I had a conversation about this bird just the other day. He defended its technology. I agreed, but attacked the moronic thinking that it was deployable and safely so for troops.
Redundancy is a key facet of military flight systems. Same goes for powerplants. This is the defect in the F35 (among others).
Remarkable in conception, it should never have been granted anything but an ‘X’ model.
With next-gen materials, the tech is right around the corner. The first truly successful VTOL of this type will be jet-powered and have twin jet engines per ‘wing’...it’s about the physics.
Isaac Newton said it best...
.02
Quad rotor VTOL.
PRoven concept. You cna have vertical and still have vertical while one pair starts shifting towards horizontal.