[Federal Register Volume 62, Number 50 (Friday, March 14, 1997)]
[Proposed Rules]
[Pages 12123-12126]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6438]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-152-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to all Boeing Model 737-100 and -200 series 
airplanes, that would have required replacement of certain outboard and 
inboard wheel halves with improved wheel halves. That action also would 
have required cleaning and inspecting certain outboard and inboard 
wheel halves for corrosion, missing paint in large areas, and cracks; 
and repair or replacement of the wheel halves with serviceable wheel 
halves, if necessary. That proposal was prompted by a review of the 
design of the flight control systems on Model 737 series airplanes. 
This action revises the proposed rule by extending the compliance time, 
revising the applicability of the AD, and clarifying part and serial 
numbers of affected wheel assemblies and halves. The actions specified 
by this proposed AD are intended to prevent failure of the wheel 
flanges, which could result in damage to the hydraulics systems, jammed 
flight controls, loss of electrical power, or other combinations of 
failures; and consequent reduced controllability of the airplane.

DATES: Comments must be received by April 3, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-152-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Allied Signal Aerospace Company, Bendix Wheels and Brakes 
Division, South Bend, Indiana 46624; and Bendix, Aircraft Brake and 
Strut Division, 3520 West Mestmoor Street, South Bend, Indiana 46624. 
This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: David Herron, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (206) 227-2672; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule.
    The proposals contained in this notice may be changed in light of 
the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-152-AD.'' The postcard will be date stamped and 
returned to the commenter.

[[Page 12124]]

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 96-NM-152-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to all 
Boeing Model 737-100 and -200 series airplanes, was published as a 
notice of proposed rulemaking (NPRM) in the Federal Register on August 
28, 1996 (61 FR 44245). That NPRM would have required replacement of 
certain outboard and inboard wheel halves with improved wheel halves. 
That NPRM also would have required cleaning and inspecting certain 
outboard and inboard wheel halves for corrosion, missing paint in large 
areas, and cracks; and repair or replacement of the wheel halves with 
serviceable wheel halves, if necessary. That NPRM was prompted by a 
review of the design of the flight control systems on Model 737 series 
airplanes. The actions specified by that NPRM are intended to prevent 
damage to the wheel flanges, which could result in failure of the 
hydraulics systems, jammed flight controls, loss of electrical power, 
or other combinations of failures; and consequent reduced 
controllability of the airplane.

Actions Since Issuance of Previous Proposal

    Due consideration has been given to the comments received in 
response to the NPRM.

Support for the Proposal

    Two commenters support the proposed rule.

Requests to Reopen Comment Period

    Several commenters request that the proposal be reissued and the 
public comment period reopened. The commenters ask that the intent of 
the proposal be clarified. The commenters state that the proposal 
appears to require that an inspection and a replacement be accomplished 
concurrently within 180 days. Allied Signal indicates that it is 
unclear why operators should be required to replace wheel halves and 
then inspect those wheel halves that were just removed.
    In its justification for the request to reopen the comment period, 
another commenter states that the issue addressed in the proposed AD 
arises from a failure that occurred on a military aircraft. The 
commenter indicates that, when maintained properly and operated on 
civilian airliners, certain wheel halves are not subject to the 
questionable maintenance practices and adverse operational conditions 
often associated with military hardware. The commenter adds that, in 
particular, the inspections required at tire replacement occur far more 
frequently due to utilization differences. The commenter believes that 
strengthened inspection requirements in accordance with the latest 
manufacturer's recommendations can provide for safe operation of the 
older wheels until replacements would normally be available.
    The FAA concurs with the commenters' requests to reopen the comment 
period for this proposed rule and to provide clarification of the 
intent of the proposal. The intent of this proposed AD is that the 
affected fleet be equipped eventually with more resilient wheel halves 
that provide greater tolerance for corrosion and handling damage. Some 
failures of wheel halves have occurred because indications of corrosion 
or handling damage were not detected in a timely manner. Therefore, the 
FAA included a requirement in the original NPRM indicating that, until 
the time that the existing wheel halves can be replaced with the more 
resilient wheel halves, repetitive cleaning and inspections of the 
wheel halves must be performed in accordance with the cleaning/
inspection method described in Allied Signal Service Bulletin No. 737-
32-026. Accomplishment of these repetitive actions will ensure that an 
acceptable level of safety is maintained until the wheel halves are 
replaced.
    The FAA has revised this supplemental NPRM to clarify these issues:
     The repetitive inspection requirement, which appeared as 
paragraph (b) of the original NPRM, is contained in paragraph (a) of 
this supplemental NPRM. Paragraph (a) of this supplemental NPRM has 
been revised to clarify that the inspections of the wheel halves must 
be repeated until the wheel halves are replaced.
     The replacement requirement, which appeared in paragraph 
(a) of the original NPRM, is contained in paragraph (b) of this 
supplemental NPRM. Paragraph (b) of this supplemental NPRM has been 
revised to clarify that accomplishment of the replacement terminates 
the repetitive inspections required by paragraph (a).

