ACFT EQUIP BREAKAGE INFLT.

Narrative

WHILE ON INITIAL CLBOUT OF MEM ENRTE TO IAD; THE ACFT EXPERIENCED A LOUD BANG AND A NOTICEABLE VIBRATION THAT SEEMED TO COME FROM UNDER THE COCKPIT AREA. THIS OCCURRED AT APPROX 16000-17000 FT. IAS WAS 330 KTS. THE AIRSPD WAS SLOWED TO 280 KTS AND THE VIBRATION DECREASED TO A MINIMUM; ALL SYS WERE CHKED AND INDICATED NORMAL. THE CREW THOUGHT WE HAD HIT A BIRD OR DUCK AROUND THE RADOME OR NOSE GEAR AREA. THE ACFT WAS FLYING OK AND AFTER CHKING EVERYTHING OUT WE WERE CLBING THROUGH FL260 AND CONTINUED TO A PLANNED FL330 AT A REDUCED CLB SPD. AFTER LEVELING OFF AT FL330; WE NOTICED CRUISE EPR HIGHER THAN THAT PLANNED FOR MACH .80. THE ACFT WAS SLIGHTLY OUT OF TRIM WITH MINOR BUFFETING AND VIBRATIONS. WE CALLED (COMPANY) VIA VHF AND ADVISED THEM OF OUR SIT AND OUR INTENTIONS TO CONTINUE TO IAD; UNLESS THEY WANTED US TO RETURN MEM. MAINT SUGGESTED VIA OPS FOR US TO CYCLE GEAR HANDLE TO THE UP POS; BUT I ADVISED THAT WE HAD ALREADY TRIED THIS; WITH NO APPARENT EFFECTS. CRUISE FUEL FLOW WAS HIGHER THAN PLANNED; BUT WE CALCULATED THAT WE HAD SUFFICIENT FUEL TO CONTINUE TO DEST; WITH PLANNED RESERVE AND ALTERNATE FUEL. WE CONTINUED ON TO IAD CRUISING AT A REDUCED MACH NUMBER; TO KEEP VIBRATIONS AT A MINIMUM. DSCNT AND APCH WERE ALSO ACCOMPLISHED AT A SLOWER THAN NORMAL SPD. AN UNEVENTFUL LNDG WAS MADE IN VISUAL CONDITIONS AT IAD ON RWY 1L. AFTER THE ACFT WAS PARKED ON OUR RAMP AT IAD; DAMAGE WAS VISIBLE TO THE L-HAND OUTER GEAR DOOR AND A PORTION OF THE UNDERSIDE OF THE WING ADJACENT TO THE GEAR DOOR. THE Z BAR AND ATTACH MECHANISMS WERE MISSING. I CALLED THE DUTY OFFICER; AND FLT SAFETY IN MEMPHIS; ADVISING THEM OF THE SIT. SUPPLEMENTAL INFO FROM ACN 294776: THE PROB APPEARED TO HAVE BEEN CAUSED BY STRUCTURAL FAILURE OF THE BAR THAT HOLDS THE GEAR DOOR TO THE GEAR STRUT. DURING PREFLT INSPECTION; I HAD CHKED THE AFFECTED GEAR AND NOTICED NO APPARENT PROB.