COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES C.A.C. CA-18 (Mustang) Series Aeroplanes AD/MUSTANG/1 Amdt 2 Wing Front Spar 4/86 Applicability: As detailed in the Requirements. Requirement: 1. Remove the wing fuel tank covers and carry out a visual inspection of the lower portion of the wing front spar. 2. Inspect the lower portion of the wing front spar for cracking at and near wing station 27 port and starboard. 3. For aircraft in which the cutout in the wing main spar lower boom flange at the wing root extends beyond wing station 2, inspect the lower portion of the spar for cracking at and near the end of the cutout port and starboard. Compliance: At intervals not exceeding 240 hours time in service. Background: This Directive has been amended to clarify the inspection requirements on the wing spar tension boom flange. In addition, the interval between inspections has been extended to 240 hours time in service.