AD 2021-10-16 Requires Tracking Hours Time-In-Service (TIS)

The FAA is adopting a new airworthiness directive (AD) for all Carson Helicopters, Inc., Model S-61L and SH-3H helicopters; Croman Corporation Model SH-3H helicopters; Sikorsky Aircraft Corporation Model S-61A, S-61D, S-61E, and S-61V helicopters; and Siller Helicopters Model CH-3E and SH-3A helicopters.

This AD was prompted by an accident. This AD requires tracking hours time-in-service (TIS) and external lift cycles (lift cycles) for certain main gearbox left and right input freewheel unit (IFWU) assemblies. This AD also requires determining the type of IFWU assembly installed and depending on the results, calculating the moving average, repetitive inspections, recording certain information, replacing parts, and marking parts. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 1, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Sikorsky Aircraft Corporation Model S-61 A, D, E, and V helicopters; Croman Corporation Model SH-3H helicopters, Carson Helicopters, Inc. Model S-61L helicopters; and Siller Helicopters Model CH-3E and SH-3A helicopters. The NPRM published in the Federal Register on October 30, 2006 (71 FR 63272). The NPRM was prompted by an accident in which the left and right IFWU assembly on a helicopter slipped or disengaged resulting in both engines overspeeding, engine shutdowns, and loss of engine power to the transmissions. In the NPRM, the FAA proposed to require creating a component history card or equivalent record and recording the hours TIS and the lift cycles for each affected main gearbox left and right IFWU assembly. The NPRM also proposed to require determining if the IFWU assembly is a repetitive external lift (REL) or non-REL IFWU assembly. The determination includes calculating a moving average of lift cycles per hour TIS at specified intervals on each IFWU assembly. For REL IFWU assemblies, the NPRM proposed to require repetitive inspections, which include visual and dimensional inspections, of the IFWU assembly for wear, surface distress, and endplay, recording certain information, and replacing affected parts with an airworthy part. In addition, the NPRM proposed to require permanently marking the REL IFWU camshafts and gear housings with the letters “REL” on the surface of these parts.

The FAA issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Carson Helicopters, Inc., Model S-61L and SH-3H helicopters; Croman Corporation Model SH-3H helicopters; Sikorsky Aircraft Corporation Model S61A, S-61D, S-61E, and S-61V helicopters; and Siller Helicopters Model CH-3E and SH-3A helicopters. The SNPRM published in the Federal Register on March 15, 2021 (86 FR 14285). The SNPRM was prompted by a determination that additional camshaft and gear housing part numbers need to be marked and the applicability and certain compliance times need clarification. The SNPRM proposed to require the same actions specified in the NPRM. The SNPRM also proposed to mark additional camshaft and gear housing part numbers. Additionally, the SNPRM clarified the applicability and certain compliance times. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov