# AD 75-22-10: Hub Lock Washer

- Type: Airworthiness directive
- Status: Current
- Products: Enstrom Helicopter Corporation, The 280 and F-28A
- Effective: October 28, 1975
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2403
- Registered aircraft: 44 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/F2CC8763C2A4A18686256A38004D417A.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/75-22-10

## The airworthiness directive

75-22-10 ENSTROM: Amendment 39-2403. Applies to Enstrom Models F-28A and 280 helicopters certified in all categories, with the following serial numbers:

F-28A - S/N's 4 through 275, 277, 278, 280 through 283. 280 - S/N's 1001 through 1006.

Note: Helicopters equipped with a 'tang' hub lock washer, Enstrom P/N 28-14263, are exempt from compliance with this Airworthiness Directive.

Compliance required as indicated unless already accomplished.

Within the next 25 hours time in service after the effective date of this Airworthiness Directive:

  (a) Remove the main rotor retention nut, Enstrom P/N 28-14004, and hub nut washer, Enstrom P/N 28-14005;

  (b) Replace hub nut washer, Enstrom P/N 28-14005, with a new retention washer, Enstrom P/N 28-14008, or an equivalent approved by the Chief, FAA Engineering and Manufacturing Branch, Great Lakes Region. The chamfer on the new washer must be installed parallel with the main rotor spline chamfer; and,

  (c) Install main rotor hub retention nut, Enstrom P/N 28-14004, and torque nut to a value of 400 ft. lbs. Re-safety with .040" diameter stainless steel safety wire in three (3) places to the hub adapter plate bolt heads.

Enstrom Service Notes 0025 and 0025A pertain to this same subject.

This amendment becomes effective October 28, 1975.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1CE](https://openairdocs.org/tcds/H1CE): The Enstrom Helicopter Corporation; names 2 of 14 models: 280, F-28A

## 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: 44 (44 by airframe model, 0 by engine model)
- Makers: Enstrom 43, Enstrom Helicopter 1

Models with the most aircraft:

- [Enstrom F-28A](https://openairdocs.org/model/enstrom-f-28a): 38 aircraft (airframe model)
- [Enstrom 280](https://openairdocs.org/model/enstrom-280): 5 aircraft (airframe model)
- [Enstrom Helicopter F-28A](https://openairdocs.org/model/enstrom-helicopter-f-28a): 1 aircraft (airframe model)

All 3 models: https://openairdocs.org/ad/75-22-10/models.md
Every aircraft: https://openairdocs.org/ad/75-22-10/aircraft.md

Its text cites no advisory circulars or STCs.

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