LIGHT TWIN JET LANDS WITH NOSE GEAR NOT CENTERED CAUSING ACFT TO SWERVE AND LEAVE RWY.

Narrative

AFTER DEPARTING BWI A NOSE GEAR UNSAFE OR TRANSIENT LIGHT REMAINED ILLUMINATED. AFTER CYCLING GEAR TWICE; LIGHT STILL REMAINED ILLUMINATED. AFTER TOUCHDOWN IN PHL RWY 35 I LOWERED NOSE SLOWLY TO THE RWY. AT 85 KTS NOSEWHEEL TOUCHED. THE ACFT TURNED ABRUPTLY 15 DEGS L. WITH HVY R BRAKING; THE CTRLINE OF THE RWY COULD NOT BE MAINTAINED AND AT 10 FT L OF CTR I CALLED FOR THE DRAG CHUTE WHICH STOPPED THE TURN AND STRAIGHTENED THE COURSE OF THE ACFT. WE ROLLED OFF THE RWY INTO THE GRASS AND BACK ONTO THE RWY USING NOSEWHEEL STEERING AT LOW SPD. NO DAMAGE OCCURRED TO ANY RWY LIGHTS OR THE ACFT AND TWR WAS NOT AWARE OF THE SIT. THE PROBABLE CAUSE OF RED UNSAFE LIGHT WAS NOT ENOUGH N2 PRESSURE TO EXTEND THE STRUT AND THE CENTERING PIN DID NOT ENGAGE IN THE SAFETY CAM CENTERING NOSEWHEEL UPON RETRACTION. THIS WAS ALSO THE PROBABLE CAUSE FOR THE MALFUNCTION OF THE CENTERING CAM UPON GEAR EXTENSION. MAINT FOUND SOME ROLLED SEALS WHICH ALLOWED FLUID AND N2 LEAKAGE. N2 PRESSURE REQUIRED TO OPERATE CENTERING MECHANISMS.