Stress
Docs have told me you need to sustain g for a "considerable time - say 20 secs or more" before the body chemistry kicks in as I described. However I have no idea if the 20 secs thrown in to the conversation represented a minimum, a mean or what. I have never seen any written reports on this research.
Brian
I watched Jim through many rehearsals and the accident flight. There is no doubt from aircraft flight test instrumentation records up to impact (which were perfectly readable) that at the end he was conscious and flying very accurately as the AOA he flew was the optimum and extremely well controlled for the last 70 degrees or so of the failed pull out. However his immediately preceding manoeuvres to my mind showed completely abnormal confusion and indecision which made me feel he had been affected by g but not to the point of passing out. In my opinion the part of his sequence that led to the accident started with a very prolonged high g low level max rate turn through some 420 deg followed by snapping the wings level and a yank to a vertical climb. As soon as the vertical was achieved he abruptly checked the pull (as one does) before rolling and pulling hard to the inverted which he maintained with a push into level flight. All this was quite normal and his usual sequence.
The inverted flight section was away from the display/crowd line and used to build distance so that he could roll through 80deg to a slightly overbanked turn where he yanked it round through 270 deg, diving the while, for a high speed low level dash along the display line.
Being the expert and perfectionist that Jim was he always wanted to do the high speed run downwind for max effect. This meant that following the inverted phase he had to do either a diving left or diving right turn depending on the wind direction that day. If the wind was strongly on crowd (as it was on the accident flight) he had to extend the inverted phase to ensure he had enough distance out for the turn back down the runway and he did this by putting in a quick roll and stopping this with about 100 deg bank one way or the other for the subsequent diving turn.
On the accident flight he stopped the distance making roll inverted and immediately did the expected hard pull, but of course this was not round the horizon but straight down. The aircraft then paused in the vertical, rolled a few degrees (say 10) right then back to the left before starting the unsuccessful dive recovery hitting the ground with about 10-20 deg still to go.
My interpretation of all this was that because he was mentally confused from the various preceding g effects he stopped the roll at the wrong bank angle, pulled as usual at that stage of the sequence before he realised that all he could see was the ground and not the expected horizon. Hence the pause in the near vertical and 'thinks bubble' type look left and right (?? where the f is the nearest horizon??) by which time the end result was inevitable.
Peekay
Thank you very interesting.