LTT DRIFTED OFF THE RWY DURING LNDG ROLL AND CAME TO STOP WITH NOSE WHEEL IN THE GRASS.

Narrative

DURING THE LNDG ROLLOUT THE ACFT BEGAN TO VEER TO THE RIGHT. IN AN EFFORT TO ASSIST THE CAPT I ATTEMPTED TO APPLY FULL LEFT RUDDER AND FOUND THAT THE CAPT HAD ALREADY DONE SO. I OBSERVED THAT THE NOSE STEERING ARMED LIGHT WAS EXTINGUISHED AND ADVISED CAPT. THE ACFT CAME TO REST WITH THE NOSE WHEEL IN THE GRASS. THE CAPT THEN ADVISED ME THAT HE HAD DISARMED THE STEERING EARLIER FEARING THERE HAD BEEN A NOSE WHEEL STEERING FAILURE. IN HINDSIGHT IT SEEMS THAT MORE EFFECTIVE USE OF DIFFERENTIAL REVERSE AND DIFFERENTIAL BRAKING MAY HAVE KEPT THE ACFT ON THE RWY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: WHEN IT DEPARTED THE RWY; THE ACFT HAD TURNED SOMEWHAT MORE THAN 45 DEGS. THERE WAS NO DAMAGE. MAINT COULD FIND NOTHING WRONG WITH THE NOSE WHEEL STEERING. THE RIGHT BRAKE WAS REPLACED AS A PRECAUTION ALTHOUGH NOTHING DEFINITE COULD BE FOUND WRONG WITH IT. THERE WERE TIRE MARKS ON THE RWY; BUT IT COULD NOT BE DETERMINED IF THEY WERE CAUSED BY A DRAGGING BRAKE OR THE SIDE LOADS OF THE TURN OFF THE RWY. NOTHING MORE HAS BEEN HEARD RE: THE INCIDENT. THE WINDS WERE LIGHT AND NO APPARENT EFFECT.