Originally Posted by
The Sultan
In none of the videos of the SB-1 have I seen the tail prop rotate even a few degrees. You may or may not know that in ground shake tests of helicopters/tilt rotors the gearboxes are routinely replaced with non-flight components prior to start of the tests to insure the bearings on flight hardware are not damaged.
The one question I cannot answer is if the SB>1 of the S-97 have a dedicated brake for their tail rotor. I am curious to know.
As far as ground shake testing on helicopters and Tiltrotors, I have supported both.
The key differences in shake testing performed on the ground versus flight is that the rotors are intentionally locked for ground testing, and the gearboxes are not designed for this environmental condition. Additionally, gearboxes used for ground testing are almost always not acceptable for flight before any testing is conducted due to design and manufacturing deviations.
Finally, remember that the pylon conversion actuators on Tiltrotors are gearbox driven ball screws. They spend long periods stationary, under load, and in a high vibration environment. The key difference is they are designed from the beginning to operate in this environment.
So the question is not if gearboxes can survive this environment, it is if they were designed to survive this environment.