A TWIN ENG MEDICAL FLT IS RAMMED ON THE R WING BY A MAINT VEHICLE THAT DID NOT SEE THE ACFT DURING ITS TAXI INTO THE W ENTRANCE OF THE FBO AT SFO; CA.

Narrative

AFTER CLRING RWY 28R AT SFO; PIC WAS CLRED TO TAXI TO PARKING VIA TXWY K AND TXWY C TO THE RAMP ON TWR FREQ. AS ACFT WAS PROCEEDING N INTO W ENTRANCE TO THE RAMP; A MAINT TRUCK ON THE VEHICLE ACCESS ROAD FAILED TO STOP AND IMPACTED THE ACFT ON R WING. ACFT WAS SECURED AT POINT OF IMPACT. DRIVER OF THE TRUCK BACKED TRUCK AWAY FROM ACFT. DRIVER FAILED TO SEE ACFT. MEDICAL ATTENDANT IN COPLT SEAT SAW VEHICLE JUST BEFORE IMPACT; BUT WAS UNABLE TO STOP EVENT. THE NTSB WAS NOTIFIED OF THIS INCIDENT. CONTRIBUTING FACTORS: 1) TXWY AND ROAD WERE WET AND BLACK. VISION WAS DIFFICULT BECAUSE OF GLARE. 2) TXWY AND ROADWAY MARKINGS WERE WASHED OUT. 3) ARPT AUTH HAD CLOSED E ENTRANCE ONTO RAMP BECAUSE OF DAMAGE TO DRAINAGE SYS. ENTRANCE AND RAMP WERE CONED OFF FOR ABOUT 200 FT. HOWEVER; THEY DID NOT APPEAR TO HAVE RELOCATED THE STOP SIGN AT E ENTRANCE. THIS CONDITION HAS EXISTED FOR SEVERAL MONTHS. 4) RAMP DID NOT PROVIDE FOLLOW-ME SUPPORT. CORRECTIVE ACTIONS: 1) ARPT AUTH SHOULD PLACE STOP SIGNS ON ROADWAY IN EACH DIRECTION AT BOTH ENTRANCES TO RAMP. 2) ARPT AUTH SHOULD FIX E ENTRANCE TO RAMP ASAP.