AD 94-09-05

This amendment adopts a new airworthiness directive (AD), applicable to certain de Havilland Model DHC-7 series airplanes, that requires a one-time inspection to assess the adequacy of the clearance between various adapter plates and seal retaining angles on the fuselage side access panel, and modification of both the forward and rear seal retention angles. This amendment is prompted by reports of incidents involving corrosion and fatigue cracking in commuter-class airplanes that are approaching or have exceeded their economic design goal. The actions specified by this AD are intended to prevent degradation of the structural capabilities of the affected airplanes.

Final Rule

94-09-05 DE HAVILLAND, INC.: Amendment 39-8893. Docket 92-NM-157-AD.

Applicability: Model DHC-7 series airplanes having serial numbers 1 through 99 inclusive, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent structural failure, accomplish the following:

(a) For airplanes having serial numbers 1 through 77 inclusive, 79 through 83 inclusive, 85, and 86: Within 12 months after the effective date of this AD, inspect the clearance between the wing forward pick-up adapter plates and the seal retaining angle on the fuselage side access panel in accordance with de Havilland Service Bulletin 7-57-11, dated December 17, 1982.

(1) If the adapter plates are undamaged or if scoring on the adapter plates does not exceed 0.050 inch in depth, prior to further flight, accomplish Modification 7/2319 in accordance with the service bulletin.

(2) If scoring on the adapter plates is equal to or exceeds 0.050inch in depth, prior to further flight, repair in accordance with a method approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, FAA, Engine and Propeller Directorate.

(b) For airplanes having serial numbers 1 through 99 inclusive: Within 12 months after the effective date of this AD, inspect the clearance between the rear mounting adapter plates and the seal retaining angle on the fuselage side access panel in accordance with de Havilland Service Bulletin 7-57-19, dated February 24, 1984.

(1) If the adapter plates are undamaged or if scoring on the adapter plates does not exceed 0.050 inch in depth, prior to further flight, accomplish Modification 7/2355 in accordance with the service bulletin.

(2) If scoring on the adapter plates is equal to or exceeds 0.050 inch in depth, prior to further flight, repair in accordance with a method approved by the Manager, New York ACO, ANE-170, FAA, Engine and Propeller Directorate.

(c) An alternativemethod of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, New York ACO, ANE-170, FAA, Engine and Propeller Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

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

(d) Special flight permits may be issued in accordance with Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

(e) The inspections and modifications shall be done in accordance with de Havilland Service Bulletin 7-57-11, dated December 17, 1982, and de Havilland Service Bulletin 7-57-19, dated February 24, 1984. This incorporation by reference was approved by theDirector 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., Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Engine and Propeller Directorate, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on June 6, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain de Havilland Model DHC-7 series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on January 4, 1994 (59 FR 266). That action proposed to require a one-time inspection to assess the adequacy of the clearance between various adapter plates and seal retaining angles on the fuselage side access panel, and modification of both the forward and rear seal retention angles.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received.

The commenter supports the proposed rule.

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.The FAA estimates that 44 airplanes of U.S. registry will be affected by this AD, that it will take approximately 8 work hours per airplane to accomplish the modifications and inspections, and that the average labor rate is $55 per work hour. Required parts will be nominal in cost. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $19,360, or $440 per airplane.

The total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the 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 finalrule 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from 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 14 CFR part 39 of the Federal Aviation Regulations as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: