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FAA Issues New AD for S-92
The Federal Aviation Administration (FAA) has issued yet another airworthiness directive for the Sikorsky S-92 in the wake of the fatal crash of a Cougar Helicopters S-92 off the coast of Newfoundland in March 2009.

Early findings from that investigation, which is ongoing, revealed that mounting studs for the main gearbox oil filter had potentially broken off in flight, leading to the loss of all lubricant. Authorities later issued ADs to replace the original factory titanium mounting studs with steel versions.
In November, The FAA issued an emergency airworthiness directive (EAD) calling on S-92 operators to repetitively inspect the helicopter's main gearbox mounting feet for cracks, defects that could lead to gearbox detachment and loss of control of the helicopter.
The FAA mandate follows a similar AD issued by the European Aviation Safety Agency on Oct. 23 after reports that cracks had been found in the feet, pads and foot ribs on main gearboxes during inspections.
"In one case, the mounting foot was completely severed from the gearbox," says EASA. "Other cases include cracks at the fore and aft mounting bolt location on the right-hand side of the mounting foot."

The latest S-92A airworthiness directive, issued Dec. 4, requires a one-time visual inspection of the main gearbox (MGB) lube system filter assembly for oil filter damage. This action also requires if either the primary or secondary oil filter is damaged, replacing both filters, all packings, and the studs before further flight.

The AD also requires replacing the oil filter bowl within 30 days after replacing a damaged filter and a daily leak inspection for an oil leak (no oil leaks allowed) during that 30-day interim period. This amendment is prompted by three reports of damaged oil filters or packings resulting from installing the filter assembly with an oversized packing possibly because of incorrect part numbers in the maintenance manual. Based on a previous accident investigation, failure of the oil filter bowl or mounting studs can result in sudden and complete loss of oil from the MGB. The actions specified in this AD are intended to prevent complete loss of oil from the MGB, failure of the MGB, and subsequent loss of control of the helicopter.
The AD is prompted by three reports of damaged oil filters or packings, also known as O-rings, resulting from installing the filter assembly with an oversized packing possibly because of incorrect part numbers in the maintenance manual.
Seventeen people were killed in the crash of a Cougar Helicopters S-92A Sikorsky on March 12 about 55 kilometers southeast of St. John's.