Originally Posted by Ian Corrigible
Good to see Alastair Campbell has found a new job. The X2TD's problem has gone from being a "transmission failure" to the "detection of a gearbox manufacturing problem" to being "currently out of service for transmission upgrades."
Ian, this failure will have resulted in a huge investigation into root cause within Sikorsky (sometimes called a six sigma investigation). The engineers involved would have systematically checked out each possible reason in turn until establishing exactly what the trouble was. This is the only way to be sure that it does not reoccur. While doing this exercise nobody would have understood exactly what the failure meant.
I mentioned earlier about the fatigue analysis depending upon many coupon tests representing the part. These all assume that the part was manufactured to a fixed process. With prototypes the process is often still in development so can be subject to more variation than anticipated. On a highly stressed part this variation is tested even more so. This does not mean anybody made a mistake, just that the manufacture of the design is still settling down.
Clearly it is not an ideal situation, but that is why flight testing is so conservative. It was picked up in a ground test specifically designed to pick up this nature of problem. Nobody was put at risk and the problem has been resolved.
Dave, that intermeshing config would not be immune from this type of problem. Don't forget that these are very high hinge offset rotors designed for a machine with a snappy response. This application would make even the most hardened stress engineer squirm in his boots.
That is just the devlopment of any engineered product. You can take my word for it that the car you drive will have seen many many problems at prototype, which were all resolved for production. X2 is a high profile project so you are getting to see the development process up close and personal.