# AD 77-20-02: Tail Rotor Spindle

- Type: Airworthiness directive
- Status: Current
- Products: Enstrom Helicopter Corporation, The 280, 280C, F-28, F-28A and F-28C
- Effective: October 6, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-3046
- Registered aircraft: 139 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6F7CE8126C3CDF1A86256A38004DC51E.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/77-20-02

## The airworthiness directive

77-20-02 ENSTROM: Amendment 39-3046. Applies to Enstrom Models F28, F28A, F28C, 280 and 280C helicopters certificated in all categories with a 3.3 inch tail rotor blade with spindle P/N 28-15202. Within the next 50 hours time in service or six (6) months calendar time, whichever occurs first, accomplish the following unless already complied with:

1. Replace tail rotor spindle P/N 28-15202 with a new spindle P/N 28-15202-13 or a manufacturer-reworked spindle which may be identified by an eight (8) character serial number acid-etched on the outside of the spindle center section. Reference should be made to Enstrom Maintenance Manual Section 15 for disassembly and reassembly instructions. Special care should be taken to have the three bearing stack positioned with the closed side toward the hub and the retaining nut properly torqued to 35-40 foot-pounds and safetied.

2. Install strike tabs P/N 28-17308 extending forward on the blade leading edge under the outer balancingscrew.

This supersedes Amendment 39-2839 (42 FR 10841) AD 77-04-04.

This amendment is effective October 6, 1977, and was effective for all recipients of the airmail letter dated August 8, 1977, as amended by airmail letter dated August 22, 1977, upon receipt thereof.

## 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 5 of 14 models: 280C, 280, F-28, F-28C, 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: 139 (139 by airframe model, 0 by engine model)
- Makers: Enstrom 90, Enstrom Helicopter 49

Models with the most aircraft:

- [Enstrom Helicopter 280C](https://openairdocs.org/model/enstrom-helicopter-280c): 48 aircraft (airframe model)
- [Enstrom F-28C](https://openairdocs.org/model/enstrom-f-28c): 46 aircraft (airframe model)
- [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)
- [Enstrom F-28](https://openairdocs.org/model/enstrom-f-28): 1 aircraft (airframe model)

All 6 models: https://openairdocs.org/ad/77-20-02/models.md
Every aircraft: https://openairdocs.org/ad/77-20-02/aircraft.md

Its text cites no advisory circulars or STCs.

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