[Federal Register Volume 69, Number 143 (Tuesday, July 27, 2004)]
[Rules and Regulations]
[Pages 44580-44586]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-16676]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-78-AD; Amendment 39-13738; AD 2004-15-04]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200, -200C, -300, -
400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing airplane models, that currently 
requires either inspections for discrepancies of the fueling float 
switch wiring in the center fuel tank and follow-on actions, or 
deactivation of the float switch. This amendment requires replacing the 
float switches in the center and wing fuel tanks with new, improved 
parts; installing a conduit liner system in the center fuel tank; and 
replacing conduit assemblies in the wing fuel tanks with new parts, 
which terminates the existing requirements. For certain airplanes, this 
amendment also requires replacing certain existing sections of the 
electrical conduit in the center fuel tank with new conduit. This 
amendment also adds one additional airplane model to the applicability 
and removes another. The actions specified by this AD are intended to 
prevent contamination of the fueling float switch by moisture or fuel, 
and chafing of the float switch wiring against the fuel tank conduit, 
which could present an ignition source inside the fuel tank that could 
cause a fire or explosion. This action is intended to address the 
identified unsafe condition.

DATES: Effective August 31, 2004.
    The incorporation by reference of certain publications, as listed 
in the regulations, is approved by the Director of the Federal Register 
as of August 31, 2004.
    The incorporation by reference of certain other publications, as 
listed in the regulations, was approved previously by the Director of 
the Federal Register as of March 18, 1999 (64 FR 10213, March 3, 1999).

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the National 
Archives and Records Administration (NARA). For information on the 
availability of this material at NARA, call (202) 741-6030, or go to: 
http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

FOR FURTHER INFORMATION CONTACT: Sherry Vevea, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone 
(425) 917-6514; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 99-05-12, 
amendment 39-11060 (64 FR 10213, March 3, 1999); which is applicable to 
certain Boeing Model 737-100, -200, -300, -400, and -500 series 
airplanes; was published as a supplemental notice of proposed 
rulemaking (NPRM) in the Federal Register on June 11, 2003 (68 FR 
34843). (A correction of AD 99-05-12 was published in the Federal 
Register on March 9, 1999 (64 FR 11533)). The action proposed to 
continue to require inspection of the fueling float switch wiring in 
the center fuel tank to detect discrepancies, accomplishment of 
corrective actions, and installation of double Teflon sleeving over the 
wiring of the float switch. The action also proposed to add new 
requirements for replacement of the float switches with new, improved 
float switches and installation of a conduit liner system in the center 
fuel tank, and replacement of the float switches and conduit assemblies 
with new, improved float switches and conduit assemblies in the wing 
fuel tanks. (The action proposed that this replacement would terminate 
the requirements of the existing AD.) For certain airplanes, the action 
also proposed to require replacement of certain sections of conduit in 
the center fuel tank with new conduit. The action also proposed to add 
one additional airplane model to the applicability and remove another.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. The FAA has given due consideration to 
the comments received.

Request To Refer to Revised Service Information

    Several commenters request that we revise the supplemental NPRM to 
refer

[[Page 44581]]

to the latest service information issued by the airplane manufacturer. 
The commenters note that the work instructions in Boeing Alert Service 
Bulletin 737-28A1141, Revision 1, dated December 19, 2002, have been 
revised to correct errors in the installation instructions.
    We concur. Since the issuance of the supplemental NPRM, we have 
reviewed and approved Boeing Alert Service Bulletin 737-28A1141, 
Revision 2, dated August 21, 2003. Revision 2 of the service bulletin, 
among other things, modifies work instructions for installing the 
bonding strap to the float switch mounting bracket in the center fuel 
tank, modifies torque values for the B-nuts on the float switch cable 
conduit, and specifies that lock wire be installed on the boltheads on 
the front spar. Due to the nature of these changes, we have revised 
paragraphs (b)(1)(i)(A), (b)(1)(ii), and (h)(1) of this final rule to 
refer to Boeing Alert Service Bulletin 737-28A1141, Revision 2, as the 
appropriate source of service information for the replacement of float 
switches required by those paragraphs. Also, we have revised paragraph 
(i) of this final rule to give credit for actions accomplished before 
the effective date of this AD per the original issue or Revision 1 of 
that service bulletin, provided that the B-nuts on the float switch 
cable conduit are torqued to the correct values, the float switch 
bonding strap is installed and securely fastened to the float switch 
bracket or main structure, and lock wire is installed in the boltheads 
on the front spar, as stated in Revision 2 of the service bulletin. We 
find that this change does not expand the scope of the proposed AD but 
merely provides necessary clarification of the work instructions.

