AD 2004-16-15: Eurocopter France Model AS-365N2, AS 365 N3, EC 155B, EC155B1, SA-365N and N1, and SA-366G1 Helicopters

SUMMARY: This amendment adopts a new airworthiness directive (AD) for the specified Eurocopter France (Eurocopter) helicopters. This action requires inspecting the main gearbox (MGB) baseplate for a crack and replacing the MGB if a crack is found in the MGB base plate. This amendment is prompted by the discovery of a crack in a MGB base plate. The actions specified in this AD are intended to detect a crack in a MGB base plate and prevent failure of one of the MGB attachment points to the frame, which could result in severe vibration and subsequent loss of control of the helicopter.

DATES: Effective September 3, 2004.

Comments for inclusion in the Rules Docket must be received on or before October 18, 2004.

SUPPLEMENTARY INFORMATION: This amendment adopts a new AD for Eurocopter Model AS-365N2, AS 365 N3, EC 155B, EC155B1, SA-365N and N1, and SA-366G1 helicopters. This action requires visually inspecting the MGB for a crack in the MGB base plate, part number (P/N) 366A32-1062-03 or P/N 366A32-1062-06, close to the attachment hole using a 10x or higher magnifying glass. Stripping paint from the inspection area is also required, but only before the initial inspection. This amendment is prompted by the discovery of a crack in the MGB base plate of a MGB installed in a Model AS-365 N2 helicopter. The cause of the crack is under investigation, therefore, this AD is an interim action until the cause of the crack can be determined. The crack was located very close to the attachment points of one of the laminated pads, and it propagated to the inside of the MGB base plate and then continued into the MGB casing. This condition, if not detected, could result in failure of one of the MGB attachment points to the frame, which could result in severe vibration and subsequent loss of control of the helicopter.

The Direction Generale De L'Aviation Civile (DGAC), the airworthiness authority for France, notified the FAA that an unsafe condition may exist on Eurocopter Model SA 365 N, N1, SA 366 G1, AS 365 N2, N3, and EC 155 B and B1 helicopters. The DGAC advises of the discovery of a crack on the MGB base plate of a Model AS 365 N2 helicopter.

FMI: AD 2004-16-15