COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
DHC-6 (Twin Otter) Series Aeroplanes
AD/DHC-6/51
Amdt 4
Engine Nacelle Lower Longerons 6/94
Applicability: Model DHC-6 series.
Requirement: Action in accordance with de Havilland Inc. Service Bulletin 6/509. If buckles or cracks are found, replace the failed longerons with serviceable parts.
Note 1: Transport Canada AD CF-81-07R4 refers.
Note 2: Prior accomplishment of Modification 6/1655 does not terminate the inspection requirements of this Directive.
Compliance: 1. For aircraft fitted with the following:
(i) High flotation tyres; or
(ii) Intermediate flotation tyres, not installed in accordance with de Havilland Standard Option Only (SOO) 6048, with or without Modification 6/1655 installed; or
(iii) Intermediate flotation tyres installed in accordance with de Havilland SOO 6048, without Modification 6/1655 installed; or
(iv) Skis or floats, without Modification 6/1655 installed:
Within 50 hours time in service after 6 March 1992, and thereafter at intervals not to exceed 50 hours time in service; and after each hard landing.
2. For aircraft fitted with the following:
(i) Intermediate flotation tyres installed in accordance with de Havilland SOO 6048, with Modification 6/1655 installed; or
(ii) Skis or floats, with Modification 6/1655 installed:
Within 50 hours time in service after 6 March 1992, and thereafter at intervals not to exceed 200 hours time in service; and after each hard landing.
3. For all other aircraft:
Within 400 hours time in service after 6 March 1992, and thereafter at intervals not to exceed 400 hours time in service; and after each hard landing.
The compliance calendar times of the previous issue of this Directive remain unchanged. This issue clarifies the compliance and changes a repeat inspection interval. This Amendment is effective from 26 May 1994.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Background: Buckles and cracks have developed in engine nacelle lower longerons, P/N C6W1512, behind the engine mount, particularly on aircraft fitted with high or intermediate flotation tyres or skis operating from unprepared surfaces, or with floats from very rough water.
Amendment 2 extended the applicability to all serial number aircraft, to eliminate a one-time inspection, and to introduce a 400 hour inspection for aircraft not equipped with high or intermediate flotation tyres, skis, or floats.
Amendment 3 was issued to reflect a revision of the related Transport Canada AD which introduced SB 6/509 and clarified the status of Modification 6/1655.
Amendment 4 is issued to extend the inspection interval for aircraft fitted with intermediate flotation tyres, or with skis or floats and Modification 6/1655 installed; in response to the latest revision of the related Transport Canada AD.