COMMUTER HELICOPTER TAIL ROTOR HIT GUARD RAIL LNDG ON OIL PLATFORM IN GULF OF MEXICO.

Narrative

DURING A 13 MIN FLT BTWN 2 OIL PLATFORMS SITUATED IN THE GULF OF MEXICO; A MUFFLED SOUND AND HIGH FREQ VIBRATION OF THE DIRECTIONAL PEDALS OF THE HELI ALERTED THE PLT OF A POSSIBLE FLT CTL MALFUNCTION. AN UNEVENTFUL LNDG AND SHUTDOWN WAS ACCOMPLISHED. INSPECTION OF HELI REVEALED THE TAIL ROTOR WAS MISSING BOTH TIP BLOCKS UP TO ABOUT 1 1/2' FROM ROTOR TIPS ON BOTH BLADES. THE LNDG ON THE OIL PLATFORM PRIOR TO THE ABOVE MENTIONED LEG/FLT WAS NORMAL WITH THE POSSIBLE EXCEPTION OF A SLIGHTLY TAIL LOW ATTITUDE DURING LAST PHASE OF LNDG. T/D WAS ON THE AFT PART OF LNDG GEAR SKIDS. (THIS IS WHEN THE TAIL ROTOR APPARENTLY CONTACTED THE 8' GUARD RAIL SURROUNDING THE HELIPAD.) THIS CONTACT WAS NOT DETECTED BY THIS PLT BY SOUND OR ANY ABNORMAL CTL FEELING (FEEDBACK). WINDS AT THE TIME WERE LIGHT AND VARIABLE LESS THAN 5 KTS. POSSIBLE CAUSE OR CONTRIBUTING CAUSES COULD BE: 1) POSSIBLE INATTN DURING THIS PHASE OF LNDG. I HAD 15 OTHER TKOF AND LNDGS DURING THE MORE THAN 5 HRS OF FLYING TIME THAT DAY. 2) DISTR DUE TO RADIO COM ON THE 2 RADIOS ABOARD THE HELI (ONE EACH FM AND VHF RADIO). 3) WEARING OF EARPLUGS IN ADDITION TO THE HEADSET TO DECREASE NOISE LEVEL (OUTSIDE NOISE FROM THE TURBINE ENG). THIS COULD HAVE PREVENTED THIS PLT FROM HEARING THE SOUND OF THE TAIL ROTOR CONTACTING THE FENCE.