[Federal Register Volume 64, Number 41 (Wednesday, March 3, 1999)]
[Rules and Regulations]
[Pages 10213-10216]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-5042]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-375-AD; Amendment 39-11060; AD 99-05-12]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, 
and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 737-100, -200, -300, -400, and -
500 series airplanes. This action requires removal of the float switch 
and wiring and inspection of the float switch wiring in the center fuel 
tank to detect discrepancies, and either reinstallation of existing 
float switch and wiring, or replacement of the float switch and wiring 
with a new float switch and wiring. This action also requires 
installation of Teflon sleeving over the wiring of the float switch. In 
lieu of the above mentioned requirements, this AD requires deactivation 
of the float switch, accomplishment of specific fueling procedures, and 
installation of Caution signs. This amendment is prompted by a report 
indicating that chafing of the direct current (DC) powered float switch 
wiring insulation in the center fuel tank has occurred on several 
airplanes. The actions specified in this AD are intended to detect and 
correct such chafing and the resultant arcing from the wiring to the 
in-tank conduit, which could present an ignition source inside the fuel 
tank and consequent fire/explosion.

DATES: Effective March 18, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 3, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before May 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-375-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 
98124-2207. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Dorr M. Anderson, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington

[[Page 10214]]

98055-4056; telephone (425) 227-2684; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received a report indicating 
that chafing of the direct current (DC) powered float switch wiring 
insulation in the center fuel tank has occurred on eight Boeing Model 
737-200 series airplanes. These airplanes had accumulated between 
32,000 and 85,000 total flight hours. Such chafing may be attributed to 
vibrational contact between the conduit and float switch wiring. 
Chafing of the float switch wiring insulation in the center fuel tank, 
if not corrected, could result in arcing from the wiring to the in-tank 
conduit, which could present an ignition source inside the fuel tank 
and consequent fire/explosion.

Similar Airplanes

    The center fuel tank float switch installation on certain Boeing 
Model 737-100, -300, -400, and -500 series airplanes is similar to that 
on the affected Boeing Model 737-200 series airplanes. Therefore, the 
FAA has determined that all of these models may be subject to the 
unsafe condition identified in this AD.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-28A1132, dated December 2, 1998, and Revision 1, dated January 15, 
1999. The alert service bulletin describes the following procedures:
    1. Removing the float switch and wiring from the center fuel tank, 
performing a visual 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), and performing corrective actions. (The major 
corrective actions include measuring the resistance between the wires 
and the float switch housing; reusing the existing float switch and 
wiring or replacing the discrepant float switch and wiring with a new 
float switch and wiring; installing double Teflon sleeving over the 
wiring of the float switch; and replacing any section of electrical 
conduit where arcing or leaking has occurred with a new section.)
    2. Deactivating the 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; or cut, stow, and splice the two wires for the float switch 
at the splices on the front spar), painting a Caution 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 installing an 
INOP placard on the fueling panel, as applicable.
    3. Performing modified fueling procedures following deactivation of 
the float switch.
    The FAA also has reviewed Boeing Telex M-7200-98-04486, dated 
December 1, 1998, which describes two manual fueling procedures for the 
center fuel tank after the float switch has been deactivated by either 
of the methods described above.
    Accomplishment of the actions specified in the alert service 
bulletin and telex is intended to adequately address the identified 
unsafe condition.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to detect and correct chafing of the float switch wiring 
insulation in the center fuel tank and the resultant arcing from the 
wiring to the conduit, which could present an ignition source inside 
the fuel tank and consequent fire/explosion. This AD requires 
accomplishment of the actions specified in the alert service bulletin 
and telex described previously; except as discussed below.
    This AD also includes a provision that supersedes the FAA-approved 
Master Minimum Equipment List (MMEL), in that it allows dispatch of the 
airplane with the center fuel tank float switch deactivated in 
accordance with Boeing Alert Service Bulletin 737-28A1132, until 
replacement float switches and wiring are available for installation. 
The FAA-approved MMEL allows dispatch of the airplane with the 
``Pressure Fueling System'' inoperative up to 10 days. (The float 
switch wiring circuit is part of the ``Pressure Fueling System.'') The 
FAA has been notified by the manufacturer that it will take 
approximately 18 months to obtain required parts from the issuance of 
Boeing Alert Service Bulletin 737-28-A1132, dated December 2, 1998. The 
FAA finds that the 18-month period will accommodate the time necessary 
for affected operators to order, obtain, and install the necessary 
parts required for the replacement of the float switch, without 
adversely affecting safety. The FAA also finds that such a provision 
will eliminate schedule disruptions. Absence of such operational relief 
could create a burden for operators if required parts were not readily 
available at certain airports or locations.

