- Effective
- December 10, 1964
- Published
- December 5, 1964
- Issued
- November 27, 1964
- Models
- 42A, 42B, H21A, H-21B, H-21B, H-21B
- Product
- Aircraft · Rotorcraft
- Amendment
- 39-9
Unofficial copy of the text in the FAA’s Dynamic Regulatory System. The FAA’s own copy is the authoritative one. DRS record last changed November 21, 2025.
Copies of the files this page was built from, with their SHA-256. Retrieved October 18, 2026.
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On this page
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 TCDS · 2
The type certificate data sheets for the models this AD names, matched by model and maker.