What was found
INSPECTION TYPE:N/A 2IR TURNBACK TO SDF DUE TO LOW CABIN AIR PRESSURE UNABLE TO KEEP CABIN BELOW 10.000 AT ANY ALTITUDE ABOVE FL 200. FOUND MAIN CARGO DOOR AFT PRESSURE SEAL FLANGE PULLED OUT OF TRACK. RE-SECURED MM 52-09, PRESSURIZED AIRCRAFT AND FOUND EQUIP COOLING FLOW CONTROL VALVE REMAINING OPEN. REMOVED AND REPLACED FLOW CONTROL VALVE IAW 747 MM 21- 58-04, PRESSURIZED AIRCRAFT TO 7.8 LBS DIFF MAINTAINED.