Airworthiness Directive · Amendment 39-15574 · Structures
Viking Air Limited Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 Airplanes
This AD applies to Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes, serial numbers (SNs) 001 through 844, certificated in any category.
We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
Unless already done, do the following actions:
(1) Within the next 90 days after August 5, 2008 (the effective date of this AD), develop a schedule for doing the initial and repeat CTs required in paragraph (f)(2) and (f)(3) of this AD.
(2) Initially, do all of the seven basic CTs defined at paragraph 3.0 of Part 3 of DHC-6 Twin Otter (Series 100/200/300) Corrosion Prevention and Control Manual PSM 1-6-5, Revision 3, released and dated January 15, 2007 (individual pages dated as specified in the List of Effective Pages on pages 7 through 12 of the document); and the temporary revisions listed in Table 1— Viking Temporary Revisions, of this AD:
| Temporary revision number and date |
|---|
| (i) Viking Temporary Revision, C57-10-18 (TR 2-2), dated December 19, 2007. |
| (ii) Viking Temporary Revision, Part 3, Supplement 1 (TR 3-2), dated December 19, 2007. |
| (iii) Viking Temporary Revision, Part 3, Supplement 1 (TR 3-3), dated December 19, 2007. |
| (iv) Viking Temporary Revision, Part 3, Supplement 1, (TR 3-4), dated December 19, 2007. |
Determine corrosion level following the definitions contained in the introduction section of DHC-6 Twin Otter (Series 100/200/300) Corrosion Prevention and Control Manual PSM 1-6-5, Revision 3, released and dated January 15, 2007 (individual pages dated as specified in the List of Effective Pages on pages 7 through 12 of the document). The initial accomplishment deadlines are specified in Table 2— Initial Accomplishment Deadline, of this AD:
| Applicable airplane serial numbers | Initial accomplishment deadline for all airplanes in applicable S/N range |
|---|---|
| (i) 001 through 199 | 15 months after August 5, 2008 (the effective date of this AD). |
| (ii) 200 through 439 | 27 months after August 5, 2008 (the effective date of this AD). |
| (iii) 440 through 659 | 51 months after August 5, 2008 (the effective date of this AD). |
| (iv) 660 through 844 | 63 months after August 5, 2008 (the effective date of this AD). |
(3) After the initial completion of each CT, repeat each CT at the repeat interval (R) specified in the manual. Determine corrosion level following the definitions contained in the introduction section of DHC-6 Twin Otter (Series 100/200/300) Corrosion Prevention and Control Manual PSM 1-6-5, Revision 3, released and dated January 15, 2007 (individual pages dated as specified in the List of Effective Pages on pages 7 through 12 of the document).
(4) If any corrosion is found during any action required by this AD, before further flight, address corrosion following paragraph 4.0 of Part 3 of DHC-6 Twin Otter (Series 100/200/300) Corrosion Prevention and Control Manual PSM 1-6-5, Revision 3, dated January 15, 2007. All repairs are to be done following a method approved by the Manager, New York Aircraft Certification Office or Transport Canada Civil Aviation (or its delegated agent).
(5) Within 21 days after the finding of Level 3 corrosion, submit a plan to the FAA to identify a schedule for accomplishing the applicable CTs on the remainder of the airplanes in the operator's fleet that are subject to this AD or data substantiating that the Level 3 corrosion that was found is an isolated case. The FAA may impose a schedule other than proposed in the plan upon finding that a change to the schedule is needed to assure that any other Level 3 corrosion is detected in a timely manner. For the purposes of this paragraph, the FAA is defined as the cognizant principal maintenance inspector (PMI) for operators that are assigned a PMI (e.g., part 121, 125, and 135 operators) and the cognizant flight standards district office for other operators (e.g., part 91 operators).
(6) If any Level 3 corrosion is found while doing any action required by this AD, within 21 days after the finding of Level 3 corrosion, report the finding on the form in Figure 1 of this AD and send it to Viking Air Limited, VP Engineering, 9574 Hampden Road, Sidney, British Columbia, Canada V8L 5V5.
(7) Incorporation of the initial and repeat CTs into your FAA-approved maintenance program constitutes terminating action for this AD. If this AD is terminated in this way, then the maintenance program must be in accordance with this AD.
Note: This AD differs from the MCAI and/or service information as follows: No differences.
