# AD 86-23-08: Main Rotor Hub Lower Plate

- 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: April 21, 1987
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-5590
- Registered aircraft: 54 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/8C6ADA721998EF3786256A4D00742F8C.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/86-23-08

## The airworthiness directive

86-23-08 SIKORSKY AIRCRAFT: Amendment 39-5590. Applies to Model S-61 series helicopters, certificated in any category, with main rotor hub lower plate, P/N S6110-23009-6 or -8, installed.

For helicopters with main rotor hub lower plates with more than 27,000 hours' time in service on the effective date of this AD, compliance is required prior to further flight, unless already accomplished, and thereafter at intervals not to exceed 27,000 hours' time in service.

For helicopters with main rotor hub lower plate with 27,000 or less hours' time in service on the effective date of this AD, compliance is required prior to the accumulation of 27,000 hours' time in service, unless already accomplished, and thereafter at intervals not to exceed 27,000 hours' time in service.

To prevent cracking of the main rotor hub lower plate, accomplish the following:

  (a) Remove and replace the main rotor hub lower plate, P/N S6110-23009-6 or -8, with a new or an airworthy part of the same part number that has less than 27,000 -hours' time in service.

  (b) In accordance with FAR sections 21.197 and 21.199, the helicopter may be flown to a base where compliance may be accomplished.

  (c) An alternate method of compliance or adjustment of the initial compliance time which provides an equivalent level of safety, may be approved by the Manager, 30 Sikorsky Boston Aircraft Certification Office, FAA, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803.

This amendment becomes effective April 21, 1987, to all persons except those persons to whom it was made immediately effective by priority letter AD 86-23-08, issued November 17, 1986, which contained this amendment.

## 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/86-23-08/models.md
Every aircraft: https://openairdocs.org/ad/86-23-08/aircraft.md

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.