I posted this on several other threads:
posted 25 November 2000 13:07
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During the design of the EH-101 I brought a potential problem to the attention of the design engineers for the rotorhead and the flight control systems.
The rotor head on the EH-101 uses elastomeric bearings that allow pitch, flap and lead/lag. In the design stage it was not decided which way the bearings were to be installed. The original concept was to install the bearings so that they operated in flight in and about the neutral position which would minimize the stresses in the bearing. The other concept was to install the bearings in the relaxed state while in low pitch thus increasing the stresses when the bearings were in high pitch while in flight. At the time of my involvement they were going with the former as opposed to the latter.
In this situation when the rotor was stopped
and folded along with the tail pylon being folded the hydraulics were still on. With the hydraulics off, the residual torsion in the elastomeric bearings would tend to relax and try to return to the neutral position.
However, with the tail folded these forces would be locked in the system which would place the entire flight control system under a compressive or tensile load ( I can't remember which).
In either case, if the system had to be maintained, requiring a disconnect of the system a control rod could injure the tech and cause a lot of damage to his/her hands and/or face.
I left the program before a final decision had been made. In any case, watch out.
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The Cat