Differences Between the AD and the Relevant Alert Service Bulletin

    Operators should note that the applicability of this AD affects 
certain Boeing Model 737-100, -200, -300, -400, and -500 series 
airplanes, on which the center wing tanks are activated; excluding 
those airplanes equipped with center wing tank volumetric topoff 
systems, or alternate current (AC) powered center tank float switches. 
This differs from the effectivity listing of the referenced alert 
service bulletin. While it is assumed that an operator will know the 
models of airplanes that it operates, there is a potential that the 
operator will not know or be aware of specific items that are installed 
on its airplanes. For this reason, it may be necessary for operators to 
check their records to determine if center wing tank volumetric topoff 
systems, or alternate current (AC) powered center tank float switches 
have been installed on their fleet of airplanes. Such a check will 
identify airplanes that are subject to the unsafe condition of this AD.
    Operators also should note that, although the referenced alert 
service bulletin contains modified fueling procedures following 
deactivation of the float switch, this AD requires accomplishment of 
the manual fueling procedures specified in Boeing Telex M-7200-98-
04486, as described above. The FAA finds that the procedures specified 
in the telex are more detailed than those in the alert service 
bulletin. The procedures specified in the telex provide step-by-step 
fueling instructions for airplanes with a deactivated center tank float 
switch to minimize the possibility of fuel spills.
    Prior to utilizing these fueling procedures, this AD requires 
operators to ensure that airplane fueling crews are properly trained in 
accordance with the procedures specified in the telex, or the 
procedures approved by the FAA. Prior to each occurrence of fueling the 
airplane, this AD requires a check to verify that the fueling panel 
center tank quantity indicator is operative, and replacement of the 
indicator with a serviceable indicator, if necessary. Accomplishment of 
such training and a check will provide the proper safeguards necessary 
to minimize fuel spills during airplane fueling.

Interim Action

    The FAA is considering further rulemaking action to supersede this 
AD to require, within 18 months after accomplishment of the actions 
specified in paragraphs (c) and (d) of this AD, and within 15,000 
flight hours after

[[Page 10215]]

reinstalling any existing float switch having worn insulation and 
double Teflon sleeving, replacement of the float switch and wiring with 
a new float switch and wiring. However, the planned compliance time for 
these actions is sufficiently long so that prior notice and time for 
public comment will be practicable.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this rule by 
submitting such written data, views, or arguments as they may desire. 
Communications shall identify the Rules Docket number and be submitted 
in triplicate to the address specified under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-375-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will not have substantial direct 
effects 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, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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

    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

    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. Section 39.13 is amended by adding the following new 
airworthiness directive:

99-05-12 Boeing: Amendment 39-11060. Docket 98-NM-375-AD.

    Applicability: Model 737-100, -200, -300, -400, and -500 series 
airplanes, on which the center wing tanks are activated; excluding 
those airplanes equipped with center wing tank volumetric topoff 
systems, or alternate 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 (f) 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 detect and correct chafing of the float switch wiring 
insulation in the center fuel tank and the resultant arcing from the 
wiring to the in-tank conduit, which could present an ignition 
source inside the fuel tank and consequent fire/explosion, 
accomplish the following:
    (a) 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.
    (b) Remove the fueling float switch and wiring from the center 
fuel tank and perform a visual 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, or Revision 1, dated January 
15, 1999. Pay particular attention to the wire bundle where it 
passes through the wing pylon vapor seals and under the wire bundle 
clamps.
    (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 the alert service bulletin.
    (A) If the resistance is less than 200 megohms, prior to further 
flight, replace the float switch with a new float switch, and 
install double Teflon sleeving over the wiring of the float switch, 
in accordance with the alert service bulletin; except, if the 
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 the alert 
service bulletin.
    (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 the alert service bulletin; 
except, if the 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.

[[Page 10216]]

    (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 the alert 
service bulletin, and accomplish the requirements specified in 
paragraph (b)(1)(ii) of this AD.
    (ii) Perform a visual inspection to detect fuel leaks of the 
electrical conduit, in accordance with the alert service bulletin.
    (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 any section of the electrical conduit where the leak is with 
a new section, in accordance with the alert service bulletin. 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 
the alert service bulletin; 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.
    (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, or Revision 1 dated January 15, 
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 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 that shows a conservative maximum 
fuel capacity for the center tank on the underside of the right-hand 
wing near the fueling station door.
    (d) For airplanes on which the requirements specified in 
paragraph (c) of this AD have been accomplished: Accomplish the 
requirements specified in paragraph (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 2: 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 3: Where there are differences between the Boeing Alert 
Service Bulletin 737-28A1132 and this AD, the AD prevails.

    (e) Dispatch with the center fuel tank float switch deactivated, 
in accordance with Boeing Alert Service Bulletin 737-28A1132, dated 
December 2, 1998, or Revision 1, dated January 15, 1999, is allowed 
until replacement float switches and wiring are available for 
installation. Where there are differences between the Master Minimum 
Equipment List (MMEL) and the AD, the AD prevails.
    (f) 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, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA PMI, who may add 
comments and then send it to the Manager, Seattle ACO.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (g) 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.
    (h) Except as provided by paragraphs (d)(1) and (d)(2) of 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; 
and Boeing Telex M-7200-98-04486, dated December 1, 1998, as 
applicable. This incorporation by reference was approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51. Copies may be obtained from Boeing Commercial 
Airplane Group, 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 Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (i) This amendment becomes effective on March 18, 1999.

    Issued in Renton, Washington, on February 23, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-5042 Filed 3-2-99; 8:45 am]
BILLING CODE 4910-13-U