[Federal Register Volume 65, Number 51 (Wednesday, March 15, 2000)]
[Rules and Regulations]
[Pages 13871-13875]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-5890]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-57-AD; Amendment 39-11623; AD 2000-05-13]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 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 certain Boeing Model 737 series airplanes, that requires 
a one-time inspection of the main landing gear (MLG) axle flange to 
detect cracking, and follow-on corrective actions. For certain 
airplanes, this amendment also requires replacement of the original 
brake mounting gasket with a more durable aluminum-nickel-bronze 
gasket, and installation of new shear studs, if necessary. For certain 
airplanes, this amendment requires modification of the mounting flange 
holes of the brake torque tube. This amendment is prompted by reports 
of cracking in the axle flange and by reports of deterioration of the 
brake mounting gasket. The actions specified by this AD are intended to 
prevent fracture of the MLG axle and separation of the wheel from the 
MLG, and consequent reduced controllability of the airplane.

DATES: Effective April 19, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 19, 2000.

ADDRESSES: 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 Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
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: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; 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 certain Boeing Model 737 series 
airplanes was published in the Federal Register on October 29, 1998 (63 
FR 57953). That action proposed to require a one-time inspection of the 
main landing gear (MLG) axle flange to detect cracking, and follow-on 
corrective actions. For certain airplanes, that action proposed to 
require replacement of the original brake mounting gasket with a more 
durable aluminum-nickel-bronze gasket, and installation of new shear 
studs, if necessary. For certain airplanes, that action proposed to 
require modification of the mounting flange holes of the brake torque 
tube.

Comments

    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

    One commenter supports the proposed rule.

Requests to Extend Compliance Time

    Several commenters request that the FAA extend the compliance time 
(i.e., within 200 days or 1,500 flight cycles after the effective date 
of this AD, whichever occurs later) for accomplishing the requirements 
of the proposed AD.
    One commenter states that the proposed AD should be carried out 
within 250 days or 2,500 aircraft cycles, whichever occurs later. The 
commenter supports this request by stating that its standard practice 
is to clean and visually inspect all landing gear axle flanges each 
time the brake assemblies and wheel assemblies are removed from the 
axle. The commenter further states that it has never experienced loss 
of a MLG wheel with BFGoodrich brake assemblies, and that BFGoodrich is 
not aware of the loss of a wheel on aircraft equipped with BFGoodrich 
brake assemblies.
    Another commenter, the airplane manufacturer, states that the 
inspection of axle flanges that have been repaired with nickel 
sulfamate or bushings would require removal of the repair. The 
commenter notes that this will have a significant impact on the cost 
and time required to perform the proposed inspection. Therefore, 
consideration should be given to increasing the compliance time or 
modifying the inspection requirements.
    One commenter states that the inspection schedule specified in 
paragraphs (b) and (c) of the proposed AD should be increased to at 
least 1 year or 4,000 cycles, whichever is later. The commenter states 
that the currently proposed inspection schedule for most of the 
operators will fall during a line maintenance check. The commenter 
points out that the inspection and repair specified in Boeing All 
Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996 [which is 
referenced in the proposed AD the appropriate source for accomplishing 
the proposed inspection in paragraphs (b)(1) and (c)(1) and the 
proposed repair in paragraphs (b)(2) and (c)(2)], involves repairs that 
should be accomplished at a heavy check or overhaul facility.
    One commenter states that the inspection should be accomplished 
during a heavy maintenance visit where equipment and trained personnel 
are more readily available.
    The FAA concurs with the commenters' requests. The FAA concurs that 
the magnetic particle inspection, high frequency eddy current (HFEC) 
inspection, modification, and repair, if necessary, required by this AD 
should be accomplished at an overhaul facility. The FAA has determined 
that an extension of the compliance time to within 1 year or 4,500 
flight cycles after the effective date of this AD, whichever occurs 
later, will not compromise safety provided that an interim detailed 
visual inspection to detect fretting and corrosion of the axle flange 
bolt holes is accomplished within 200 days or 1,500 flight cycles after 
the effective date of this AD, whichever occurs later. The FAA has 
added a new paragraph (d) to the final rule to include such an option. 
The FAA also has added a note to the final rule to clarify the 
definition of the detailed visual inspection.
    One commenter states that, if the FAA mandates modifications to the 
ten or eleven bolt configuration, it requests that the compliance time 
for paragraph (c) of the proposed AD be extended to 5 years. (This 
comment is discussed in more detail below under the heading ``Requests 
to Exclude Actions on the Basis of Configuration'').
    The FAA does not concur with the commenter's request. Although the 
two stud/ten bolt configuration provides better clamp-up between the 
brake

