More on ducted propeller systems

By popular request, a video that explains the strange effect which helped scuttle several military flying craft of the 1950s and 1960s.
The Hiller Flying Platform was a great idea but one of the factors which contributed to its failure was the fact that the self-stabilizing effect of the duct lip made it simply too stable and thus, too slow.
Whether this effect played any part in the failure of the Avrocar or the SoloTrek is up for debate.
Hope you enjoyed the video.