Request To Extend Compliance Time for Replacement

    Three commenters request that we extend the compliance time for the 
proposed replacement. One commenter requests that we extend the 
compliance time from 2 years to 36 months due to concerns about parts 
availability. The commenter notes that the replacement of the fuel tank 
float switch that would be required by the proposed AD is also required 
on Model 737-600, -700, -700C, -800, and -900 series airplanes by AD 
2002-26-18, amendment 39-13006 (68 FR 481, January 6, 2003). Also, 
another Boeing service bulletin specifies installing the same float 
switches on auxiliary tanks of Boeing Model 737 series airplanes. The 
other commenters request that we extend the compliance time from 2 
years to 4 years. One of these commenters states that this would enable 
operators to accomplish the replacements and installations during a 
scheduled heavy maintenance visit. We infer that the other commenter's 
request is intended to minimize the number of fuel tank entries by 
allowing the proposed actions to be accomplished at the same time as 
other ADs that require fuel tank entry.
    We do not concur with the commenters' request. We have confirmed 
with Boeing that the necessary parts will be available for the affected 
airplanes within the 2-year compliance time stated in this final rule. 
In developing an appropriate compliance time for this final rule, we 
considered the manufacturer's recommendation, the degree of urgency 
associated with the subject unsafe condition, and the maintenance 
schedules of affected operators. In light of all of these factors, we 
find that 2 years represents an appropriate interval of time for 
affected airplanes to continue to operate without compromising safety. 
We have made no change to this final rule in this regard.

Request To Allow Repetitive Inspections in Lieu of Replacement

    One commenter requests that we revise the supplemental NPRM to 
allow operators to perform repetitive inspections of the fueling float 
switches and wiring, at intervals not to exceed 30,000 flight hours, in 
lieu of accomplishing the replacement of the float switches and conduit 
assemblies with new, improved parts. The commenter explains that it has 
accomplished the actions currently required by AD 99-05-12 and has 
found no discrepancy and has installed double Teflon sleeving on the 
wiring for the float switch in the center fuel tank. The commenter also 
states that it has installed grease in the interior of the float switch 
electrical conduits per AD 93-17-02, amendment 39-8672 (58 FR 54945, 
October 25, 1993).
    We do not concur with the commenter's request. The repetitive 
inspections only address issues with the wiring. The repetitive 
inspections do not correct the unsafe condition in the float switch. We 
can better ensure long-term continued operational safety by 
modifications or design changes to remove the source of the problem, 
rather than by repetitive inspections. Long-term inspections may not 
provide the degree of safety necessary for the transport airplane 
fleet. This, coupled with a better understanding of the human factors 
associated with numerous repetitive inspections, has led us to consider 
placing less emphasis on special procedures and more emphasis on design 
improvements. The proposed replacement and installation requirements 
are consistent with these considerations. We have made no change to 
this final rule in this regard.

Request To Require Installation of Transient Suppression Devices (TSDs)

    Two commenters request that we require the installation of TSDs for 
the fuel tank float switches to limit the transfer of electrical energy 
and power through the float switch wires in lieu of requiring the 
installation of new, improved float switches and a conduit liner system 
or conduit assemblies. Both commenters note that a modification for 
installing TSDs on the float switches has been developed for use on 
other airplanes, including on Boeing Model 737-600, -700, -800, and -
900 series airplanes. One of the commenters considers that the proposed 
requirements to install improved float switches and associated 
modifications are not consistent with the requirements of Special 
Federal Aviation Regulation (SFAR) No. 88, ``Transport Airplane Fuel 
Tank System Design Review, Flammability Reduction, and Maintenance and 
Inspection Requirements'' (66 FR 23086, May 7, 2001). The commenter 
notes that the new, improved float switch is powered by 28 volts direct 
current (DC), which exceeds the intrinsically safe level for equipment 
located in fuel tanks, as defined by SFAR No. 88. The commenter states 
that installation of TSDs would be a more attractive solution for 
operators because installation of TSDs would not involve entry into and 
replacement of complex parts in the fuel tank.
    We agree in principle with the commenters' statements that 
installation of TSDs on the fuel tank float switches may be an 
acceptable alternative to the requirement to replace the float switches 
with new, improved float switches and install a conduit liner system or 
conduit assemblies. We have previously approved installation of TSDs on 
the float switches on Model 737-600, -700, -700C, -800, and -900 series 
airplanes. However, at this time, a float switch TSD has not been 
approved for installation on the airplane models affected by this final 
rule. Should a float switch TSD for these airplanes be developed and 
approved in the future, operators may request approval of an 
alternative method of compliance (AMOC) for the requirements of this 
final rule, as provided by paragraph (k)(1) of this final rule.
    With regard to the one commenter's concerns about potential non-

