Originally Posted by
Euclideanplane
Is it clear why the malfeceance, as it were, seemed to cause effect on only the number three engine, but miss both the others? By coincidence, or somehow by design of the 727?
Think of the engine inlet locations on the 727 - one in the center top (aka 'S-Duct') and one on each side. The blue ice isn't going to fly over the top of the fuselage and hit the center or opposite engine - it's going to hit the engine on the same side as the lav dump.