[Federal Register Volume 63, Number 189 (Wednesday, September 30, 1998)]
[Rules and Regulations]
[Pages 52147-52152]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-25972]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-272-AD; Amendment 39-10808; AD 98-20-40]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100, -200, -300, SP, 
and SR Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to all Boeing Model 747-100, -200, -300, SP, and SR series 
airplanes, that requires the installation of shielding and separation 
of the electrical wiring of the fuel quantity indication system (FQIS). 
This amendment is prompted by a failure analysis of the FQIS, and by 
testing results, which revealed that excessive energy levels in the 
electrical wiring and probes of the fuel system could be induced by 
electrical transients. The actions specified by this AD are intended to 
prevent electrical transients, induced by electromagnetic interference 
(EMI), or electrical short circuit conditions from causing arcing of 
the FQIS electrical wiring or probes in the fuel tank(s). Such arcing 
could result in ignition of the fuel tank(s).

EFFECTIVE DATE: November 4, 1998.

ADDRESSES: Information pertaining to this amendment may be examined at 
the Federal Aviation Administration (FAA), Transport Airplane 
Directorate, Rules

[[Page 52148]]

Docket, 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: Chris Hartonas, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (425) 227-2864; fax (425) 
227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to all Boeing 747-100, -200, and -300 
series airplanes was published in the Federal Register on December 1, 
1997 (62 FR 63624). [An action to reopen the comment period for the 
proposal was issued on March 23,1998 (63 FR 14850, March 27, 1998).] 
That action proposed to require the installation of components for the 
suppression of electrical transients and/or the installation of 
shielding and separation of the electrical wiring of the fuel quantity 
indication system (FQIS).
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    Two commenters support the proposed rule.

Request To Withdraw Proposed AD: Lack of Evidence

    Three commenters, including the manufacturer, state that the 
proposed AD should be withdrawn or significantly delayed, based on the 
lack of conclusive evidence that the Trans World Airlines Flight 800 
accident on July 17, 1996 (hereinafter referred to as TWA Flight 800), 
which involved a Model 747-100 series airplane, was caused by failure 
of the FQIS components and wiring that is routed to the tanks. In 
addition, the manufacturer comments extensively on the features of the 
existing system that are intended to prevent an ignition source from 
existing in the fuel tanks due to FQIS wiring or component failures. 
The manufacturer further comments that it believes that the current 
design of the FQIS is safe in the originally delivered configuration, 
when it is maintained in accordance with the manufacturer's approved 
maintenance documents. The manufacturer states that multiple failures 
within the FQIS would be required to create an ignition source within a 
fuel tank.
    The FAA does not concur that the proposed AD should be withdrawn or 
delayed. The FAA agrees that no conclusive evidence exists that failure 
of the FQIS components or wiring that is routed to the tanks caused the 
TWA Flight 800 airplane accident. However, during such accidents, 
evidence that could lead to a conclusive identification of the cause of 
the accident is often destroyed. Even without the destruction caused by 
the accident, there often is no specific physical evidence of low-
energy electrical arcing. In addition, in consideration of the amount 
of wiring installed on a Boeing Model 747 series airplane, and in 
consideration of the amount of damage to the wiring that occurred 
during the airplane fire, breakup, and subsequent recovery, conclusive 
identification of a specific wire that was damaged before the fire and 
breakup is extremely unlikely.
    Following the determination that a fire in the center wing fuel 
tank of the TWA Flight 800 airplane was the initial event in the 
airplane breakup, and the determination that the fire was not caused by 
an external source such as a bomb or missile, the National 
Transportation Safety Board (NTSB) has necessarily used systems 
analysis methods to determine what systems on the airplane are most 
likely to have been the source of ignition energy. That analysis 
included an examination of system failure modes and effects, an 
examination of service history, and examinations of similar airplanes. 
It was that analysis that led the FAA to propose the requirements 
specified in the notice of proposed rulemaking (NPRM).
    In commenting on the specific design features of the FQIS on Model 
747 series airplanes, the manufacturer points out that multiple 
independent failures would be required to create an FQIS-related 
ignition source in the fuel tank, implying that such an event is 
therefore impossible. The FAA agrees that more than one failure would 
be required to create an ignition source inside the fuel tank. The fact 
that fuel tank explosions on Model 747 series airplanes have been rare 
would seem to support a claim that single failures have not been the 
cause of fuel tank explosions. However, during the accident 
investigation, the FQIS safety analysis and the examinations of Model 
747 series airplanes performed by the NTSB revealed several scenarios 
where a combination of a latent failure or aging condition within the 
fuel tank and a subsequent single failure or electrical interference 
condition outside the tank can cause an ignition source to occur inside 
a fuel tank.
    Examples of these in-tank and out-of-tank conditions that can 
contribute to a multiple-failure ignition scenario were found in 
airplane service records and on airplanes that were inspected by the 
FAA and the NTSB. Various center wing fuel tanks were found with 
conductive debris in the tanks, damaged FQIS wire insulation at the 
fuel probes, and contamination of probes and in-tank wiring by 
conductive copper/sulfur or silver/sulfur films. Each of these 
conditions can create latent potential ignition locations inside the 
fuel tank.
    In addition, several conditions have been identified that can lead 
to sufficient energy in the FQIS wiring to create an ignition source if 
combined with one of the latent conditions described above. For 
example, electromagnetic coupling between systems routed together in 
bundles can occur. In addition, direct short circuit conditions can 
occur in wire bundles containing FQIS wiring. Airplanes were found with 
aluminum drill shavings on and inside various wire bundles in several 
locations between the flight deck and the fuel tank. Such shavings can, 
with vibration or other motion, cut through wire insulation and provide 
a conductive path between wires in a bundle. Service history contains 
records of wire bundle fires, which may have been due to such 
conditions. An examination of one wire bundle involved in such a fire 
revealed the presence of aluminum globules, presumably from molten 
shavings.
    The manufacturer also stated that, if a failure in a wire bundle 
involving the FQIS were to occur, the FQIS indications would be 
affected and the failure would be noted and repaired. No arc would be 
created inside the fuel tank due to the inherently safe design of the 
in-tank components and wiring. The FAA does not agree. If one of the 
latent in-tank conditions discussed above existed on the accident 
airplane, the first indication of a wire bundle failure or 
electromagnetic interference (EMI) event outside the tank may have been 
ignition of the fuel vapor in the tank. In the minutes immediately 
preceding the in-flight breakup of the TWA Flight 800 airplane, the 
cockpit voice recorder indicates that the crew noticed a fuel flow 
indicator that was providing erratic indications. Such indications 
could have been due to a failure occurring in a wire bundle. The NTSB 
investigation determined that the fuel flow indicator wiring was routed 
in the same wire bundle as FQIS wiring on the TWA Flight 800 airplane.
    An examination of the service history for transport category 
airplanes on which shielding and separation of the

[[Page 52149]]

FQIS wiring from other systems have been incorporated has shown that 
fewer fuel tank fire/explosion events have occurred (a tabulation of 
transport airplane fuel tank fires was included in the FAA Notice of 
Request for Comments on NTSB Safety Recommendations published in the 
Federal Register on April 3, 1997 (62 FR 16014)). The two most recent 
fuel tank explosion accidents--a Boeing Model 737-300 series airplane 
operated by Philippine Airlines in 1990, and a Boeing Model 747-100 
series airplane operated as TWA Flight 800 in 1996--remain unsolved, 
and both airplane types follow the wiring practices addressed by this 
rule.
    Therefore, the FAA has determined that, to address the potential 
for fuel tank ignition due to a latent failure plus one subsequent 
failure, the type design of the Model 747 series airplane must be 
brought up to the same wiring standards as other transport category 
airplanes certificated during the same time period that the Model 747 
series airplane was certificated. (Similar rulemaking has been proposed 
for Model 737 series airplanes. Reference Rules Docket No. 98-NM-50-AD 
(63 FR 38524, April 22, 1998).) No change to this final rule is 
necessary.

Request To Withdraw Proposed AD: Inaccurate Test Results

    Four commenters state that the proposed AD should be withdrawn and 
the problem studied further. The commenters claim that the results of 
laboratory EMI testing performed by the manufacturer are not 
representative of actual conditions on an airplane.
    These commenters further state that results of additional testing 
performed by the manufacturer on an airplane did not agree with the 
findings obtained in the laboratory, and showed much lower levels of 
electromagnetic coupling between the FQIS and other systems on the 
airplane. The FAA does not concur that the proposed AD should be 
withdrawn. The laboratory testing performed by the manufacturer was 
based on an industry-accepted procedure (FAA Advisory Circular 21-16C, 
``Radio Technical Commission for Aeronautics'' Document DO-160C). The 
test set-up and procedure re-create a well-known electrical transient 
event resulting from switching of airplane electrical systems.
    The industry-accepted test set-up and procedure were developed by 
industry with key support from the manufacturer, and were based, in 
part, on data provided by the manufacturer for typical switching 
transients on the manufacturer's airplanes.
    Also, the FAA has determined that the test procedures used during 
the manufacturer's airplane test were not representative of all the 
possible conditions on an airplane in operation. The test was performed 
on an out-of-service airplane with only some of the relevant systems 
powered and switched. No attempt was made to represent any system 
failure conditions or compromised shielding/grounding provisions on the 
systems that were powered and switched. Also, because of the way 
airplane wire bundles are manufactured and installed, significant 
variation in levels of coupling among systems has been seen in the past 
and would be expected on Model 747 series airplanes.
    Moreover, the FAA's determination of the existence of an unsafe 
condition is not wholly dependent on the results of the tests discussed 
above. In the FQIS system safety analysis and airplane inspections 
performed by the NTSB, several tank ignition scenarios were identified 
involving a combination of a latent failure or aging condition inside 
the fuel tank and a subsequent failure or electromagnetic coupling 
outside the tank. Various FAA and NTSB activities identified actual 
examples of, or the specific potential for, each of those types of 
contributing conditions. The FAA has proposed a separate AD action to 
address contributing in-tank failure or aging conditions that have been 
identified. [Reference Rules Docket No. 98-NM-163-AD (63 FR 39765, 
dated July 24, 1998).] This final rule is intended to address the out-
of-tank contributing conditions that could lead to tank ignition.
    By requiring ``best practices'' to be used both inside the tank (to 
eliminate the possibility for the creation of latent ``spark-gap'' 
locations in the event of high voltage on the FQIS wires) and outside 
the tank (to avoid introduction of ignition energy onto the FQIS 
wires), the FAA believes that the FQIS design of the Model 747 series 
airplane will meet appropriate fail-safe standards. The modified design 
will then provide the level of safety (i.e., tank ignition events 
should never occur) intended by the regulations in place at the time of 
original certification of the design, and the unsafe condition will be 
eliminated from this threat. No change to the final rule is necessary.

Request To Withdraw Proposed AD: Potential for Other Safety 
Problems

    Seven commenters state that the proposed rule should be withdrawn 
and the need for the rule should be studied further. The commenters are 
concerned that the proposed changes may introduce other unforeseen 
problems onto an airplane that has an excellent safety record. The 
commenters are specifically concerned about transient suppression 
devices reducing the accuracy of the FQIS and the replacement of wiring 
causing damage to remaining wiring on older airplanes. These commenters 
also express concern that transient suppression devices could have 
latent failure conditions under which electrical transients would not 
be suppressed, and therefore would require added repetitive inspections 
or tests.
    The FAA does not concur that the proposed AD should be withdrawn. 
However, the FAA agrees with comments from the manufacturer and one of 
the operators that the use of transient suppression devices to perform 
a critical function of preventing tank ignition is new, and that the 
industry should be cautious in exploring that option. Therefore, the 
FAA is not including a requirement for the incorporation of such 
devices in the final rule. The FAA instead is requiring that the FQIS 
wiring be shielded and separated from other wiring, as explained 
previously. This requirement is merely a subset of those requirements 
specified in the proposed AD. The modified wiring configuration 
proposed by the manufacturer caps and stows the existing wiring and 
requires the new wiring to be installed as a separate bundle in most 
parts of the airplane. This method minimizes the disturbance of 
existing wiring, which reduces the likelihood that additional problems 
will be caused by the modification of the FQIS wiring. The FAA has 
revised the final rule to eliminate the proposed requirement for 
installation of transient suppression devices.

Request To Delay Issuance of the AD: Make Service Information 
Available

    Two commenters, including the manufacturer of FQIS components, 
state that the proposed AD should not be issued until service 
information to accomplish the required actions is available from the 
manufacturer. These commenters state that the cost of the proposed rule 
could not be assessed accurately in the absence of service information, 
and that a significant portion of the proposed compliance time would be 
used up in the preparation of service information.
    The FAA does not concur. The FAA does not consider that delaying 
this action until after the release of the service bulletin planned by 
the manufacturer is warranted because sufficient technology currently 
exists to devise and install the required features within the 
compliance time. However,

[[Page 52150]]

paragraph (a) of the final rule has been revised to allow 36 months for 
the modification of airplanes. The extension of the compliance time 
afforded by this change is intended to allow sufficient time for the 
preparation of a manufacturer's service bulletin and for the subsequent 
modification of the affected airplanes during scheduled maintenance. 
The FAA has determined that this extension of the compliance time will 
not have a significant adverse effect on the safety of the fleet of 
Model 747 series airplanes.
    At the time the NPRM was issued, the manufacturer had not prepared 
service information with specific cost information; the FAA estimated 
the costs based on similar modifications accomplished previously on 
other airplane models. The cost estimate has been revised based on 
information provided by the manufacturer, as discussed below.