[[Page 44582]]

compliance with SFAR No. 88, we do not agree. We note that the design 
standards are contained within Part 25 (``Airworthiness Standards: 
Transport Category Airplanes'') of the Federal Aviation Regulations (14 
CFR part 25), not in SFAR 88. We agree that a finding of direct 
compliance with the requirements of part 25 could not be made for the 
new, improved float switch and conduit liner or conduit assemblies 
because the design is not fail-safe. However, we have approved the 
fueling float switch, conduit liner system, and conduit assemblies 
having a conduit liner, as providing a level of safety equivalent to 
the requirements of Sections 25.901 (``Powerplant installation'') and 
25.981(a) and (b) (``Fuel tank ignition prevention'') of the Federal 
Aviation Regulations (14 CFR 25.901 and 25.981), relative to the fuel 
tank float switch installation and maintenance instructions for the 
subject airplane models. We find that the new, improved design of the 
float switch provides an equivalent level of safety because of special 
compensating design features and maintenance that is required. The new, 
improved float switch is hermetically sealed and is more resistant than 
the old design to contamination by fuel or water. A new flexible 
ethylene tetrafluorethylene (ETFE) conduit liner installed in the float 
switch wiring conduit protects the wiring from chafing inside the 
conduit. Maintenance documents specify that this conduit liner be 
replaced with a new liner whenever the wiring is removed from the 
conduit for any reason. Also, the design of the new, improved float 
switch, conduit, liner, and wiring system will be listed as a Critical 
Design Configuration Control Limitation for the Model 737 fuel system, 
to ensure that operators do not modify the system without appropriate 
design review.
    We have made no change to this final rule in this regard.

Request To Revise Cost Impact Information

    One commenter states that the cost impact for replacing the float 
switches and installing a conduit liner or conduit assemblies is higher 
than stated in the supplemental NPRM. The commenter states that 87 work 
hours are required, and the cost of required parts is $7,500. A second 
commenter also states that the estimated cost of parts is conservative 
and that the actual cost is higher.
    We agree with the commenter's statement that the total number of 
work hours for accomplishing the required actions is somewhat higher 
than stated in the supplemental NPRM. Accordingly, we have revised the 
estimated work hours stated in the Cost Impact section of this final 
rule to 94.
    We do not concur with the commenters' request to revise the 
estimated cost of required parts. We note that the estimated cost of 
required parts, between $3,633 and $5,061, is consistent with figures 
provided in the referenced service bulletin. We have made no change to 
this final rule in this regard.

Request To Require Similar Actions on Auxiliary Fuel Tanks

    One commenter, the airplane manufacturer, requests that we revise 
the supplemental NPRM to refer to Boeing Alert Service Bulletin 737-
28A1192, Revision 1, dated August 21, 2003. This service bulletin 
describes procedures for replacing the fuel tank float switch and 
installing a conduit liner system on Model 737 series airplanes with 
auxiliary fuel tanks.
    We do not concur with the commenter's request. We may consider 
additional rulemaking to require replacing the fuel tank float switch 
with a new, improved float switch and installing a conduit liner system 
on Model 737 series airplanes with auxiliary fuel tanks. However, we 
have determined that it is not appropriate to add such a requirement to 
this AD. We have made no change to this final rule in this regard.

Request To Allow Installation of Existing Float Switch

    One commenter requests that we revise the proposed AD to remove 
paragraph (j). The commenter notes that this paragraph prohibits the 
installation of the existing float switch, part number F8300-146, as of 
the effective date of this AD. The commenter is concerned about the 
need to replace an inoperative main or center tank fuel float switch on 
an in-service airplane that has not been modified per Boeing Alert 
Service Bulletin 737-28A1141.
    We do not concur with the commenter's request. The new, improved 
float switch is more resistant to fuel and water contamination than the 
existing float switch. Fluid contamination in the existing float switch 
design could provide an electrical path between the float switch and 
the airplane structure, which could result in a potential ignition 
source in the fuel tank. Considering the criticality of the unsafe 
condition, we find that it would be inappropriate to allow installation 
of the existing float switch after the effective date of this final 
rule. However, in the case of a need to replace an inoperative main or 
center fuel tank float switch, paragraphs (c) and (d) of this final 
rule provide for deactivation of the float switch until the necessary 
replacement can be accomplished. No change to this final rule is 
necessary in this regard.

Request To Remove Inaccurate Statements

    One commenter requests that we revise the ``Actions Since Issuance 
of Previous Proposal'' section of the supplemental NPRM to remove the 
statement that ``the new conduit assemblies for the float switch 
eliminate sharp bends within the conduit. * * *'' The commenter notes 
that this statement is not true for the affected airplane models.
    We acknowledge that this statement is incorrect for the airplane 
models subject to this AD. This statement pertains to the new conduit 
assemblies that are installed in the center and wing fuel tanks on 
Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. 
However, the ``Actions Since Issuance of Previous Proposal'' section is 
not restated in this final rule, so no change is possible in this 
regard.
    The same commenter requests that we revise the ``Other Relevant 
Rulemaking'' section of the supplemental NPRM to clarify that this AD 
would not require the replacement of float switch conduit assemblies in 
the center fuel tank.
    We concur that this AD does not require replacement of all conduit 
assemblies in the center fuel tank. However, for airplanes subject to 
the inspections required by paragraph (b)(3)(ii)(A) of this final rule, 
this final rule does require replacement of any section of conduit 
where arcing or a fuel leak has occurred. Since the ``Other Relevant 
Rulemaking'' is not restated in this final rule, no change is possible 
in this regard.
    The same commenter requests that we delete the last sentence of 
paragraph (b) of the supplemental NPRM, which states, ``Pay particular 
attention to the wire bundle where it passes through the wing pylon 
vapor seals and under the wire bundle clamps.'' The commenter notes 
that the wing pylon vapor seal is not in the area of rework.
    We concur with the commenter's request, and have deleted this 
sentence from paragraph (b) of this final rule.

Request To Clarify Requirement To Replace Electrical Conduit

    One commenter requests that we revise the ``Summary'' and 
``Explanation of Proposed Requirements of Supplemental NPRM'' sections 
of the supplemental NPRM to clarify what sections of the conduit in the 
center fuel

[[Page 44583]]

tank need to be replaced with new conduit. Specifically, the commenter 
requests that we revise these sections to specify that sections of the 
conduit found to have damage due to arcing must be replaced.
    We acknowledge the commenter's concern, but we do not agree that 
any change to this final rule is necessary. The summary of an AD is 
intended to provide only a general description of the requirements of 
the AD. The reference in the ``Summary'' section to replacing ``certain 
existing sections of the electrical conduit'' is an accurate, although 
general, description of the required action. Further, we acknowledge 
that the wording of the ``Explanation of Proposed Requirements of the 
Supplemental NPRM'' section could have been more precise as to which 
sections of the conduit may need to be replaced. However, this section 
is not restated in this final rule, so no change is possible in this 
regard. We find that the requirement stated in paragraph (h)(2) of the 
supplemental NPRM and this final rule clearly states that any section 
of the electrical conduit in the center fuel tank where arcing or a 
leak occurred must be replaced with new conduit. We have made no change 
to this final rule in this regard.

Explanation of Additional Changes to Final Rule

    For clarification, we have revised paragraph (b)(4) of this final 
rule to refer specifically to Boeing Alert Service Bulletin 737-
28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; or 
Revision 2, dated June 17, 1999; instead of to ``the alert service 
bulletin.''
    Also, paragraph (e) of the supplemental NPRM states that dispatch 
with the float switch deactivated ``is allowed until replacement float 
switches and wiring are available for installation or until the 
compliance time for the replacement required by paragraph (h) of this 
AD.'' For clarification, we have revised that paragraph to state that 
dispatch with the float switch deactivated ``is allowed until 
replacement float switches and wiring are available for installation, 
but not later than the compliance time for the replacement required by 
paragraph (h) of this AD.''
    Also, paragraph (f) of the supplemental NPRM states that, ``If the 
actions required by paragraph (h) of this AD are accomplished within 
the compliance time specified in this paragraph, operators are not 
required to do paragraph (b) or (c) of this AD.'' Our intent was that 
accomplishment of paragraph (h) of this final rule also entails 
accomplishment of paragraph (h)(2) of this final rule (as applicable). 
Thus, for clarification, we have revised paragraph (f) of this final 
rule to explicitly state that operators must accomplish the 
requirements of paragraph (h)(2) for the provision in paragraph (f) of 
this final rule to apply.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
significantly increase the economic burden on any operator nor increase 
the scope of the AD.

Changes to 14 CFR Part 39/Effect on the AD

    On July 10, 2002, the FAA issued a new version of 14 CFR part 39 
(67 FR 47997, July 22, 2002), which governs the FAA's airworthiness 
directives system. The regulation now includes material that relates to 
altered products, special flight permits, and alternative methods of 
compliance (AMOCs). Because we have now included this material in part 
39, only the office authorized to approve AMOCs is identified in each 
individual AD. However, for clarity and consistency in this final rule, 
we have retained the language of the supplemental NPRM regarding that 
material.

Change to Labor Rate Estimate

    Since the issuance of the supplemental NPRM, we have reviewed the 
figures we have used over the past several years to calculate AD costs 
to operators. To account for various inflationary costs in the airline 
industry, we find it necessary to increase the labor rate used in these 
calculations from $60 per work hour to $65 per work hour. The cost 
impact information, below, reflects this increase in the specified 
hourly labor rate.

Cost Impact

    There are approximately 2,886 Model 737-200, -200C, -300, -400, and 
-500 series airplanes of the affected design in the worldwide fleet. 
The FAA estimates that 1,111 airplanes of U.S. registry will be 
affected by this AD.
    The removal and inspection of the fueling float switch in the 
center fuel tank and installation of double Teflon sleeving, which are 
provided as one alternative for compliance with AD 99-05-12, takes 
approximately 18 work hours per airplane to accomplish, at an average 
labor rate of $65 per work hour. Required parts cost approximately $30 
per airplane. Based on these figures, the cost impact of the removal 
and inspection of the float switch and installation of double Teflon 
sleeving, if accomplished, is estimated to be $1,200 per airplane.
    The deactivation of the float switch and installation of 
``Caution'' signs that are provided as the other alternative for 
compliance with AD 99-05-12, takes approximately 3 work hours per 
airplane to accomplish, at an average labor rate of $65 per work hour. 
Based on these figures, the cost impact of the deactivation and 
installation, if accomplished, is estimated to be $195 per airplane.
    The new replacement of float switches and installation of a conduit 
liner in the center fuel tank, and the replacement of float switches 
and conduit assemblies in the wing fuel tanks, that are required by 
this AD will take approximately 94 work hours per airplane to 
accomplish, at an average labor rate of $65 per work hour. Required 
parts will cost between $3,633 and $5,061 per airplane. Based on these 
figures, the cost impact of this replacement is estimated to be between 
$9,743 and $11,171 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the requirements of this 
AD action, and that no operator would accomplish those actions in the 
future if this AD were not adopted. The cost impact figures discussed 
in AD rulemaking actions represent only the time necessary to perform 
the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions.

Regulatory Impact

    The regulations adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under 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

[[Page 44584]]

substantial number of small entities under the criteria of the 
Regulatory Flexibility Act. A final evaluation has been prepared for 
this action and it is contained in the Rules Docket. A copy of it may 
be obtained from the Rules Docket at the location provided under the 
caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. Section 39.13 is amended by removing amendment 39-11060 (64 FR 
10213, March 3, 1999), corrected at 64 FR 11533, March 9, 1999, and by 
adding a new airworthiness directive (AD), amendment 39-13738, to read 
as follows:

2004-15-04 Boeing: Amendment 39-13738. Docket 99-NM-78-AD. 
Supersedes AD 99-05-12, Amendment 39-11060.
    Applicability: Model 737-200, -200C, -300, -400, and -500 series 
airplanes; on which the center wing tanks are activated; excluding 
those airplanes equipped with center wing tank volumetric top-off 
systems, or alternating current (AC) powered center tank float 
switches; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (k)(1) 
of this AD. The request should include an assessment of the effect 
of the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent contamination of the fueling float switch by moisture 
or fuel, and chafing of the float switch wiring against the fuel 
tank conduit, which could present an ignition source inside the fuel 
tank that could cause a fire or explosion, accomplish the following:

Requirements of AD 99-05-12

Compliance Time for Initial Action

    (a) For Model 737-200, -300, -400, and -500 series airplanes 
having line numbers (L/N) 1 through 3108 inclusive: Prior to the 
accumulation of 30,000 total flight hours, or within 30 days after 
March 18, 1999 (the effective date of AD 99-05-12, amendment 39-
11060), whichever occurs later, accomplish the requirements of 
paragraph (b) or (c) of this AD.

Initial Inspection: Procedures

    (b) Remove the fueling float switch and wiring from the center 
fuel tank and perform a detailed inspection of the float switch 
wiring to detect discrepancies (i.e., evidence of electrical arcing, 
exposure of the copper conductor, presence or scent of fuel on the 
electrical wires, or worn insulation), in accordance with Part 1 of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 
1999; or Revision 2, dated June 17, 1999. After the effective date 
of this AD, only Revision 2 may be used.

