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ASN Wikibase Occurrence # 145393
Last updated: 29 November 2015
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Time:11:55 CDT
Type:Silhouette image of generic S76 model; specific model in this crash may look slightly different
Sikorsky S-76B
Owner/operator:RDC Marine Inc
Registration: N56RD
C/n / msn: 760368
Fatalities:Fatalities: 0 / Occupants: 7
Other fatalities:0
Airplane damage: Written off (damaged beyond repair)
Location:near Vermilion VR376A, Gulf of Mexico -   United States of America
Phase: Landing
Nature:Non Scheduled Passenger
Departure airport:KARA
Destination airport:Joe Douglas offshore drilling rig
Ditched in the Gulf of Mexico near the Joe Douglas oil drilling rig (Vermilion VR376A). Operated as a Part 91 business flight. Day visual meteorological conditions prevailed and no flight plan was filed.

The pilot reported that he made a visual approach on a 190 degree heading to the landing platform. He reported that the wind was from 220 degrees at 5 to 6 knots, according to the Garmin 500 GPS that was installed in the helicopter. He was flying directly towards the platform while decelerating from 60 to 45 knots while maintaining a 12 degree approach angle. The helicopter was about 60 feet from the landing pad and about 15 to 20 feet higher than the landing pad with a nose high attitude in the flare when a loss of engine power occurred. The pilot was unsure which engine had the loss of power. With the loss of power, the pilot reported that the trajectory of the helicopter would place it short of the landing pad. The pilot reported that the helicopter was going to hit the platform, so he pulled collective pitch, banked aft and to the left to avoid contact with the platform. Once clear of the platform, he attempted to lower the collective and gain airspeed, but the helicopter was in a high rate of descent with low airspeed. He pulled collective pitch and flared the helicopter before water impact. The pilot reported about 3 to 4 seconds transpired from the time he tried to avoid hitting the platform to when the helicopter impacted the water. After impacting the water, the helicopter remained on top of the surface as the pilot kept engine power on the helicopter to keep it from sinking. He deployed the emergency floatation bags and attempted to water taxi toward the oil platform, but there was no directional control since the tailboom was partially separated from the fuselage.

The pilot continued to keep engine power on the helicopter as a rescue pod from the Joe Douglas was lowered to the water. The passengers in the cabin were preparing to deploy the life rafts as the rescue pod was being launched. When the rescue pod was near the helicopter, the pilot shut down the engines. The passengers deployed the life rafts as the helicopter began to list to the left. All six passengers and the pilot got into the rafts, and then transferred into the rescue pod, which was then winched back up to the deck of the platform. None of the occupants reported any injuries.

Sometime after the occupants egressed, the helicopter inverted in the water with the four floatation bags keeping it from sinking. However, the bags were compromised during the initial recovery effort and the helicopter later sank in about 310 feet of water. The helicopter was recovered on April 25, 2012, and taken to Port Fourchon where it was examined on April 27, 2012.

The Rowan Company representative to the investigation provided the NTSB a schematic of the Rowan "Joe Douglas" Vermilion 376A rig as it was positioned on the day of the accident. It also showed direction of the Joe Douglas and the helicopter approach angles as they existed on the day of the accident. The schematic showed that the helicopter landing pad was located on the north side of the oil platform. An approach heading of 190 degrees, as reported by the accident pilot, put the approach path aiming for the center of the oil platform super structure. This approach angle provided limited clearance for a go-around. Likewise, an approach angle between about 160 to 220 degrees heading provided limited clearance for a go-around due to the location of the super structure. An approach path heading from about 060 to 140 degrees, or from about 230 to 320 degrees, would have provided good go-around capability since there was no super structure behind the landing platform on those headings.

The examination of the wreckage revealed an anomaly within the stepper motor for the No. 2 engine's fuel control. The examination revealed that the end of the output shaft of the stepper motor had overstress fractures and that the shaft was bent. During the overhaul of the stepper motor 8 years before the accident, the pin that attaches the flapper valve lever to the output shaft was pressed onto the output shaft. The force applied to the external lever was sufficient to both crack and bend the output shaft. This condition eventually resulted in a "stuck" stepper motor which limited the fuel flow to the engine and resulted in an intermittent loss of engine power. The EECs did not monitor the performance of the output shaft or the flapper valve lever; therefore, no fault codes were generated by the EECs.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows: The intermittent loss of engine power due to a "stuck" stepper motor in the No. 2 engine's fuel control as a result of an inadequate overhaul. Contributing to the accident was the pilot's decision to continue flying the helicopter with a known defect, his decision to depart with the helicopter over its maximum gross weight, and his decision to fly the approach to the oil platform at a high gross weight in a direction that provided limited go-around potential.

The aircraft had suffered an engine fault previously on 13 April 2012.


Revision history:

02-May-2012 17:44 Geno Added
14-Sep-2012 06:21 TB Updated [Location, Destination airport, Source, Damage, Narrative]
22-Dec-2014 14:50 Aerossurance Updated [Location, Nature, Destination airport, Source, Narrative]
23-Dec-2014 13:00 Aerossurance Updated [Location, Source, Narrative]
22-Mar-2015 14:30 TB Updated [Location]
Number of views: 594

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