COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES American Champion (Aeronca, Bellanca) Series Aeroplanes AD/CHA/21 Wing Rib/Spar Attachment and L.E. Support Block Nails 4/80 Applicability: All models 7GC, 7GCA, 7GCB, 7GCBA, 7HC, 7KC and 7KCAB; All models 7ECA with S/Nos. 1 to 1350-80; All models 7GCAA with S/Nos. 1 to 396-80; All models 7GCBC with S/Nos. 1 to 1213-80; All models 8KCAB with S/Nos. 3-70 to 638-80; All models 8GCBC with S/Nos. 1-74 to 355-80. Requirement: Action in accordance with Bellanca SL No. C-139. Compliance: In accordance with Requirement Document. Background: The manufacturer has received reports of the rib/spar attachment and leading edge support block nails loosening and backing out of the spar.