AD 94-26-02 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain de Havilland Model DHC-8 series airplanes, that requires repetitive inspections of the passenger service unit (PSU) printed circuit boards and power supply connectors to detect corrosion and evidence of overheating; repair or replacement of the circuit boards or replacement of connectors, if necessary; and eventual installation of a terminating modification. This amendment is prompted by reports that certain PSU printed circuit boards and power supply connectors have overheated in service. The actions specified by this AD are intended to prevent overheating of the PSU printed circuit board and power supply connectors, which could lead to a fire in the PSU.

Final Rule

94-26-02 DE HAVILLAND, INC.: Amendment 39-9098. Docket 93-NM-46-AD.
Applicability: Model DHC-8 series airplanes, serial numbers 003 through 369, inclusive; equipped with passenger service units (PSU) have part numbers 10-1418-1 or -2, or 10-1081-1 through -8; certificated in any category.

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 use the authority provided in paragraph (c) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect ofthe changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent overheating of the passenger service unit (PSU) printed circuit board and power supply connectors, which could lead to a fire in the PSU, accomplish the following:

(a) Within 300 hours time-in-service after the effective date of this AD, or within 30 days after the effective date of this AD, or within 12 months after any previous inspection conducted prior to the effective date in accordance with this paragraph, whichever occurs later: Conduct a visual inspection of all PSU printed circuit boards and power supply connectors to detect corrosion and evidence of overheating, in accordance with paragraph III. of de Havilland Alert Service Bulletin S.B. A8-33-30, Revision 'A', dated December 18, 1992.

NOTE 2: The overheat condition referred to in this paragraph is the discoloration of the printed circuit board around the connector interfaces, and not the light conformal coating discoloration resulting from the normal operation of high current devices mounted on the printed circuit board.

(1) If no corrosion or evidence of overheating is detected, repeat the inspection at intervals not to exceed 12 months.

(2) If any corrosion or evidence of overheating of the PSU printed circuit board is detected as a result of any inspection, prior to further flight, either repair or replace the PSU printed circuit board in accordance with the service bulletin. Thereafter, repeat the inspection at intervals not to exceed 12 months.

(3) If any corrosion or evidence of overheating of the power supply connectors is detected as a result of any inspection, prior to further flight, replace the affected power supply connector in accordance with the service bulletin. Thereafter,repeat the inspection at intervals not to exceed 12 months.

(b) Within 24 months after the effective date of this AD, install Modification 8/1950 in accordance with de Havilland Service Bulletin S.B. 8-33-34, dated August 10, 1993. Installation of this modification constitutes terminating action for the inspections required by paragraph (a) of this AD.

(c) 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 3: 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 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) The inspections shall be done in accordance with de Havilland Alert Service Bulletin S.B. A8-33-30, Revision 'A', dated December 18, 1992. The modification shall be done in accordance with de Havilland Service Bulletin S.B. 8-33-34, dated August 10, 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 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 January 26, 1995.

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 certain de Havilland Model DHC-8 series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on April 29, 1994 (59 FR 22138). That action proposed to require repetitive inspections of the passenger service unit (PSU) printed circuit boards and power supply connectors to detect corrosion and evidence of overheating; repair or replacement of the circuit boards or replacement of connectors, if necessary; and eventual installation of a modification that would terminate the required inspections.

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

One commenter supports the proposal.

Another commenter requests that the proposed requirement to submitinspection results to de Havilland be deleted. The commenter states that, since the proposed rule would require that a terminating action be accomplished, and since de Havilland has been aware of the addressed problem for several years, any data supplied to de Havilland through inspection reports would not shed any new light on the problem. The FAA concurs. Upon reconsideration of this proposed requirement, the FAA considers the submission of reports to be unnecessary. Additionally, de Havilland has advised the FAA that it foresees no future need to receive such reports. Accordingly, the FAA has revised the final rule by deleting the reporting requirement.

This same commenter requests that the compliance time for the proposed initial inspection be revised to account for new airplanes. The commenter suggests that new airplanes should not be required to be inspected for at least 12 months since new. In considering this comment, the FAA has determined that the applicability ofthe final rule must be revised to limit it only to airplanes having serial numbers 3 through 369, inclusive. Airplanes having serial numbers higher than 369 were delivered with the equivalent of Modification 8/1950 (the terminating modification required by this AD) installed. In light of this, a revision to the final rule to address "new" airplanes, as suggested by the commenter, is unnecessary since all of the affected airplanes have accumulated more than 12 months since new.

The FAA has revised the applicability of the final rule to clarify the specific part numbers of the subject PSU's installed on the affected airplanes.

As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out thatall airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been added to this final rule to clarify this requirement.

The FAA has recently reviewed the figures it has used over the past several years in calculating the economic impact of AD activity. In order to account for various inflationary costs in the airline industry, the FAA has determined that it is necessary to increase the labor rate used in these calculations from $55 per work hour to $60 per work hour. The economic impact information, below, has been revised to reflect this increase in the specified hourly labor rate.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

The FAA estimates that 133 airplanes of U.S. registry will be affected by this AD.

The required inspections will take approximately 2 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the total cost impact of the proposed inspections on U.S. operators is estimated to be $15,960, or $120 per airplane, per inspection.

The required terminating modification will require approximately 3 work hours per PSU to accomplish, at an average labor cost of $60 per work hour. Required parts would cost approximately $62 per PSU. Each airplane is equipped with between 18 and 26 PSU's. Based on these figures, the total cost impactof the proposed modification on U.S. operators is estimated to be $242 per PSU, or between $4,356 and $6,292 per airplane.

The total cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. However, the FAA has been advised that the initial inspection has already been accomplished on approximately 22 airplanes; therefore the future economic impact of this rule is reduced by at least $2,640.

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:

The service information referenced in this AD may be obtained from de Havilland, Inc., Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 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.

Michele Maurer, Aerospace Engineer, Systems and Equipment Branch, ANE-173, FAA, Engine and Propeller Directorate, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York 11581; telephone (516) 791-6428; fax (516) 791-9024.