C-130 crews from the U.S. Air Force suffered from physiological problems when the aircraft’s pressurization system failed and could not be controlled effective. The cause remained unknown until recently.
By U.S. Air Force photo by Tech. Sgt. Howard Blair [Public domain], via Wikimedia Commons
There were many attempts over a decade to discover the root of the problem and the 403rd Wing recently solve the riddle.
They spent two days stripping the pressurization system off one of their C-130Js and discovered a corroded rivet inside an air vale was shedding metal shards into the pressurization system’s air lines.
Source: Alert 5