COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/51 Horizontal Stabiliser Skin Disbonding 5/98 DM Applicability: DHC-8 aircraft, models 102 and 103, with serial numbers 003 through 050. Requirement: Perform a one-time ultrasonic bond inspection of the upper and lower skin panels (part number 85510025 and 85510026) of the horizontal stabiliser for disbond as outlined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01. Note: Transport Canada AD CF-98-01 and Bombardier AOM 469 refer. Compliance: For aircraft serial numbers 010 through 040: within 20 flight cycles or 7 calendar days after 25 February 1998, whichever occurs first, unless already accomplished within the last 6 months. For aircraft serial numbers 003 through 009, and 041 through 050: within 60 flight cycles or 7 calendar days after 25 February 1998, whichever occurs first, unless already accomplished within the last 6 months. Disbonds found to be beyond the local disbond limits defined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01, shall be repaired before further flight. This airworthiness directive becomes effective on 25 February 1998. Background: Transport Canada has received two reports of cases of disbonding of the doubler and stringers on the upper and lower skin panels of the horizontal stabiliser, on two separate aircraft. This condition, if not detected and corrected, could result in structural failure of the horizontal stabiliser and possible loss of control of the aircraft.