N108PHDassault-Breguet MYSTERE FALCON 900 · 1990

On June 10, 2010, approximately 1034 central daylight time, N108PH, a Bell 206 L-3 helicopter experienced a possible tail rotor failure and made a forced landing to the water and subsequently rolled inverted due to a partial deployment of the emergency floats. The helicopter was registered to and operated by Petroleum Helicopters Incorporated (PHI), Lafayette, Louisiana. The commercial pilot was not injured and the two passengers sustained minor injuries. A company visual flight rules flight plan was filed for the flight that departed the company's base in Port O'Connor, Texas, around 1000, and destined for an oil platform (Mustang Island Block 103) in the Gulf of Mexico. Visual meteorological conditions prevailed for the on-demand air taxi flight conducted under 14 Code of Federal Regulations Part 135. The pilot and the two passengers exited the helicopter after it was inverted and were rescued within 15 minutes by a nearby boat.

In a written statement, the pilot stated that this was his third flight of the day. The flight was normal until they were approximately 10 minutes from the platform at an altitude of 900 feet. He said, "I heard a pop and the aircraft pitched down and to the right with strong vibrations. I lowered the collective and stabilized the aircraft scanning the gauges which indicated the engine was running normally (Nr approximately 101 percent). No response from the pedals, pulled some collective to see if the aircraft would be flyable, right rotation beginning showed that it would not." The pilot then entered a full autorotation and brought the throttle to idle. Prior to the flare, he deployed the emergency floats and observed them start to inflate. The pilot said he made a controlled landing with a soft touchdown on the top of a swell. As the helicopter settled, he noted that the center float on the right side did not inflate and he was concerned that the helicopter would roll to the right, which it did almost immediately. The pilot did not have time to activate the emergency life raft switch, and exited the helicopter once it was fully inverted. While still under water, he inflated his life vest and immediately rose to the surface where he observed the two passengers. One of the passengers did not have his life vest inflated, so the other passenger was helping him get it inflated. The three of them then held onto the skids of the helicopter, which had now sunk about one-foot under the water, and waited for the rescue boat to reach them. While waiting for the boat, the pilot did a quick check of the helicopter and saw there was no damage to the underside of the tail boom, and he could see one of the tail rotor blades. The pilot did not attempt to use the external emergency t-handle mounted on the upper end of the forward cross tubes to inflate the life rafts due to the fact that the rescue boat was rapidly approaching.

The passenger, who was seated in the front left seat, described the flight as “normal” except for a strong headwind. He knew the captain from previous flights and said that he didn’t talk much during the flight. About 30 minutes into the flight, at an altitude of 900-950 feet, the helicopter suddenly, and without warning, pitched over almost 90 degrees. The passenger said it was a sudden “nose dive” and he had immediate “tunnel vision on the water.” He also said that he and the pilot hit their heads on the roof of the cabin when the helicopter nosed over. During this time, he did not feel any vibrations, hear any warning noises or see any caution lights illuminated. The passenger said the captain got control of the helicopter, leveled it, and tried to fly it forward. He heard the pilot say, “This ain’t gonna work…we lost our tail rotor.” Almost immediately after, the captain deployed the emergency floats and said “we’re gonna roll.” The passenger said from the time the helicopter nosed over to the time they landed was 10 seconds and he described the landing “like any other landing on a platform.” The passenger said the captain tried to keep the helicopter upright as long as possible, but within 1 or 2 seconds the main rotors blades started hitting the water (engine was still under power) and the helicopter rolled right and went inverted.

The passenger said when the helicopter started to roll to the right, he immediately took off his headset, unbuckled his seatbelt and exited out the left front door. Once he got his head out of the water, the helicopter was completely inverted and floating just under the water. He saw the other passenger, swam two strokes toward him and inflated his life vest. Then, all three of them got onto the belly of the helicopter. The passenger said the tail boom was still attached to the helicopter but he wasn’t sure about the tail rotor. It was at that time they saw the rescue boat from a nearby barge about 150 yards away and headed directly towards them. He said the pilot never discussed using the external life raft because the rescue boat was so close. Persons on the boat used a ladder to help him and the pilot onto the boat. Divers got into the water to assist the other passenger who was injured. At that time, a tug boat approached the scene and coordinated with the divers to tie the helicopter to the tug boat so they could drag it to the barge. The passenger said the seas had started to pick up. The rescue boat returned to the barge, but was told not to dock because the Coast Guard needed a clear deck for landing. So, the rescue boat returned to the tug boat to pick up the divers. The passenger said by the time they reached the tug boat it was “really rockin” from the rough seas. He also noted that the tail boom was no longer attached to the helicopter and figured it had broken off from being tied to the tug and the force of the waves.

The tail boom and the aft portion of the left skid along with the attached aft float separated from the helicopter and were not recovered. However, the main body of the helicopter including the main rotor system and the engine were recovered and taken to PHI's main facility in Lafayette, Louisiana, where it was examined by the Investigator-in-Charge, along with representatives from Apical Industries, Incorporated, Bell Helicopter, PHI, and Rolls Royce on June 14-15, 2010.

Examination of the engine and airframe (minus the tail boom and tail rotor) revealed no pre-mishap anomalies.

Examination of the float system revealed that the right-side mid float had burst from excessive pressure and that the aft float did not fully inflate. The hoses from the mid and aft floats were found installed incorrectly to the port fitting, having been interchanged (crossed). This allowed non-restricted and excessive gas flow to the mid float, resulting in the burst. The float system has a total of six floats: one attached to each skid at the forward, mid, and aft positions on each side of the helicopter. The emergency floats are connected to a helium reservoir that supplies compressed gas to all six floats through a system of hoses. The hoses connect to specific fittings that regulate the flow of gas to the floats. Each fitting is designed to distribute gas to a specific float so that all of the floats inflate simultaneously despite their varied capacities and distances from the gas reservoir.

In October, 2006, Apical Industries, Incorporated, released a Service Instruction Letter, due to customer concerns about the proper installation of the emergency floats. It stated, “CAUTION…The port fitting incorporates restricted orifices to manage the flow of gas to each of the floats. Incorrect routing of hoses from the port fitting may result in low inflation pressures in some chambers of the floats and rupture of other chambers. Check to ensure that the hoses are routed according to the figures below.” Included in the letter were photographs and figures (including part numbers) to illustrate in more detail how the hoses were to be installed.

A review of maintenance records revealed that the three-year test/inspection of the emergency float system was last completed by PHI maintenance personnel in March 2010, and the improper installation of the hoses on the incident helicopter should have been identified at that time.

The Safety Board also made a Safety Recommendation to Apical Industries, Incorporated, to re-design the hoses to minimize the risk of maintenance personnel from interchanging the hoses during installation.

The pilot held a commercial certificate for rotor-craft-helicopter along with an instrument rating for rotorcraft-helicopter. His last Federal Aviation Administration (FAA) second class medical was issued on April 6, 2010. He reported a total time of 9,525 hours: of which, 7, 161 hours were in rotorcraft and 4,858 hour were in the Bell 206 L-3 helicopter. The pilot has been employed with PHI since 1996.