Request To Delay Issuance of the AD Until a Meeting Is Held

    One commenter states that the rule should be withdrawn or delayed 
until a meeting can be held among representatives of operators, 
manufacturers, and the FAA. The FAA does not concur. The commenter 
provided no technical justification for the proposed delay. As 
indicated previously, the compliance time has been extended from 12 
months, as proposed, to 36 months in this final rule. To delay this 
action further would be inappropriate, since the FAA has determined 
that an unsafe condition exists and that affected airplanes must be 
modified to ensure continued safety. No change to the AD is necessary.

Request To Extend Compliance Time

    Seven commenters, including the manufacturer, a vendor of transient 
suppression systems, and several operators, state that a longer 
compliance time should be allowed to allow modification of airplanes 
during heavy maintenance activities scheduled previously and to allow 
time for service information to be prepared. The manufacturer states 
that 18 to 24 months would be required to prepare service information.
    The FAA concurs partially. Although, as explained previously, the 
FAA does not agree that 18 to 24 months would be required solely to 
prepare service information, the FAA does agree that schedule 
interruptions should be minimized in performing the modifications to 
the Model 747 series airplane fleet. The FAA has attempted to determine 
a compliance time that provides for the most timely modification 
possible without causing unnecessary schedule interruptions. As stated 
previously, the FAA has revised paragraph (a) of the final rule to 
extend the compliance time to 36 months for accomplishment of the 
modification. This compliance time is expected to allow sufficient time 
for preparation of service information, and for the affected airplanes 
to be modified during scheduled ``C'' or ``D'' checks.

Preference for a Specific Design Solution

    Three commenters, including the manufacturer, propose no specific 
change to the rule, but state a preference for a particular design 
change to address the unsafe condition. The manufacturer states that it 
believes that wire separation and shielding is currently the preferable 
solution because of concerns about transient suppression devices 
reducing the accuracy of the fuel quantity indication and concerns 
about those devices having latent failure conditions under which 
electrical transients would not be suppressed. Another commenter, an 
operator, prefers that transient suppression alone be used because it 
would be less costly and disruptive to install. A specific technical 
and marketing proposal for transient suppression devices was submitted 
by a vendor of such devices for other types of installations.
    The FAA infers that the commenters request that a particular design 
be required rather than offering optional methods of compliance. The 
FAA concurs partially. As discussed previously, the FAA agrees that 
wire separation and shielding provide the preferred design solution. 
Based on comments from the manufacturer and on its own further 
analysis, the FAA has determined that transient suppression devices 
alone may not meet the intent of the rule. The FAA has concerns that 
transient suppression devices may have latent failure modes that render 
the transient suppression function inoperative, or may have failure 
modes that may allow introduction of high voltage signals into the fuel 
tank that otherwise would not have occurred.
    Based on the comments and the FAA's concerns, paragraph (a) of the 
final rule has been revised to eliminate the general requirement for 
transient suppression. Operators that have specific design changes 
other than those required by the AD that may provide an acceptable 
level of safety may request approval of an alternative method of 
compliance in accordance with paragraph (b) of the AD.

Request for Inclusion of Optional Method of Compliance

    Three commenters suggest that the installation of a BFGoodrich 
Aerospace FQIS be allowed as an optional method of compliance in the 
proposed AD. The commenters state that the BFGoodrich system, already 
approved by a Supplemental Type Certificate and installed on 
approximately 75 airplanes, incorporates shielding and separation of 
the FQIS wiring from the wiring for other airplane systems.
    The FAA does not concur. Until specific design data are reviewed, 
the FAA cannot determine whether the BFGoodrich design should be 
approved as an alternative method of compliance. To delay this action 
while the FAA reviews the BFGoodrich design would be inappropriate, 
since the FAA has determined that an unsafe condition exists and that 
affected airplanes must be modified to ensure continued safety. 
Interested operators may request approval of an alternative method of 
compliance in accordance with the provisions of paragraph (b) of the 
AD. No change to the final rule is necessary.

