2011-1226. Airworthiness Directives; The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would result in all airplanes having new relays with a ground fault interrupter (GFI) feature. This proposed AD would require, depending on airplane configuration, doing certain wiring changes, replacing the fuel pump power control relays for the main, center and auxiliary tanks, as applicable, with new relays having a GFI feature, performing certain bonding resistance measurements, and modifying relay module assemblies. The proposed AD also would require revising the maintenance program to incorporate Airworthiness Limitations (AWLs) 28-AWL-23 (for Model 737-100, 737-200, and 737-200C series airplanes), and 28-AWL-22 (for Model 737-300, 737-400, and 737-500 series airplanes). This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent damage to the fuel pumps caused by electrical arcing that could introduce an ignition source in the fuel tank, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

DATES:

We must receive comments on this proposed AD by March 7, 2011.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, 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, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; e-mail me. [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Georgios Roussos, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2011-0028; Directorate Identifier 2009-NM-228-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

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 a fuel tank explosion and consequent loss of the airplane.

As part of an SFAR88 analysis, Boeing determined that the power control relays for the main tank fuel boost pumps, the center tank fuel boost pumps, and for certain airplanes, the auxiliary tank fuel boost pumps should be replaced with new relays having a ground fault interrupter (GFI) feature. The relays are located in the P6 circuit breaker panel in the flight compartment. The GFI relay feature is intended to protect the fuel boost pumps from damage caused from electrical arcing by removing electrical power from the pump if a ground fault is detected. Electrical arcing, if not prevented could introduce an ignition source in the fuel tank which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010. Depending on airplane configuration and on whether the actions in Boeing Alert Service Bulletin 737-28A1212, dated July 23, 2009, were accomplished, Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010, describes procedures for the following actions, depending on airplane configurations:

• Doing wiring changes,
• Replacing the fuel pump power control relays for the main, center and auxiliary tanks with new relays having a GFI feature,
• Doing certain bonding resistance measurements to verify certain bonding requirements are met, and
• Modifying the M181, M182, M183 relay module assemblies.

Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010, specifies a compliance time of 60 months for replacing the power control relays.

For certain airplanes, Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010, refers to BAE Systems Service Bulletin 65-49808-24-01, Revision 1, dated July 19, 2010, as an additional source of guidance for doing the modification of the relay module assemblies and bond resistance measurements.

In addition, we have reviewed Section 9 of Boeing 737-100/200/200C/300/400/500 Airworthiness Limitations (AWLs) and Certification Maintenance Requirements, D6-38278-CMR, Revision May 2009 (hereafter referred to as “Document D6-38278-CMR”). Document D6-38278-CMR describes, among other actions, new AWLs for the applicable fuel boost pumps that incorporate ground fault interrupter relays for certain Model 737-100, -200, and -200C airplanes (i.e., AWL 28-AWL-23), and for certain other Model 737-300, -400, and -500 airplanes (i.e., AWL 28-AWL-22). The AWL reference to boost pumps applies also to all pumps where the GFI has been installed by incorporating Boeing Alert Service Bulletin 737-28A1212.

FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This proposed AD would require accomplishing the actions specified in the service information described previously, except as described under “Difference Between the Proposed AD and Service Information.”

Difference Between the Proposed AD and Service Information

AWL 28-AWL-23 of Section 9 of Boeing 737-100/200/200C/300/400/500 Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), Document D6-38278-CMR, Revision May 2009, is applicable to Model 737-100, -200, and -200C airplanes, although it specifies only the Model 737-100 and -200 airplanes.

Costs of Compliance

We estimate that this proposed AD would affect 750 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Table—Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per product	Number of U.S.-registered airplanes	Fleet cost
Replacement of power control relays	4 to 9 1	$85	$14,500	$14,840 to $15,265 1	750	$11,130,000 to $11,448,750.1
Modification	5	85	0	$425	750	$318,750.
Maintenance program revision	1	85	0	$85	750	$63,750.
1 Depending on airplane configuration.

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 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 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. 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• 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

[Amended]

2. The FAA amends § 39.13 by adding the following new AD:

The Boeing Company: Docket No. FAA-2011-0028; Directorate Identifier 2009-NM-228-AD.

Comments Due Date

(a) We must receive comments by March 7, 2011.

Affected ADs

(b) None.

Applicability

(c) This AD applies to The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010.

Note 1:

This AD requires revisions to certain operator maintenance documents to include new inspections. Compliance with these inspections is required by 14 CFR 91.403(c). For airplanes that have been previously modified, altered, or repaired in the areas addressed by these inspections, the operator may not be able to accomplish the inspections described in the revisions. In this situation, to comply with 14 CFR 91.403(c), the operator must request approval for an alternative method of compliance according to paragraph (m) of this AD. The request should include a description of changes to the required inspections that will ensure the continued operational safety of the airplane.

Subject

(d) Air Transport Association (ATA) of America Code 28: Fuel.

