Action
Supplemental notice of proposed rulemaking (SNPRM); reopening of comment period.
Summary
We are revising the proposals in an earlier notice of proposed rulemaking (NPRM) 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. The NPRM proposed superseding an existing AD but retaining some requirements of that AD, removing certain dowel pin bores, expanding the applicability to include additional helicopters, and implementing a new retirement life for each main rotor shaft (MRS) based on a reevaluation of the MRS service life. This SNPRM is prompted by the comments received in response to the NPRM and a reevaluation of the relevant data. 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.