# AD 97-10-04: Blade Trailing Edge Pocket Assemblies - Type: Airworthiness directive - Status: Historical - Products: Sikorsky S-61A, S-61D, S-61E, S-61L, S-61N, S-61NM, S-61R and S-61V - Superseded by: [AD 97-19-06](https://openairdocs.org/ad/97-19-06) - Product type: Aircraft, Rotorcraft - Docket: 97-SW-11-AD - Registered aircraft: 54 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/037D3B50415DB6D286256CC5005F0255.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/97-10-04 ## The airworthiness directive 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. ## Rule preamble ### Supplementary information 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. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1H15](https://openairdocs.org/tcds/1H15): Sikorsky Aircraft; names 4 of 4 models: S-61R, S-61N, S-61L, S-61NM - [TCDS H2EA](https://openairdocs.org/tcds/H2EA): Sikorsky Aircraft Corporation; names 4 of 4 models: S-61A, S-61D, S-61V, S-61E ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 54 (54 by airframe model, 0 by engine model) - Makers: Sikorsky 53, Carson Helicopters / Sikorsky 1 Models with the most aircraft: - [Sikorsky S-61N](https://openairdocs.org/model/sikorsky-s-61n): 45 aircraft (airframe model) - [Sikorsky S-61A](https://openairdocs.org/model/sikorsky-s-61a): 5 aircraft (airframe model) - [Sikorsky S-61L](https://openairdocs.org/model/sikorsky-s-61l): 1 aircraft (airframe model) - [Sikorsky S-61NM](https://openairdocs.org/model/sikorsky-s-61nm): 1 aircraft (airframe model) - [Sikorsky S-61R](https://openairdocs.org/model/sikorsky-s-61r): 1 aircraft (airframe model) - [Carson Helicopters / Sikorsky S61A](https://openairdocs.org/model/carson-helicopters-sikorsky-s61a): 1 aircraft (airframe model) All 6 models: https://openairdocs.org/ad/97-10-04/models.md Every aircraft: https://openairdocs.org/ad/97-10-04/aircraft.md ## Related documents - [AD 97-19-06](https://openairdocs.org/ad/97-19-06): Blade Trailing Edge Pocket Assemblies ยท Sikorsky S-61A, S-61D, S-61E and 5 more. Effective Oct 6, 1997. Supersedes this AD Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.