Request To Revise Cost Estimate of the Proposed AD

    Three commenters propose no specific change to the rule, but 
disagree with the cost estimate in the proposed rule, and offer 
differing specific cost estimates. One commenter, an operator, states 
that at least 200 work hours per airplane would be required to perform 
the proposed modification, and even more hours would be required if the 
FQIS wire routing is changed significantly. A vendor of FQIS's states 
that, based on its own experience retrofitting such systems in Model 
747 series airplanes, 600 to 1,200 work hours per airplane would be 
required to perform the proposed modifications. The manufacturer states 
that 450 work hours and $9,000 for parts would be required to separate 
and shield the FQIS wiring, and that 16 to 24 work hours and $25,000 
for parts would be required to install transient suppression devices.
    The FAA infers that the commenters are requesting revision of the 
cost impact information of the AD. The FAA concurs. At the time the 
NPRM was issued, the manufacturer had not prepared service information 
with specific cost information. The FAA made an estimate of the costs 
based on similar modifications accomplished previously on other 
airplane models. The cost estimate in this final rule has been revised 
based on information provided by the manufacturer, and now reflects 
that modification of affected

[[Page 52151]]

Model 747 series airplanes to install shielded FQIS wiring and to 
separate the FQIS wiring from other wiring is expected to require 450 
work hours and $9,000 for parts.

Request for Clarification of Affected Fuel Tanks

    One commenter states that the proposed AD refers only to fuel tanks 
and is not clear as to whether it is intended to apply to all fuel 
tanks or just the center wing fuel tank. The FAA concurs that 
clarification is necessary, and has changed the final rule to clearly 
indicate that it is applicable to all fuel tanks.

Clarification of Systems Affected

    Since the issuance of the NPRM, the FAA recognized that the 
proposed AD may be unclear with respect to which electrical circuits 
were intended to be affected by the proposed AD. The FAA considers the 
FQIS wiring to include all electrical circuits associated with the 
control or indication of the fuel quantity on the airplane. This would 
include, but is not limited to, the FQIS tank probe circuits, the 
volumetric shutoff compensator circuits, densitometer circuits, and 
float switch circuits. The term ``circuits'' is considered by the FAA 
to include airplane wiring as well as wiring within components. No 
change to the final rule is necessary.

Clarification of Airplane Models Affected

    The NPRM indicated that the airplanes affected by the proposed AD 
were Boeing Model 747-100, -200, and -300 series airplanes. The 
proposed AD was intended to apply to all Boeing Model 747 series 
airplanes that do not have shielded and separated FQIS wiring, 
including the 747SR and 747SP series airplanes. The estimate of the 
affected fleet size that was provided in the NPRM included those 
airplanes, which many, including the manufacturer, consider to be part 
of the Model 747-100 series. Those models are listed separately on the 
Model 747 Type Certificate Data Sheet. Therefore, in order to clarify 
that this AD does apply to those models, the final rule has been 
revised to list the affected airplanes as Boeing Model 747-100, -200, -
300, SP, and SR series.

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.

Cost Impact

    There are approximately 650 Model 747-100, -200, -300, SP, and SR 
series airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 202 airplanes of U.S. registry will be affected by this 
AD, that it will take approximately 450 work hours per airplane to 
accomplish the required actions, and that the average labor rate is $60 
per work hour. Required parts will cost approximately $9,000 per 
airplane. Based on these figures, the cost impact of the AD on U.S. 
operators is estimated to be $7,272,000, or $36,000 per airplane.
    The cost impact figure discussed above is 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.

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.
    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 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, 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:

98-20-40  Boeing: Amendment 39-10808. Docket 97-NM-272-AD.

    Applicability: All Model 747-100, -200, -300, -SP, and -SR 
series airplanes, 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 (b) 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 electrical transients induced by electromagnetic 
interference (EMI) or electrical short circuit conditions from 
causing arcing of the fuel quantity indication system (FQIS) 
electrical wiring or probes in the fuel tank(s), which could result 
in ignition of the fuel tank(s), accomplish the following:
    (a) Within 36 months after the effective date of this AD, 
replace all of the FQIS wiring outside of the fuel tanks and surge 
tank with shielded wiring, and install that wiring so as to provide 
separation of that wiring from other airplane systems wiring, in 
accordance with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate.
    (b) 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 ACO. 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.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (c) 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.

[[Page 52152]]

    (d) This amendment becomes effective on November 4, 1998.

    Issued in Renton, Washington, on September 23, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-25972 Filed 9-29-98; 8:45 am]
BILLING CODE 4910-13-U