[[Page 13872]]

assembly and the MLG axle flange, the FAA has determined that improved 
clamp-up by itself does not justify a 5-year compliance time.

Requests to Exclude Actions on the Basis of Configuration

    One commenter requests that operators utilizing ten or eleven bolt 
configurations regardless of gasket material not be subject to the 
requirements of the proposed AD. One commenter states that, according 
to Boeing AOT M-7272-96-1442, dated March 29, 1996, previous failures 
are primarily due to poor maintenance of finish, improper plating 
repairs, and installation of incorrect wheel bearings, rather than 
design deficiencies. The commenter suggests that no evidence exists 
which shows that a ten or eleven bolt brake mounting configuration with 
phenolic gaskets is unsafe or susceptible to cracking, and subsequent 
axle failure.
    The FAA does not concur with the commenter's request. Although the 
two stud/ten bolt configuration provides better clamp-up between the 
brake assembly and the MLG axle flange, the FAA has determined that an 
improved clamp-up by itself will not prevent fretting. Furthermore, 
Boeing AOT M-7272-96-1442 lists deterioration of the phenolic gasket as 
another of the basic causes of reported axle fractures. Brake heat and 
vibration can lead to deterioration of the phenolic gasket. The FAA 
finds that an increase in clamp-up with the two stud/ten bolt 
configuration will help decrease the magnitude of vibration, but will 
not alleviate the gasket deterioration brake heat caused by the gasket. 
The FAA has determined that the aluminum-nickel-bronze (Al-Ni-Br) 
gasket used in conjunction with brake mounting hardware, which includes 
two studs and ten bolts, will ensure proper clamp-up and resistance to 
brake heat and vibration.
    Another commenter requests that operators with a one stud/eleven 
bolt brake mounting configuration be required to add one stud and one 
nickel bronze gasket to comply with the intent of the proposed rule. No 
justification was provided.
    The FAA does not concur with the commenter's request. The FAA has 
determined that the existing shear studs used with the phenolic gasket 
will not properly mate with the aluminum-nickel-bronze gasket. 
Therefore, two new studs will be required. Furthermore, prior to 
installing the gasket, magnetic particle or HFEC inspections are 
required to evaluate the existing integrity of the axle flange and bolt 
holes.

