COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Boeing 747 Series Aeroplanes
AD/B747/41
Amdt 1
Fuselage Section 41, Stringer 6 - Stations 340 to 400 8/96
Applicability: B747 aircraft as detailed in the Requirement Document.
Requirement: 1. Conduct close detailed visual and eddy current inspections of the stringer S-6L and S-6R fuselage skin lap joints for cracks, between body stations BS 340 and BS
400. Inspect in accordance with Boeing SB 747-53-2253, Revision 3.
2. Modify the stringer S-6L and S-6R fuselage skin lap joints between body stations BS 340 and BS 400, in accordance with Boeing SB 747-53-2253, Revision 3.
Note: FAA AD 90-23-14 refers.
Compliance: 1. For aircraft with less than 10,000 flights as of 20 June 1996, initially inspect in accordance with Requirement 1 before exceeding 10,000 flights. Thereafter, repeat the inspections at intervals not to exceed 3000 flights.
For aircraft with 10,000 flights or more as of 20 June 1996, initially inspect in accordance with Requirement 1 within 3000 flights since last inspected in accordance with Requirement 2 of AD/B747/46. Thereafter, repeat the inspections at intervals not to exceed 3000 flights.
Areas that have been modified in accordance with Requirement 2 of this AD need not be inspected until 10,000 flights after modification.
Areas that have had both the Requirement 2 modification and the Boeing SB 747- 53-2272 Zone 1 modification accomplished, may be inspected using external methods only in accordance with Boeing SB 747-53 2253, Revision 3, but must be inspected at intervals not to exceed 1000 flights.
2. Modify in accordance with Requirement 2 before exceeding 20,000 flights.
Note: For the purposes of this AD, flights on which the cabin pressure differential does not exceed 1.5 psi need not be counted.
This amendment is effective 18 July 1996.
Background: Pressure cycle fatigue has led to skin cracks in the subject area up to 470 mm long, on aircraft with between 12,400 and 14,800 flights. The modifications and inspections of this AD are based on the recommendations of the 747 Aging Fleet Structures Working Group. The stringer 6 areas affected have been determined to be 'structurally significant items' and critical to the structural integrity of the airframe.
Undetected skin cracks in this area may result in sudden in-flight cabin depressurisation and the inability to withstand required loads.
The original issue of this AD was cancelled when the requirement was incorporated into AD/B747/46 Amdt 2. In an effort to simplify that AD, AD/B747/41 has now been reinstated at Amendment 1.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
The original issue of this Airworthiness Directive became effective on 31 May 1985.
AD/B747/41 was cancelled (and AD/B747/46 Amdt 2 became effective) on 31 December 1986.