SHORTLY AFTER TKOF, THE PLT CONTACTED HIS COMPANY (OPNS) & SAID HE HAD INADVERTENTLY ENCTRD IFR CONDS. HE ASKED OPNS TO RELAY INFO TO HIM FM THE APCH PLATE FOR THE ILS RWY 17 APCH TO BRAZORIA COUNTY ARPT. AFTER RCVG THE INFO, HE CONTACTED HOUSTON APCH CTL & ASKED FOR THE ILS. VECTORS WERE PROVIDED & HE WAS CLRD FOR THE ILS; HOWEVER, HE WAS UNABLE TO GET ESTABLISHED ON THE APCH. THREE ATMTS WERE MADE WITH THE LAST BEING A NO-GYRO APCH. DRG THIS TIME, SIMULTANEOUS RADIO CONTACT WAS MAINTD WITH APCH CTL & OPNS. HIS GND SPEED VARIED FM 106 TO 28 KTS. JUST BFR THE ACDNT, HE SAID, '. . . I'VEGOT AN ALTITUDE PROBLEM,' THEN AFTER A SHORT DELAY, HE STATED '. . . I AM GOING TO CRASH.' THE WRECKAGE WAS FND APRX 1 MI NW OF THE OUTER MARKER, SCATTERED OVR A 2445' AREA. THERE WAS EVIDENCE THE MAIN ROTOR BLADES HAD HIT THE TAIL BOOM & RADOME & SEPD IN FLT. ONE BLADE HAD A PREEXISTING CRACK, BUT BLUE PAINT MATCHING THE TAIL BOOM WAS FND ON THE BLADE. THE1950 CDT WX AT GALVESTON (32 MI ENE), WAS IN PART: 400' OVC, 3 MI VIS WITH FOG & HAZE, WIND FM 080 DEG AT 18KTS.