AD 95-22-07

This amendment supersedes Airworthiness Directive (AD) 83-26-05 and AD 86-15-08, which currently require repetitively inspecting the horizontal stabilizer attachment fittings for cracks or looseness on certain de Havilland DHC-6 series airplanes, and, if a cracked or loose part is found, modifying the horizontal stabilizer. This action retains the repetitive inspection requirement of the existing AD's, requires incorporating an improved modification for airplanes with a certain modification design as terminating action for the repetitive inspections, and making these inspection-terminating modifications optional for other affected airplanes. Reports of loose horizontal stabilizer attachment fittings on airplanes incorporating the inspection-terminating modifications required by AD 83-26-05 prompted this action. The actions specified by this AD are intended to prevent separation of the horizontal stabilizer from the airplane caused by a cracked attachment fitting, and subsequent loss of control of the airplane.

Final rule.

95-22-07 DE HAVILLAND: Amendment 39-9415; Docket No. 93-CE-51-AD. Supersedes AD 83-26-05, Amendment 39-4793, and AD 86-15-08, Amendment 39-5362.

Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes (serial numbers 3 through 820), certificated in any category, that do not have Modifications 6/1890, 6/1891, and 6/1892 incorporated on all four horizontal stabilizer fittings in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland Service Bulletin (SB) No. 6/513, dated October 25, 1991.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e)of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless already accomplished.

To prevent separation of the horizontal stabilizer from the airplane caused by a cracked attachment fitting, and subsequent loss of control of the airplane, accomplish the following:

(a) For airplanes without Modification Nos. 6/1808 and 6/1809 incorporated, accomplish the following:

(1) Within the next 50 hours time-in-service (TIS) after the effective date of this AD or 800 hours TIS after the last inspection required by superseded AD 83-26-05, whichever occurs later, and thereafter at intervals not to exceed 800 hours TIS, inspect the horizontal stabilizer forward and rear attachment fittings for cracks in accordance with deHavilland SB No. 6/438, Revision D, dated March 28, 1986.

(2) If any cracks are found, prior to further flight, replace the cracked fitting with a serviceable fitting, part number (P/N) C6TPM1049-27 (forward fitting) or P/N C6TPM1050-27 (rear fitting), and incorporate Modifications 6/1890, 6/1891, and 6/1892 at each replacement fitting location in accordance with and as specified in de Havilland SB No. 6/513, dated October 25, 1991. Accomplishing these modifications terminates the repetitive inspection requirement of this AD.

(b) For airplanes that have Modifications 6/1808 and 6/1809 incorporated, accomplish the following:

(1) Within the next 400 hours TIS after the effective date of this AD, and thereafter at intervals not to exceed 800 hours TIS until the modifications required by paragraph (b)(3) of this AD are incorporated, inspect the rivets attaching the fittings to the horizontal stabilizer forward and rear spars for looseness in accordance with the III. ACCOMPLISHMENT INSTRUCTIONS A. INSPECTION section of de Havilland SB No. 6/513, dated October 25, 1991.

(2) If rivets are found loose, prior to further flight, incorporate Modifications 6/1890, 6/1891, and 6/1892 in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 6/513, dated October 25, 1991.

(3) Within the next 2,400 hours TIS after the effective date of this AD, unless already accomplished as required by paragraph (b)(2) of this AD, incorporate Modifications 6/1890, 6/1891, and 6/1892 on all four horizontal stabilizer fittings in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 6/513, dated October 25, 1991.

(c) Incorporating Modifications 6/1890, 6/1891, and 6/1892 on all four horizontal stabilizer fittings in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of de Havilland SB No. 6/513, dated October 25, 1991, is considered terminating action for the repetitive inspection requirements of this AD.(d) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(e) An alternative method of compliance or adjustment of the initial or repetitive compliance times that provides an equivalent level of safety may be approved by the Manager, New York Aircraft Certification Office (ACO), FAA, 10 Fifth Street, 3rd Floor, Valley Stream, New York 11581. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

NOTE 3: Alternative methods of compliance approved in accordance with AD 83-26-05 or AD 86-15-08 (both superseded by this action) are not considered approved as alternative methods of compliance with this AD.

(f) The inspections required by this AD shall be done in accordance with de Havilland Service Bulletin No. 6/438, Revision D, dated March 28, 1986. The modifications required by this AD shall be done in accordance with de Havilland Service Bulletin No. 6/513, dated October 25, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5 Canada. Copies may be inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., 7th Floor, suite 700, Washington, DC.

(g) This amendment (39-9415) supersedes AD 83-26-05, Amendment 39-4793, and AD 86-15-08, Amendment 39-5362.

(h) This amendment becomes effective on December 27, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain de Havilland DHC-6 series airplanes was published in the Federal Register on November 23, 1994 (59 FR 60337). The action proposed to supersede both AD 83-26-05 and AD 86-15-08 with a new AD that would require repetitively inspecting the horizontal stabilizer attachment fittings for cracks; and, if a cracked fitting is found, replacing with a serviceable fitting, part number (P/N) C6TPM1049-27 (forward fitting) or C6TPM1050-27 (rear fitting), and incorporating Modifications 6/1890, 6/1891, and 6/1892. The proposed action would also require the eventual incorporation of the above-referenced modifications for airplanes that have Modifications 6/1808 and 6/1809 incorporated. Accomplishment of the proposed inspections would be in accordance with de Havilland Service Bulletin (SB) No. 6/438, Revision D, dated March 28, 1986. Accomplishment of the proposed modifications would be in accordance with de Havilland SB 6/513, dated October 25, 1991.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

The FAA estimates that 169 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 1 workhour per airplane to accomplish the required inspection, that it will take approximately 10 workhours to accomplish the modification for those airplanes having Modifications 6/1808 and 6/1809 incorporated, and that the average labor rate is $60 per hour. The FAA has no way of knowing how many airplanes have incorporated these modifications. In estimating the total cost impact of this AD on U.S. operators, the FAA is only using the inspection criteria (1 workhour). With this in mind and based on those figures above, the total cost impact of this AD upon U.S. operators of the affected airplanes is estimated to be $10,140. This figure only includes the cost for the initial inspection and does not include replacement costs if an attachment fitting is found cracked and does not include repetitive inspection costs. The FAA has no way of determining how many horizontal stabilizer attachment fittings may be cracked or how many repetitive inspections each owner/operator may incur over the life of the airplane.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship betweenthe national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption "ADDRESSES".

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40101, 40113, 44701.

Section 39.13 - [AMENDED]
2. Section 39.13 is amended by removing Airworthiness Directive (AD) 83-26-05, Amendment 39-4793, and AD 86-15-08, Amendment 39-5362, and by adding a new AD to read as follows: