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CFR Citation: 14 CFR Part 39

Docket ID: [Docket No. 2001-NM-295-AD]

RIN ID: RIN 2120-AA64

NOTICE: PROPOSED RULES

ACTION: Airworthiness directives:

DOCUMENT ACTION: Notice of proposed rulemaking (NPRM).

SUBJECT CATEGORY: Airworthiness Directives; Boeing Model 777-200 and 777-300 Series Airplanes

DATES: Comments must be received by January 2, 2003.

DOCUMENT SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 777200 and 777300 series airplanes. This proposal would require application of hightemperature sealant to the strut aft dry bay. This action is necessary to prevent leakage of hydraulic fluid into the strut aft dry bay, where high temperatures associated with the adjacent primary exhaust nozzle may ignite the fluid, resulting in an uncontrolled fire in the strut aft dry bay. This action is intended to address the identified unsafe condition.

SUMMARY: Boeing,

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 2001NM295AD.'' 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. 2001NM295AD, 1601 Lind Avenue, SW., Renton, Washington 980554056.

Discussion

The FAA has received a report indicating that one operator had found coked hydraulic fluid in the strut aft dry bay, which is located directly above the primary exhaust nozzle. Investigation revealed that hydraulic fluid had leaked from the strut aft fairing through an unsealed gap between the strut aft bulkhead, the diagonal brace fitting, and the cowl fairing. This unsealed gap, if not corrected, permits leakage of hydraulic fluid into the strut aft dry bay, where high temperatures associated with the adjacent primary exhaust nozzle may ignite the fluid. The result would be an uncontrolled fire in the strut aft dry bay, which lacks fire detection or fire extinguishing equipment.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 77754A0016, dated January 25, 2001, which describes procedures for application of high temperature sealant to fill the gap between the strut aft bulkhead, the diagonal brace fitting, and the aft cowl fairing. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.
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Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously.

Cost Impact

There are approximately 298 airplanes of the affected design in the worldwide fleet. The FAA estimates that 95 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 4 work hours per airplane to accomplish the proposed application of sealant, and that the average labor rate is $60 per work hour. Required materials would cost approximately $20 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $24,700, or $260 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 proposed 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.

The manufacturer may cover the cost of required materials and labor associated with this NPRM, subject to warranty conditions. As a result, the costs attributable to the proposed AD may be less than stated above.

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:

Boeing: Docket 2001NM295AD.

Applicability: Model 777200 and 777300 series airplanes having line numbers 2 through 297 inclusive, 299, and 300; 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 request approval for an alternative method of compliance in accordance with paragraph (b) 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 accomplished previously.

To prevent leakage of hydraulic fluid into the strut aft dry bay, where high temperatures associated with the adjacent primary exhaust nozzle may ignite the fluid, resulting in an uncontrolled fire in the strut aft dry bay; accomplish the following:
Application of Sealant
(a) Within 1,000 flight hours after the effective date of this

FOR FURTHER INFORMATION CONTACT John Vann, Aerospace Engineer, Propulsion Branch, ANM140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980554056; telephone (425) 2271024; fax (425) 2271181.