Originally Posted by
pattern_is_full
Just a reminder - since it hasn't been mentioned yet - that what counts in a stall is AoA, not a particular speed. Making a 180° turn in a narrowing valley may require a rather steep bank to avoid the valley walls, with associated G forces (accelerated stall). If there is altitude below one, one can unload the wing a bit with a descent in the turn (a bit of forward stick to lower AoA). But maybe the space isn't there.
The crash location (see top photo post #51) looks like a classic "box canyon," which have killed many fliers, and even if the "numbers" say it should be a piece of cake (ein klacks?) to outclimb the terrain, factors such as +ISA, downdrafts or other turbulence, the angle of the valley floor, weather seen on the far side of the ridge or pass, etc. can all cut off one's options rather rapidly. Even a competent, experienced pilot/crew can get trapped, if the holes in the cheese line up fast enough.
I am - equivocal - about machinbird's image and analysis. Only because I know how much a telephoto lens' compressed "perspective" can sometimes distort visual geometry, and because without motion, I am not full persuaded the "smoke trail" is not, perhaps, a highlight on the exposed mountain rock in the background, or other artifact. It is suggestive, but not definitive.
The observer descriptions (however flawed) and the aircraft condition/position are strongly suggestive of a stall/spin.
My thoughts were the same. The terrain looks challenging and visual illusions are all to easy to encounter. A 180 turn to escape from a box valley could be very challenging in an old aircraft even for very experienced pilots.