Requests for Credit for Previous Incorporation of Certain Service 
Information

    One commenter requests that the FAA give credit for airplanes on 
which MLG assemblies with an Al-Ni-Br gasket have been installed in 
accordance with Boeing Service Bulletin 737-32-1253, and that have been 
inspected/reworked/overhauled in accordance with Boeing AOT M-7272-96-
1442 and/or original equipment manufacturer/FAA-approved operator 
designed rework procedures.
    The FAA concurs with the commenter's request provided that the 
inspection has been accomplished concurrent with or after installation 
of the Al-Ni-Br gasket. The FAA has determined that accomplishment of 
the magnetic particle or HFEC inspections in accordance with Boeing AOT 
M-7272-96-1442, dated March 29, 1996, concurrent with or after 
installation of an aluminum-nickel-bronze gasket and shear studs, is 
considered acceptable for compliance with the requirements of 
paragraphs (a)(1) and (c)(1) of this final rule. Therefore, the FAA has 
added a new note after paragraph (a) of this AD to provide credit for 
accomplishing the required inspection concurrently with or after 
accomplishment of the subject installation.
    Two commenters request that the inspection required by paragraph 
(a)(1) of the proposed AD be deleted. One of these commenters requests 
that the inspection required by paragraph (b)(1) also be deleted. One 
commenter states that the inspection should not be required because a 
new aluminum-nickel-bronze gasket has been installed in accordance with 
Boeing Service Bulletin 737-32-1253, dated November 7, 1991, and the 
torque tube mounting holes on the mounting flange have been modified in 
accordance with AlliedSignal Service Bulletin 2601042-32-003, dated 
March 15, 1997. If operators installed this new gasket along with the 
modification on the axle flange and brake flange, the commenter 
contends that they have already accomplished the initial inspection in 
accordance with Boeing Service Bulletin 737-32-1253. One commenter 
states that there have been no reported axle failures on airplanes that 
have incorporated Boeing Service Bulletin 737-32-1253. The commenter 
further states that the inspection of these airplanes will impose an 
unreasonable financial burden on the operators.
    Another commenter states that paragraph (c) of the proposed AD 
contains no requirement for repetitive inspections after incorporation 
of Boeing Service Bulletin 737-32-1253. Therefore, the commenter 
requests that no further action be required, if the magnetic particle 
inspection and modification specified in that service bulletin were 
already accomplished during the previous landing gear overhaul or at a 
maintenance opportunity.
    Another commenter requests that, if an MLG has been inspected, 
overhauled, and modified in accordance with Boeing Service Bulletins 
737-32-1253, dated November 7, 1991, and 737-32-1235, dated April 12, 
1990, affected airplanes should not be subject to the requirements of 
the proposed AD. The commenter also states that In Service Report (ISR) 
#95-03-3210-20, dated February 16, 1995, states that incorporation of 
these service bulletins is the recommended action according to Boeing.
    The FAA does not concur with the commenters' requests. The FAA has 
determined that, for airplanes on which the installation of the brake 
mounting hardware in accordance with Boeing Service Bulletin 737-32-
1253, dated November 7, 1991, and Boeing Service Bulletin 737-32-1235, 
dated April 12, 1990, has been accomplished, the magnetic particle or 
HFEC inspection required by this AD must be accomplished because these 
service bulletins do not contain inspection procedures. These service 
bulletins only describe procedures for installing the improved brake 
mounting hardware and an additional shear stud. The FAA points out that 
there is a possibility that some of the aluminum-nickel-bronze gaskets 
could have been installed on axle flanges that already had cracks or 
fretting damage. A magnetic particle or HFEC inspection of this area 
will ensure detection of cracks in the axle flange and brake attach 
bolt holes.
    One commenter further requests that airplanes on which the shear 
stud replacement in accordance with Boeing Service Bulletin 737-32-1253 
has been incorporated not be required to install new studs, as required 
in paragraph (a)(4) of the proposed AD. The commenter believes this to 
be unnecessary since Service Bulletin 737-32-1253 already requires 
replacement of the shear studs.
    The FAA concurs with the commenter's request. The FAA finds that 
accomplishment of the gasket replacement in accordance with the subject 
service bulletin includes replacing the shear studs. The FAA notes that 
paragraph (a) of the AD applies to certain airplanes ``on which the 
original gaskets have been replaced with aluminum-nickel-bronze gaskets 
in accordance with Boeing Service Bulletin

[[Page 13873]]

737-32-1253, dated November 7, 1991.'' The FAA finds it unnecessary for 
those airplanes to accomplish the replacement of the shear studs a 
second time. Therefore, the FAA has deleted paragraph (a)(4) of the 
proposed AD from the final rule.

