Airworthiness Directives; Boeing Model 777-200, -300, and -300ER Series Airplanes

Summary:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 777-200, -300, and -300ER series airplanes. This proposed AD would require installing Teflon sleeving under the clamps of the wire bundles routed along the fuel tank boundary structure, and cap sealing certain penetrating fasteners of the main and center fuel tanks. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent electrical arcing on the fuel tank boundary structure or inside the fuel tanks, which could result in a fire or explosion.

Table of Contents

Table of Figures

Dates:

We must receive comments on this proposed AD by March 15, 2007.

Addresses:

Use one of the following addresses to submit comments on this proposed AD.

DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.

Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.

Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, Washington, DC 20590.

Fax:(202) 493-2251.

Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for the service information identified in this proposed AD.

For further information contact:

Margaret Langsted, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6500; fax (425) 917-6590.

Supplementary information:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2007-27042; Directorate Identifier 2006-NM-225-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

The FAA has examined the underlying safety issues involved in fuel tank explosions on several large transport airplanes, including the adequacy of existing regulations, the service history of airplanes subject to those regulations, and existing maintenance practices for fuel tank systems. As a result of those findings, we issued a regulation titled “Transport Airplane Fuel Tank System Design Review, Flammability Reduction and Maintenance and Inspection Requirements” (66 FR 23086, May 7, 2001). In addition to new airworthiness standards for transport airplanes and new maintenance requirements, this rule included Special Federal Aviation Regulation No. 88 (“SFAR 88,” Amendment 21-78, and subsequent Amendments 21-82 and 21-83).

Among other actions, SFAR 88 requires certain type design (i.e., type certificate (TC) and supplemental type certificate (STC) holders to substantiate that their fuel tank systems can prevent ignition sources in the fuel tanks. This requirement applies to type design holders for large turbine-powered transport airplanes and for subsequent modifications to those airplanes. It requires them to perform design reviews and to develop design changes and maintenance procedures if their designs do not meet the new fuel tank safety standards. As explained in the preamble to the rule, we intended to adopt airworthiness directives to mandate any changes found necessary to address unsafe conditions identified as a result of these reviews.

In evaluating these design reviews, we have established four criteria intended to define the unsafe conditions associated with fuel tank systems that require corrective actions. The percentage of operating time during which fuel tanks are exposed to flammable conditions is one of these criteria. The other three criteria address the failure types under evaluation: Single failures, single failures in combination with a latent condition(s),and in-service failure experience. For all four criteria, the evaluations included consideration of previous actions taken that may mitigate the need for further action.

We have determined that the actions identified in this AD are necessary to reduce the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.

We have received a report that seven operators discovered pinched insulation or wiring damage under the clamps of wire bundles routed along the fuel tank boundary structure of Model 777 airplanes. In some cases, bare wires were discovered. Also, it was determined that certain penetrating fasteners of the main and center fuel tanks were not adequately sealed against fault currents induced by short circuits or lightning strikes, and that certain other fasteners of the center fuel tank had not been sealed during production. During a short circuit event or lightning strike, damaged wires could cause electrical arcing on the fuel tank boundary structure or conduct electrical current to unsealed fasteners that penetrate the fuel tanks, which could create arcing inside the fuel tanks. This condition, if not corrected, could result in a fire or explosion.

Relevant Service Information

We have reviewed the following service information:

• Boeing Alert Service Bulletin 777-57A0050, dated January 26, 2006 (applicable to Model 777-200, -200ER, -300, and -300ER airplanes), which describes procedures for installing Teflon sleeving under the clamps of the power feeder wire bundles routed along certain fuel tank boundary structure and for cap sealing selected fasteners of the main and center fuel tanks;

• Boeing Alert Service Bulletin 777-57A0051, dated May 15, 2006 (applicable to Model 777-200 and -300 airplanes), which describes procedures for cap sealing the spoilers numbers 5 and 10 outboard hinge fitting fasteners in the main fuel tanks; and

• Boeing Alert Service Bulletin 777-57A0057, dated August 7, 2006 (applicable to Model 777-200, -300, and -300ER airplanes), which describes procedures for cap sealing certain fasteners in the center fuel tanks that were not sealed during production.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Clarification of Model Number Reference

Although Alert Service Bulletin 777-57A0050 refers to “Model 777-200ER” airplanes, this is a European designation that does not apply to airplanes of U.S. registry. Therefore, the applicability of this proposed AD will not specify Model 777-200ER airplanes. However, U.S. operators should take any reference to Model 777-200ER airplanes in Alert Service Bulletin 777-57A0050 as applicable to Model 777-200 airplanes as designated by the type certificate data sheet.

Costs of Compliance

There are about 446 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 123 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD at an estimated labor rate of $80 per work hour.

Estimated Costs for Airplanes of U.S. Registry
Airplane groupWork hoursParts costCost perairplane Number of airplanesFleet cost
Group 1 278 $2,241 $24,481 19 $465,139
Group 2 358 2,241 30,881 104 3,211,624

Currently, there are no affected Group 3 airplanes on the U.S. Register. However, if a Group 3 airplane is imported and placed on the U.S. Register in the future, the required actions would take about 480 work hours, at an average labor rate of $80 per work hour. Required parts would cost about $2,241. Based on these figures, we estimate the cost of this AD to be $40,641 per airplane.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of subjects in 14 cfr part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-27042; Directorate Identifier 2006-NM-225-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by March 15, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 777-200, -300, and -300ER series airplanes, certificated in any category; as identified in the service bulletins specified in Table 1 of this AD.

Table 1.—Service Bulletins
Boeing Alert Service Bulletin—Revision level—Dated—
777-57A0050 Original January 26, 2006.
777-57A0051 Original May 15, 2006.
777-57A0057 Original August 7, 2006.

Note 1:

Although Alert Service Bulletin 777-57A0050 refers to “Model 777-200ER” airplanes, this is a European designation that does not apply to airplanes of U.S. registry. Therefore, the applicability of this AD will not specify Model 777-200ER airplanes. However, U.S. operators should take any reference to Model 777-200ER airplanes in Alert Service Bulletin 777-57A0050 as applicable to Model 777-200 airplanes as designated by the type certificate data sheet.

Unsafe Condition

(d) This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent electrical arcing on the fuel tank boundary structure or inside the main and center fuel tanks, which could result in a fire or explosion.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Corrective Actions

(f) Within 60 months after the effective date of this AD, install Teflon sleeving under the clamps of the wire bundles routed along the fuel tank boundary structure, and cap seal certain penetrating fasteners of the fuel tanks as applicable, in accordance with the Accomplishment Instructions of the applicable service bulletins specified in Table 1 of this AD.

Alternative Methods of Compliance (AMOCs)

(g)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Issued in Renton, Washington, on January 18, 2007. Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

References

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