[Federal Register Volume 64, Number 178 (Wednesday, September 15, 1999)]
[Rules and Regulations]
[Pages 49971-49973]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-23474]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-251-AD; Amendment 39-11314; AD 99-19-27]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, 
and -500 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 737-100, -200, -300, -400, and -500 
series airplanes, that requires a one-time inspection of the main 
landing gear (MLG) wheel assemblies to determine whether certain parts 
are installed, and follow-on corrective actions, if necessary. For 
certain airplanes, this amendment also requires eventual modification 
of MLG wheel assemblies, which terminates the requirements of this AD. 
This amendment is prompted by incidents of multiple tie bolt failures 
on certain BFGoodrich wheel assemblies. The actions specified by this 
AD are intended to prevent failure of multiple tie bolts of MLG wheel 
assemblies, which could result in failure of the wheel rim, rapid 
release of tire pressure, and possible consequent damage to the 
airplane and injury to passengers and flightcrew.

DATES: Effective October 20, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 20, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from BFGoodrich Aerospace, Aircraft Wheels and Brakes, P.O. 
Box 340, Troy, Ohio 45373. 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: Don Kurle, Senior 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) 227-2798; 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 Model 737-100, -200, -
300, -400, and -500 series airplanes was published in the Federal 
Register on November 18, 1998 (63 FR 64013). That action proposed to 
require a one-time inspection of the main landing gear (MLG) wheel 
assemblies to determine whether certain parts are installed, and 
follow-on corrective actions, if necessary. For certain airplanes, that 
action also proposed to require eventual modification of MLG wheel 
assemblies, which would terminate the requirements of this AD.

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 has no objection to the proposed AD.

Explanation of Change Made to Proposal

    The FAA has clarified the inspection requirement contained in the 
proposed AD. Whereas the proposed specified a visual inspection, the 
FAA has revised paragraphs (b)(2)(i) and (b)(2)(ii) of this final rule 
to clarify that its intent is to require a detailed visual inspection. 
Additionally, Note 2 has been added to the final rule to define that 
inspection.

Request to Revise Applicability

    One commenter requests that the applicability of the proposed AD be 
revised to read, ``All Model 737-100, -200, -300, -400, and -500 series 
airplanes certificated in any category, having wheel assemblies 
manufactured by BFGoodrich installed.'' In support of its request, the 
commenter states that the current applicability does not exclude 
airplanes that do not have BFGoodrich wheel and brake assemblies 
installed.
    The FAA does not concur. The purpose of the AD is to assure that 
all operators verify part numbers, determine if BFGoodrich wheel 
assemblies are installed, and if so, take appropriate action. No change 
to the applicability section of the AD is made in this regard. However, 
the FAA recognizes that a records review can verify part numbers, and 
as discussed below, paragraph (a) of the AD has been revised to 
essentially accomplish the result sought by the commenter.

Request to Revise Inspection Procedures

    Several commenters request that the proposed inspection procedures 
of the main landing gear (MLG) wheel assemblies be revised to allow for 
a records review in lieu of a visual inspection to determine whether 
certain parts are installed. In support of this request, the commenters 
noted that other wheel assemblies (AlliedSignal) are not 
interchangeable with BFGoodrich wheel assemblies, and since it is not 
necessary to determine the type of wheel assemblies that are installed, 
a review of records would be less expensive than a visual inspection.
    The FAA concurs with the commenters' request to revise the 
inspection procedures required by paragraph (a) of this AD. The FAA 
recognizes that a visual inspection is not necessary to determine the 
type of wheel assemblies that are installed. In light of this, the FAA 
has revised paragraph (a) of this final rule to

[[Page 49972]]

require, ``an inspection of the MLG wheel assemblies or perform other 
verifications (such as a records review) to determine the part number 
(P/N) of each assembly.''

Request for Clarification of Discussion Section

    One commenter requests that the FAA clarify the description in the 
Discussion Section of the proposed AD of the tie bolt failures to 
indicate that they occurred only on certain BFGoodrich wheel assemblies 
that are installed on the main landing gear (MLG) of Boeing Model 737-
300 and -400 series airplanes.
    The FAA agrees that the Discussion section of the proposed rule may 
have been unclear regarding the incidents of tie bolt failures on 
certain BFGoodrich wheel assemblies. The FAA acknowledges that no 
reports of failures have been reported for Boeing Model 737-100, -200, 
or -500 series airplanes. However, because the Discussion section is 
not restated in the final rule, no change to this final rule is 
necessary in this regard.

