Originally Posted by
Outwest
I agree. What safety factor do you think EC would have built into those suspension bars? Double, triple? Meaning that if the design gross weight is 11000 KGS how many G's of loading would they design it for? 3 G's? 4G's? Look at what Spectral has described how the 725 is operated.
Still not saying that loosing one suspension was the cause of this crash but if you would loose one suspension bar and especially if it was the longitudinal one the result would be a tilting of the rotor disc axis against the movement of the helicopter. Imagine having a chair with three legs. Guess what happens if one of those three legs brake. You end up on the floor, no matter how strong the remaining two legs are.
The only difference the strength of the remaining bars would have made in this case is that the rotor would have sliced through the rear fuselage/tail and stayed attached by the remaining two bars to the remains of the helicopter while tumbling down to Earth.
Now, why would the head shear off completely?
If the loss of the forward suspension happens at cruise speed resulting in the rotor disc tilting backwards the resulting g- load would be pretty high (up to the instantaneous Stall limit of the rotor which at 100% RRPM would surely be >>4g) and would have to be taken by only 2 remaining bars. Therefore especially losing the front suspension would very likely result in very quick separation of the whole head.
So with that in mind and knowing the load capabilities the other 2 bars must have, would a very slow decent on an a/c relatively lightly loaded have such a catastrophic failure with no warning even if and I do mean IF one bar failed?
As said that would be simply the consequence of the rotor disc axis instantly tilting to the rear (looking at the geometry of the suspension points probably ~30° from neutral) and building up massive g loads very quickly and without any chance to counter. The resulting loads on the remaining two bars would be massive and that is even without considering the rotor slicing through the fuselage/tail.