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Proposed Rule

Airworthiness Directives; Boeing Model 757 Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

Start Preamble

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 757-200, -200PF, -200CB, and -300 series airplanes. This proposed AD would require, for certain airplanes, reworking the spar bonding path and reapplying sealant; and, for certain other airplanes, testing the electrical bond between the engine fuel feed hose and the wing front spar and, if applicable, reworking the spar bonding path and reapplying sealant. This proposed AD would also require, for all airplanes, an inspection to ensure the electrical bonding jumper is installed between the engine fuel feed hose and the adjacent wing station. This proposed AD is prompted by the results of fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent arcing or sparking at the interface between the bulkhead fittings of the engine fuel feed tube and the front spar during a lightning strike, which could provide a possible ignition source for the fuel vapor inside the fuel tank and result in a fuel tank explosion.

DATES:

We must receive comments on this proposed AD by May 9, 2005.

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.
  • By 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.

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

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW, room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2005-20689; the directorate identifier for this docket is 2004-NM-197-AD.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Tom Thorson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6508; fax (425) 917-6590.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments Start Printed Page 14595regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2005-20689; Directorate Identifier 2004-NM-197-AD” in the subject line 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 submitted 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 website, 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 can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

Examining the Docket

You can 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 DMS receives them.

Discussion

We have examined the underlying safety issues involved in recent 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” (67 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 another 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 proposed 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.

In addition, we have received a report indicating that, during electrical bonding and grounding tests of Boeing Model 747 series airplane wing fuel tank penetrations, the bulkhead fittings of the engine fuel feed tube were found not to be electrically bonded to the front spar. The same condition is found on certain Model 707 series airplanes; on all Model 737-100, -200, -300, -400, and -500 series airplanes; on all Model 747 series airplanes; and on certain Model 757 and Model 767 series airplanes. We also received a report indicating that a lightning test showed a higher-than-expected electrical current in the engine fuel feed tubes inside the wing fuel tank on Model 747 series airplanes. This condition could also exist on certain Model 757 series airplanes.

If the bulkhead fittings of the engine fuel feed tubes are not electrically bonded, there is a potential for arcing or sparking at the interface between the bulkhead fittings of the engine fuel feed tube and the front spar during a lightning strike, which could provide a possible ignition source for the fuel vapor inside the fuel tank and result in a fuel tank explosion.

Related Rulemaking

On November 10, 2004, we issued notice of proposed rulemaking (NPRM) Docket No. FAA-2004-19680 (Directorate Identifier 2003-NM-215-AD), which is applicable to certain Boeing Model 767 series airplanes. That NPRM would require performing a test of the bonding resistance between the engine fuel feed tube fitting and the front spar, applying sealant on a hex nut inside the dry bay, and performing any applicable corrective actions. The actions specified by that NPRM are intended to prevent an ignition source from entering the fuel tank during a lightning strike event, which could cause a fuel tank explosion.

On July 15, 2004, we issued NPRM Docket No. FAA-2004-18759 (Directorate Identifier 2003-NM-280-AD), which is applicable to certain Boeing Model 707-100, -100B, -300, -300B (-320B Variant), -300C, and -E3A (Military) series airplanes; Model 720 and 720B series airplanes; Model 737-100, -200, -200C, -300, -400, and -500 series airplanes; and Model 747 series airplanes. That NPRM would require repetitive tests of the overwing fuel fill ports for certain wing tanks; an electrical bonding resistance test between the bulkhead fittings of the engine fuel feed tube and the front spar inside the fuel tank of the wings; other specified actions; and applicable corrective actions if necessary. The actions specified by that NPRM are intended to prevent arcing or sparking at the interface between the bulkhead fittings of the engine fuel feed tube and the front spar inside the fuel tank of the wings and between the overwing fuel fill ports and the airplane structure during a lightning strike. Such arcing or sparking could provide a possible ignition source for the fuel vapor inside the fuel tank and cause consequent fuel tank explosions.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletins 757-28A0076 (for Model 757-200, -200CB, and -200PF series airplanes); and 757-28A0077 (for Model 757-300 series airplanes); both dated August 27, 2004. The service bulletins describe procedures for testing Start Printed Page 14596the electrical bond between the engine fuel feed hose and the wing front spar; reworking the bonding path between the end fitting of the fuel hose and the front spar; adding sealant to hose fittings and tube couplings, as applicable; and performing a general visual inspection and applicable corrective actions to ensure that an electrical bonding jumper is installed between the engine fuel feed hose and the adjacent wing station 285.65 rib in the left and right wing fuel tanks.

