I seem to remember that the Gazelle had a "two-stage" problem. There was "Jack Stall" and there was "Deep Jack Stall". The Gazelle IFTU crash referred to happened to an acquaintance of mine and was apparently a case of the latter. What's the difference? I can only guess that Jack Stall can be recovered by reducing the flight loads and that maybe Deep Jack Stall occurs when you have had Jack Stall for so long that your ability to reduce pitch or adjust the cyclic is no longer possible.
When I did my Dauphin conversion I had to experience Jack Stall so the instructor (a test pilot) made me fly to VNe in a shallow dive then wrap it into a climbing right hand turn. As soon as you get it you know what it is and can roll off the turn and reduce collective pitch. Scary but worthwhile.
G
