What was found
DURING PREFLIGHT, AFTER STARTING APU, EICAS WARNING INDICATED NR 1 AIR CONDITIONING PACK WAS INOP, OUTSIDE NOISE SOUNDED LIKE A DUCT HAD COME OFF. MEL'D NR 1 AIR CONDITIONING SYS IAW COMPANY PROCEDURES, FLEW ACFT BELOW 23,000 FEET TO MRO FACILITY. FOUND RUBBER DUCT BLOWN OFF ON NR 1 AIR CONDITIONING PACK.