Request for Extended Compliance Time

    Three commenters express concern that replacement of certain 
outboard and inboard wheel halves with improved halves cannot be 
supported within the proposed compliance time of 180 days. One of these 
commenters, Allied Signal, suggests that the compliance time be 
extended to 365 days, and that paragraph (c) of the original NPRM be 
deleted. Allied Signal indicates that the lead time necessary to order 
and receive forgings, machine, finish, and ship replacement wheels 
involves approximately 120 days, which is a significant portion of the 
proposed 180-day compliance time. Allied Signal states that it does not 
have sufficient information to determine how many wheels need 
replacement, and may not have this information until a final rule is 
effective and orders for replacements arrive.
    In light of these requests, the FAA has reconsidered the compliance 
times proposed in the original NPRM. The FAA considers that the 
compliance time of 180 days (and thereafter at each tire change) for 
inspections of the wheel halves, as proposed in paragraph (b) of the 
original NPRM, is appropriate. The FAA considers that these repetitive 
inspections must be accomplished at the originally proposed intervals 
in order to provide an acceptable level of safety until the replacement 
can be accomplished.
    However, in consideration of parts availability, the FAA has 
determined that the compliance time for replacement of the wheel halves 
can be extended from 180 days to two years without compromising safety, 
and that paragraph (c) of the original NPRM can be removed from this 
supplemental NPRM. Given this revised compliance time for 
accomplishment of the replacement, the FAA estimates that approximately 
four tire changes would be accomplished in the two-year period prior to 
the time the replacement would be required. The compliance time 
specified in paragraph (b) of this supplemental NPRM has been revised 
accordingly. In addition, paragraph (c) of the original NPRM has been 
removed from this supplemental NPRM.

Requests for Clarification of Part Numbering System

    Two commenters request clarification of the part numbering system 
specified in the proposal. Further, Allied Signal recommends that 
serial number H-1049 be used in all places where serial number H-999 
appeared in the NPRM to avoid numerical discrepancies and to ensure 
adequate coverage of these wheel halves. Allied Signal submits two sets 
of suggested changes to the NPRM: one set based on an intent to remove 
all affected wheels from service, and the other set based on an intent 
to inspect all affected

[[Page 12125]]

wheels and remove from service only those with cracks.
    Allied Signal states that a misunderstanding exists with regard to 
the serial numbering system used by Aircraft Landing Systems (formerly 
Bendix). Allied Signal clarifies that wheels having a ``B'' prefix 
serial number are original equipment wheels shipped from the factory. 
Individual inboard and individual outboard wheel halves are given the 
same ``B'' serial number on the final production line and mated 
together to form a complete wheel assembly. Wheel halves having serial 
numbers with an ``H'' prefix are replacement service halves. 
Availability of a service wheel half allows an operator to replace a 
damaged wheel half instead of the entire wheel assembly. Individual 
inboard and outboard service halves are not mated together to form a 
complete assembly; they are shipped independently of each other.
    Allied Signal also clarifies that Bendix Service Information Letter 
(SIL) 392, Revision 1, dated November 15, 1979, and Allied Signal 
Service Bulletin No. 737-32-026, dated April 26, 1988, apply to both 
the ``H'' and ``B'' prefix serial numbers, not just the ``H'' prefix 
serial numbers used in the ``B'' prefix wheel assemblies.
    The FAA agrees that clarification of the part and serial numbers 
specified in the original NPRM is necessary. As stated previously, the 
FAA intends that all affected wheels be removed from service; the FAA 
concurs with the changes suggested by Allied Signal based on that 
intent. Paragraphs (a) and (b) of this supplemental NPRM reflect the 
appropriate part and serial numbers provided by Allied Signal. In 
addition, serial number H-1049 has been specified in this supplemental 
NPRM in place of serial number H-999.

