Commonwealth legislation

AD/B747/148 Amdt 1 - Fuselage Skin Stringer 12 Lap Joint

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Requires operators of Boeing 747s (Line Numbers 201–230) to carry out high-frequency eddy-current inspections of the stringer 12L/12R lap joints (BS 520–BS 741.1) and to replace countersunk fasteners with raised-head fasteners per a Boeing Service Bulletin, with flight-based deadlines and recurring inspection intervals. The aim, as stated in the instrument, is to maintain structural airworthiness by finding and preventing multi-site fatigue cracking that could lead to rapid depressurisation.

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AD/B747/148 Amdt 1 - Fuselage Skin Stringer 12 Lap Joint

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Boeing 747 Series Aeroplanes

AD/B747/148

Amdt 1

Fuselage Skin Stringer 12 Lap Joint 10/95

Applicability: B747 aircraft Line Number 201 to 230 inclusive.

Requirement: 1. High frequency eddy current inspect the fuselage skin around the upper row of fasteners in the stringer 12L and 12R lap joints. Inspect from Body Station (BS) 520 to BS 741.1 in accordance with Boeing Service Bulletin (SB) 747-53-2366 Accomplishment Instructions, Part I.

2. Modify the stringer 12L and 12R lap joints by removing the countersunk fasteners and installing raised head fasteners in accordance with Boeing SB 747-53-2366 Accomplishment Instructions, Part III.

3. Inspect in accordance with Requirement 1.

Note: FAA AD 94-15-17 refers.

Compliance: 1. Pre Requirement 2 modification: Inspect in accordance with Requirement 1 before 15 000 flights or within 1000 flights after 25 May 1995, whichever occurs later.

Re-inspect at intervals not to exceed 4000 flights.

2. Modify in accordance with Requirement 2 before 20 000 flights or before 25 May 1999 whichever occurs later.

3. Post Requirement 2 modification: Inspect in accordance with Requirement 1 before 10 000 flights after modification.

Re-inspect at intervals not to exceed 3000 flights.

This Amendment is effective 14 September 1995.

Background: The waffle doubler to skin panel bonded joint has, on other aircraft types, experienced disbonding. The countersinks in the three rows of fasteners of the stringer 12 lap joints are deeper than the upper skin panel and multi-site fatigue cracking, leading to a rapid depressurisation, may result. The inspections and modifications of this Directive will assist in maintaining the structural airworthiness of the aircraft.

Amendment 1 corrects the Service Bulletin number called up in Requirement 2. As there is no change to Requirement 1 the Compliance date of 25 May 1995 is unchanged from the original issue of this Directive.

Source text

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

1 AD/B747/148 Amdt 1 - Fuselage Skin Stringer 12 Lap Joint