01-27189. Airworthiness Directives; Boeing Model 777-200 Series Airplanes Equipped With General Electric Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 777-200 series airplanes equipped with General Electric engines. This proposal would require installation of a high-temperature silicone foam seal on the aft fairing of the strut. This action is necessary to prevent primary engine exhaust from entering the aft fairing of the strut, elevating the temperature in the aft fairing of the strut, and creating a potential source of ignition, which could lead to an uncontrolled fire in the aft fairing of the strut. Such a fire would expose the wing fuel tank to high-temperature gasses and flames and result in a potential ignition source for the fuel tank, and reduced structural integrity of the wing. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by December 14, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-93-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-93-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

John Vann, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

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:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• 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 FAA-public 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2001-NM-93-AD.” 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, ANM-114, Attention: Rules Docket No. 2001-NM-93-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports that, during routine inspections of the aft fairing of the strut, evidence of an elevated temperature in the interior cavity of the aft fairing has been found on several Boeing Model 777-200 series airplanes equipped with General Electric engines. The evidence includes charred seals, soot build-up, and discoloration. Investigation revealed that primary engine exhaust entering through a gap in the heat shield of the aft fairing of the strut elevates the temperature in the aft fairing. The aft fairing of the strut is a flammable leakage zone. An elevated temperature in this area would create a potential source of ignition, and an ignition source is not allowed to exist in a flammable leakage zone because there is no provision for detecting or extinguishing a fire in these zones. A potential source of ignition due to an elevated temperature in the aft fairing of the strut, if not corrected, could result in an uncontrolled fire in the aft fairing of the strut. Such a fire would expose the wing fuel tank to high-temperature gasses and flames and result in a potential ignition source for the fuel tank, and reduced structural integrity of the wing.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 777-54A0015, dated January 18, 2001, which describes procedures for installation of a high-temperature silicone foam seal to fill the gap in the heat shield of the aft fairing of the strut on the left- and right-hand sides of the airplane. The procedures involve removing certain heat shield castings for the aft fairing of the strut, cleaning the area, bonding a foam seal to the upper surface of the heat shield cover plates, re-installing the heat shield castings, restoring the leveling compound and seal application, and doing a leak check of the aft fairing.

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, except as discussed below.

Difference Between Proposed AD and Service Bulletin

The referenced service bulletin states that all actions for which the Boeing 777 Airplane Maintenance Manual (AMM) is specified as the appropriate source of service information for work instructions may instead be done according to an “operator's equivalent procedure.” However, the FAA finds that Chapter 54-55-01 of the AMM must be used to accomplish the leak check of the aft fairing of the strut, which is specified in the Work Instructions in the service bulletin. For this leak check, an “operator's equivalent procedure” may be used only if approved as an alternative method of compliance per paragraph (c) of this AD.

Interim Action

This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

Cost Impact

There are approximately 97 airplanes of the affected design in the worldwide fleet. The FAA estimates that 18 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 15 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $16,200, or $900 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.

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 39—AIRWORTHINESS DIRECTIVES

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

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

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2001-NM-93-AD.

Applicability: Model 777-200 series airplanes equipped with General Electric engines, 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 (c) 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 primary engine exhaust from entering the aft fairing of the strut, elevating the temperature in the aft fairing of the strut, and creating a potential source of ignition, which could lead to an uncontrolled fire in the aft fairing of the strut and exposure of the wing fuel tank to high-temperature gasses and flames, and result in a potential ignition source for the fuel tank and reduced structural integrity of the wing, accomplish the following:

Installation of Seal

(a) Within 1,000 flight hours after the effective date of this AD, install a high-temperature silicone foam seal to fill the gap in the heat shield of the aft fairing of the strut on the left- and right-hand sides of the airplane. Do the installation according to Boeing Alert Service Bulletin 777-54A0015, dated January 18, 2001, except as provided by paragraph (b) of this AD. (Procedures for the installation include removing certain heat shield castings for the aft fairing of the strut, cleaning the area, bonding a foam seal to the upper surface of the heat shield cover plates, re-installing the heat shield castings, restoring the leveling compound and seal application, and doing a leak check of the aft fairing.)

“Operator's Equivalent Procedure”

(b) Though Boeing Alert Service Bulletin 777-54A0015, dated January 18, 2001, specifies that an “operator's equivalent procedure” may be used for the leak check described in the service bulletin, that leak check must be done according to Chapter 54-55-01 of the Boeing 777 Airplane Maintenance Manual, as specified in the service bulletin.

Alternative Methods of Compliance

(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, Seattle Aircraft Certification Office (ACO), FAA. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 2:

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

Special Flight Permits

(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.

Issued in Renton, Washington, on October 23, 2001.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.