AS355 STRUCK THE ROTOR BLADES OF A PARKED HELICOPTER DURING TKOF.

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I WAS FLYING AN AS355 TWINSTAR HELI TO HELP ASSIST IN SIGHTSEEING OPS OUT OF ZZZ HELIPORT. I WAS PARKED ON SPOT X. TO MY L AND IN FRONT OF ME WAS A BUILDING AND TO MY R IN SPOT Y WAS ANOTHER HELI. AFTER LOADING MY PAX; I BRIEFED THEM ON SAFETY AND POSITIONED MY THROTTLE INTO THE FLT GATE. ONCE IN A HOVER I MATCHED TORQUES ON BOTH ENGS AND CONTINUED TO LIFT TO A HIGHER HOVER AND BACK OUT OF MY PARKING SPOT. I WAS KEEPING A CLOSE EYE ON MY TORQUES AS I DID NOT WANT TO OVER-TORQUE THE ACFT AND WAS ALSO WATCHING THE BUILDING TO MY L. BY BEING CONCERNED ABOUT MY TORQUES I HAD FORGOTTEN ABOUT THE HELI PARKED TO MY L. I HAD BELIEVED MY POS TO BE HIGHER AND FURTHER BACK THAN IT ACTUALLY WAS AND PROCEEDED TO MAKE A L PEDAL TURN INTO THE WIND. I THEN HEARD A SMALL NOISE AND KNOWING IT DIDN'T SOUND RIGHT; I STRAIGHTENED THE NOSE AND LANDED THE HELI. AFTER THE PAX WERE OFFLOADED; I SHUT THE HELI DOWN AND REALIZED MY STINGER HAD COME INTO CONTACT WITH THE MAIN ROTOR BLADES OF THE OTHER HELI. I BELIEVE THE CAUSE OF THE PROB WAS NOT MAINTAINING COMPLETE SITUATIONAL AWARENESS. I WAS IN A NEW ACFT AND WAS HVY AND TAKING OFF FROM A VERY TIGHT SPOT. MY CONCENTRATION WAS TOO MUCH ON INSIDE THE HELI AND THE BUILDING TO MY L THAT I HAD FORGOTTEN ABOUT WHAT WAS TO MY R. I SHOULD HAVE BEEN MORE FOCUSED ON THE ENTIRE SURROUNDINGS. IN THE FUTURE; I NEED TO TAKE THE EXTRA SECOND AND MAKE SURE EVERY PLACE AROUND ME IS CLR BEFORE MOVING THE HELI.