I was asked to comment on an Army Lynx crash too many years ago. No obvious cause for the crash, and after some sleuthing and drawing of wind directions and flight paths concluded that vortex ring state might be a cause. Looking at the rest of the evidence (witness statements of vibrations, non-responsiveness of controls, total length of damaged aircraft and parts less than 90 feet, etc) it became obvious that vortex ring state was probably the cause.
The fact that the official Army Board of Inquiry never considered it showed me that they probably didn't teach or understand it. Don't know what's happened since then.
(and the reason I was asked to comment was that the widow of the pilot was going to be denied her survivor pension because, in the BOI's view, the pilot was responsible for the machine crashing - since the BOI hadn't considered VRS, and the pilot probably had not been trained to recognize it, how could he be at fault??? - she got the pension)