Federal Aviation Administration (FAA), Department of Transportation (DOT).
Notice of proposed rulemaking (NPRM).
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would require an inspection for chafing of certain wire Start Printed Page 7698bundles located above the center fuel tank, corrective actions if necessary, and replacement of wire bundle clamps with new clamps. This proposed AD is prompted by the results of fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent chafed wire bundles near the center fuel tank, which could cause electrical arcing through the tank wall and ignition of fuel vapor in the fuel tank, and result in a fuel tank explosion.
We must receive comments on this proposed AD by April 1, 2005.
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-2005-20354; the directorate identifier for this docket is 2004-NM-166-AD.Start Further Info
FOR FURTHER INFORMATION CONTACT:
Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6485; fax (425) 917-6590.End Further Info End Preamble Start Supplemental Information
We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2005-20354; Directorate Identifier 2004-NM-166-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.
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.
Based on this process, we have determined that the actions identified in this proposed AD are necessary to reduce the potential of ignition sources near fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.
A Boeing and FAA team inspected several 737 airplanes as part of the SFAR 88 system safety analysis. The team identified wire bundles in close proximity of the center fuel tank. The wire bundles were located below the passenger compartment, above the center fuel tank, aft of station 540 at right buttock line (RBL) and left buttock line (LBL) 24.50. Although no chafing was found on these wire bundles, if these wire bundles chafe, they could arc through the center fuel tank wall, which could result in a fuel tank explosion.
Relevant Service Information
We have reviewed Boeing Service Bulletin 737-28-1208, dated July 8, 2004. For all airplane groups, as specified in the service bulletin, the service bulletin describes procedures for inspecting for chafed wire bundles located below the passenger compartment, above the center fuel tank, aft of station 540 to approximately station 663.75, at RBL and LBL 24.50, and corrective actions. Depending on the airplane group, the corrective actions include repairing any wire damage in accordance with chapter 20-Start Printed Page 769910-13 of the Boeing Standard Wiring Practices Manual (BSWPM) or an “approved equivalent procedure.” For all airplane groups, the service bulletin also includes procedures for replacing the wire bundle clamps located immediately aft of station 540. For certain airplane groups, the service bulletin includes procedures for adjusting a certain wire bundle clamp. 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 Service Bulletin.”
Difference Between the Proposed AD and Service Bulletin
For Group 1 airplanes, as specified in Boeing Service Bulletin 737-28-1208, the service bulletin states that operators may repair wire damage according to either chapter 20-10-13 of the BSWPM or an approved equivalent procedure. This proposed AD would require operators to accomplish the repair of any wire damage according to the procedures in the BSWPM. An approved equivalent procedure for the repair of wire damage may be used only if approved as an alternative method of compliance under the provisions of paragraph (h) of this proposed AD.
Where the service bulletin states that a specific chapter of the Boeing 737 Airplane Maintenance Manual or an approved equivalent procedure may be used for removing and re-installing passenger cabin furnishings, and removing and returning power to the airplane, an approved equivalent procedure may be used.
Clarification of Inspection Terminology
In this proposed AD, the “inspection” specified in the Boeing service bulletin is referred to as a “detailed inspection.” We have included the definition for a detailed inspection in a note in the proposed AD.
Costs of Compliance
This proposed AD would affect about 2,871 airplanes worldwide. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.
|Action||Work hours||Average labor rate per hour||Parts||Cost per airplane||Number of U.S.-registered airplanes||Fleet cost|
|Replacement of wire bundle clamps||2||65||$190||320||1042||333,440|
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.
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
- Air transportation
- Aviation 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:Start Part
PART 39—AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):
Boeing: Docket No. FAA-2005-20354; Directorate Identifier 2004-NM-166-AD.
Comments Due Date
(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by April 1, 2005.
(c) This AD applies to all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category.
(d) This AD was prompted by the results of fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent chafed wire bundles near the center fuel tank, which could cause electrical arcing through the tank wall and ignition of fuel vapor in the fuel tank, and result in a fuel tank explosion.
(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. Start Printed Page 7700
Inspection of Wire Bundles and Corrective Actions
(f) Within 60 months after the effective date of this AD: Perform a detailed inspection for chafing of the wire bundles located below the passenger compartment, above the center fuel tank, aft of station 540 to approximately station 663.75, right buttock line and left buttock line 24.50, and any applicable corrective actions, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Service Bulletin 737-28-1208, dated July 8, 2004. Any corrective actions must be done before further flight. Where the service bulletin states that repair of wire damage may be done in accordance with an “approved equivalent procedure,” the repair must be accomplished according to the chapter of the Boeing Standard Wiring Practices Manual specified in the service bulletin. Approved equivalent procedures may be used for removing and re-installing passenger cabin furnishings, and removing and returning power to the airplane.
For the purposes of this AD, a detailed inspection is: “An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.”
Adjustment/Replacement of Wire Bundle Clamps
(g) After performing the actions required by paragraph (f) of this AD: Before further flight, adjust and replace, as applicable, the wire bundle clamps located aft of station 540, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Service Bulletin 737-28-1208, dated July 8, 2004.
Alternative Methods of Compliance
(h) 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.
Issued in Renton, Washington, on February 6, 2005.
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 05-2836 Filed 2-14-05; 8:45 am]
BILLING CODE 4910-13-P