    Note 2: For the purposes of this AD, a detailed inspection is 
defined as: ``An intensive visual examination of a specific 
structural area, system, installation, or assembly to detect damage, 
failure, or irregularity. Available lighting is normally 
supplemented with a direct source of good lighting at intensity 
deemed appropriate by the inspector. Inspection aids such as mirror, 
magnifying lenses, etc., may be used. Surface cleaning and elaborate 
access procedures may be required.''

Initial Inspection: Follow-On Actions

    (1) If no discrepancy is detected, prior to further flight, 
accomplish either paragraph (b)(1)(i) or (b)(1)(ii) of this AD.
    (i) Measure the resistance between the wires and the float 
switch housing, in accordance with Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 
1999; or Revision 2, dated June 17, 1999.
    (A) If the resistance is less than 200 megohms, prior to further 
flight, replace the float switch and wiring with a new float switch 
and wiring, and install double Teflon sleeving over the wiring of 
the float switch, in accordance with Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 
1999; or Revision 2, dated June 17, 1999; or replace the float 
switch and wiring with a new, improved float switch and wiring in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-28A1141, Revision 2, dated August 21, 2003. 
After the effective date of this AD, only a new, improved float 
switch and wiring may be installed. If a replacement float switch 
and wiring are not available, prior to further flight, accomplish 
the requirements specified in paragraphs (c) and (d) of this AD.
    (B) If the resistance is greater than or equal to 200 megohms, 
prior to further flight, blow dirt out of the conduit, install 
double Teflon sleeving over the wiring of the float switch, and 
reinstall the existing float switch, in accordance with Boeing Alert 
Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, 
dated January 15, 1999; or Revision 2, dated June 17, 1999.
    (ii) Replace the float switch and wiring with a new float switch 
and wiring, and install double Teflon sleeving over the wiring of 
the float switch, in accordance with Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 
1999; or Revision 2, dated June 17, 1999; or replace the float 
switch and wiring with a new, improved float switch and wiring in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-28A1141, Revision 2, dated August 21, 2003. 
After the effective date of this AD, only a new, improved float 
switch and wiring may be installed. If a replacement float switch 
and wiring are not available, prior to further flight, accomplish 
the requirements specified in paragraphs (c) and (d) of this AD.
    (2) If any worn insulation is detected, and if no copper 
conductor is exposed, and if no evidence of arcing is detected; 
accomplish the requirements specified in either paragraph (b)(1)(i) 
or (b)(1)(ii) of this AD.
    (3) If any electrical arcing or exposed copper conductor is 
detected, prior to further flight, accomplish either paragraph 
(b)(3)(i) or (b)(3)(ii) of this AD.
    (i) Replace any section of the electrical conduit where the 
arcing occurred with a new section, in accordance with Boeing Alert 
Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, 
dated January 15, 1999; or Revision 2, dated June 17, 1999; and 
accomplish the requirements specified in paragraph (b)(1)(ii) of 
this AD.
    (ii) Perform a detailed inspection to detect fuel leaks of the 
electrical conduit, in accordance with Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998; Revision 1, dated January 15, 
1999; or Revision 2, dated June 17, 1999.
    (A) If no fuel leak is detected, prior to further flight, 
accomplish the requirements specified in paragraph (b)(1)(ii) of 
this AD. Repeat the inspection required by paragraph (b)(3)(ii) of 
this AD thereafter at intervals not to exceed 1,500 flight hours, 
until the replacement required by paragraph (b)(3)(ii)(B) of this AD 
is accomplished.
    (B) If any fuel leak is detected, prior to further flight, 
replace, with new conduit, any section of the electrical conduit 
where a leak is found, in accordance with Boeing Alert Service 
Bulletin 737-28A1132, dated December 2, 1998; Revision 1, dated 
January 15, 1999; or Revision 2, dated June 17, 1999. Prior to 
further flight after accomplishment of the replacement, accomplish 
the requirements specified in paragraph (b)(1)(ii) of this AD. 
Accomplishment of electrical conduit replacement constitutes 
terminating action for the repetitive inspection requirements of 
paragraph (b)(3)(ii)(A) of this AD.
    (4) If any presence or scent of fuel on the electrical wires is 
detected, prior to further flight, locate the source of the leak and 
replace the damaged conduit with a new conduit, in accordance with 
Boeing Alert

[[Page 44585]]

Service Bulletin 737-28A1132, dated December 2, 1998; Revision 1, 
dated January 15, 1999; or Revision 2, dated June 17, 1999; and 
accomplish the requirements specified in either paragraph (b)(1)(i) 
or (b)(1)(ii) of this AD, unless accomplished previously in 
accordance with paragraph (b)(1), (b)(2), or (b)(3) of this AD.

