COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Aircraft - General AD/GENERAL/50 Whelen Strobe Light - Modification 4/75 Applicability: All aircraft equipped with Whelen A427 strobe light flash tubes manufactured before 1 November 1974. Requirement: Install on the base of Whelen Engineering Company Incorporated A427 strobe light flash tubes a pressure sensitive-vinyl label conforming to Whelen Engineering Company Incorporated Drawing A-300052, Revision 1, dated October 15, 1974, or a strip of Scotch Brand Type 33 vinyl plastic electrical tape can be used in lieu of the vinyl label. If the vinyl plastic electrical tape is used, it must be formed to cover the rivet at the rear of the flash tube without covering the identifying part number. If the flash tube incorporates a label, the new label or tape may be installed directly over the old label. Note: To ensure proper adhesion install the label or tape only when the label or tape and the flash tube are at a temperature above 10 degrees C. Compliance: Within the next 100 hours time in service after 30 May 1975.