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. Therefore, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Difference Between the Proposed AD and Referenced Service Bulletins.”

Difference Between the Proposed AD and Referenced Service Bulletins

Although the referenced service bulletins would allow operator's equivalent procedures to be used for aircraft maintenance manuals (AMM) referenced in the service bulletins, this proposed AD would require you to use the referenced AMMs except as provided in paragraph (j) of this proposed AD.

Costs of Compliance

There are about 1,040 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 700 airplanes of U.S. registry. The average labor rate is estimated to be $65 per work hour. Parts would be supplied from operator stock. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

Action/airplanes affectedWork hoursCost per airplane
Hose fitting and spar bonding rework and sealant application (Group 1 airplanes)11$715
Bonding test and sealant application (Group 2 airplanes that pass bonding test)9585
Bonding test, hose fitting and spar bonding rework and sealant application (Group 2 airplanes that fail bonding test)13845

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. See the ADDRESSES section for a location to examine the regulatory evaluation.

Start List of Subjects

List of Subjects in 14 CFR Part 39

End List of Subjects

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

Start Part

PART 39—AIRWORTHINESS DIRECTIVES

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

Start Authority

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

End Authority
[Amended]

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

Boeing: Docket No. FAA-2005-20689; Directorate Identifier 2004-NM-197-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by May 9, 2005.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 757-200, -200PF, and -200CB, series airplanes as listed in Boeing Alert Service Bulletin 757-28A0076, dated August 27, 2004; and Model 757-300 series airplanes as listed in Boeing Alert Service Bulletin 757-28A0077, dated August 27, 2004; certificated in any category.

Unsafe Condition

(d) This AD was prompted by the results of fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent arcing or sparking at the interface between the bulkhead fittings of the engine fuel feed tube and the front spar during a lightning strike, which could provide a possible ignition source for the fuel vapor inside the fuel tank and result in a fuel tank 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.

Service Bulletin References

(f) The term “service bulletin(s),” as used in this AD, means the Accomplishment Instructions of the following service bulletins, as applicable.

(1) For Model 757-200, -200CB, and -200PF series airplanes: Boeing Alert Service Bulletin 757-28A0076, dated August 27, 2004.Start Printed Page 14597

(2) For Model 757-300 series airplanes: Boeing Alert Service Bulletin 757-28A0077, dated August 27, 2004.

Hose Fitting and Spar Bonding Rework and Sealant Application

(g) For Group 1 airplanes as identified in the service bulletins: Within 48 months after the effective date of this AD, rework the spar bonding path between the end fitting of the fuel feed hose and the front spar, and apply sealant to the hose fitting on the forward and aft side of the front spar and to the fitting and tube coupling on both sides of the dry bay wall, in accordance with the service bulletins.

Bonding Resistance Test

(h) For Group 2 airplanes as identified in the service bulletins: Within 48 months after the effective date of this AD, do a bonding resistance test between the fuel feed hose and the front spars of the left and right wings, in accordance with the service bulletins.

(1) If the test meets required resistance limits, before further flight, apply sealant to the end fitting of the fuel feed hose on the aft side of the front spar and to the fitting and tube coupling on both sides of the dry bay wall, in accordance with the service bulletins.se

(2) If the test does not meet required resistance limits, before further flight, remove any existing sealant at the front spar; rework the spar bonding path between the end fitting of the fuel feed hose and the front spar to meet bonding resistance test requirements; and apply sealant to the end fitting of the fuel feed hose on the forward and aft sides of the front spar, and to the fitting and tube coupling on both sides of the dry bay wall, in accordance with the service bulletins.

Inspection of Electrical Bonding Jumper

(i) For all airplanes as identified in the service bulletins: Within 48 months after the effective date of this AD, perform a general visual inspection and applicable corrective actions to ensure that an electrical bonding jumper is installed between the engine fuel feed hose and the adjacent wing station 285.65 rib in the left and right wing fuel tanks, in accordance with the service bulletins.

Exception to Accomplishment Instructions in Service Bulletins

(j) Although Boeing Alert Service Bulletin 757-28A0076, and Boeing Alert Service Bulletin 757-28A0077, both dated August 27, 2004, permit operator's equivalent procedures (OEP), this AD would require you to use the referenced AMMs, except that operators may use their own FAA-approved OEPs to drain the left and right engine fuel tubes, to drain and ventilate the fuel tanks, and for entering the fuel tanks.

Alternative Methods of Compliance (AMOCs)

(k) 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.

Start Signature

Issued in Renton, Washington, on March 14, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 05-5698 Filed 3-22-05; 8:45 am]

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