All three North Sea oil and gas helicopter operators have halted operations of the AS332L2 Super Puma helicopter as investigators begin their probe into why a CHC-operated Super Puma ditched into the sea just minutes before its planned landing in the Shetland Islands, resulting in the deaths of four passengers.

The accident has come at a difficult time for the North Sea helicopter industry, still recovering from the aftereffects of the nine-month grounding of the EC225. Eurocopter has said that the AS332L2 involved in the Aug. 23 accident was equipped with a main gearbox using a carburized vertical shaft, not the nitrided shaft involved in the two EC225 ditchings.

The flight suspensions are in accordance with a request from the Helicopter Safety Steering Group (HSSG). The HSSG recommended temporary suspension of all Super Puma commercial passenger flights to and from offshore oil and gas installations within the U.K., including the AS332L/L1 and EC225, although some operators have decided to continue operations with other models of the aircraft.

The accident has prompted an outcry over the safety of oil workers flying on helicopters in the North Sea. A Facebook page, called Destroy the Super Pumas, was set up within hours of the crash and promptly attracted almost 30,000 followers, who have called for the type to be permanently pulled from oil and gas operations.

CHC, which is one of the largest operators of the L2 model Super Puma, said it is suspending worldwide operations with the type, and is also halting use of the AS332L1 and EC225 in the U.K. The company is planning to continue worldwide operations Aug. 26 with its AS332L1 and EC225 models, as the “engineering and operating differences” associated with AS332L/L1 and EC225 aircraft “warrant continuing flights with those aircraft,” it said.

Bristow says it has suspended operations of its two Eurocopter AS332 L2 Super Pumas in Nigeria while it evaluates the incident, although its AS332L/L1s and EC225s are flying normal operations.

Manufacturer Eurocopter has sent members of its senior management team to Aberdeen, Scotland, to support the investigation work.

The Super Puma accident claimed the lives of four passengers, while 12 other passengers and two crew escaped with minor injuries. The aircraft, registered G-WNSB and owned by CHC Scotia, was flying an oil and gas support flight on behalf of energy company Total from the drilling platform Borgsten Dolphin.

The accident happened as the aircraft was making its approach into Sumburgh airport on the southern tip of the Shetland Islands. When it was 2 mi. from the airport, reports indicate that the aircraft suffered a “catastrophic” loss of power and dropped into the Bay of Quendale at 6:20 p.m. local time.

According to CHC, the aircraft had flown from Aberdeen to two platforms in the North Sea before returning to Sumburgh.

Emergency services have recovered the four bodies and the wreckage of the aircraft, which was partly floating on the surface following the activation of the aircraft’s flotation gear. The fuselage has been loaded onto the oil and gas support ship, Bibby Polaris.

The accident is the second involving a CHC aircraft in less than a year. In October 2012, a CHC EC225 ditched into the North Sea. Although all onboard were rescued, the incident prompted the temporary grounding of the EC225 and military EC725 helicopters from operating over hostile environments such as open water, after the discovery of a failure in a main gearbox component. EC225s began returning to operations earlier this month after a series of interim fixes were approved by European regulators.

The last AS332L2 accident in the North Sea was in April 2009, when a catastrophic main gearbox failure onboard a Bond Offshore aircraft resulted in the deaths of all 16 people on board.