Ted wrote:
If your C-172 or TB20 did this at the stall we would have to update the training syllabus.
I’m quite certain the J35 didn’t do that by itself in a stall…
Ted wrote:
At a guess I think this is what is happening. i.e. the CP is moving forward in front of the CG or at least much closer at high alpha.
Exactly. There is no way physics will allow such a violent pitch up (a bit beyond 90 degrees) if the configuration is stable in pitch. I don’t think this “feature” was intended, but it is a result of the wing planform. Very cool maneuver though 
No necessarily, it could be easily stable in pitch in normal alpha ranges and unstable at high alpha.
Correct. The Draken is stable from 0-20°, unstable from 20-45° and superstable above 45°.
That is not as much a cobra maneuver as much as recovery demonstration (or probably flight testing chase videos) for the superstall that happens at high altitude and low IAS – which, if not recovered rapidly and aggressively would result in all sorts of unpleasantness (flameout, ejection, even death).
It was a “feature” known of since the development of the Saab 201 technology demonstrator.
It would be very interesting to read/watch the “real” story about the J35 from those who designed and (test)flew it. As a little boy, driving through Sweden on family holyday we sometimes saw these Drakens landing and taking off from the main road (although I guess one could argue if the runway was used as a road, or the road was used as a runway ). Later the Viggen was designed to use considerably smaller stretches of road.
Inone of the Eric Brown books he describes a late 1940s glider as “the worst aircraft I have ever flown” (forget the name and my books are in a container somewhere in the Atlantic). It was an early swept wing design and, like the Draken, would pitch up into a stall. The difference being that this would typically happen close to the ground, and with no engine to help recovery. It killed just about everyone who tried to fly it, except Brown, including the factory chief test pilot.
The (in)famous GAL 56.
Longitudinal stability. A down-force stab is self stabilizing (aerodynamically) to a pitch input, an up-force stab is not.
In a big jet you can trim with fuel, and with the A/P’s helps you need minimum lift either way from the elevator (lift = induced drag, you want to minimize it). The stab’s airfoil is still cambered for force downwards.
