# AD 74-16-05: Main Rotor Head Spindle Lock Nut

- Type: Airworthiness directive
- Status: Current
- Products: Erickson Air-Crane S-64A and S-64E
- Effective: December 12, 1974
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2033
- Registered aircraft: 16 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E5B0D6772B3A9A9086256E120055AC09.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/74-16-05

## The airworthiness directive

74-16-05 SIKORSKY AIRCRAFT: Amendment 39-1910 is amended by Amendment 39-2033. Applies to S-64A, S-64E, and S-56 helicopters certificated in all categories.

Compliance required as indicated.

To prevent fatigue failures of the main rotor head spindle lock nut, accomplish the following:

  (a) Before the accumulation of 750 hours time in service on a main rotor head spindle lock nut, P/N S1510-23031-0, or within the next 25 hours time in service after the effective date of this AD, whichever occurs later, replace the affected lock nut with a serviceable part of the same part number and thereafter repeat replacement at intervals not to exceed 750 hours time in service.

  (b) Before the accumulation of 10,500 hours time in service on a main rotor head spindle lock nut, P/N S1510-23031-1, or within the next 25 hours time in service after the effective date of this AD, whichever occurs later, replace the affected lock nut with a serviceable part of the same part number and thereafter repeat replacement at intervals not to exceed 10,500 hours time in service.

Amendment 39-1910 became effective August 15, 1974.

This amendment 39-2033 becomes effective December 12, 1974.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1EA](https://openairdocs.org/tcds/H1EA): Erickson Air-Crane Incorporated DBA Erickson Air-Crane; names 1 of 1 models: S-64A

## 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: 16 (16 by airframe model, 0 by engine model)
- Makers: Sikorsky 11, Erickson 4, Erickson Air Crane 1

Models with the most aircraft:

- [Sikorsky S-64E](https://openairdocs.org/model/sikorsky-s-64e): 11 aircraft (airframe model)
- [Erickson S64E](https://openairdocs.org/model/erickson-s64e): 4 aircraft (airframe model)
- [Erickson Air Crane S-64E](https://openairdocs.org/model/erickson-air-crane-s-64e): 1 aircraft (airframe model)

All 3 models: https://openairdocs.org/ad/74-16-05/models.md
Every aircraft: https://openairdocs.org/ad/74-16-05/aircraft.md

Its text cites no advisory circulars or STCs.

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