ACR CARGO ACFT WENT OFF RWY WHEN NOSEWHEEL STEERING DEVELOPED AN ELECTRICAL HARD OVERSTEERING COMMAND.

Narrative

UPON LNDG AT BHM; ACFT VEERED TO THE R AS SOON AS THE NOSEWHEEL TOUCHED DOWN. WHILE ON THE MAIN GEAR; DIRECTIONAL CTL WAS NORMAL; BUT WHEN NOSE WAS LOWERED TO GND; ACFT PULLED HARD TO THE R. FULL L RUDDER WAS APPLIED; BUT WOULD NOT CORRECT THE DEV. NOSEWHEEL STEERING WAS ENGAGED BY SETTING THE SPD TO LOW AND NOSEWHEEL STEERING BUTTON ON L PWR LEVER; BUT HAD NO EFFECT. THEN APPLIED MASSIVE AMOUNT OF DIFFERENTIAL BRAKING AND REVERSE THRUST; BUT COULD NOT CORRECT PROB. EXITED SIDE OF RWY AT APPROX 70 KTS. TRIED TO AVOID ALL OBSTACLES; BUT STRUCK RWY SIGN. PERFORMED EMER EVAC AND EXITED ACFT. THE ACFT WAS COMPLETELY UNCTLABLE FROM THE TIME THE NOSEWHEEL TOUCHED THE GND (APPROX 100 KTS). I FELT LIKE IT WAS LOCKED IN AN OFF CTR TO R POS. I AM NOT SURE ANYTHING I DID MADE ANY DIFFERENCE AT ALL. I WAS JUST ALONG FOR THE RIDE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT WAS FLYING A FAIRCHILD METROLINER SA227-AT ACFT. PLT RPTED THAT THE NOSEWHEEL STEERING APPEARED TO BE JAMMED AT A 5-10 DEG NOSE R POS. THE PLT ATTEMPTED TO ENGAGE THE ELECTRICAL NOSEWHEEL STEERING COMMAND BY BOTH ENGAGING THE ENG LOW SPD AND ACTIVATING THE NOSEWHEEL STEERING BUTTON ON THE THROTTLE QUADRANT. NEITHER OF THESE HAD ANY AFFECT. THE PLT RPTS THAT THERE WAS ANOTHER OFF RWY INCIDENT AT HIS ACR THE NEXT NIGHT; FROM THE SAME CAUSE. WHEN HE RPTED THE INCIDENT TO THE ACR CHIEF PLT HE SAID THERE ARE THOSE WHO HAVE BEEN OFF THE RWY AND THOSE WHO WILL BE OFF THE RWY IN THE METROLINER. THIS IS ONE OF THE ACR'S MAIN PROBS.