Request to Revise the Applicability of the Proposed AD

    The Air Transport Association (ATA) of America, on behalf of one of 
its members, requests that the applicability of the proposed AD be 
limited only to the Bendix main wheel assemblies that prompted the 
airworthiness concern. The ATA states that the proposed applicability 
affects even operators with BFGoodrich brakes. The commenter concludes 
that, unless operators of airplanes equipped with BFGoodrich brakes 
submit a request for and receive approval of an alternative method of 
compliance (AMOC), those operators are considered in noncompliance with 
the AD.
    The FAA concurs with the commenter's request to revise the 
applicability of the original NPRM. This FAA has revised the 
applicability of this supplemental NPRM to specify that the proposed 
rule applies only to Boeing Model 737-100 and -200 series airplanes 
equipped with Bendix main wheel assemblies having part number 2601571-
1. Paragraphs (a) and (b) of the supplemental NPRM specify the serial 
numbers of the inboard and outboard wheel halves that are affected.
    The FAA also clarifies that operators of airplanes equipped with 
BFGoodrich brakes would not be required to submit a request for 
approval of an AMOC. Although the applicability of the original NPRM 
identified the affected airplanes as ``all Model 737-100 and -200 
series airplanes,'' paragraphs (a) and (b) specified clearly that only 
those airplanes equipped with Bendix main wheel assemblies having 
certain part and serial numbers are affected by the proposed rule. 
Therefore, operators of airplanes equipped with other main wheel 
assemblies are not subject to the requirements of this AD, and would 
have no reason to apply for approval of an AMOC.

Request to Revise Statement of Findings of Critical Design Review 
Team

    One commenter requests the second paragraph of the Discussion 
section that appeared in the preamble to the proposed rule be revised 
to accurately reflect the findings of the Critical Design Review (CDR) 
team. The commenter asks that the FAA delete the one sentence in that 
paragraph, which read: ``The recommendations of the team include 
various changes to the design of the flight control systems of these 
airplanes, as well as correction of certain design deficiencies.'' The 
commenter suggests that the following sentences should be added: ``The 
team did not find any design issues that could lead to a definite cause 
of the accidents that gave rise to this effort. The recommendations of 
the team include various changes to the design of the flight control 
systems of these airplanes, as well as incorporation of certain design 
improvements in order to enhance its already acceptable level of 
safety.''
    The FAA acknowledges that the CDR team did not find any design 
issue that could lead to a definite cause of the accidents that gave 
rise to this effort. However, as a result of having conducted the CDR 
of the flight control systems on Boeing Model 737 series airplanes, the 
team indicated that there are a number of recommendations that should 
be addressed by the FAA for each of the various models of the Model 
737. In reviewing these recommendations, the FAA has concluded that 
they address unsafe conditions that must be corrected through the 
issuance of AD's. Therefore, the FAA does not concur that these design 
changes merely ``enhance [the Model 737's] already acceptable level of 
safety.''

Conclusion

    Since these changes provide significant clarification of the intent 
and requirements of the originally proposed rule, the FAA has 
determined that it is in the public interest to reopen the comment 
period to provide additional opportunity for public comment.

