# AD 71-21-03: Link in Servo Valve Input Linkage

- Type: Airworthiness directive
- Status: Current
- Products: Sikorsky S-61A, S-61D, S-61E, S-61L, S-61N, S-61NM, S-61R and S-61V
- Effective: October 7, 1971
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-1303
- Registered aircraft: 54 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/5A388B53B827E16886256A55006DFFB9.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/71-21-03

## The airworthiness directive

71-21-03 SIKORSKY: Amdt. 39-1303. Applies to all S-61 Type Helicopters certified in all categories.

Compliance required as indicated.

To prevent a hardover in the auxiliary servo system, as the result of fracture of the servo valve input linkage, accomplish the following:

a. Within the next 50 hours' time in service after the effective date of this AD, unless already accomplished, install a secondary link in the servo valve input linkage in accordance with Section 2, paragraphs A., B., C., and G., of Sikorsky Service Bulletin No. 61B65-6A, dated 1 July 1971, or later approved revisions or an equivalent installation, both approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

b. Install secondary links per paragraph (a) on all spare units, prior to installation on the aircraft.

This amendment is effective October 7, 1971.

## 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/71-21-03/models.md
Every aircraft: https://openairdocs.org/ad/71-21-03/aircraft.md

Its text cites no advisory circulars or STCs.

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