MD88 FLC ATTEMPT 180 DEG TURN ON TXWY BUT DEPART CONCRETE SURFACE AND REQUIRE A TOW TO GATE.

Narrative

AFTER A NORMAL LNDG IN ATL; WE WERE INFORMED OF A LAST MIN GATE CHANGE. WE INFORMED GND CTL THAT OUR RAMP HAD CHANGED FROM RAMP A TO RAMP B. WE WERE EBOUND ON TXWY E AND HAD JUST BEGUN THE TURN FROM TXWY E ONTO TXWY F4. GND CTL ASKED IF WE WERE ABLE TO MAKE A 180 DEG TURN BACK TO TXWY E SO HE DIDN'T HAVE TO STOP TFC ON TXWY F. THERE APPEARED TO BE ENOUGH WIDTH AT THE JUNCTION OF TXWY E AND TXWY F4; AND OUR NOSE WAS ALREADY ON TXWY F4; SO WE COMPLIED AND BEGAN A L TURN BACK TO TXWY E. DURING THE TURN; THE NOSEWHEELS DEPARTED THE CONCRETE ONTO ASPHALT SHOULDER. THERE WAS APPROX A 2 INCH HT DIFFERENCE BTWN THE ASPHALT AND THE CONCRETE. THE ACFT WAS STOPPED WHEN THE NOSEWHEELS WENT ONTO THE ASPHALT; AND THE CONCRETE LIP PREVENTED THE NOSEWHEEL'S RETURN ONTO THE TXWY. AT THIS POINT; MAINT WAS CALLED TO USE A TUG TO CTR THE NOSEWHEELS AND MOVE THEM BACK ONTO THE TXWY. THE DECISION WAS MADE TO HAVE MAINT TOW THE ACFT BACK TO THE GATE. NO DAMAGE OR INJURIES RESULTED. THE CREW MISJUDGED THE AREA OF THE TXWY INTXN RESULTING IN THE NOSEWHEEL DEPARTING THE MARKED TXWY ONTO THE PAVED SHOULDER. WE CAN PREVENT THIS IN THE FUTURE; AND WOULD HAVE PREVENTED THIS OCCURRENCE BY TAXIING E ON TXWY F TO THE NEXT INTXN F5; THEN TURNING W ON TXWY E. WE WILL NOT ATTEMPT A 180 DEG TURN AT A TXWY INTXN.