Galliano, LA, USA
N480RA
Bell B-206L-1
The 1,514-hour pilot landed and remained parked on a platform in the Gulf of Mexico for approximately 10 minutes with the main rotor RPM at ground idle. While parked, the pilot grabbed the flight manifest and placed it in his lap to make an entry. While his head was down making the entry, the pilot had a sensation that the helicopter was "rocking backwards", and he grabbed both controls in an effort to "level" the helicopter. The pilot lifted up on the collective and pushed forward on the cyclic. The tail boom separated from the fuselage and both sections of the helicopter fell off the platform and into the water. Bell Helicopter Operations Safety Notice (OSN 206L-82-4), addressed tail boom skin compression wrinkles in all Bell model 206L/L-1/L-3 helicopter operations. The Notice stated, "Past 206 experience and flight tests...have revealed the tail boom and aft fuselage can be damaged if during an autorotation landing the main rotor RPM is allowed to decay below 70 percent RPM. Applying collective pitch in excess of that required will in some instances result in excessive flapping of the main rotor during or after touch down. This can cause a resonant response that can damage the tail boom and or aft of the fuselage. Touch down rotor RPM above 70 percent RPM is preferred. Upon ground contact collective pitch should be reduced smoothly without delay while maintaining cyclic pitch near the center position. Long ground runs with the collective up, or any tendency to float for a long distance prior to skid contact should be avoided." When asked how this accident could have been prevented, the operator stated, "Pilot should have remained more vigilant in monitoring control input and position. More aggressive use of control friction would have minimized the possibility of this occurrence." Examination of the wreckage revealed the tail boom separated forward of the horizontal stabilizer, consistent with an autorotation/low RPM failure.
On March 14, 2005, about 0905 central standard time, a Bell 206L-3 single-engine helicopter, N480RA, was destroyed following an uncontrolled departure from an offshore oil rig platform located in the Gulf of Mexico, near Galliano, Louisiana, and collided with the water. The commercial pilot, sole occupant of the helicopter was seriously injured. The helicopter was registered to Ranger Aviation Parts, LLC, of Lafayette, Louisiana, and was being operated by Rotorcraft Leasing Company, LLC, of Broussard, Louisiana. Visual meteorological conditions prevailed and no flight plan was filed for the intended positioning flight conducted under 14 Code of Federal Regulations Part 91. According to the operator, the pilot had just dropped off two passengers at the South Timbalier Block 220 (ST220) and was headed to South Timbalier Block 161 (ST161) to re-fuel. Shortly after take-off, the pilot heard another pilot land on ST161, which accommodated only one parked helicopter at a time, so he circled back around and landed back on ST220. The pilot remained parked on the platform for approximately 10 minutes with the RPM at ground idle. While waiting for the other hekicopter to depart, the pilot reached up and grabbed the flight manifest from the map case above the instrument panel and placed it in his lap to make an entry. While his head was down making the entry, the pilot reported having a sensation of the helicopter "rocking backwards." He said he dropped the manifest and grabbed both controls in an effort to "level" the helicopter. He lifted up on the collective and pushed forward on the cyclic, and he "may" have attempted to open the throttle. The next thing the pilot remembered was being in the water. A witness, who was located on a lower tier of the platform, stated that he heard a "crunching" noise and then observed the main fuselage of the helicopter falling over the side of the platform in a 45-degree nose down attitude. He said the tail boom was separated from the fuselage and it followed the same trajectory path of the fuselage into the water. The main fuselage and tail boom (plus the tail rotor) were recovered from 175 feet of water and transported to a hangar at the operator's maintenance facility. A Federal Aviation Administration (FAA) inspector performed an examination of the wreckage. According to the inspector, the tail boom was severed about 18-inches forward of the horizontal stabilizer. The tail rotor was intact. In addition, there was no evidence that the tail boom was struck by a main rotor blade. Bell Helicopter Operations Safety Notice (OSN 206L-82-4), issued September 5, 1984, addressed tail boom skin compression wrinkles in all Bell model 206L/L-1/L-3 helicopter operations. The notice stated: "Past 206 experience and flight tests with an OH 58A (a military helicopter with similar tail boom and aft fuselage structure) have revealed the tail boom and aft fuselage can be damaged if during an autorotation landing the main rotor RPM is allowed to decay below 70 percent RPM. Applying collective pitch in excess of that required will in some instances result in excessive flapping of the main rotor during or after touch down. This can cause a resonant response that can damage the tail boom and or aft of the fuselage. Touch down rotor RPM above 70 percent RPM is preferred. Upon ground contact collective pitch should be reduced smoothly without delay while maintaining cyclic pitch near the center position. Long ground runs with the collective up, or any tendency to float for a long distance prior to skid contact should be avoided." When asked how this accident could have been prevented, the operator stated, "Pilot should have remained more vigilant in monitoring control input and position. More aggressive use of control friction would have minimized the possibility of this occurrence." The pilot held a commercial certificate with ratings for airplane single-engine land, rotorcraft-helicopter, and instrument helicopter. He had a total of approximately 1,514 flight hours, of which 1,429 hours in were in helicopters and 106 hours were in make and model.
The pilot's abrupt input of the collective while the main rotor RPM was at idle, which resulted in a separation of the tail boom.
Source: NTSB Aviation Accident Database
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