# AD 84-11-03: Possible Flange Failure

- Type: Airworthiness directive
- Status: Current
- Products: Sikorsky S-61A, S-61L and S-61N
- Effective: June 6, 1984
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-4866
- Registered aircraft: 52 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6E2EFBACEE49CCD586256A4E0044EBD4.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/84-11-03

## The airworthiness directive

84-11-03 SIKORSKY AIRCRAFT DIVISION: Amendment 39-4866. Applies to all Sikorsky Model S-61 L/N/A series helicopters, certificated in all categories and authorized for flight with gross weights in excess of 19,500 pounds, when equipped with the following tail rotor drive system components:

a. Flange Part Number (P/N) S6135-66228-0 installed at the input and output couplings of the intermediate gearbox.

b. Flange P/N S6135-64013-0 installed at either end of the pylon drive shaft and at the aft end of the section IV tail drive shaft (shaft immediately forward of the intermediate gearbox).

c. Flange P/N S6135-66657-0 installed at the input coupling of the tail gearbox.

Compliance is required as indicated (unless already accomplished).

To intercept impending failure of the flanges identified above, accomplish the following:

d. For flanges with more than 800 hours time in service since new, inspect the flange for cracks utilizing a 5-power or greater magnifying glass in the area surrounding the bolt attachments within the next 15 hours time in service after the effective date of this AD, unless already accomplished, and thereafter at intervals no to exceed 15 hours time in service from the last inspection.

e. If cracks are found, replace the flange and assure proper alignment of intermediate gearbox, tail gearbox, and pylon drive shaft before further flight.

f. Upon request, with substantiating data submitted through an FAA maintenance inspector, equivalent methods of compliance or adjustment in the inspection intervals or compliance time may be approved by the Manager, Boston Aircraft Certification Branch, FAA, New England Region.

This amendment becomes effective June 6, 1984.

## 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 2 of 4 models: S-61N, S-61L
- [TCDS H2EA](https://openairdocs.org/tcds/H2EA): Sikorsky Aircraft Corporation; names 1 of 4 models: S-61A

## 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: 52 (52 by airframe model, 0 by engine model)
- Makers: Sikorsky 51, 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)
- [Carson Helicopters / Sikorsky S61A](https://openairdocs.org/model/carson-helicopters-sikorsky-s61a): 1 aircraft (airframe model)

All 4 models: https://openairdocs.org/ad/84-11-03/models.md
Every aircraft: https://openairdocs.org/ad/84-11-03/aircraft.md

Its text cites no advisory circulars or STCs.

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