Originally Posted by
lynnx
To assist Birmingham,
The entire weight of the L1/L2/225 is supported on those 3 struts and their associated hardware whilst airborne.
The rear of the engines are effectively supported by the same struts, as they are bolted to the gearbox which is held in position between the top of the struts and the BBQ plate.
The rear of the engines is not a lift path.
The BBQ plate only allows for torque and is not a lift path.
I cannot imagine any scenario where a failure of a lift strut, for any reason, would allow the aircraft to continue flying.
You only have to look at the Norn Incident to see the effect of strut failure (for an identified reason)
I WAS going to say "unconnected" reason but, in fact, there is nothing in the public domain to base that on.
I think that we simply cannot imagine the forces acting on the conical housing and airframe once it all goes wrong - torque, gyroscopic, mechanical, aerodynamic, 1500 shp and 6/7 tonnes, 140 knts.
Ugh.
I am an engineer working for a helicopter OEM in the helicopter system design department.
As per FAR 29.571 any PSE (principal structural element, a failure of which would cause a catastrophic failure), must be substantiated damage tolerant or safe-life. This roughly speaking means that 1)in the damage tolerant case you must show that the element is able to withstand flight loads notwithstanding a failure of prescribed (and controlled) amplitude should occurs, 2) in the safe-life case you must show that the element subjected to loads will not have any failure in the whole operative life.
In other words the possibility to avoid any catastrophic failure is achievable also in case of failure of one component (for sure at high cost in terms of structural redundancy and weight penalty).
Hope this clarify a bit.