The part about high reliability “aint necessarily so”. During the design phase all references to catastrophic failures were removed from the Failure Mode Effects Analyses and because of that, they were never considered in the Safety hazards Analyses. The rotor brake problem was one of the failure modes that were removed from the FMEAs.
The most serious failure mode that was removed from consideration is a lock-up of the main transmission. The EH 101 main rotor shaft as originally designed had a shear point that would fracture in the event of a lock-up allowing a successful autorotation. The energy that was required to effect this fracture is the inertia of the main rotor system. At the instant of the lock-up, the rotor would stop rotating and the inertia of the blades would compress the dampers to their stops providing a mechanical lock-up and the inertial energy would pass into the rotor head and then to the shaft causing the fracture. The dampers in the process of this action would destruct because the stress levels would be very much higher than the damper design stress level. In the process of the damper failure the load would be transmitted to the elastomeric bearings and apply a side load that the bearings are incapable of reacting quite possibly causing complete failure of the bearings and the subsequent loss of the helicopter.
I would strongly suggest that the Royal Navy request access to the FMEAs and check to see if my statements are true.
Edit by Heliport
Good idea of yours to seek comments from military pilots - I've put a link on the Mil Aircrew Forum inviting contributions.
[ 18 July 2001: Message edited by: Heliport ]