CAPT OF A FAIRCHILD SA-226 METROLINER SW4 LOST CTL OF ACFT DURING FINAL APCH DUE TO ENCOUNTER WITH LOW LEVEL WINDSHEAR AND HIGH GUSTY XWIND CONDITION. THIS RESULTED IN AN INADVERTENT LNDG BEFORE A GAR COULD BE INITIATED. IN ADDITION; THE RPTR HAD LIMITED VISION THROUGH THE WINDSHIELD DUE TO ACFT ICING.

Narrative

AFTER A VOR APCH TO THE LEWISTON ARPT; ACR X WAS CLRED FOR A VISUAL APCH TO RWY 11. MODERATE ICE AND TURB WERE ENCOUNTERED ENRTE AND ON THE DSCNT FOR THE VOR APCH TO THE ARPT. ICE WAS OBSCURING SOME OF THE VISION OUTSIDE THE ACFT. IT MADE IT DIFFICULT TO IDENT RWY 11 WITH THE BLENDING TOWN AND ARPT LIGHTS. THE LOWER THE ACFT DSNDED THE MORE FREQUENT MODERATE TURB BECAME WITH STRONGER UP- AND DOWN-DRAFTS EXPERIENCED. INCREASED AIRSPD WAS USED DURING FINAL APCH AND MANEUVERING FOR LNDG. WHEN THE ACFT TURNED FINAL APCH THE WIND WAS 60 DEGS TO THE RWY GUSTING TO 34 KTS. BECAUSE OF THE REDUCED VISIBILITY OUT THE WINDSHIELD; DUE TO THE RESIDUAL ICE THAT WAS STILL PRESENT (EXCEPT WHERE HEATING ELEMENTS WERE IN THE WINDOWS) AND THE LACK OF A VISUAL APCH SLOPE INDICATOR SYS FOR THAT RWY; THE ACFT WAS LOW AND BELOW A NORMAL GLIDE PATH. ON VERY SHORT FINAL WINDSHEAR WAS ENCOUNTERED; CAUSING THE ACFT TO DSND DANGEROUSLY LOW. THE INCREASED AIRSPD ALLOWED THE ACFT TO RECOVER AND THE AIRPLANE LANDED BEFORE A GAR COULD BE INITIATED. THE WORKLOAD FOR THE PIC DURING SIMILAR CONDITIONS COULD BE REDUCED IF A VASI WAS INCORPORATED FOR RWY 11 AT LEWISTON; ID.