High G load departure.
First post here. I have been edified by the recollections of old Gnat hands in response to this unfortunate accident and loss of life, have viewed the videos multiple times and have a couple of observations.
1. Common things occur commonly. Having displayed vintage jet fighters at airshows for years I believe pilot error accounts for the great majority of accidents in general. System or structural failure far less probable.
2. I believe that the videos depict a high G load stall and departure as the aircraft enters its first revolution prior to striking the ground. In the seconds prior to impact the aircraft starts to lose altitude and energy rapidly consistent with a high G stalled airfoil.
Stall speed increases in proportion to the square of the load factor. A 90 degree bank exerts significant load factor which is further increased by the pilot pulling perhaps 6-8G sustained in order to re form with the second ship of the 2 ship formation. Buffet, high ROD, and if not recognized by prompt unloading of the airfoil, evolution to full departure occurs which seems to be what I am seeing.
3. AOA is proportional to relative wind irrespective to attitude. An aircraft accelerating downwards through the vertical can depart if you pull enough G.
4. The other point is that due to the low broken layer of perhaps 2,000 feet or less, they were flying a low show which decreases the margin of safety tremendously.
Pilot error is the default diagnosis when the investigators are able to rule out structural and systemic causes. Statistically in the high performance jet airshow context the former is far more probable than the latter. Many vintage warbird, jet and piston, pilots are lost in this way.We shall doubtless see.