Requests to Allow Flight with Cracks

    Two commenters request that repair of cracks, prior to further 
flight, as required by paragraphs (a)(1), (b)(1), and (c)(1) of the 
proposed AD, apply only to those axle flange cracks found progressing 
inward from the brake attach holes towards the MLG axle. The commenters 
suggest that operations should be allowed to continue on airplanes with 
axle flanges that have cracks on up to four bolt holes, as long as they 
progress towards the outer edge of the flange. One of the commenters 
states that this type of cracking is sufficiently covered under the 
current Boeing Overhaul Manual 32-11-11. One commenter further states 
that if repair is deemed necessary, then the FAA should develop and 
include an approved repair scheme in the final rule.
    The FAA partially concurs with the commenter's request. The FAA 
does not concur that operations should be allowed to continue on 
airplanes with axle flanges that have any crack. While outwardly 
progressing cracks should not affect axle integrity, if such cracks are 
completely ignored, they could change direction and begin progressing 
inwards towards the MLG axle. Therefore, the FAA has determined that 
any subject axle flange that is found to be cracked must be repaired 
prior to further flight in accordance with a method approved by the 
FAA.
    However, the FAA does concur that accomplishment of the repair in 
accordance with Boeing Overhaul Manual 32-11-11 is considered 
acceptable for compliance with the repair requirements of paragraphs 
(a)(1), (b)(1), and (c)(1) of the AD. Therefore, the FAA has revised 
the final rule to include as new note to clarify this point. In 
addition, operators may request approval of an alternative method of 
compliance if data are provided to substantiate that such a method 
would provide an acceptable level of safety.

Request to Change Terminology

    Two commenters request that the term ``brake assemblies'' in 
paragraphs (b)(4) and (c)(3) of the proposed AD be changed. One 
commenter suggests ``brake mounting hardware,'' and the other commenter 
suggests ``axle flange assemblies'' as alternative terms.
    One commenter further suggests that the term ``torque tube'' be 
changed to ``brake torque tube'' in paragraphs (a)(3) and (b)(3) of the 
proposed AD; delete ``on the mounting flange'' from paragraph (a)(3) of 
the proposed AD; and change ``brake modification'' to ``brake mounting 
hardware modification'' in the Cost Impact section of the proposed AD.
    The FAA concurs with the commenters' requests. The FAA has revised 
paragraphs (b)(4) and (c)(3) of the final rule to read ``brake mounting 
hardware.'' The FAA also has revised the term ``torque tube'' to 
``brake torque tube'' in the Summary, Supplementary Information, and 
Cost Impact sections of the AD; and deleted the phrase ``of the 
mounting flange'' from paragraph (b)(3) of this AD to be consistent 
with the changes noted previously.

Other Changes Made to the Proposed AD

    The FAA inadvertently omitted information from paragraphs (b)(1) 
and (c)(1) of the proposed rule for HFEC inspections of axle flanges 
that have not been repaired previously and coated with a nickel 
sulfamate finish. As stated in paragraph (a)(1) of the proposed rule, 
an HFEC inspection may only be accomplished if the axle flange has not 
been repaired previously and coated with a nickel sulfamate finish. 
However, the FAA inadvertently omitted this clarification in paragraphs 
(b)(1) and (c)(1) of the proposed AD, which applies to airplanes 
equipped with certain AlliedSignal brake assemblies on which the 
original gaskets have not been replaced and on all other affected 
airplanes, respectively. The clarification regarding HFEC inspections 
applies to all repaired axle flanges, independent of gasket replacement 
and independent of whether the airplanes are equipped with certain 
AlligedSignal brake assemblies. Therefore, the FAA has revised 
paragraphs (b)(1) and (c)(1) of the final rule to include the 
clarification that an HFEC inspection is not appropriate for repaired 
axle flanges.
    As published, the NPRM contains a typographical error in paragraph 
(a)(1). It references Boeing All Operators Telex (AOT) ``M-7272-76-
1442,'' dated ``Mach 29, 1996,'' as the appropriate source of service 
information for accomplishment of the magnetic particle or HFEC 
inspection. However, as indicated throughout the rest of the proposed 
AD, the correct reference is ``Boeing All Operators Telex (AOT) ``M-
7272-96-1442, dated March 29, 1996.''

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 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 2,015 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 893 airplanes of U.S. 
registry will be affected by this AD.
    The FAA estimates that it will take approximately 4 work hours per 
airplane to accomplish the required inspection, and that the average 
labor rate is $60 per work hour. Based on these figures, the cost 
impact of the inspection required by this AD on U.S. operators is 
estimated to be $214,320, or $240 per airplane.
    It will take approximately 32 work hours per airplane at an average 
labor rate of $60 per work hour should an operator be required to 
accomplish the required brake mounting hardware modification. Required 
parts will cost approximately $2,052 per airplane. Based on these 
figures, the cost impact of the brake mounting hardware modification 
required by this AD on U.S. operators is estimated to be $3,972 per 
airplane.
    Additionally, the FAA estimates that it will take approximately 5 
work hours per airplane to accomplish the required brake torque tube 
modification, and that the average labor rate is $60 per work hour. The 
FAA estimates that this action will be required to be accomplished on 
approximately 400 U.S.-registered airplanes. Based on these figures, 
the cost impact of this modification required by this AD on U.S. 
operators is estimated to be $120,000, or $300 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.

