Getting the shaft.
This is a problem for the engineering types out there:
On the EH-101 many accessories are driven off of a separate gearbox that is mounted in front of the main transmission. This gearbox is driven by two redundant drive shafts that are of thin wall construction. During normal operation there is minimal torsional stress on the drive shafts. Here is the problem. The rotor brake is also mounted on this gearbox as opposed to being mounted on the main transmission. During the preparation of the FMEAs it was determined that there was a possibility of the rotorbrake dragging to the point of generating sufficient heat to start a fire. It was also determined that the rotor brake could come on hard with a solid lock-up of the disc. Both of these comments in the FMEAs were purged as the management of the R&M group arbitrarily determined that there would be no catastrophic failures on the EH-101. Well it is obvious that he was wrong as at least two EH-101s have crashed due to fire in the area of the rotorbrake and the possibility of a hard lock-up is waiting in the wings. I had indicated in the FMEA that if the rotorbrake had a hard lock-up the kinetic energy of the spinning rotor which was still being driven by two (or three) engines would build up sufficient torsional stresses as to twist the shafts to the point of separation. Thus, causing loss of a hydraulic system and some electrical generation capability, which would jeopardize the reliability, and safety of the helicopter. I was told that the shafts would not fail due to the gear reduction of the main transmission. If one end of the system is stopped and the other end of the system is still rotating at speed the only thing between the main transmission and the rotorbrake were the two thin wall shafts. What do you think? Will the shafts fail or will they not fail.