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ETA: Another anecdote I read somewhere involved crews who would "forget" to tell their crewchief that the pitot was used, leaving a rather messy surprise for him to find...the tubes operated off a sorta venturi-effect, the slipstream running past the plane's fuselage would create a sorta vacuum that would suck urine down the tube and expel it out the plane....well, a suitably "pissed" crew chief might "accidentally" reverse that pitot tube outlet, so that the slipstream was actually forced UP the tube! Aircrews usually got the hint after the first time their deposits were blasted back at them.
Try having a "blue water" explosion on an aircraft, and having to clean it all out and remove the corrosion because the "crew" left it in the aircraft for a year...