A CESSNA CITATION 750 EXPERIENCED ACFT VIBRATION AND LOSS OF THE R MAIN LNDG GEAR DOOR ON DSCNT.

Narrative

JAN/XX/98; WHILE CLBING OUT OF BUR FOR DAL; FELT A VIBRATION IN THE ACFT. WE WERE AT ABOUT 13000 FT AND 300 KIAS. FO DECREASED THE AIRSPD BY PITCHING UP; AND THE VIBRATION CEASED AT 270 KIAS. OUT OF 18000 FT I WENT INTO THE BACK CABIN; AND FO DECREASED PITCH; INCREASING THE SPD TO 300 KIAS AND THE VIBRATION RETURNED. IT FELT WORSE IN THE REAR CABIN FLOOR AREA. NO FURTHER VIBRATIONS WERE FELT; SO THE CLB WAS CONTINUED TO FL450 AT 270 KIAS. ON DSCNT; KNOWING THE VIBRATION MAY RETURN; WE ELECTED TO REDUCE DSCNT AIRSPD TO 300 KIAS. THIS WORKED FINE UNTIL ABOUT FL330 OR SO; WHEN THE VIBRATION RETURNED. IT FELT JUST LIKE A TIRE STILL SPINNING AFTER ROTATION. WE WERE ABLE TO REDUCE AIRSPD TO 270 KIAS AGAIN TO ELIMINATE THE VIBRATION. HOWEVER; ATC THEN REQUIRED A STEEP DSCNT ON THE STAR; SO SPD WAS INCREASED TO 300 KIAS WITH THE SPD BRAKES DEPLOYED TO MEET THE RESTR. THE VIBRATION RETURNED UNTIL ABOUT FL270 WHEN I HEARD A 'POP' AND THE VIBRATION IMMEDIATELY STOPPED. FO SAYS HE DID NOT HEAR ANY NOISE; ONLY THE VIBRATION STOPPING. THE REMAINDER OF THE DSCNT; APCH AND LNDG WERE PERFECTLY NORMAL. NO RPTS WERE MADE TO ATC. FLAPS/SPOILERS 5 DEGS DEPLOYED AT 210 KIAS ON DOWNWIND; FLAPS 15 AT ABOUT 185 KIAS; GEAR AT ABOUT 185 KIAS; AND FLAPS FULL AT ABOUT 160 KIAS. ONCE AGAIN; ALL INDICATIONS WERE NORMAL. NORMAL LNDG; BRAKING; AND TAXIING WERE ACCOMPLISHED. UPON SHUTDOWN; I DISCOVERED THE R MAIN GEAR LARGE DOOR HAD DEPARTED THE ACFT. THE SMALL DOOR WAS SWINGING LOOSE ON ITS HINGE. THE LARGE DOOR ATTACH ROD WAS HANGING BEHIND THE MAIN GEAR ASSEMBLY. DAMAGE WAS NOTED ON THE WHEELWELL AFT LIP (IT WAS BENT DOWN ABOUT 1 INCH). UPON INSPECTION OF THE L MAIN GEAR; THIS SAME DAMAGE WAS NOTED THERE. ALSO; THE BOLT ATTACHING THE BOTTOM OF THE LARGE GEAR DOOR TO THE MAIN LNDG GEAR ASSEMBLY WAS SHEARED. THE DOOR MOVED FREELY FORE AND AFT; BUT NOT SIDE TO SIDE. BOTH LNDG GEAR ASSEMBLIES SHOWED EVIDENCE OF RUBBING FROM THE GEAR DOORS. ALSO; THE REAR EDGE OF THE L DOOR SHOWED EVIDENCE OF RUBBING; PROBABLY FROM THE AFT LIP OF THE WHEELWELL; WHICH MAY BE WHAT BENT IT DOWN. MAINT MGR WAS NOTIFIED UPON DISCOVERY OF THE DAMAGE. I DID NOT INFORM THE PAX OF THE DAMAGE; ONLY THAT WE HAD A MECHANICAL; AND ANOTHER ACFT WAS ON ITS WAY. THE SEPARATION OCCURRED BTWN TURKI AND KAGLE INTXNS; S OF SPS; ON THE BOWIE STAR TO DAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE DOOR WAS MOUNTED ON THE LNDG GEAR STRUT AND BELIEVES IT MAY ONLY BE A RIGGING PROB. THE RPTR STATED THE FASTENERS AT THE TOP AND BOTTOM OF THE R MAIN GEAR STRUT HAD FAILED AND WHEN THE L GEAR DOOR WAS EXAMINED ON THE GND IT WAS FOUND THE LOWER FASTENER WAS SHEARED. THE RPTR STATES THE CHIEF PLT ADVISED THE RPTR THAT IN THE 35 AIRPLANES DELIVERED SO FAR THIS IS THE 5TH INCIDENT OF GEAR DOORS DEPARTING THE ACFT.