What was found
(CAN) DURING MAINTENANCE, TROUBLESHOOTING FOR LOW FLOW FROM CABIN GASPERS, MAINTENANCE, WHILE INSIDE THE AFT CARGO COMPARTMENT FELT THE REAR PRESSURE BULKHEAD AS BEING WARM/HOT. INVESTIGATION IN THE AFT EQUIPMENT BAY, FOUND THE ENGINE BLEED AIR / APU / AIR-CONDITIONING PACKS JUNCTION DUCT CRACKED, CRACK EXTENDED AT LEAST 50 PERCENT OF CIRCUMFERENCE AND WAS OPEN BY APPROX .2500 INCH. DUCT ASSEMBLY REPLACED, FUNCTION CHECKS CARRIED OUT. AIRCRAFT RETURNED TO SERVICE. (TC NR 20070306005)