What was found
ACCORDING TO CAPTAIN'S REPORT, THEY DEPARTED ON RUNWAY 10 WITH FLAPS 5 DEGREES FOR IMPROVED PERFORMANCE AND UNPRESSURIZED DUE TO DEFERRED APU. AT 2,000 FT AND 210 KM/H, ENGINE BLEEDS UTILIZED FOR PRESSURIZATION. PERFORMED CLIMBING RIGHT TURN TO CROSS VALENCIA VOR WHILE CLIMBING TO 10,000 FT. DURING CLIMB OUT AT 7,000 FT, RECEIVED MASTER/CAUTION WITH ASSOCIATED AFT CARGO DOOR INDICATION. CABIN PRESSURIZATION LOST. PERFORMED DOOR ANNUNCIATOR ILLUMINATED CHECKLIST. RETURNED TO LANDING RUNWAY 10, SMOOTH LANDING. POST FLIGHT INSPECTION REVEALED IMPROPERLY SECURED AFT CARGO DOOR HANDLE. MAINTENANCE FOUND PROXIMITY SENSOR AND ALSO HOLD CLOSE SPRING OUT OF ADJUSTMENT.