# AD 76-05-11: Tail Cone Attach Bolts

- Type: Airworthiness directive
- Status: Current
- Products: Enstrom Helicopter Corporation, The 280 and F-28A
- Effective: March 18, 1976
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2545
- Registered aircraft: 44 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/AACC9A1227BCF94A86256A38004D43EF.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/76-05-11

## The airworthiness directive

76-05-11 ENSTROM: Amendment 39-2545. Applies to Enstrom Model F-28A and 280 helicopters certified in all categories with the following serial numbers:

F-28A Models - S/N 03 thru 347 280 Models - S/N 1001 thru 1030

Compliance required as indicated unless already accomplished:

  (a) Within the next ten (10) hours time in service after the effective date of this AD remove the three (3) tail cone attach bolts and perform a dye penetrant inspection of the bolts for fatigue cracks or an equivalent inspection method approved by the Chief, Engineering and Manufacturing Branch of the Federal Aviation Administration, Great Lakes Region.

Note: Particular attention should be given to the threaded area and the radius under the base of the bolt head.

  (b) Replace any defective bolts with a new bolt of the same part number or a stronger equivalent listed in paragraph (d) prior to further flight.

  (c) Tail cone bolts of the original design shall be inspected again at 50 hours from the inspection required in paragraph (a) unless replaced with the stronger bolts as listed in paragraph (d).

  (d) Within 110 hours time in service from the effective date of this AD unless already accomplished replace the three (3) AN bolts attaching the tail cone with the following NAS bolts:

Upper attachment point - NAS146DH-24 bolt Lower attachment points - NAS146DH-22 bolt

MS20002C6 washers are to be installed under the head. Care should be exercised to insure that the proper bolt grip length is maintained.

  (e) Torque bolts to 240 in. - lbs. and safety wire.

  (f) Upon compliance with paragraphs (d) and (e) the inspections listed in paragraph (c) are no longer required.

Note: When installing the NAS hardware on some helicopters in the field, it may be necessary to install an additional MS20002C6 or an AN 960-616 washer on the NAS bolts. The additional washers will insure that the bolts will not bottom out on the grip portion of the bolt when torqued to the airframe.

Enstrom Service Notes 0029 and 0029A pertain to this same subject.

This amendment becomes effective March 18, 1976.

## 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/76-05-11/models.md
Every aircraft: https://openairdocs.org/ad/76-05-11/aircraft.md

Its text cites no advisory circulars or STCs.

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