AD 94-17-08

This amendment adopts a new airworthiness directive (AD), applicable to all de Havilland Model DHC-7 series airplanes, that requires removal of the aluminum or brass hardware in the firewall terminal block assembly and replacement with steel hardware. This amendment is prompted by the results of an investigation, which revealed that corroded aluminum washers in the DC firewall terminal block assembly may loosen the electrical connections. The actions specified by this AD are intended to prevent interruption of DC electrical power due to connections that may have loosened from corrosion.

Final rule

94-17-08 DE HAVILLAND, INC.: Amendment 39-9003. Docket 94-NM-19-AD.
Applicability: All Model DHC-7 series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent interruption of DC electrical power due to connections that may have loosened from corrosion, accomplish the following:

(a) Within 60 days after the effective date of this AD, remove the aluminum or brass hardware in the firewall terminal block assembly and replace with steel hardware (Modification 7/2617), in accordance with de Havilland Service Bulletin S.B. 7-24-69, dated October 8, 1993.

(b) An alternative method 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 Aircraft Certification Office (ACO), 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.

(c) 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.

(d) The removal and replacement shall be done in accordance with de Havilland Service Bulletin S.B. 7-24-69, dated October 8, 1993. 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 Bombardier, Inc., Bombardier Regional Aircraft Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; orat 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.

(e) This amendment becomes effective on September 21, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all de Havilland Model DHC-7 series airplanes was published in the Federal Register on April 22, 1994 (59 FR 19154). That action proposed to require removal of the aluminum or brass hardware in the firewall terminal block assembly and replacement with steel hardware (Modification 7/2617).

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were submitted in response to the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

The FAA estimates that 55 airplanes of U.S. registry will be affected by this AD, that it will take approximately 3 work hours per airplane to accomplish the required actions, 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 $9,075, or $165 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 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 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 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 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: