AN ACR DHC6 FLC DEPARTED THE RWY AFTER LNDG IN AN 80 DEG; GUSTING XWIND AND THEN TAXIED BACK ONTO THE RWY.

Narrative

THE INCIDENT OCCURRED ON TOUCHDOWN AND ROLLOUT. WE WERE ENRTE FROM ANCHORAGE; AK; TO HOMER; AK. WE HAD EXPERIENCED MODERATE TURB THROUGHOUT THE FLT UNTIL LNDG. WHILE ON THE APCH TO LAND STRAIGHT-IN ON RWY 21 WE ENCOUNTERED LIGHT TO MODERATE TURB. WE THEN REQUESTED A WIND CHK ON ABOUT A 3 MI FINAL. THE RPT WAS GIVEN AS WINDS 130 DEGS AT ABOUT 12 KTS. WE CONTINUED THE APCH. AT ABOUT 300 FT THE WIND SEEMED TO DIE DOWN. JUST PRIOR TO ENTERING THE FLARE; WE ENCOUNTERED EXTREME GUSTS REQUIRING FULL CTL MOVEMENTS AND EXTREME THROTTLE ADJUSTMENTS. WE TOUCHED DOWN SMOOTH AND ON CTRLINE. WE HAD BRIEFED THE APCH THAT I; THE FO; WOULD HOLD THE AILERONS INTO THE WIND ON TOUCHDOWN. I DID AS THE CAPT TRIED TO MAINTAIN CTRLINE. WE WERE HIT BY NUMEROUS GUSTS THAT ALMOST PICKED UP THE UPWIND WING DESPITE THE AILERON DEFLECTION. THE CAPT USED FULL R RUDDER AND FULL THROTTLE ON THE UPWIND ENG AND REVERSE ON THE OTHER ENG TO TRY AND REGAIN CTRLINE. WE WERE HEADED FOR THE L SIDE OF THE RWY STILL BEING HIT BY THE GUSTY WINDS. DESPITE ALL THE ATTEMPTS TO REGAIN CTRLINE THEY WERE ALL UNSUCCESSFUL. WE WENT OFF THE L SIDE OF THE RWY BTWN 2 RWY LIGHTS. BY NOW WE WERE ABLE TO GET SOME DIRECTIONAL CTL BACK AND MADE IT BACK ONTO THE RWY BTWN 2 OTHER RWY LIGHTS. WE WERE ABLE TO TAXI CLR OF THE RWY WITHOUT ANY OTHER PROBS. AFTER THE EVENT THE CAPT AND I TALKED ABOUT WHAT WE COULD HAVE DONE IF GIVEN TO DO AGAIN. WE SHOULD HAVE GONE AROUND THE MOMENT WE ENCOUNTERED THE EXTREME WIND GUSTS. ALTHOUGH WE WERE IN THE LNDG FLARE AT THE TIME; WE SHOULD HAVE GONE AROUND.