# AD 81-21-04: Main Rotor Scissors Assembly

- Type: Airworthiness directive
- Status: Current
- Products: Sikorsky S-76A
- Effective: October 8, 1981
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-4228
- Registered aircraft: 19 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6CC1F6E3C89782ED86256A4E0044AE70.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/81-21-04

## The airworthiness directive

81-21-04 SIKORSKY AIRCRAFT: Amendment 39-4228. Applies to S-76A series helicopters certificated in all categories.

To prevent fatigue failures of the main rotor scissors assembly:

1. Replace P/Ns 76104-08020-044, -045, and -046, and P/N 76070-10005-042 main rotor rotating scissors assemblies with a serviceable part prior to the accumulation of 500 hours time in service or within 25 hours time in service after the effective date of this AD, whichever occurs later.

2. Within the next 50 hours time in service after the effective date of this AD, unless already accomplished within the last 50 hours time in service, and thereafter at intervals not to exceed 100 hours from the last inspection, conduct inspections of the hub/scissors bearings for play and wear and the scissors center pivot bolt for fretting, scoring, and corrosion pits in accordance with Temporary Revision No. 5-24, dated September 8, 1981, or an FAA approved equivalent, Items 42A (Inspection Check 65-14-00, Page 207, dated February 16, 1980, including Temporary Revision No. 65-15, dated September 8, 1981, or an FAA approved equivalent) and 42B of the Sikorsky S-76A Maintenance Manual, 5A 4047-76-2.

NOTE: "FAA approved" means approved by the Chief, Engineering and Manufacturing Branch, New England Region.

The manufacturer's specifications and procedures identified and described herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Sikorsky Aircraft, Division of United Technologies Corporation, Stratford, Connecticut 06602. These documents may also be examined at FAA, New England Region, 12 New England Executive Park, Burlington, Massachusetts, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C.

This amendment becomes effective October 8, 1981.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1NE](https://openairdocs.org/tcds/H1NE): Sikorsky Aircraft Corporation; names 1 of 4 models: S-76A

## 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: 19 (19 by airframe model, 0 by engine model)
- Makers: Sikorsky 19

Models with the most aircraft:

- [Sikorsky S-76A](https://openairdocs.org/model/sikorsky-s-76a): 19 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/81-21-04/models.md
Every aircraft: https://openairdocs.org/ad/81-21-04/aircraft.md

Its text cites no advisory circulars or STCs.

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