What was found
DESCENT THRU 290 TO 200 F/A REPORTED LOUD RUSHING AIR SOUND AREA OF CLOSET 346 MID-CABIN. FOUND FWD CARGO HEATING DUCT BLOWN BELOW AIR COND MIX CHAMBER. FWD CARGO HEATING MADE INOP AND DEACTIVATED. THIS DUCT IS MISSING 2 FT AND NOT REPAIRABLE. IAD HAS DUCT 214T6113-89 & WILL KEEP AT IAD TO REPAIR DUCT ON RETURN FLT 874-21 OVERNIGHT. REPLACED FWD CARGO HEAT MOST AFT DUCT FROM STA 786 TO 654. REACTIVATED CARGO HEAT VALVE, RAN CARGO HEAT NO LEAKS FOUND. OPS CHECKS NORMAL.