The way I see it, a pitch changing effect on the CofG would require significant (and sustained) vertical acceleration to cause any effect of acting as a lever around the centre of lift. The CofG and centre of lift are very close and I can't see an updraft having the sustained effect to cause a pitch change on such a mass- there is just not enough lever arm moment. We're told there is not much change in altitude, so the acceleration force acting on the CofG is nothing more than momentary. I think the weathercocking of the tailplane is overriding.
I think the effect we see in the flight recorder traces is an encounter with a downdraft causing pitch up. This is countered with large control inputs nose down, just as the plane comes out of the downdraft into the surrounding updraft. Combine the effects of weathercocking again, but nose down this time, with a strong control input which is already held nose down, and that explains the violently large and rapid nose down pitch. Did it exceed structural limits and break up? It obviously goes into strong negative 'g' territory from 12.20 onwards. I can't see anything more complicated than that scenario.
I've found the accident report now. I thought I didn't remember this one! The inflight structural break up explains the damage to the artificial horizons- it's not possible it was structurally sound and pitching 90 degrees nose down! There is no way the integrity of the fuselage could be partially maintained if it pitched enough to damage the AH stops- sadly I think the spinning and pitching that occured to the cockpit as it disintegrated and after caused the violent movement that damaged the stops. We're looking for mysterious effects that just aren't there because of the faulty premise given to us earlier.
Last edited by Notso Fantastic; 15th Jan 2005 at 22:52.