Request for Revision of Cost Impact Information

    One commenter requests that the cost impact information of the 
proposed AD be revised to clarify the usage of parts should an operator 
elect to accomplish the replacement. The commenter requests adding a 
phrase to clarify that if the same part number steel tie bolt fasteners 
were used, such replacement will require no additional work hours if 
accomplished during a regularly scheduled tire change.
    The FAA concurs with the commenter's request. The cost impact 
information, below, has been revised accordingly.
    The same commenter requests that the cost impact information of the 
proposed AD be revised to clarify the types of parts to be used. The 
commenter requests adding a phrase to clarify that the modification of 
the wheel assembly be accomplished by installing improved, Inconel tie 
bolt fasteners, and that it would require no additional work hours per 
airplane if the modification is accomplished during a regularly 
scheduled tire change.
    The FAA concurs with the commenter's request. The cost impact 
information, below, has been revised accordingly.

Request for Clarification of Requirements

    One commenter requests that the proposed rule be revised to clarify 
certain requirements. The commenter suggests that additional 
information be provided to clarify the visual inspections, 
replacements, and terminating action.
    The FAA does not concur. The FAA acknowledges the comment, however, 
the commenter did not make any specific recommendations. Therefore, no 
change to the final rule in this regard is necessary.

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 460 Model 737-100, -200, -300, -400, and -
500 series airplanes of the affected design in the worldwide fleet. The 
FAA estimates that 118 airplanes of U.S. registry will be affected by 
this AD.
    It will take approximately 1 work hour per airplane to accomplish 
the required one-time inspection, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the one-time 
inspection required by this AD on U.S. operators is estimated to be 
$7,080, or $60 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.
    Should an operator elect to accomplish the repetitive visual 
inspection, it would take approximately 1 work hour per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the repetitive inspections, if 
accomplished, is estimated to be $60 per airplane, per inspection 
cycle.
    Should an operator elect to accomplish the replacement using the 
same part number steel tie bolt fasteners, such replacement would 
require no additional work hours if accomplished during a regularly 
scheduled tire change. Required parts would cost $2,840 per airplane 
($710 per wheel). Based on these figures, the cost impact of the 
replacement, if accomplished, is estimated to be $2,840 per airplane, 
per replacement cycle.
    Should an operator elect to accomplish the revisions to the FAA-
approved maintenance program, it would take approximately 1 work hour 
per airplane to accomplish, at an average labor rate of $60 per work 
hour. Based on these figures, the cost impact of the maintenance 
program revision, if accomplished, is estimated to be $60 per airplane.
    Should an operator be required to accomplish the necessary 
modification of the wheel assembly by installing improved Inconel tie 
bolt fasteners, it would require no additional work hours per airplane, 
if the modification is accomplished during a regularly scheduled tire 
change. Required parts would cost $4,848 per airplane ($1,212 per 
wheel). Based on these figures, the cost impact of any necessary 
modification is estimated to be $4,848 per airplane.

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, 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:


[[Page 49973]]


    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

99-19-27  Boeing: Amendment 39-11314. Docket 98-NM-251-AD.

    Applicability: Model 737-100, -200, -300, -400, and -500 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 (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 failure of multiple tie bolts of main landing gear 
(MLG) wheel assemblies, which could result in failure of the wheel 
rim, rapid release of tire pressure, and possible consequent damage 
to the airplane and injury to passengers and flightcrew, accomplish 
the following:
    (a) Within 60 days after the effective date of this AD, perform 
an inspection of the MLG wheel assemblies or perform other 
verifications (such as a records review) to determine the part 
number (P/N) of each assembly. If no wheel assembly manufactured by 
BFGoodrich Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 
is installed on the airplane, no further action is required by this 
AD.
    (b) Except as provided by paragraph (d) of this AD, if any MLG 
wheel assembly manufactured by BFGoodrich Aerospace and having P/N 
3-1398-1, 3-1439-2, or 3-1439-3 is installed on the airplane, within 
60 days after the effective date of this AD, accomplish the actions 
specified by paragraph (b)(1) or (b)(2) of this AD.
    (1) Accomplish the actions specified by (b)(1)(i) or (b)(1)(ii) 
of this AD.
    (i) Replace all tie bolts, nuts, and washers of the MLG wheel 
assembly with parts having the same P/N's, in accordance with the 
BFGoodrich component maintenance manual. Thereafter, repeat the 
replacement of tie bolts, nuts, and washers, at intervals not to 
exceed 5 tire changes, until the actions specified by paragraph 
(b)(2) or paragraph (c) of this AD have been accomplished. Or
    (ii) Perform a detailed visual inspection to detect fractures of 
any of the 16 tie bolts on each MLG wheel assembly, in accordance 
with the Boeing 737 airplane maintenance manual. Thereafter, repeat 
the inspection at intervals not to exceed 100 flight cycles until 
the actions specified by paragraph (b)(2) or paragraph (c) of this 
AD have been accomplished. If any fracture of any tie bolt is found 
during any inspection performed in accordance with this requirement, 
prior to further flight, replace the tie bolt, nut, and washer, in 
accordance with the BFGoodrich component maintenance manual, with 
new parts having the same P/N's.

