[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