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

[[Page 13874]]

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 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:

2000-05-13-Boeing: Amendment 39-11623. Docket 98-NM-57-AD.

    Applicability: Model 737-100, -200, -300, -400, and -500 series 
airplanes; line positions 1 through 2135 inclusive; 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 (e) 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 fracture of the main landing gear (MLG) axle and the 
separation of the wheel from the MLG, and consequent reduced 
controllability of the airplane, accomplish the following:

Inspection, Modification, and Corrective Action

    (a) For Model 737-100 and -200 series airplanes equipped with 
AlliedSignal (ALS/Bendix) brake assembly installations having Boeing 
part numbers (P/N) 10-61063-14, -18, or -21, on which the original 
gaskets have been replaced with aluminum-nickel-bronze gaskets in 
accordance with Boeing Service Bulletin 737-32-1253, dated November 
7, 1991: Except as provided by paragraph (d) of this AD, within 200 
days or 1,500 flight cycles after the effective date of this AD, 
whichever occurs later, accomplish the requirements of paragraphs 
(a)(1), (a)(2), and (a)(3) of this AD.
    (1) Perform either a one-time magnetic particle inspection or a 
one-time high frequency eddy current inspection of the MLG axle 
flange to detect cracking, except that a high frequency eddy current 
inspection may only be accomplished if the axle flange has not been 
repaired previously and coated with a nickel sulfamate finish. The 
magnetic particle inspection or high frequency eddy current 
inspection is to be accomplished in accordance with procedures 
specified in paragraph B. of the ``Recommended Operator Action'' 
section of Boeing All Operators Telex (AOT) M-7272-96-1442, dated 
March 29, 1996. If any cracking is detected, prior to further 
flight, repair the MLG flange, in accordance with Boeing Overhaul 
Manual 32-11-11, or other method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.
    (2) If any corrosion or fretting is found during accomplishment 
of the inspection required by paragraph (a)(1) of this AD: Prior to 
further flight, accomplish the repair procedures specified in the 
``Recommended Operator Action'' section of Boeing AOT M-7272-96-
1442, dated March 29, 1996.
    (3) Accomplish the modification of the brake torque tube 
mounting holes, in accordance with AlliedSignal Service Bulletin 
2601042-32-003, dated March 15, 1997.

Inspection, Modification, and Corrective Action

    (b) For Model 737-100 and -200 series airplanes equipped with 
AlliedSignal (ALS/Bendix) brake assembly installations having Boeing 
P/N 10-61063-14, -18, or -21, on which the original gaskets have not 
been replaced with new aluminum-nickel-bronze gaskets in accordance 
with Boeing Service Bulletin 737-32-1253, dated November 7, 1991: 
Except as provided by paragraph (d) of this AD, within 200 days or 
1,500 flight cycles after the effective date of this AD, whichever 
occurs later, accomplish the requirements of paragraphs (b)(1), 
(b)(2), (b)(3), and (b)(4) of this AD.
    (1) Perform either a one-time magnetic particle inspection or a 
one-time high frequency eddy current inspection of the MLG axle 
flange to detect cracking, except that a high frequency eddy current 
inspection may only be accomplished if the axle flange has not been 
repaired previously and coated with a nickel sulfamate finish. The 
magnetic particle inspection or high frequency eddy current 
inspection is to be accomplished in accordance with procedures 
specified in paragraph B. of the ``Recommended Operator Action'' 
section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any 
cracking is detected, prior to further flight, repair the MLG 
flange, in accordance with Boeing Overhaul Manual 32-11-11, or other 
method approved by the Manager, Seattle ACO.
    (2) If any corrosion or fretting is found during accomplishment 
of the inspection required by paragraph (b)(1) of this AD: Prior to 
further flight, accomplish the repair procedures specified in the 
``Recommended Operator Action'' section of Boeing AOT M-7272-96-
1442, dated March 29, 1996.
    (3) Accomplish the modification of the brake torque tube 
mounting holes, in accordance with AlliedSignal Service Bulletin 
2601042-32-003, dated March 15, 1997.
    (4) Accomplish the modification of the affected brake mounting 
hardware in accordance with Boeing Service Bulletin 737-32-1253, 
dated November 7, 1991.

