[Federal Register Volume 72, Number 131 (Tuesday, July 10, 2007)]
[Proposed Rules]
[Pages 37484-37487]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-13366]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28662; Directorate Identifier 2007-NM-014-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 
and -900 Series Airplanes; and Model 757-200, -200PF, -200CB, and -300 
Series Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing airplanes, identified above. This proposed AD would 
require inspecting to determine if certain motor-operated shutoff valve 
actuators for the fuel tanks are installed, and related investigative 
and corrective actions if necessary. This proposed AD would also 
require revising the Airworthiness Limitations (AWLs) section of the 
Instructions for Continued Airworthiness to incorporate AWL No. 28-AWL-
21, No. 28-AWL-22, and No. 28-AWL-24 (for Model 737-600, -700, -700C, -
800 and -900 series airplanes), and No. 28-AWL-23, No. 28-AWL-24, and 
No. 28-AWL-25 (for Model 757-200, -200PF, -200CB, and -300). This 
proposed AD results from a design review of the fuel tank systems. We 
are proposing this AD to prevent electrical energy from lightning, hot 
shorts, or fault current from entering the fuel tank through the 
actuator shaft, which could result in fuel tank explosions and 
consequent loss of the airplane.

DATES: We must receive comments on this proposed AD by August 24, 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: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue, SE., 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: Judy Coyle, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6497; 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-
28662; Directorate Identifier 2007-NM-014-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 Operations office

[[Page 37485]]

between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Operations office (telephone (800) 647-5527) is 
located on the ground floor of the West Building at the 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 for ignition sources inside fuel 
tanks caused by latent failures, alterations, repairs, or maintenance 
actions, which, in combination with flammable fuel vapors, could result 
in fuel tank explosions and consequent loss of the airplane.
    Boeing has found that, under specific conditions, it was possible 
for electrical current to flow through certain motor operated shutoff 
valve actuators in the fuel tank. Boeing has developed a new valve 
actuator to replace those actuators. A motor-operated shutoff valve 
actuator that does not have sufficient protection against electrical 
energy from lightning, hot shorts, and fault current, could allow 
electrical energy to enter the fuel tank through the actuator drive 
shaft, which could result in fuel tank explosions and consequent loss 
of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletins 737-28A1207, dated 
February 15, 2007, and 757-28A0088, dated January 25, 2007. Boeing 
Alert Service Bulletin 757-28A0088 describes procedures for inspecting 
to determine the part number (P/N) of motor-operated valve (MOV) 
actuators for the fuel tanks; Boeing Alert Service Bulletin 737-28A1207 
also specifies removing MOV actuators having a certain P/N. The service 
bulletins specify that no more work is necessary if the P/N is 
acceptable.
    For Boeing Model 737-600, -700, -700C, -800 and -900 series 
airplanes, the affected MOVs are at 3 locations: The left engine fuel 
shutoff (spar) valve, the right engine fuel shutoff (spar) valve, and 
the fuel crossfeed valve. For Boeing Model 757-200, -200PF, -200CB, and 
-300 series airplanes, the affected MOVs are at 6 locations for 
airplanes in the single crossfeed configuration, or at 7 locations for 
airplanes in the dual crossfeed configuration.
    If the P/N is not acceptable, the service bulletins specify related 
investigative and corrective actions as follows:
    For all airplanes: Reworking the index plate; reworking the adapter 
plate if necessary; installing the adapter/shaft plate with sealant; 
installing the index plate with sealant; installing a new MOV actuator 
on the index plate with sealant; installing bonding jumpers with 
sealant. For Boeing Model 737-600, -700, -700C, -800 and -900 series 
airplanes the actions also include installing shield ground terminals 
using sealed fay surface bonding for the main tank fuel quantity 
indicating system (FQIS). All of these actions include steps that 
specify measuring the electrical bonding resistance between various 
components and reworking the bonding if necessary.
    We have also reviewed Subsection F, ``AIRWORTHINESS LIMITATIONS--
FUEL SYSTEM AWLs,'' of Boeing 737-600/700/700C/700IGW/800/900 
Maintenance Planning Data (MPD) Document D626A001-CMR, Section 9, 
Revision May 2006; and Subsection G, ``AIRWORTHINESS LIMITATIONS--FUEL 
SYSTEM AWLs,'' of Boeing 757 MPD Document D622N001, Section 9, Revision 
October 2006 (hereafter referred to as Revisions May 2006 and October 
2006 of the MPDs). These sections of the MPDs describe the critical 
design configuration control limitations (CDCCL) and inspections 
applicable to the MOV installation. CDCCLs are limitation requirements 
to preserve a critical ignition source prevention feature of the fuel 
tank system design that is necessary to prevent the occurrence of an 
unsafe condition. The purpose of a CDCCL is to provide instruction to 
retain the critical ignition source prevention feature during 
configuration change that may be caused by alterations, repairs, or 
maintenance actions. A CDCCL is not a periodic inspection.
    Subsection F of Revision May 2006 of the Boeing 737-600/700/700C/
700IGW/800/900 MPD adds new fuel system AWLs 28-AWL-21 (lightning and 
fault current protection--MOV actuator), No. 28-AWL-22 (repair of the 
MOV actuator), and 28-AWL-24 (lightning and fault current protection--
MOV actuator).
    Subsection G of Revision October 2006 of the Boeing 757 MPD adds 
new fuel system AWLs No. 28-AWL-23 (lightning and fault current 
protection--MOV actuator), No. 28-AWL-24 (repair of the MOV actuator), 
and No. 28-AWL-25 (lightning and fault current protection--MOV 
actuator).
    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 the following actions:
     Inspecting to determine if certain motor-operated shutoff 
valve actuators for the fuel tanks are installed, and

