Recommends Inspection Of Rotor Drive-Tail Rotor Drive Flange Shur-Lok Nut

The FAA has issued a Special Airworthiness Information Bulletin (SAIB) calling for the inspection of Shur-Lok nuts on Airbus Helicopters (formerly Eurocopter, Eurocopter France, or Aerospatiale) Model SA 365 C, SA 365 C1, SA 365 C2, SA 365 C3, SA 365 N, SA 365 N1, AS 365 N2, AS 365 N3, and SA 366 G1 helicopters, all serial numbers with modification 0763B64; and EC 155 B, EC 155 B1 helicopters, all serial numbers.

The SAIB follows several reports of loss of tightening torque of a Shur-Lok nut reported to Airbus Helicopters. The Shur-Lok nut serves as a retainer of the tail rotor drive flange to the main gearbox (MGB). After investigating the cause of this tightening torque loss, Airbus Helicopters issued:

• Alert Service Bulletin (ASB) No. AS365-63.00.18, Revision 0, dated July 9 2014;
• ASB No. SA365-65.50, Revision 0, dated July 9, 2014;
• ASB No. SA366-63.09, Revision 0, dated July 9 2014; and
• ASB No. EC155-63A012, Revision 1, dated July 21, 2014.

The ASBs specify inspecting the condition of the Shur-Lok nut and performing certain corrective actions if necessary. EASA, which is the Technical Agent for the Member States of the European Union, issued AD No. 2014-0179R1 to require the actions specified in the ASBs. However, after reviewing the available information, the FAA has determined that, at this time, the airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39. We base this determination on the understanding that loss of torque alone may not result in an unsafe condition.

The FAA recommends following the actions specified in the ASBs. Also, owners and operators of these helicopters should be thoroughly familiar in using the special tool (assembly/disassembly wrench) for removing and installing the Shur-Lok nut properly without damaging the two anti-rotation tabs.

(Image from file)

FMI: SAIB