Unsafe Condition

(e) This AD results from fuel system reviews conducted by the manufacturer. The Federal Aviation Administration is issuing this AD to prevent the damage to the fuel pumps caused by electrical arcing that could introduce an ignition source in the fuel tank, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

Compliance

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

Part 1: Wiring Changes, Relay Replacements, and Certain Bonding Resistance Measurements for Certain Airplanes

(g) For airplanes on which Boeing Alert Service Bulletin 737-28A1212, dated July 23, 2009, has not been incorporated as of the effective date of this AD: Within 60 months after the effective date of this AD, do the applicable action required by paragraph (g)(1) or (g)(2) of this AD.

(1) Airplanes without the M181, M182, and M183 supplier relay modules installed: Do the wiring changes; replace the fuel pump power control relays for the main, center, and auxiliary tanks, as applicable, with new relays having a ground fault interrupter (GFI) feature; and do certain bonding resistance measurements to verify that certain bonding requirements are met; in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010.

(2) Airplanes with the M181, M182, and M183 supplier relay modules installed: Modify the M181, M182, and M183 relay module assemblies, and do certain bonding resistance measurements to verify that certain bonding requirements are met, in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010.

Note 2:

Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010, refers to BAE Systems Service Bulletin 65-49808-24-01, Revision 1, dated July 19, 2010, as an additional source of guidance for doing the modification and certain bonding resistance measurements.

Part 2: Wiring Changes and Certain Bonding Measurements for Certain Airplanes

(h) For airplanes on which Boeing Alert Service Bulletin 737-28A1212, dated July 23, 2009, has been incorporated as of the effective date of this AD, and on which the M181, M182, and M183 supplier relay modules have not been installed: Within 60 months after the effective date of this AD, do the wiring changes and certain bonding measurements to verify that certain bonding requirements are met, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010.

Part 3: Certain Bonding Measurements for Certain Airplanes

(i) For airplanes on which Boeing Alert Service Bulletin 737-28A1212, dated July 23, 2009, has been incorporated as of the effective date of this AD, and that the M181, M182, and M183 supplier relay modules are installed: Within 60 months after the effective date of this AD, do certain bonding measurements to verify that certain bonding requirements are met, in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010.

Note 3:

Boeing Alert Service Bulletin 737-28A1212, Revision 1, dated August 27, 2010, refers to BAE Systems Service Bulletin 65-49808-24-01, Revision 1, dated July 19, 2010, as an additional source of guidance for doing the modification and certain bonding resistance measurements.

Maintenance Program Revisions

(j) Concurrently with accomplishing the actions required by paragraph (g), (h), or (i) of this AD, as applicable, or within 30 days after the effective date of this AD, whichever occurs later, revise the maintenance program by incorporating the applicable airworthiness limitation (AWL) specified in paragraph (j)(1) or (j)(2) of this AD.

(1) For Model 737-100, -200, and -200C series airplanes: Airworthiness Limitation 28-AWL-23 of Section 9 of Boeing 737-100/200/200C/300/400/500 AWL and Certification Maintenance Requirements (CMRs), Document D6-38278-CMR, Revision May 2009. The initial compliance time for the actions specified in AWL 28-AWL-23 is within 1 year after accomplishing the installation required by paragraph (g), (h), or (i) of this AD, or within 1 year after the effective date of this AD, whichever occurs later.

(2) For Model 737-300, -400, and -500 series airplanes: AWL 28-AWL-22 of Section 9 of Boeing 737-100/200/200C/300/400/500 Airworthiness Limitation (AWL) and Certification Maintenance Requirements (CMRs), Document D6-38278-CMR, Revision May 2009. The initial compliance time for the actions specified in AWL 28-AWL-22 is within 1 year after accomplishing the installation required by paragraph (g), (h), or (i) of this AD, or within 1 year after the effective date of this AD, whichever occurs later.

No Alternative Inspections or Inspection Interval

(k) After accomplishment of the action required by paragraph (g), (h), or (i) of this AD, as applicable, no alternative inspections or inspection intervals may be used, unless the inspections or intervals are approved as an alternative means of compliance in accordance with the procedures specified in paragraph (m) of this AD.

Credit for Actions Accomplished in Accordance With Earlier Revisions of AWLs

(l) Revising the maintenance program to incorporate AWLs 28-AWL-22 (for Model 737-300, -400, and -500 airplanes) and 28-AWL-23 (for Model 737-100, -200, and -200C airplanes) in accordance with paragraphs (g)(1) and (g)(2) of AD 2008-10-09 R1, amendment 39-16148, terminates the requirements of paragraph (j) of this AD.

Alternative Methods of Compliance (AMOCs)

(m)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Georgios Roussos, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office (ACO), 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Or, e-mail information to [e-mail].

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

Issued in Renton, Washington, on January 12, 2011.

Jeffrey E. Duven,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.