As a next-generation compound helicopter, it promised to replace the Black Hawk with advanced technology. Despite its impressive capabilities, it ultimately lost out to Bell’s V-280 Valor in the ...

The compound helicopter also had two low-mounted stub wings that during high speeds provided lift as increased trust was produced by the pusher propeller reducing the lift needed by the main rotor.

When that happens, the helicopter rolls off to the retreating blade side and the pilot can no longer control it. Sikorsky’s X2 is a compound helicopter (see “Hot Rod Helicopters,” Sept.

Hover over the red squares to read more about the UH-60 Black Hawk heliocopter and the downed helicopter used in the raid on Osama bin Laden's compound (right). Photos of the wreckage of one of ...