Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Sikorsky Aircraft Corporation (Sikorsky) Model S-61A, D, E, L, N, NM (serial number 61454), R, and V; Croman Corporation Model SH-3H, Carson Helicopters, Inc., Model S-61L; Glacier Helicopters, 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. This SNPRM is prompted by comments received in response to a previous SNPRM and a reevaluation of the relevant data. This SNPRM retains the proposed actions in the previous SNPRM, provides an increased estimated cost of the main rotor shaft (MRS) replacement, and clarifies some of the language in the Required Actions section of the AD. The proposed actions are intended to prevent MRS structural failure, loss of power to the main rotor, and subsequent loss of control of the helicopter.