https://www.popsci.com/technology/article/2010-10/video-darpa-and-boeings-retractable-blade-heliplane/
Video: DARPA and Boeing's DiscRotor Retractable-Blade Heliplane
The CSAR DiscRotor, a collaboration between Boeing and DARPA, was approved back in 2008. It's taken two years to get an animated video of the insane...
videodarpaboeingretractableblade