AN AEROSTAR 600 PILOT VEERED OFF THE RUNWAY AFTER TOUCHDOWN BECAUSE THE NOSE GEAR FAILED TO EXTEND SUFFICIENTLY TO LOCK THE NOSEWHEEL.

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AIRPLANE VEERED OFF RWY TO L AND WAS RETURNED TO RWY WITHOUT DAMAGE TO EITHER AIRPLANE OR ARPT. CAUSE WAS FAILURE OF THE NOSE GEAR STRUT TO EXTEND SUFFICIENTLY TO PERMIT LOCKING CAM IN NOSE GEAR ASSEMBLY TO LOCK NOSEWHEEL IN STRAIGHT AHEAD POS. AIRPLANE WAS ALIGNED WITH THE CTRLINE OF RWY 32 AT TOUCHDOWN. MAIN WHEELS CONTACTED RWY WITHOUT INCIDENT. WHEN NOSEWHEEL TOUCHED RWY; THE AIRPLANE MADE SHARP L TURN OFF RWY UNTIL R RUDDER AND BRAKES COULD RETURN AIRPLANE TO RWY. INSPECTION THE NEXT MORNING REVEALED THAT NOSE GEAR STRUT HAD LOST NITROGEN CHARGE DUE TO A LEAK PREVENTING THE LOCKING CAM FROM ENGAGING AND ALLOWING NOSEWHEEL TO TURN FROM SIDE TO SIDE. STRUT WAS FILLED WITH NITROGEN AND GEAR RECYCLED SEVERAL TIMES DURING WHICH STRUT EXTENDED AND NOSEWHEEL LOCKED IN STRAIGHT AHEAD POS WITHOUT ANY SIDE TO SIDE MOVEMENT. AIRPLANE DEPARTED ARPT 4 1/2 HRS PRIOR TO INCIDENT AT WHICH TIME NOSE STRUT APPEARED TO HAVE NORMAL 3-4 INCH EXTENSION. HENCEFORTH; WT WILL BE APPLIED TO NOSE DURING PREFLT TO MAKE SURE STRUT WORKING CORRECTLY. MAINT TO FIND SOURCE OF LEAK HAS BEEN SCHEDULED.