Douglas DC3 Series Aeroplanes AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DC3/29 Amdt 3 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. AD/DC3/29 Amdt 4 Lower Centre Section Skin and Structure 7/2000 Applicability: All models. Requirement: 1. Visually inspect those parts of the front face of the wing front spar, the lower spar cap and lower wing skin and doublers accessible from within the main landing gear bay and through the access holes in the landing gear drag strut tunnels between approximately Wing Station (WS) 90 and WS 130. 2. For aircraft which have not been modified with the repair or preventive doublers at both WS 94.25 and WS 127.75 in accordance with McDonnell Douglas (MD) Service Bulletin (SB) 229, any revision, or McDonnell Douglas Service Bulletin 263, any revision up to and including Revision 8, or McDonnell Douglas Service Rework Drawing (SRD) SR03578003: Note 1: Alternative designs of repair or preventive doublers are acceptable for the purposes of this AD only where they have been assessed and approved as at least equivalent to the above data, by the holder of an appropriate CAR 35 design authorisation. 1. Incorporate access holes in accordance with MD SRD03548001, Revision A; Note 2: Aircraft which have previously been modified to incorporate access holes, do not have to be re-modified provided that the necessary access and visibility can be obtained. b. Inspect the wing using the visual and radiographic procedures specified in MD SRD SR03578001 or MD SRD SR03578002 Revision A, whichever is applicable; and Note 3: Radiographic Technique DCA NCI/R/8 is an acceptable alternative procedure provided that for exposures 4 and 5 additional film is placed on the lower wing skin to inspect the lower spar between the drag strut fairing and the centre line of the nacelle. c. Modify the wing to incorporate wing skin doublers at both WS 94.25 and 127.75 in accordance with MD SRD SR03578003. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES 3. For aircraft which have been modified to incorporate wing skin doublers in accordance with SB 229, SB 263 and/or SRD SR03578003, inspect the wing using the visual procedure specified by SRD03578001 or SRD SR03578002 Revision A, whichever is applicable. Note 4: Transport Canada AD CF-92-15 refers. Compliance: For Requirement Para 1: Inspect before exceeding 500 hours time in service since last inspected in accordance with the previous issue of this AD, and thereafter at intervals not exceeding 500 hours time in service. In addition, inspect before further flight following flight in severe turbulence or following a heavy landing. For Requirement Para 2.a: Incorporate the access holes not later than the next inspection in accordance with Requirement Para 2.b. For Requirement Para 2.b: Inspect before exceeding 900 hours time in service since last inspected in accordance with the previous issue of this AD, or within 100 hours time in service after (date of issue), whichever occurs later, and thereafter at intervals not exceeding 900 hours time in service. For Requirement Para 2.c: Modify the wing before exceeding 900 hours time in service after 27 April 1995, or within 100 hours time in service after (date of issue), whichever occurs later. For Requirement Para 3: Inspect before exceeding 2000 hours time in service after 1 September 1969, or before exceeding 2000 hours time in service since last inspected in accordance with the previous issue of this AD, whichever occurs later, and thereafter at intervals not exceeding 2000 hours time in service. This Amendment becomes effective on 13 July 2000. Background: Previous issues of this AD promulgated inspection and modification in accordance with early issues of the reference documents. Amendment 3 introduced an additional modification to improve access for inspection; revised the inspection procedures; and required mandatory incorporation of the preventive doublers at the critical wing stations. These changes were prompted by an in-flight wing separation in Canada, and were intended to bring the Australian AD into line with recommendations from McDonnell Douglas and the FAA. FAA AD 92-06-15 refers. Subsequently the Authority was made aware that the requirement of Amdt 3 was ambiguous and that it provided a loophole whereby aircraft modified in accordance with SB 229, were not required to comply with Paragraphs 2.a, b or c. However, SB 229 specifies modification at WS 127.75 only, but not WS 94.25. This is contrary to the intent of the AD, which was to install the reinforcing doublers at both locations. Airworthiness inspectors have reported a number of aircraft in service in Australia which do not have the WS 94.25 modification and which, by virtue of the AD wording, are not receiving the detailed visual and radiographic inspection at either location. It has also been reported that some aircraft have doublers installed which do not appear to conform to the SB or SRD specifications. This issue makes it clear that both wing stations are critical and that modification and inspection at both locations is required, and that the modifications must accord with the specified data. Aircraft which are in full compliance with the intent of the previous issue as outlined above, including correct doubler installation and detailed visual and radiographic inspection at both locations WS 94.25 and WS 127.75, left and right sides, need no additional work as a result of this amendment. Ongoing inspection is of course still required. Amendment 3 of this directive became effective on 27 April 1995. William Ronald Smith Delegate of the Civil Aviation Safety Authority 15 May 2000 The above AD is notified in the Commonwealth of Australia Gazette on 14 June 2000.