# AD 64-27-04: Wood Rotor Blade Root Socket

- Type: Airworthiness directive
- Status: Current
- Products: Boeing Defense & Space Group 42A, 42B, H21A, H-21B, H-21B and H-21B
- Effective: December 10, 1964
- Published: December 5, 1964
- Issued: November 27, 1964
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-9
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/28575FB30D5B1F1586256A34005B5FA5.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/64-27-04

## The airworthiness directive

64-27-04 VERTOL: Amdt. 39-9 Part 39 (New) Federal Register December 5, 1964. Applies to Models H-21 and 42 Series Helicopters.

Compliance required as indicated.

As a result of a fatigue failure of a wood rotor blade root socket, P/N 22R1364-1, accomplish the following:

  (a) Conduct a daily visual inspection, using a magnifying glass of at least 8-power, of wood rotor blade root sockets, P/N 22R1364-1, with 750 or more hours' time in service as of the effective date of this AD, for cracks in the slot area between the inboard clamp bolt and the relief hole at the inboard end of the slot while supporting the rotor blade tip so that the blade does not rest on the droop stop.

  (b) Replace any cracked socket before further flight.

  (c) Within 25 hours' time in service after the effective date of this AD retire from service all wood rotor blade root sockets, P/N 22R1364-1, having 725 or more hours' time in service on the effective date of this AD.

  (d) Upon theaccumulation of 750 hours' time in service, retire from service all wood rotor blade root sockets, P/N 22R1364-1, having less than 725 hours' time in service on the effective date of this AD.

This directive effective December 10, 1964.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1H12](https://openairdocs.org/tcds/1H12): Boeing Defense & Space Group; names 2 of 4 models: 42A, 42B
- [TCDS HR-35](https://openairdocs.org/tcds/HR-35): Heli-Crane Corporation; names 1 of 1 models: H21A

## Registered aircraft it may apply to (OpenAirDocs)

No registered aircraft matched the models it names.

Its text cites no advisory circulars or STCs.

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