from version #3 rotor, the blade weave problem was still masked due to the control system's friction and dampening. See Nov. 4th, 1998 press release for its description on how the rotor was spun up to 400 RPM and the cyclic stick moved in a full stop to stop cycle without a blade weave developing. However, once the hydraulic control system was replaced with a new system using linear ball bearing control cables which have very low friction and no damping, a blade weave developed.

The rotor blade should be designed so there is no tendency to develop blade weave or blade flutter. Click on the colored "blade weave" text above to obtain more information about blade weave.

The new control system without the friction and dampening of the hydraulic system is a big improvement and was necessary.

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