[[Page 37486]]

related investigative and corrective actions if necessary.
     Revising the Airworthiness Limitations (AWLs) section of 
the Instructions for Continued Airworthiness to incorporate AWL No. 28-
AWL-21, No. 28-AWL-22, and No. 28-AWL-24 (for 737-600, -700, -700C, -
800 and -900 series airplanes).
     Revising the Airworthiness Limitations (AWLs) section of 
the Instructions for Continued Airworthiness to incorporate AWL No. 28-
AWL-23, No. 28-AWL-24, and No. 28-AWL-25 (for Model 757-200, -200PF, -
200CB, and -300).
    This proposed AD would also allow accomplishing the revision to the 
AWLs section of the Instructions for Continued Airworthiness in 
accordance with later revisions of the MPD as an acceptable method of 
compliance if they are approved by the Manager, Seattle Aircraft 
Certification Office, FAA.

Costs of Compliance

    There are about 2,916 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 1,406 airplanes of 
U.S. registry. The average labor rate is $80 per work hour.

                                                 Estimated Costs
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                                                                                  Number of U.S.-
                     Action                         Work hours       Cost per       registered      Fleet cost
                                                                     airplane        airplanes
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Inspection for MOV actuators....................               1             $80           1,406        $112,480
AWL revisions...................................               3             240           1,406         337,440
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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.


Sec.  39.13  [Amended]

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

Boeing: Docket No. FAA-2007-28662; Directorate Identifier 2007-NM-
014-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by August 
24, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-600, -700, -700C, -800 
and -900 series airplanes; and Boeing Model 757-200, -200PF, -200CB, 
and -300 series airplanes, certificated in any category; as 
identified in Boeing Alert Service Bulletins 737-28A1207, dated 
February 15, 2007, and 757-28A0088, dated January 25, 2007.

    Note 1: This AD requires revisions to certain operator 
maintenance documents to include new inspections and maintenance 
actions. Compliance with these limitations is required by 14 CFR 
43.16 and 91.403(c). For airplanes that have been previously 
modified, altered, or repaired in the areas addressed by these 
limitations, the operator may not be able to accomplish the actions 
described in the revisions. In this situation, to comply with 14 CFR 
43.16 and 91.403(c), the operator must request approval for revision 
to the airworthiness limitations (AWLs) in the Boeing 737-600/700/
700C/700IGW/800/900 Maintenance Planning Data (MPD) Document 
D626A001-CMR and the Boeing 757 MPD Document D622N001-9, as 
applicable, according to paragraph (h) of this AD.

Unsafe Condition

    (d) This AD results from a design review of the fuel tank 
systems. We are issuing this AD to prevent electrical energy from 
lightning, hot shorts, or fault current from entering the fuel tank 
through the actuator shaft, which could result in fuel tank 
explosions and consequent loss of the airplane.

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 Reference

    (f) The term ``service bulletin,'' as used in this AD, means the 
Accomplishment Instructions of the following service bulletins, as 
applicable:
    (1) For Model 737-600, -700, -700C, -800 and -900 series 
airplanes: Boeing Alert Service Bulletin 737-28A1207, dated February 
15, 2007; and
    (2) For Model 757-200, -200PF, -200CB, and -300 series 
airplanes: Boeing Alert Service Bulletin 757-28A0088, dated January 
25, 2007.

[[Page 37487]]

Inspection and Related Investigative/Corrective Actions

    (g) Within 60 months after the effective date of this AD: 
Inspect the applicable motor-operated valves (MOVs) to determine 
whether an MOV with the affected part number (P/N) identified in the 
Accomplishment Instructions of the applicable service bulletin is 
installed. A review of airplane maintenance records is acceptable in 
lieu of this inspection if the P/N of the part can be conclusively 
determined from that review. Do all applicable related investigative 
and corrective actions before further flight. Do all actions in 
accordance with the Accomplishment Instructions of the applicable 
service bulletin.

Revision of AWLs Section

    (h) Concurrently with the actions in paragraph (g) of this AD: 
Revise the AWLs section of the Instructions for Continued 
Airworthiness by incorporating the information in paragraphs (h)(1) 
and (h)(2) of this AD, as applicable. Accomplishing the revision in 
accordance with a later revision of the MPD is an acceptable method 
of compliance if the revision is approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA.
    (1) Section F., ``AIRWORTHINESS LIMITATIONS--FUEL SYSTEM AWLs,'' 
of Boeing 737-600/700/700C/700IGW/800/900 Maintenance Planning Data 
(MPD) Document D626A001-CMR, Section 9, Revision May 2006, into the 
MPD to incorporate AWL No. 28-AWL-21, No. 28-AWL-22, and No. 28-AWL-
24.
    (2) Section G., ``AIRWORTHINESS LIMITATIONS--FUEL SYSTEM AWLs,'' 
of Boeing 757 MPD Document D622N001, Section 9, Revision October 
2006, into the MPD to incorporate AWL No. 28-AWL-23, No. 28-AWL-24, 
and No. 28-AWL-25.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle ACO, FAA, has the authority to 
approve AMOCs for this AD, if requested in accordance with the 
procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

    Issued in Renton, Washington, on June 26, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E7-13366 Filed 7-9-07; 8:45 am]
BILLING CODE 4910-13-P