Deactivation of Float Switch

    (c) Accomplish the requirements specified in either paragraph 
(c)(1) or (c)(2) of this AD, in accordance with Part 2 of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
28A1132, dated December 2, 1998; Revision 1, dated January 15, 1999; 
or Revision 2, dated June 17, 1999.
    (1) Deactivate the center tank float switch (i.e., cut the two 
wires for the float switch at the splices on the front spar and cap 
and stow the four wire ends), paint a ``Caution'' sign that shows a 
conservative maximum fuel capacity for the center tank on the 
underside of the right-hand wing near the fueling station door, and 
install an INOP placard on the fueling panel.
    (2) Deactivate the center tank float switch (i.e., cut, stow, 
and splice the two wires for the float switch at the splices on the 
front spar), and paint a ``Caution'' sign that shows a conservative 
maximum fuel capacity for the center tank on the underside of the 
right-hand wing near the fueling station door.

Deactivation of Float Switch: Additional Requirements

    (d) For airplanes on which the requirements specified in 
paragraph (c) of this AD have been accomplished: Accomplish the 
requirements specified in paragraphs (d)(1), (d)(2), and (d)(3) of 
this AD.
    (1) Operators must ensure that airplane fueling crews are 
properly trained in accordance with the procedures specified in 
Boeing Telex M-7200-98-04486, dated December 1, 1998, or procedures 
approved by the FAA. This one-time training must be accomplished 
prior to utilizing the procedures specified in paragraph (d)(3) of 
this AD.
    (2) Prior to fueling the airplane, perform a check to verify 
that the fueling panel center tank quantity indicator is operative. 
Repeat this check thereafter prior to fueling the airplane. If the 
fueling panel center tank quantity indicator is not operative, prior 
to further flight, replace the fueling panel center tank quantity 
indicator with a serviceable part.
    (3) One of the two manual fueling procedures for the center fuel 
tank must be used for each fueling occurrence, in accordance with 
Boeing Telex M-7200-98-04486, dated December 1, 1998, or a method 
approved by the FAA.

    Note 3: For the purposes of this AD, the term ``the FAA,'' is 
defined in paragraph (d) of this AD as ``the cognizant Principal 
Maintenance Inspector (PMI).''


    Note 4: Where there are differences between Boeing Alert Service 
Bulletin 737-28A1132 and this AD, the AD prevails.

Deactivation of Float Switch: Dispatch

    (e) Dispatch with the center fuel tank float switch deactivated, 
in accordance with Boeing Alert Service Bulletin 737-28A1132, dated 
December 2, 1998; Revision 1, dated January 15, 1999; or Revision 2, 
dated June 17, 1999; is allowed until replacement float switches and 
wiring are available for installation, but not later than the 
compliance time for the replacement required by paragraph (h) of 
this AD. Where there are differences between the Master Minimum 
Equipment List (MMEL) and the AD, the AD prevails.

New Requirements of This AD

Compliance Time for Initial Action for Model 737-200C Series 
Airplanes

    (f) For Model 737-200C series airplanes having L/Ns 1 through 
3108 inclusive: Prior to the accumulation of 30,000 total flight 
hours, or within 30 days after the effective date of this AD, 
whichever occurs later, accomplish the requirements of paragraph (b) 
or (c) of this AD. (If the actions specified in paragraph (b) or (c) 
of this AD have been accomplished before the effective date of this 
AD, no further action is required by this paragraph.) If the actions 
required by paragraph (h) of this AD, including the replacement 
required by paragraph (h)(2) of this AD, are accomplished within the 
compliance time specified in this paragraph, operators are not 
required to do paragraph (b) or (c) of this AD.

Replacement of Conduit

    (g) For airplanes having L/Ns 1 through 3108 inclusive, on which 
the inspection required by paragraph (b)(3)(ii) of this AD has been 
accomplished prior to the effective date of this AD, and on which 
replacement of conduit specified in paragraph (b)(3)(ii)(B) has not 
been accomplished: Within 1,500 flight hours or 6 months after the 
effective date of this AD, whichever occurs first, replace, with new 
conduit, any section of the electrical conduit where arcing or a 
leak occurred, in accordance with the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-28A1132, Revision 2, dated June 
17, 1999. Such replacement of the conduit constitutes terminating 
action for the repetitive inspection requirements of paragraph 
(b)(3)(ii)(A) of this AD.

