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CFR Citation: 14 CFR Part 39

Docket ID: [Docket No. 2002-NM-78-AD]

RIN ID: RIN 2120-AA64

NOTICE: PROPOSED RULES

ACTION: Airworthiness directives:

DOCUMENT ACTION: Notice of proposed rulemaking (NPRM).

SUBJECT CATEGORY: Airworthiness Directives; Bombardier Model DHC-8-400, -401, and - 402 Airplanes

DATES: Comments must be received by November 10, 2003.

DOCUMENT SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Bombardier Model DHC8 400, 401, and 402 airplanes. This proposal would require a onetime inspection of the forward engine mount assemblies on the left and right engine nacelles for installation of preproduction engine mount assemblies, and followon corrective actions if necessary. This action is necessary to prevent failure of the forward engine mount, which could result in reduced structural integrity of the nacelle and engine support structure. This action is intended to address the identified unsafe condition.

SUMMARY: Bombardier,

SUPPLEMENTAL INFORMATION

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:
[sbull] Organize comments issuebyissue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
[sbull] For each issue, state what specific change to the proposed AD is being requested.
[sbull] Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAApublic contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a selfaddressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 2002NM78AD.'' The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM114, Attention: Rules Docket No. 2002NM78AD, 1601 Lind Avenue, SW., Renton, Washington 980554056.

Discussion

Transport Canada Civil Aviation (TCCA), which is the airworthiness authority for Canada, notified the FAA that an unsafe condition may exist on certain Bombardier Model DHC8400, 401, and 402 airplanes. TCCA advises that the manufacturer of the forward engine mount assembly has indicated that an unapproved preproduction engine mount assembly was found installed in place of a production engine mount assembly. Preproduction engine mount assemblies are more susceptible to fatigue cracking than production engine mount assemblies. In addition, there is a possibility that preproduction assemblies having part number (P/N) 9604207 are incorrectly marked with P/N 9604209, which is the P/N on the production assemblies. Operation with preproduction engine mount assemblies could result in failure of the forward engine mount, and consequent reduced structural integrity of the nacelle and engine support structure.

Explanation of Relevant Service Information

Bombardier has issued Alert Service Bulletin A847106, Revision ``A,'' dated December 5, 2001, which describes procedures for a visual inspection to determine the P/N and configuration of the forward engine mount assemblies on the left and right engine nacelles. If the inspection shows that any preproduction engine mount assembly is installed, the service bulletin describes procedures for followon corrective actions for that assembly.
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Those actions include repetitive detailed visual inspections of each assembly for cracking at intervals of 250 flight cycles, and replacement of the preproduction engine mount assembly with a production engine mount assembly before further flight if cracking is found. If no cracking is found, the service bulletin specifies that the preproduction engine mount assembly may remain in service for up to 1,000 flight cycles after the initial inspection, and then reworked or replaced with a production engine mount assembly. If both engine mounts on the same nacelle have the preproduction configuration, the service bulletin specifies that one preproduction engine mount assembly must be replaced with a production engine mount assembly before further flight. The service bulletin also includes a repair letter issued by the engine manufacturer which contains rework procedures for the pre production engine mount assembly. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

TCCA classified this service bulletin as mandatory and issued Canadian airworthiness directive CF200207, dated January 21, 2002, to ensure the continued airworthiness of these airplanes in Canada. FAA's Conclusions

These airplane models are manufactured in Canada and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, TCCA has kept us informed of the situation described above. We have examined the findings of TCCA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.
Differences Between Canadian Airworthiness Directive, Service Bulletin, and Proposed Rule

The service bulletin and Canadian airworthiness directive specify a visual inspection to determine the P/N and configuration of the forward engine mount assemblies, but this proposed rule would require a general visual inspection. A note has been added to the proposed rule to define that inspection.

The service bulletin and Canadian airworthiness directive also specify a detailed visual inspection for cracking if a preproduction engine mount is installed, but this proposed rule would require a detailed inspection. A note has been added to the proposed rule to define that inspection.

Cost Impact

We estimate that 11 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 2 work hours per airplane to accomplish the proposed inspection, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $1,430, or $130 per airplane.

The cost impact figure discussed above is 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this proposed regulation (1) is not a ``significant regulatory action'' under Executive Order 12866; (2) is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 draft regulatory 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, Safety. The Proposed Amendment

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

PART 39AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:
Bombardier, Inc. (Formerly de Havilland, Inc.): Docket 2002NM78 AD.

Applicability: Model DHC8400, 401, and 402 airplanes; serial numbers 4005, 4006, 4008 through 4016 inclusive, 4018 through 4051 inclusive, and 4053; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the forward engine mount, which could result in reduced structural integrity of the nacelle and engine support structure, accomplish the following:
Inspection
(a) Within 100 flight cycles after the effective date of this

FOR FURTHER INFORMATION CONTACT Douglas G. Wagner, Aerospace Engineer, Systems and Flight Test Branch, ANE172, FAA, New York Aircraft Certification Office, 10 Fifth Street, Third Floor, Valley Stream, New York 11581; telephone (516) 2567506; fax (516) 5682716.