Airworthiness Directive · Amendment 39-11861 · Sikorsky Aircraft Corporation Model S-76 Series Helicopters
Sikorsky Aircraft Corporation Model S-76 Series Helicopters
Model S-76 series helicopters, certificated in any category.
Note 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2000-11-52, which was sent previously to all known U.S. owners and operators of Sikorsky Aircraft Corporation (Sikorsky) Model S-76 series helicopters by individual letters. This AD requires determining the serial number (S/N) of each main rotor blade and removing certain serial numbered main rotor blades. This AD also requires visually inspecting and replacing, if necessary, other certain serial numbered main rotor blades. This AD is prompted by a report of a crack in a main rotor blade and three reports of root end pocket separation from main rotor blades during flight. The crack and the main rotor blade root end pocket separation were due to improper manufacture of certain main rotor blade skins. The actions specified by this AD are intended to prevent main rotor blade root end pocket separation, impact with main rotor or tail rotor blades, and subsequent loss of control of the helicopter.
To prevent main rotor blade root end pocket separation, impact with main rotor or tail rotor blades, and subsequent loss of control of the helicopter, accomplish the following:
(a) Before further flight, determine the serial number of each main rotor blade.
(b) Any main rotor blade identified in paragraphs (c) or (d) of this AD that has been repaired in accordance with Sikorsky Aircraft Corporation Overhaul and Repair Instructions (ORI) No. 76150-023, Revision A, dated May 26, 2000, and marked as RS-023-1 is not affected by the requirements of this AD.
(c) Before further flight, remove any main rotor blade identified by serial number (S/N) in the Group 1, paragraph 1.A. Planning Information of Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-65-50, dated May 25, 2000 (ASB).
(d) Before each flight and at intervals not to exceed 3 hours time-in-service, visually inspect any main rotor blade, identified by S/N in Group 2, paragraph 1.A. of the ASB Planning Information, for a span-wise crack in the upper and lower root end area, in accordance with paragraph 3.B. of the ASB Accomplishment Instructions. Remove any main rotor blade with a span-wise crack and replace with an airworthy blade before further flight.
(e) Accomplishing ORI 76150-023, Revision A, dated May 26, 2000, on each affected blade is terminating action for the requirements of this AD.
Note 2: A crack, other than a span-wise crack, in the root end cap of the main rotor blade should be dispositioned in accordance with the applicable Maintenance Manual.