Replacement of Center and Wing Tank Float Switches

    (h) Within 2 years after the effective date of this AD, 
accomplish paragraphs (h)(1) and (h)(2) of this AD, as applicable. 
Except as provided by paragraph (j) of this AD, accomplishment of 
the actions in paragraphs (h)(1) and (h)(2) of this AD, as 
applicable, terminates the requirements of this AD.
    (1) For all airplanes: In the center fuel tank, replace the 
existing float switches with new, improved float switches, and 
install a conduit liner system; and in the wing fuel tanks, replace 
the existing float switches and conduit assemblies with new, 
improved float switches and conduit assemblies that include a liner 
system inside the conduit. Do these replacements in accordance with 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
737-28A1141, Revision 2, dated August 21, 2003.
    (2) For airplanes subject to the repetitive inspections required 
by paragraph (b)(3)(ii)(A) of this AD, on which the electrical 
conduit in the center fuel tank has not been replaced as specified 
in paragraph (b)(3)(ii)(B) or (g) of this AD: Prior to or 
concurrently with the replacement of the float switch in the center 
fuel tank required by paragraph (h)(1) of this AD, replace, with new 
conduit, any section of the center fuel tank electrical conduit 
where arcing or a leak occurred, in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
28A1132, Revision 2, dated June 17, 1999. Such replacement 
constitutes terminating action for the repetitive inspection 
requirements of paragraph (b)(3)(ii)(A) of this AD.

Credit for Previously Accomplished Actions

    (i) Replacement of float switches and conduit assemblies, and 
installations of conduit liner systems, as applicable, accomplished 
before the effective date of this AD in accordance with Boeing Alert 
Service Bulletin 737-28A1141, dated September 5, 2002; or Revision 
1, dated December 19, 2002; are considered acceptable for compliance 
with the corresponding action specified in this AD, provided that 
the requirements of paragraphs (i)(1), (i)(2), and (i)(3) of this AD 
are met.
    (1) The B-nuts on the float switch cable conduit must be torqued 
to the values specified in the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-28A1141, Revision 2, dated August 21, 
2003.
    (2) The float switch bonding strap must be installed and 
securely fastened to the float switch bracket or main structure, as 
specified in the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-28A1141, Revision 2, dated August 21, 2003.
    (3) Lock wire must be installed in the boltheads on the front 
spar, as specified in the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-28A1141, Revision 2, dated August 21, 
2003.

Parts Installation

    (j) As of the effective date of this AD, no person may install a 
float switch having part number F8300-146 on any airplane.

Alternative Method of Compliance

    (k)(1) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA. Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Seattle ACO.
    (2) Alternative methods of compliance, approved previously in 
accordance with AD 99-05-12, amendment 39-11060, are approved as 
alternative methods of compliance with the corresponding 
requirements of this AD.

    Note 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.


[[Page 44586]]



Special Flight Permits

    (l) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

Incorporation by Reference

    (m) Unless otherwise specified in this AD, the actions shall be 
done in accordance with Boeing Alert Service Bulletin 737-28A1132, 
dated December 2, 1998; Boeing Alert Service Bulletin 737-28A1132, 
Revision 1, dated January 15, 1999; Boeing Alert Service Bulletin 
737-28A1132, Revision 2, dated June 17, 1999; Boeing Alert Service 
Bulletin 737-28A1141, Revision 2, dated August 21, 2003; and Boeing 
Telex M-7200-98-04486, dated December 1, 1998; as applicable.
    (1) The incorporation by reference of Boeing Alert Service 
Bulletin 737-28A1132, Revision 2, dated June 17, 1999; and Boeing 
Alert Service Bulletin 737-28A1141, Revision 2, dated August 21, 
2003; is approved by the Director of the Federal Register in 
accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) The incorporation by reference of Boeing Alert Service 
Bulletin 737-28A1132, dated December 2, 1998; Boeing Alert Service 
Bulletin 737-28A1132, Revision 1, dated January 15, 1999; and Boeing 
Telex M-7200-98-04486, dated December 1, 1998; was approved 
previously by the Director of the Federal Register as of March 18, 
1999 (64 FR 10213, March 3, 1999).
    (3) Copies may be obtained from Boeing Commercial Airplanes, 
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, call (202) 741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html html.

Effective Date

    (n) This amendment becomes effective on August 31, 2004.

    Issued in Renton, Washington, on July 1, 2004.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-16676 Filed 7-26-04; 8:45 am]
BILLING CODE 4910-13-P