COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Boeing 747 Series Aeroplanes
AD/B747/132 Fuselage - Upper Lobe Skin Panel Joints 11/94
Applicability: Boeing 747 series aircraft line positions 001 to 200 inclusive.
Requirement: 1. Initially, perform a detailed external visual inspection of the upper lobe skin panel lap joints for evidence of corrosion or cracking in accordance with Boeing SB 747- 53-2307 Revision 2, within 1000 flights after 13 October 1994.
Repeat at intervals not exceeding 2000 flights.
2. Initially, perform a HFEC inspection to detect cracks in the upper row of fasteners of the skin panel lap joints forward of BS 1000 in accordance with Boeing SB 747- 53-2307 Revision 2, within 1000 flights after 13 October 1994.
Repeat at intervals not exceeding 4000 flights.
3. Initially, perform a HFEC inspection to detect cracks in the upper row of fasteners of the skin panel lap joints between BS 1480 and 2360 in accordance with Boeing SB 747-53-2307 Revision 2, within 1000 flights after 13 October 1994.
Repeat at intervals not exceeding 6000 flights.
Note: It is required that all fastener heads are readily visible prior to conducting any of the above inspections. If necessary the lap joint shall be paint stripped.
4. If corrosion is found but does not exceed 10% of the skin thickness, on the affected lap joint:
- Inspect the area using HFEC inspection at reduced intervals not exceeding 500 flights, and
b. Install the “full” modification in SB 747-53-2307 Revision 2 within 36 months of the inspection during which the corrosion was found.
5. If cracks or corrosion exceeding 10% of the thickness are found, repair before further flight and install the “full” modification within 18 months of the inspection during which the corrosion was found.
6. Install the “full” modification, before 20000 flights or within 1000 flights from 13 October 1994, whichever is the later, at:
- The skin lap joints between stringer 12 left and right from BS 520 to 1000 and between stringer 19 left and right from BS 520 to 740 on aircraft line numbers 001 to 058 inclusive, or
b. The skin lap joints between stringer 12 left and right from BS 740 to 1000 and between stringer 19 left and right from BS 520 to 740 on aircraft line numbers 059 to 200 inclusive,
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
The inspections in paragraphs 1 to 4 are no longer required after “full” or “partial” modification in accordance with SB 747-53-2307 Revision 2.
7. HFEC inspect the modified lap joints:
- Initially, within 10000 flights from installing the “full” modification. Repeat at intervals not exceeding 3000 flights.
b. Initially, within 7000 flights from installing the “partial” modification. Repeat at intervals not exceeding 3000 flights.
8. The “partial” modification may be installed in lieu of the “full” modification where the existing skin panels have no cracks, corrosion or repairs and have a thickness of 0.09" or less. The “partial” modification shall not be installed at deep countersink locations.
Note: FAA AD 94-12-09 refers.
Compliance: Effective 13 October 1994.
Background: Corrosion and corrosion induced cracking in the lap joints have been experienced on early model B747 aircraft.