Commonwealth legislation

AD/DHC-6/16 Amdt 5 - Wing Front Spar Attachment Fittings

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legislative instrument

Plain English Summary

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CASA requires owners/operators of de Havilland DHC‑6 (Twin Otter) serials 1–210 to carry out the maintenance actions in de Havilland Service Bulletin 6/174 Revision D: repeated inspections (Part A) at ≤500 flight hours or every 3 months, or required corrective action (Part B) within 100 hours after 31 July 1974. Installing unused fittings P/N C6WM 1133‑1 or ‑2 stops the recurring inspections.

The rule responds to stress‑corrosion cracks found in front spar attachment fittings. Owners bear costs; they must choose between ongoing inspection costs or a one‑off replacement to eliminate the inspection burden.

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AD/DHC-6/16 Amdt 5 - Wing Front Spar Attachment Fittings

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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DHC-6 (Twin Otter) Series Aeroplanes

AD/DHC-6/16

Amdt 5

Wing Front Spar Attachment Fittings 3/87

Applicability: All models with serial numbers 1 to 210 inclusive.

Requirement: Action in accordance with de Havilland of Canada Service Bulletin No 6/174 Revision D, Part A or Part B as applicable.

Compliance: For Part A of SB 6/174: At intervals not exceeding 500 hours time in service or 3 months, whichever occurs first.

For Part B of SB 6/174: Within 100 hours time in service after 31 July 1974, unless already accomplished.

Note: The repetitive inspections of Part A may be discontinued upon installation of unused de Havilland fittings P/N C6WM 1133-1 and -2.

Background: Stress corrosion cracks have been found in service. The Service Bulletin requires inspection of the fittings and re- torquing of the wing attach bolts. This revision implements Revision D to the SB. Canadian AD’s CF-69-4, CF-69-5 and CF-76-08 refer.

Source text

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

1 AD/DHC-6/16 Amdt 5 - Wing Front Spar Attachment Fittings