Sikorsky S-55 accident at Grand Isle, Louisiana, 2 Dec 1954 (N-737A)

Accident narrative

On December 2, 1954, a Sikorsky S-55 helicopter, registration N 737A, crashed in the Gulf of Mexico approximately 200 yards offshore near Grand Isle, Louisiana. The aircraft, operated by Petroleum Helicopters, Inc., was attempting to land in heavy fog at approximately 0235. Four of the five passengers died from injuries or drowning. One passenger and the two crew members received minor injuries. The helicopter was demolished by the impact and a subsequent fire.

**The flight**

The helicopter departed the Grand Isle heliport at 0115 to transport oil drilling employees from an offshore rig designated ST-6, located about six miles away. The crew consisted of pilot Alvin D. Allen and copilot Richard F. Bicknell. Both were qualified first pilots; company safety rules required two pilots for night operations in the S-55, trading the flight commander's position every other flight.

After a normal landing on a platform constructed on an LST anchored adjacent to the rig, the crew waited for a shift change. Five returning employee-passengers boarded, and the flight departed for Grand Isle at 0218. The trip normally required about ten minutes. The helicopter climbed to 1,000 feet. At departure, lights on shore and on other rigs six to ten miles away were clearly visible, though with a slight halo attributed to haze.

**The accident sequence**

As the flight proceeded toward the shore, vertical visibility decreased rapidly. The crew recognized dimly visible shore lights and followed the shoreline eastward toward the heliport. Upon reaching the landing area, the crew could see the hangar lights and a continuously burning oil residue flare—a 15-foot diameter pit—only as a glow through the fog from an altitude of 500 to 600 feet.

The flight passed over the hangar and flare, made a 180-degree left turn, and began a letdown. During the descent, visibility worsened and visual reference with the lights was lost. The pilot executed a pull-up to about 50 feet, which was the top of the fog layer. At the copilot's suggestion, they attempted to land on a clearing near the hangar, but this was abandoned when the hangar lights could no longer be seen, and a second pull-up was made. By this time, the pilot could no longer see the offshore rig lights.

At 0232, the fuel warning light illuminated, indicating about 30 minutes (20 gallons) of fuel remained. The pilot decided to land on the clearing near the flare, approaching from the east and using the flare as a ground reference through the fog. The descent started with approximately zero knots of forward speed. The approach seemed normal until the pilot realized he was overshooting the flare, at which point considerable glare reflected in the cockpit.

The pilot asked the copilot to take over the controls. The copilot applied full power, noting an exaggerated nose-down but laterally level attitude on the pilot's gyro horizon, and an altimeter reading of about 250 feet. Seconds later, the helicopter struck the water.

Both crew members and one passenger escaped the wreckage before fire spread to gasoline and oil on the water's surface. The fire prevented them from approaching the wreckage to help the others, and they swam to shore guided by a dim light.

**What the investigation found**

Most of the wreckage was recovered from the Gulf. Examination revealed the helicopter struck the water nearly level, descending at an angle of approximately 35 degrees. Impact forces were severe in an upward and rearward direction. The fuselage was telescoped and broken off at the rear of the passenger cabin, while the tail boom and rotor remained generally intact. The investigation found no evidence of structural failure, fire, or engine malfunction prior to impact. The aircraft's gross weight was well under the maximum allowable 7,200 pounds, and the load was properly distributed.

The Board noted that the S-55 helicopter was not approved for commercial instrument operations, and the company did not intend for flights to be made without continuous visual ground reference.

Weather analysis indicated that a cold front north of Grand Isle, combined with night radiation cooling the land surfaces, produced fog along the coast ahead of the front. The company did not have arrangements for official aviation forecasts, relying instead on marine weather forecasts provided twice daily by a commercial service. The crew stated they had read a bulletin indicating the possibility of patchy inland fog and were observant of the haze prior to takeoff.

The Board believed that during the emergency, the crew should have called the ST-6 rig by radio to determine if fog existed there, though evidence indicated the rig would have been fog-bound within the time required for a return flight.

The Board believed that during the pilot's attempt to make a visual landing near the flare, he began to lose visual reference regarding the attitude and position of the aircraft. As the helicopter passed over and beyond the flare, this condition was aggravated by reflected glare and the immediate darkness that followed, causing the pilot to lose control.

**Probable cause**

The Board determined that the probable cause of this accident was "the loss of visual reference caused by fog and glare, which resulted in a loss of control by the pilot during an attempt to land."