Inspection, Modification, and Corrective Action

    (c) For Model 737-100, -200, -300, -400, and -500 series 
airplanes other than those identified in paragraphs (a) and (b) of 
this AD: Except as provided by paragraph (d) of this AD, within 200 
days or 1,500 flight cycles after the effective date of this AD, 
whichever occurs later, accomplish the requirements of paragraphs 
(c)(1), (c)(2), and (c)(3) of this AD.
    (1) Perform either a one-time magnetic particle inspection or a 
one-time high frequency eddy current inspection of the MLG axle 
flange to detect cracking, except that a high frequency eddy current 
inspection may only be accomplished if the axle flange has not been 
repaired previously and coated with a nickel sulfamate finish. The 
magnetic particle inspection or high frequency eddy current 
inspection is to be accomplished in accordance with procedures 
specified in paragraph B. of the ``Recommended Operator Action'' 
section of Boeing AOT M-7272-96-1442, dated March 29, 1996. If any 
cracking is detected, prior to further flight, repair the MLG 
flange, in accordance with Boeing Overhaul Manual 32-11-11, or other 
method approved by the Manager, Seattle ACO.
    (2) If any corrosion or fretting is found during accomplishment 
of the inspection required by paragraph (c)(1) of this AD: Prior to 
further flight, accomplish the repair procedures specified in the 
``Recommended Operator Action'' section of Boeing AOT M-7272-96-
1442, dated March 29, 1996.
    (3) Accomplish the modification of the affected brake mounting 
hardware in accordance with Boeing Service Bulletin 737-32-1253, 
dated November 7, 1991.

    Note 2: Accomplishment of the magnetic particle or HFEC 
inspections of unrepaired axle flanges in accordance with Boeing 
Telex M-7272-96-1442, dated March 29, 1996, concurrent with or after 
installation of an aluminum-nickel-bronze gasket and shear studs, is 
considered acceptable for compliance with the requirements of 
paragraphs (a)(1) and (c)(1) of this AD.


[[Page 13875]]



Optional Visual Inspection

    (d) The actions required by paragraphs (a), (b), and (c) of this 
AD may be accomplished at the time specified in paragraph (d)(1) of 
this AD, provided that the action specified in paragraph (d)(2) is 
accomplished.
    (1) Within 1 year or 4,500 flight cycles after the effective 
date of this AD, whichever occurs later, accomplish the actions 
specified in paragraph (a), (b), or (c) of this AD, as applicable; 
and
    (2) Within 200 days or 1,500 flight cycles after the effective 
date of this AD, whichever occurs later, perform a detailed visual 
inspection to detect fretting or corrosion of the axle flange bolt 
holes. If any fretting or corrosion is detected, prior to further 
flight, accomplish the repair procedures specified in the 
``Recommended Operator Action'' section of Boeing AOT M-7272-96-
1442, dated March 29, 1996.

    Note 3: 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.''

Alternative Methods of Compliance

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

Special Flight Permits

    (f) Special flight permits may be issued in accordance with 
Secs. 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

    (g) Except as provided by paragraphs (a)(1), (b)(1), and (c)(1) 
of this AD, the actions shall be done in accordance with Boeing All 
Operators Telex (AOT) M-7272-96-1442, dated March 29, 1996; 
AlliedSignal Service Bulletin 2601042-32-003, dated March 15, 1997; 
and Boeing Service Bulletin 737-32-1253, dated November 7, 1991; 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.
    (h) This amendment becomes effective on April 19, 2000.

    Issued in Renton, Washington, on March 6, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-5890 Filed 3-14-00; 8:45 am]
BILLING CODE 4910-13-U