Commonwealth legislation

AD/ENST 28/35 - Inadvertent Trim Motor Operation

In ForceCTH

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Commonwealth

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legislative instrument

Plain English Summary

3/10 complexity

Requires owners/operators of specified Enstrom F‑28 and 280 series helicopters with 24‑volt DC systems to modify and inspect the pitch trim system according to Enstrom Service Directive Bulletin 0082 Revision A. The modification must be done within five hours TIS and inspections repeated every 100 hours or at each annual inspection. The rule responds to reports of sticking relays that can drive the trim motor to full travel; operators pay for and schedule the work while the regulator mandates the safety action.

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AD/ENST 28/35 - Inadvertent Trim Motor Operation

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 28/35 Inadvertent Trim Motor Operation 2/94

Applicability: All F-28C, F-28C-2, F-28F, 280C, 280F and 280FX series helicopters equipped with a 24 volt DC electrical system.

Requirement: 1. Inspect and modify the trim system in accordance with Enstrom Helicopter Corporation Service Directive Bulletin 0082 Revision A dated 18 March 1993.

Inspect the trim system in accordance with Enstrom Helicopter Corporation Service Directive Bulletin 0082 Revision A dated 18 March 1993.

Note: FAA Priority Letter AD 93-12-14 issued 6 December 1993.

Compliance: 1. Within five hours time in service from 13 December 1993.

At intervals not to exceed 100 hours time in service or at each annual inspection, whichever occurs first.

Background: There have been three reports of inadvertent trim motor operation as a result of sticking relays. A stuck relay causes the trim motor to rapidly deploy to the full trim position, resulting in high cyclic control forces that significantly reduce the controllability of the helicopter and possibly lead to total loss of control.

Source text

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

1 AD/ENST 28/35 - Inadvertent Trim Motor Operation