Airworthiness Directive · Amendment 39-14345 · Sikorsky Aircraft Corporation Model S-76A, B, and C Helicopters
Sikorsky Aircraft Corporation Model S-76A, B, and C Helicopters
Superseded. A later AD replaced this one: AD 2014-08-06. Comply with the one in force.
Model S-76A, B, and C, with a main rotor hub pilot fitting (pilot fitting), part number (P/N) 76103-08003-101, with 1500 or more hours time-in-service (TIS), installed, certificated in any category.
This amendment adopts a new airworthiness directive (AD) for the Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, B, and C helicopters. This action requires certain inspections of the main rotor lower bifilar arm assembly in the attachment area around the lower bifilar lugs for a crack. If a crack is found on any bifilar lug, this AD requires replacing the bifilar arm assembly with an airworthy bifilar arm assembly. If no crack is found, this AD requires a one-time test for the required torque on the lug nuts and, if necessary, applying the required torque and conducting the torque stabilization tests. This amendment is prompted by four reports of cracked bifilars. The actions specified in this AD are intended to prevent failure of a bifilar lug, damage to the main rotor control system, and subsequent loss of control of the helicopter.
To prevent failure of a bifilar lug, damage to the main rotor system, and subsequent loss of control of the helicopter, accomplish the following:
(a) Within 50 hours TIS, and thereafter at intervals not to exceed 50 hours TIS, inspect the lower bifilar arm assembly for a crack in the lug attachment area. Conduct the inspection of the lower bifilar arm assembly by following the Accomplishment Instructions, paragraph 3.A.(1) through 3.A.(6), of Sikorsky Alert Service Bulletin No. 76-65-62, dated December 14, 2004 (ASB).
(1) If you find a crack on any bifilar arm assembly lug, before further flight, replace the bifilar arm assembly with an airworthy bifilar arm assembly.
(2) If no crack is found at the initial inspection, perform a one-time torque test. Perform the torque test and the additional torque procedures as stated in the Accomplishment Instructions, paragraph 3.B.(1) through 3.B.(3) of the ASB. The torque test is not required at the recurring inspection intervals of the lower bifilar arm assembly.
(b) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Boston Aircraft Certification Office, FAA, for information about previously approved alternative methods of compliance.
(c) Inspect the lower bifilar arm assembly and perform the torque test by following the specified portions of Sikorsky Alert Service Bulletin No. 76-65-62, dated December 14, 2004. The Director of the Federal Register approved this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Tech Support, 6900 Main Street, Stratford, Connecticut 06614, phone (203) 386-3001, fax (203) 386-5983. Copies may be inspected at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Aircraft
