WHILE ON FINAL APCH TO A HELIPORT, THE HELICOPTER WAS AT APRX 70 KTS & 100 FT AGL WHEN THE PLT APPLIED POWER TO BEGIN DECELERATING. AS COLLECTIVE PITCH WAS APPLIED, HE HEARD A SERIES OF BANGING NOISES WHICH HE DESCRIBED AS SIMILAR TO COMPRESS STALLS. SIMULTANEOUSLY, HE NOTED A DECAY OF THE ENG POWER. THE PLT CHANGED HIS COURSE TO MINIMIZE THE DISTANCE TO THE LANDING AREA & RAISED THE NOSE TO FURTHER DECELERATE FOR A VERTICAL DESCENT. HOWEVER, DURING TOUCHDOWN, THE TAILWHEEL STRUT FAIRING HIT A BARRIER AT THE EDGE OF THE HELIPORT, SEPARATING THE VERTICAL STABILIZER & FENESTRON. THE SEPARATED COMPONENT TRAVELED UPWARD & STRUCK THE MAIN ROTOR BLADES. REPORTEDLY, THE LOW RPM WARNING HORN SOUNDED JUST BEFORE THE COMPRESSOR STALL. CORRECTIVE ACTION FOR A LOW RPM WARNING HORN IN THIS SITUATION SHOULD HAVE BEEN TO REDUCE THE POWER DEMAND BY LOWERING THE COLLECTIVE AND/OR REDUCING RIGHT PEDAL APPLICATION. AN ENG CHECK REVEALED IT WAS CAPABLE OF EXCEEDING THE MAX REQUIRED TORQUE, BUT IT HAD SLIGHT FOULING OF THE FUEL INJECTOR WHEEL & COMPRESSOR AIR FLOW