Noise and vibration
On one trip across the pond we took a bod from the Inst of Aviation Medicine with us to monitor noise levels, he got off in Gander and wouldn't go any further as he considered it a danger to his hearing.
I have always wondered how Israeli Hercs differed from ours as in "the Raid on Entebbe" they all start off singing nice and quietly and gradually join in. When we used to go on detachment to El Adem from Thorney the bridge school had a board with the suits and numbers on for their bidding as you couldn't hear any bidding even down by the Para door