The G can be generated pretty easily by the short, sharp knock that follows when the fuselage hits something solid. Very short duration.
I've had the crash lights come on in what I thought was a pretty 'normal' landing, but which investigation revealed could generate a G load in exactly the right axis to be enough to automatically switch on the 'hard landing' lights.
So 2.9 is not that unusual for something like the landing gear collapsing.
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