THE HELICOPTER WAS BEING USED IN FIRE FIGHTING OPERATIONS. A WATER BUCKET WAS ATTACHED TO THE EXTERNAL HOOK. A HOVER LANDING WAS BEING ATTEMPTED ON AN ALUMINUM MAT HELIPAD. THE PAD SLOPED DOWNHILL, INTO THE WIND. WIND GUSTS WERE HIGH. TO PRECLUDE DAMAGE TO THE HELICOPTER FROM THE WATER BUCKET, THE HELICOPTER HAD TO BE HOVERED AND LANDED BEHIND THE BUCKET, AFTER THE BUCKET HAD BEEN PLACED ON THE PAD. ALSO, THE HELICOPTER WOULD ROLL 18' TO ONE FOOT AFTER TOUCH DOWN. WHILE HOLDING THE WHEEL BRAKE PEDAL, SLIGHT ANTI-TORQUE CONTROL INPUT WAS MADE. COUPLED WITH THE CROSSWIND CONTROL INPUT, MAST BUMPS RESULTED. ON THE FIFTH LANDING ATTEMPT, ONE MAIN ROTOR BLADE CONTACTED ONE OF THE VERTICAL STABILIZERS, WHICH SEPARATED THE CONTROL TAB FROM THE BLADE. THE PILOT REDUCED ENGINE POWER & ALLOWED THE HELICOPTER TO SETTLE TO THE GROUND.