Cost Impact

    There are approximately 634 Boeing Model 737-100 and -200 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 241 airplanes of U.S. registry would be affected by this 
proposed AD.
    The FAA estimates that it would take approximately 4 work hours per 
airplane to accomplish the proposed replacement of wheel halves, and 
that the average labor rate is $60 per work hour. Required parts would 
cost approximately $20,212 per airplane. Based on these figures, the 
cost impact of the proposed replacement on U.S. operators is estimated 
to be $4,928,932, or $20,452 per airplane.
    The FAA also estimates that it would take approximately 2 work 
hours per airplane to accomplish the proposed cleaning and inspection, 
and that the average labor rate is $60 per work hour. Based on these 
figures, the cost impact of the proposed cleaning and inspection on 
U.S. operators is estimated to be $28,920, or $120 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation: (1) Is not a ``significant regulatory action''

[[Page 12126]]

under Executive Order 12866; (2) is not a ``significant rule'' under 
the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 
1979); and (3) if promulgated, 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 copy of the 
draft regulatory evaluation prepared for this action is contained in 
the Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

BOEING: Docket 96-NM-152-AD.

    Applicability: Boeing Model 737-100 and -200 series airplanes 
equipped with Bendix main wheel assemblies having part number 
2601571-1, certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (c) 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 the wheel flanges, which could result in 
damage to the hydraulics systems, jammed flight controls, loss of 
electrical power, or other combinations of failures; and consequent 
reduced controllability of the airplane, accomplish the following:
    (a) For airplanes equipped with a Bendix main wheel assembly 
having part number (P/N) 2601571-1 with an inboard wheel half with 
serial number (S/N) B-5999 or lower, or S/N H-1799 or lower; or with 
an outboard wheel half with S/N B-5999 or lower, or S/N H-1049 or 
lower; accomplish the following:
    (1) Within 180 days after the effective date of this AD, and 
thereafter at each tire change until the replacement required by 
paragraph (b) of this AD is accomplished:
    Accomplish the actions specified in paragraphs (a)(1)(i), 
(a)(1)(ii), and (a)(1)(iii) of this AD, in accordance with the 
Accomplishment Instructions of Allied Signal Service Bulletin No. 
737-32-026, dated April 26, 1988, including Attachments 1 and 2.
    (i) Clean any inboard and outboard wheel half specified in 
paragraph (a) of this AD. And
    (ii) Inspect the wheel halves for corrosion or missing paint. If 
any corrosion is found, or if any paint is missing in large areas, 
prior to further flight, strip or remove paint, and remove any 
corrosion. And
    (iii) Perform an eddy current inspection to detect cracks of the 
bead seat area.
    (2) If any cracking is found during the inspections required by 
this paragraph, prior to further flight, repair or replace the wheel 
halves with serviceable wheel halves in accordance with procedures 
specified in the Component Maintenance Manual.
    (b) For airplanes equipped with a Bendix main wheel assembly 
having P/N 2601571-1 with an inboard wheel half with S/N B-5999 or 
lower, or S/N H-1799 or lower; or with an outboard wheel half with 
S/N B-5999 or lower, or S/N H-1049 or lower; accomplish the 
following: Within 2 years after the effective date of this AD, 
accomplish the actions specified in paragraphs (b)(1) and (b)(2) of 
this AD, in accordance with Bendix Service Information Letter (SIL) 
392, Revision 1, dated November 15, 1979. Accomplishment of the 
replacement constitutes terminating action for the repetitive 
inspections required by paragraph (a) of this AD.
    (1) Remove any inboard wheel half specified in paragraph (b) of 
this AD, and replace it with an inboard wheel half having P/N 
2607046, S/N B-6000 or greater, or S/N H-1800 or greater. And
    (2) Remove any outboard wheel half specified in paragraph (b) of 
this AD, and replace it with an outboard wheel half having P/N 
2607047, S/N B-6000 or greater, or S/N H-1050 or greater.
    (c) 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) 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. Issued in Renton, 
Washington, on March 7, 1997.

Darrell M. Pederson,
 Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-6438 Filed 3-13-97; 8:45 am]
BILLING CODE 4910-13-U