    Note 2: For the purposes of this AD, a detailed visual 
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.''

    (2) Revise the FAA-approved maintenance program as specified in 
paragraph (b)(2)(i) or (b)(2)(ii) of this AD.
    (i) Revise the FAA-approved maintenance program to require 
replacement of all tie bolts, nuts, and washers of the MLG wheel 
assembly with parts having the same P/N's, in accordance with the 
BFGoodrich component maintenance manual, at intervals not to exceed 
5 tire changes. Or
    (ii) Revise the FAA-approved maintenance program to require a 
detailed visual inspection to detect fractures of any of the 16 tie 
bolts on each MLG wheel assembly, in accordance with the Boeing 737 
airplane maintenance manual, at intervals not to exceed 100 flight 
cycles. If any fracture of any tie bolt is found during any 
inspection performed in accordance with this requirement, prior to 
further flight, replace the tie bolt, nut, and washer, in accordance 
with the BFGoodrich component maintenance manual, with new parts 
having the same P/N's.

    Note 3: After the maintenance program has been revised to 
include the procedures specified in paragraph (b)(2)(i) or 
(b)(2)(ii) of this AD, operators are not required to subsequently 
record AD compliance each time the replacement or inspection is 
performed.

    (c) If any MLG wheel assembly manufactured by BFGoodrich 
Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 is 
installed on the airplane: Except as provided by paragraph (d) of 
this AD, within 2 years after the effective date of this AD, modify 
any BFGoodrich Aerospace wheel assembly, having P/N 3-1398-1, 3-
1439-2, or 3-1439-3; by replacing all existing tie bolts, nuts, and 
washers, with new, improved parts; and by converting the P/N of the 
MLG wheel assembly to 3-1398-2 (for BFGoodrich wheel assemblies 
having the old P/N 3-1398-1), 3-1439-5 (for BFGoodrich wheel 
assemblies having the old P/N 3-1439-2), or 3-1439-6 (for BFGoodrich 
wheel assemblies having the old P/N 3-1439-3), as applicable; in 
accordance with BFGoodrich Aerospace Service Bulletin 3-1439-32-13, 
or BFGoodrich Aerospace Service Bulletin 3-1398-32-16, both dated 
August 20, 1993, as applicable. Such modification constitutes 
terminating action for the requirements of this AD, and the FAA-
approved maintenance program procedures specified by paragraph 
(b)(2) of this AD may be removed following accomplishment of the 
requirements of this paragraph.
    (d) Airplanes on which the modification required by paragraph 
(c) of this AD is accomplished within the compliance time specified 
in paragraph (b) of this AD are not required to accomplish the 
actions required by paragraph (b).

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 Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. 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 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

Incorporation by Reference

    (g) The modification shall be done in accordance with BFGoodrich 
Aerospace Service Bulletin 3-1439-32-13, dated August 20, 1993; or 
BFGoodrich Aerospace Service Bulletin 3-1398-32-16, dated August 20, 
1993, 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 BFGoodrich 
Aerospace, Aircraft Wheels and Brakes, P.O. Box 340, Troy, Ohio 
45373. 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 October 20, 1999.

    Issued in Renton, Washington, on September 2, 1999.
Dorenda D. Baker,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-23474 Filed 9-14-99; 8:45 am]
BILLING CODE 4910-13-P