Airworthiness Directives; Various Helicopters

The FAA is superseding Airworthiness Directive (AD) 2015-20-12 for certain Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V; Croman Corporation Model SH-3H; Carson Helicopters, Inc., Model S-61L and SH-3H; Glacier Helicopter, Inc., Model CH-3E; Robinson Air Crane, Inc., Model CH-3E, CH-3C, HH-3C and HH-3E; and Siller Helicopters Model CH-3E and SH-3A helicopters. AD 2015-20-12 required performing calculations to determine whether the main rotor shaft (MRS) was used in repetitive external lift (REL) operations or non-REL operations, performing a nondestructive inspection (NDI) of the REL MRS for cracks and, depending on the results of the NDI, replacing the MRS, marking any REL MRS at the time of the NDI, establishing retirement lives for each REL MRS, and removing from service any MRS with oversized dowel pin bores. Since the FAA issued AD 2015-20-12, a design re-evaluation shows that the MRS on certain helicopter models requires a lower life limit. This AD retains some of the requirements of AD 2015-20-12, and also reduces the retirement life for a certain MRS installed on certain helicopters and updates the type certificate holder name for some of the affected helicopter models. The FAA is issuing this AD to address the unsafe condition on these products.