AD 97-10-04 SUPERSEDED

97-10-04 SIKORSKY AIRCRAFT CORPORATION: Priority Letter issued on April 30, 1997. Docket No. 97-SW-11-AD.

Applicability: Model S-61A, D, E, L, N, NM, R, and V helicopters, certificated in any category, equipped with a main rotor blade assembly (blade), part number (P/N) S6115-20501 or P/N 61170-20201, having one of the following four-digit or eight-digit serial numbers:

1282-1554
2721
3016-2850
3305-3106
3517-3311
4787-4793
2183
2751
3019
3317-3115
3525-3310
4800-4794
2380-2498
2781-2644
3138
3343-3147
3637-3459
4835-4790
2495
2800-2671
3168-3585
3343-3648
3694-3481
5484-5363
2500
2817
3192-2999
3364-3180
3748-3543
5974-5816
2520
2819
3215-3012
3451-3239
3752-3527
5981-5813
2521
2839
3216-3023
3491-3278
3753-3528
7096-6583
2644
2883
3242-3044
3499-3936
3840-3620
7779-7083
2673
2919-2771
3249-3052
3511-3293
3966-3737
8099-8054
2716-2683
3008
3250-3043
3512-3292
4216-4392

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been 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 use the authority provided in paragraph (b) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

Compliance: Required before further flight, unless accomplished previously.

To prevent disbonding and separation of portions ofthe blade, subsequent excessive vibrations, and loss of control of the helicopter, accomplish the following:

(a) Inspect each blade having one of the affected serial numbers in accordance with Section 2A of the Accomplishment Instructions of Sikorsky Alert Service Bulletin (ASB) No. 61B15-29, dated April 25, 1997, to determine the anodizing date for all blade trailing edge pocket assemblies (pocket assemblies) installed on the blade in locations as specified in the Planning Information Section, paragraph 1D(3) of the ASB, that were anodized by Poly-Metal Company. Remove any blade having a pocket assembly anodized by Poly-Metal Company during the period from October 1, 1996 through December 31, 1996, and replace the blade with an airworthy blade.

(b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Boston Aircraft Certification Office, FAA. Operators shall submit theirrequests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Boston Aircraft Certification Office.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Boston Aircraft Certification Office.

(c) A one-time only special flight permit may be issued to operate the helicopter to a location where the requirements of this AD can be accomplished, after inspecting all pocket assemblies for disbonding.

(d) Copies of the applicable service information may be obtained from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Tech Support, 6900 Main Street, P.O. Box 9729, Stratford, Connecticut 06497-9129. This information may be examined at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas.

(e) Priority Letter AD 97-10-04, issued April 30, 1997, becomes effective upon receipt.

This priority letter airworthiness directive (AD) is prompted by the discovery of a manufacturing defect that may cause disbonding and separation of portions of a main rotor blade assembly (blade). This defect is the result of an anodizing process, used during the manufacture of the blade trailing edge pocket assembly (pocket assembly), that did not meet the Type Design specifications. The FAA has determined that this defect may exist on pocket assemblies that were anodized by Poly-Metal Company during the period from October 1, 1996 through December 31, 1996. This condition, if not corrected, could result in disbonding and separation of portions of the blade, subsequent excessive vibrations, and loss of control of the helicopter.

The FAA has reviewed and approved Sikorsky Aircraft Corporation Alert Service Bulletin No. 61B15-29, dated April 25, 1997, which describes instructions for performance of a one-time inspection of certain serial-numbered blades to determine if any pocket assembly was anodized by Poly-Metal Company during the specified time period.

Since an unsafe condition has been identified that is likely to exist or develop on other Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V helicopters of the same type design, this AD requires, before further flight, inspecting certain blades in accordance with the service bulletin described previously, and if a blade has a pocket assembly that was anodized by Poly-Metal Company during a specified time period, replacing it with an airworthy blade.

This rule is issued under 49 U.S.C. Section 44701 (formerly section 601 of the Federal Aviation Act of 1958) pursuant to the authority delegated to me by the Administrator, and is effective immediately upon receipt of this priority letter.

Mr. Bob Mann, Aerospace Engineer, Boston Aircraft Certification Office, ANE-150, 12 New England Executive Park, Burlington, MA 01803, telephone (617) 238-7190, fax (617) 238-7199.