BK117 PLT TURNS TO AVOID LOWERING CEILING AND INADVERTENTLY DSNDS; STRIKING A PWR LINE. AFTER ASSESSING CTLABILITY; PLT RETURNS TO HOME BASE WHERE MINOR DAMAGE IS NOTED.

Narrative

I WAS THE SOLE OCCUPANT OF THE ACFT. THE TKOF AND ENTRY INTO CRUISE FLT WAS NORMAL. THE CEILING HAD LOWERED AND I NEEDED TO STAY AT AN ALT OF 600-700 FT AGL TO REMAIN IN VFR CONDITIONS. I CHKED THE RADAR ALTIMETER SHORTLY AFTER LIFTOFF AND ESTIMATED THE CEILING TO BE RAGGED AT APPROX 800-900 FT. APPROX 4 MINS INTO THE FLT; I NOTICED THAT THE SCATTERED CLOUDS AHEAD OF MY PATH WERE APPEARING TO BECOME BROKEN AND ALSO APPEARED TO BE LOWERING. I REMAINED IN VFR CONDITIONS; HOWEVER; IT QUICKLY BECAME APPARENT TO ME THAT I COULD NOT REMAIN VFR IF I CONTINUED ON A DIRECT FLT PATH BACK. I REALIZED THAT I WAS NEEDING TO DSND TO REMAIN CLR OF THE CLOUDS. I GLANCED AT THE RADAR ALTIMETER AND NOTICED THAT IT READ APPROX 425 FT. I DECIDED THAT I COULD NO LONGER CONTINUE AND ELECTED TO START A SHALLOW L TURN. I COULD STILL SEE VFR TO THE L; BUT IFR TO MY R. AS I TURNED THE ACFT TO THE L; I OBVIOUSLY ALLOWED THE ACFT TO DSND INADVERTENTLY. A SECOND OR TWO LATER; I BELIEVE THAT I NOTICED THE ALERT LIGHT ON THE RADAR ALTIMETER FLASH ON; THE BUG ON THE RADAR ALT WAS SET FOR 300 FT. AT THE SAME MOMENT I SAW 2 BRIGHT FLASHES; ONE ABOVE AND R AND THE OTHER TO MY L. I ALSO HEARD A LOUD 'POP' SOUND. THE ACFT JERKED SLIGHTLY BUT CONTINUED TO FLY. I NEVER SAW ANY WIRES BUT IMMEDIATELY REALIZED THAT I MUST HAVE STRUCK PWR WIRES. AFTER THE INITIAL JERK; I REALIZED THAT THE ACFT WAS STILL FLYING. I IMMEDIATELY BEGAN AN ASSESSMENT OF THE HEALTH OF THE ACFT AND ITS SYS. ALL OF THE ENG INSTS APPEARED TO BE NORMAL AND IN THE GREEN. THE ROTOR RPM'S STAYED NORMAL; TORQUE WAS NORMAL AND BOTH TURBINES REMAINED MATCHED. UPON REALIZING THAT THE ACFT WAS APPARENTLY FUNCTIONING NORMALLY; MY NEXT CONCERN WAS TO GET THE ACFT OVER A SUITABLE LNDG AREA IN THE EVENT THAT THINGS BEGAN TO GO WRONG AND I WOULD BE FORCED TO MAKE A PRECAUTIONARY LNDG. I CONTINUED TO FLY SW. I CONTACTED APCH AND ADVISED THEM THAT I HAD POSSIBLY STRUCK PWR WIRES AND WISHED TO PROCEED DIRECTLY TO ZZZ ARPT. I DID NOT DECLARE AN EMER OR ASK FOR RESCUE EQUIP. I DID; HOWEVER; ASK THE CTL TWR PERSONNEL TO CONTACT COMPANY PERSONNEL TO MEET ME BY THE RAMP IN FRONT OF OUR HANGAR SO THAT THEY COULD VISUALLY INSPECT THE UNDERSIDE OF THE ACFT PRIOR TO MY SETTING THE ACFT DOWN. I WAS CONCERNED THAT THE LNDG GEAR MAY HAVE BEEN DAMAGED; CAUSING IT TO COLLAPSE UPON SET-DOWN. UPON INSPECTION; THE LNDG GEAR APPEARED NORMAL. THE SET-DOWN WAS UNEVENTFUL. A CURSORY INSPECTION OF THE ACFT REVEALED DAMAGE TO THE RADAR DOME AT THE NOSE OF THE ACFT; DAMAGE TO UPPER EDGE OF THE COPLT WINDSHIELD; ALSO DAMAGE TO THE LOWER WIRE STRIKE BRACE. HUMAN PERFORMANCE CONSIDERATIONS: I FEEL THAT I SHOULD HAVE REALIZED EARLIER AND; THEREFORE; TURNED THE ACFT EARLIER; PRIOR TO THE NEED TO DSND. I WAS WELL RESTED AND ALERT AT THE TIME OF THE INCIDENT; SO I DO NOT BELIEVE THAT FATIGUE WAS THE PROB.