COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/136 Amdt 1 Fuselage - Nose Wheel Well 7/99 Applicability: B747 Line No 001 to 685 inclusive. Requirement: 1. Externally inspect for cracks in the nose wheel well top panel and intercostals. Inspect in accordance with Boeing SB 747-53-2293 Rev 6 using either detailed close visual (Option 1) or a combination of detailed close visual and high frequency eddy current (Option 2) methods. 2. Perform a detailed close visual inspection, internally and externally, for cracks in the nose wheel well vertical beam clips and the adjacent side wall panel web. If cracks are found, extend the inspection area and inspect using high frequency eddy current methods. Inspect in accordance with Boeing SB 747-53-2293 Rev 6. 3. Inspect, internally and externally, for cracks in the nose wheel well vertical beam webs. Inspect in accordance with Boeing SB 747-53-2293 Rev 6 using either a detailed close visual (Option 1) or a combination of detailed close visual and high frequency eddy current (Option 2) methods. Note: FAA AD 90-06-14R1 refers. Compliance: 1. Initially inspect the nose wheel well top panel and intercostals before 4000 flights or within 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 1500 flights (Option 1) or intervals not exceeding 3000 flights (Option 2). 2. Initially inspect the vertical beam clips and side wall panels before 10000 flights or within 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 3000 flights. 3. Inspect the vertical beam webs before 10000 flights or before 1500 flights from 27 April 1995, whichever is the later. Reinspect at intervals not exceeding 1500 flights (Option 1) or intervals not exceeding 3000 flights (Option 2). 4. For the purposes of this AD a flight may be taken as a ground-air-ground cycle where the pressure differential exceeds 2.0 psi. 5. Modification in accordance with Boeing SB 747-53-2293 Rev 6 constitutes terminating action for the inspection requirements of this AD for those areas so modified. The compliance times of the original issue of this Directive remains unchanged except for the Requirement 2 repetitive inspection. This Amendment becomes effective on 15 July 1999. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Background: There have been approximately 70 reported instances of cracking in the nose wheel well structure. Cracks up to 11" long have been reported. Continued operation with undetected cracks could lead to rapid cabin depressurisation. Inspections in accordance with this AD will ensure timely detection of critical cracks. Amendment 1 is issued to align the Requirement 2 repetitive inspection interval with the related FAA AD requirement. The original issue of this Airworthiness Directive became effective on 27 April 1995.