[Federal Register Volume 72, Number 107 (Tuesday, June 5, 2007)]
[Proposed Rules]
[Pages 30996-30998]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-10755]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28348; Directorate Identifier 2007-NM-060-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 
and -900 Series Airplanes

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 737-600, -700, -700C, -800 and -900 series 
airplanes. This proposed AD would require sealing the fasteners on the 
front and rear spar inside the main fuel tank and on the lower panel of 
the center fuel tank, inspecting the wire bundle support installation 
in the equipment cooling system bays to identify the type of clamp 
installed and determine whether the Teflon sleeve is installed, and 
doing related corrective actions if necessary. This proposed AD results 
from a design review of the fuel tank systems. We are proposing this AD 
to prevent arcing at certain fuel tank fasteners, in the event of a 
lightning strike or fault current event, 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 July 20, 2007.

[[Page 30997]]


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: Kathrine Rask, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6505; 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-
28348; Directorate Identifier 2007-NM-060-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'' 
(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 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.
    Boeing determined during the SFAR 88 review that certain non-
conductive fasteners, which penetrate the main and center fuel tanks, 
could be subject to lightning strikes or fault currents induced by 
short circuits. During a lightning strike or fault current event, 
electrical current may be conducted to those non-conductive fasteners, 
which if unsealed could create arcing inside the fuel tanks. This 
condition, if not corrected, could result in a fuel tank explosion and 
consequent loss of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-57A1279, dated 
January 24, 2007. The service bulletin describes procedures for the 
following actions (depending on airplane configuration):
     Sealing the fasteners on the front and rear spar inside 
the main fuel tank and on the lower panel of the center fuel tank;
     Inspecting the wire bundle support installation in the 
equipment cooling system bays to identify the type of clamp installed 
and determine whether the Teflon sleeve is installed;
     Replacing any incorrect clamp with a new correct clamp; 
and
     Installing any missing Teflon sleeving.
    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.

[[Page 30998]]

Costs of Compliance

    There are about 1,754 airplanes of the affected design in the 
worldwide fleet; of these, 645 airplanes are U.S. registered. The 
following table provides the estimated costs for U.S. operators to 
comply with this proposed AD, at an average hourly labor rate of $80.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                         Number of
                                                       Work     Average      Cost per      U.S.-
                   Action                      Group   hours     hourly      airplane    registered   Fleet cost
                                                               labor rate                airplanes
----------------------------------------------------------------------------------------------------------------
Sealant application.........................       1      62          $80       $4,960          586   $2,906,560
                                                   2      28           80        2,240           44       98,560
                                                   3      28           80        2,240           15       33,600
Inspection..................................       1       3           80          240          586      140,640
                                                   2       3           80          240           44       10,560
                                                   3       2           80          160           15        2,400
----------------------------------------------------------------------------------------------------------------

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-2007-28348; Directorate Identifier 2007-NM-
060-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by July 20, 
2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Model 737-600, -700, -700C, -800 and -900 
series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-57A1279, dated January 24, 2007.

Unsafe Condition

    (d) This AD results from a design review of the fuel tank 
systems. We are issuing this AD to prevent arcing at certain fuel 
tank fasteners, in the event of a lightning strike or fault current 
event, which, in combination with flammable fuel vapors, 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.

Fastener Sealant

    (f) Within 60 months after the effective date of this AD: Seal 
the fasteners on the front and rear spar inside the main fuel tank 
and on the lower panel of the center fuel tank, as applicable, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-57A1279, dated January 24, 2007.

Inspection

    (g) Within 60 months after the effective date of this AD: 
Perform a general visual inspection of the wire bundle support 
installation in the equipment cooling system bays to identify the 
type of clamp installed, and determine whether the Teflon sleeve is 
installed. Do these actions in accordance with the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-57A1279, dated 
January 24, 2007. Do all applicable corrective actions within 60 
months after the effective date of this AD in accordance with the 
service bulletin.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office (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 May 25, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E7-10755 Filed 6-4-07; 8:45 am]
BILLING CODE 4910-13-P