COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
De Havilland DHC-1 (Chipmunk) Series Aeroplanes
AD/DHC-1/12
Amdt 6
Applicability: All models.
Wing Spar Booms and Centre Section - Fatigue Life Limitation
8/86
Requirement: Retire the wing spar boom and centre section components in accordance with British Aerospace (Hawker Siddeley) TNS CT (C1) No. 138 Issue 5.
Note 1: With regard to the light alloy wing root insert fittings (para 2.3 of TNS 138), the inspection, reaming and re- bushing operation of TNS 160 may only be carried out once.
Note 2: With regard to the steel centre-section lower tie-bar (para 2.2 of TNS 138), it will be necessary to perform an inspection in accordance with TNS 175 to determine which retirement life is applicable.
Compliance: As detailed in the Requirement Document.
Note 1: The Role Factor classifications of TNS 138 shall be determined in consultation with the appropriate Regional Office. However, notwithstanding the provisions of TNS 138, in all future assessments a Role Factor of 2.5 shall be assigned to Glider Towing operations.
Note 2: The life limitations given in TNS 138 are directly applicable to British built DHC-1 aircraft, but are not directly applicable to Canadian built aircraft which are structurally significantly different in the fatigue critical locations. Owners/operators of Canadian built aircraft must contact the Secretary, through any Regional office of the Department, for a fatigue life assessment.
Background: Australian recorded flight loads data show that Glider Towing is a more severe fatigue environment than that indicated by TNS 138.
The fatigue lives given in TNS 138 are based on fatigue testing of a British built aircraft. Canadian built aircraft are structurally different from British aircraft and could also differ from one another in build standard and modification status. Each Canadian aircraft must therefore be assessed individually. The only Canadian aircraft assessed at the time of issue of this amendment showed fatigue lives comparable to those in TNS 138.