Commonwealth legislation

AD/ENST 28/33 - Tail Rotor Drive Flexible Couplings

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Commonwealth

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legislative instrument

Plain English Summary

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Owners/operators of Enstrom F‑28 series helicopters must replace the existing 5‑plate tail‑rotor flex coupling with a 7‑plate unit and follow the manufacturer’s flange and coupling inspection procedures. The change is mandated because testing showed excessive distortion of the 5‑plate pack; the 7‑plate is intended to reduce that safety risk.

This imposes a short‑term retrofit and recurring inspection burden (inspection intervals not to exceed 100 hours TIS), raising maintenance cost and scheduling requirements for affected operators.

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AD/ENST 28/33 - Tail Rotor Drive Flexible Couplings

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Enstrom F-28 Series Helicopters

AD/ENST 28/33 Tail Rotor Drive Flexible Couplings 11/90

Applicability: All model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F and 280 FX series helicopters.

Requirement: 1. Replace the 5 plate flex pack coupling P/N A005-1991 with 7 plate flex pack coupling P/N A005-1992. During pack replacement inspect flange condition in accordance with Paragraph 5.2 of Enstrom Service Directive Bulletin No 0080.

Inspect 7 plate flex pack coupling in accordance with Paragraph 11 and 12 of Enstrom Service Directive Bulletin No 0080.

Note: FAA AD 90-17-02 Amdt 39-6688 refers.

Compliance: 1. Within 25 hours time in service after 7 September 1990.

At intervals not exceeding 100 hours time in service.

Background: Due to excessive distortion of the 5 plate coupling and the results of subsequent strain gauge testing by the manufacturer, replacement with a 7 plate coupling is mandatory.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

1 AD/ENST 28/33 - Tail Rotor Drive Flexible Couplings