A SMALL LOW WING TURBOJET ON CLBOUT AT 9000 FT DECLARED AN EMER AND RETURNED TO THE FIELD DUE TO NOSE GEAR VIBRATION AND NOISE CAUSED BY A FAILED UPLOCK SYS.

Narrative

AFTER DEPARTING LAS WE WERE ON A RADAR VECTOR TO ASSIGNED ALT OF 9000 FT. DURING CLBOUT I HAD NOTICED A FLICKERING OF THE HYD PRESSURE ON LIGHT. AT ABOUT 8500 FT WE ENCOUNTERED MODERATE TURB. WHILE LEVELING OFF AT 9000 FT SEVERAL LOUD BANGING NOISES OCCURRED IN THE NOSEWHEEL AREA CAUSING THE ACFT TO SHAKE AND VIBRATE. WHILE ATTEMPTING TO DETERMINE WHAT THE PROB WAS AND MAINTAIN ALT AND ATTITUDE IN THE MODERATE TURB; THE ACFT DRIFTED UP 300 FT AND SET OFF THE ALT ALERT. RETURNED TO 9000 FT. TURNED ACFT OVER TO FO WHILE I LOCATED THE LNDG GEAR CIRCUIT BREAKER; WHICH WAS ON MY SIDE. PULLING THE CIRCUIT BREAKER STOPPED THE BANGING. ALSO THERE WAS NOTHING IN THE CHKLIST WHICH ADDRESSED THE PROB. REQUESTED IMMEDIATE RETURN TO LAS AND EQUIP TO STAND BY IN CASE GEAR WAS NOT LOCKED DOWN. APPARENTLY NOSE GEAR WAS SLIPPING OUT OF UPLOCK AND SYS WAS PRESSURIZING; SLAMMING GEAR INTO UPLOCK EACH TIME IT FELL OUT. MAINT ADJUSTED THE UPLOCK POS AND THE PROB DID NOT RECUR. PRIOR TO THIS DEP; THERE HAD BEEN NO PROBS WITH THE NOSE GEAR UPLOCK.