407 tail rotor
The Delta hinge on a Bell 407 is backwards. In other words the pitch change induced by tail rotor flapping is in the direction where it increases flapping rather than decreasing it like on most other helicopters.
Does anyone know the real reason why it is like that? To me it seems like an unwise design but maybe there is a good reason for it. No one I have asked has ever had a good answer. Makes me wonder about those 407 accidents where the tail rotor flapped too far.