[Federal Register Volume 66, Number 166 (Monday, August 27, 2001)]
[Rules and Regulations]
[Pages 44947-44950]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-21393]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-310-AD; Amendment 39-12409; AD 2001-17-18]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, and -200C 
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, and -200C series 
airplanes; that requires repetitive inspections of certain floor beams 
and transverse beams, and corrective actions, if necessary. For certain 
airplanes, this AD also provides optional terminating action for the 
repetitive inspections. The actions specified by this AD are intended 
to detect and correct cracking at the aileron control quadrant cutouts 
and in the cabin floor beams and pressure web transverse beams above 
the main wheel well, which could result in rapid loss of cabin pressure 
and reduced structural integrity of the airframe.

DATES: Effective October 1, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 1, 2001.

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: Scott Fung, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-1221; 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 737-100, -
200, and -200C series airplanes was published in the Federal Register 
on March 9, 2001 (66 FR 14096). That action proposed to require 
inspection of certain floor beams and transverse beams, and corrective 
actions, if necessary.

Recommendation of 737 Aging Fleet Structures Working Group

    The 737 Aging Fleet Structures Working Group has recommended 
accomplishment of Boeing Service Bulletin 737-57-1139, Revision 4, 
dated April 16, 1992, which this AD identifies as the appropriate 
source of service information for the actions required by this AD. This 
AD is in consonance with the group's recommendation.

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.

Applicability of AD

    Several commenters request that the FAA revise the applicability 
statement of the proposed AD for clarification. The commenters point 
out that not all Boeing Model 737-100, -200, and -200C series airplanes 
with line numbers 1 through 1585 inclusive are included in the 
effectivity listing of Boeing Service Bulletin 737-57-1139, Revision 4, 
dated April 16, 1992 (which the proposed rule lists as the appropriate 
source of service information for the proposed actions). One of the 
commenters specifically states that not all Model 737-200C series 
airplanes are included in the effectivity listing. The commenters 
suggest that the FAA revise the applicability statement to include only 
those Model 737-100, -200, and -200C series airplanes listed in the 
service bulletin.
    The FAA concurs with the commenters' request. Certain Model 737-200 
and -200C series airplanes have different structure in the area subject 
to this AD. Thus, these airplanes are not subject to the unsafe 
condition addressed by this AD. We have revised the applicability 
statement of this final rule accordingly.

Initial Inspection Thresholds and Repetitive Intervals: Paragraph 
(a)

    Two commenters request that the FAA extend the compliance time for 
the initial inspection in paragraph (a) of the proposed AD and the 
interval for the repetitive inspections in paragraph (a)(1) of the 
proposed AD. One commenter, an operator, requests that the grace period 
and repetitive interval be extended from 3,000 to 4,000 flight cycles. 
This commenter's rationale is that such an increase would allow it to 
accomplish the requirements of paragraph (a) of the proposed AD during 
a ``C'' check. Another commenter requests that the repetitive interval 
in paragraph (a)(1) be increased to 6,000 flight cycles. This commenter 
states that an investigation by the airplane manufacturer shows that a 
repetitive interval of 6,000 flight cycles would adequately ensure the 
safety of the affected airplanes. The commenter also notes that this 
change will be incorporated into a future revision of Boeing Service 
Bulletin 737-57-1139.
    The FAA concurs with the commenters' requests to extend the 
compliance time for the initial inspection in paragraph (a) of this AD 
and the repetitive interval for the inspections in paragraph (a)(1) of 
this AD. Based upon our review of the airplane manufacturer's 
investigation, we have determined that a grace period and repetitive 
interval of 6,000 flight cycles is adequate to ensure safety. This 
determination is based in part on the airplane manufacturer's 
recommendation to which the second commenter refers.
    In addition, the FAA finds it appropriate to add a new option for a 
grace period for the initial inspection required by paragraph (a) of 
this AD. The compliance time for paragraph (a) is now 12,000 total 
flight cycles, 6,000 flight cycles after the effective date of this AD, 
or 15 months after the effective date of this AD, whichever occurs 
latest. The FAA finds that this new option is consistent with other 
inspections of aging airplane structure mandated previously and will 
allow operators of affected airplanes more flexibility in planning 
compliance.
    Paragraphs (a) and (a)(1) of this AD have been revised accordingly.

[[Page 44948]]

Initial Inspection Thresholds and Repetitive Intervals: Paragraph 
(b)

    One commenter requests that the FAA extend the compliance time for 
certain initial and repetitive inspections. Though the commenter does 
not specify which paragraph its comments apply to, the FAA infers, 
based on the context, that the commenter is requesting changes to 
paragraph (b). The commenter requests that the FAA extend the grace 
period for the initial inspection in paragraph (b) and the interval for 
the repetitive inspections in paragraph (b)(1) from 6,000 to 9,000 
flight cycles. The commenter's rationale is that such increases will 
facilitate accomplishing the inspections at a regularly scheduled 
maintenance visit. The commenter states that the proposed compliance 
time would potentially adversely affect its operations and could damage 
its level of service to its customers. The commenter justifies its 
request based on the fact that, in inspections of its fleet, it has 
found only one airplane with cracks in the areas subject to this AD.
    The FAA does not concur with the commenter's request. The FAA finds 
that there is insufficient data to justify revising the compliance time 
and repetitive interval in paragraph (b) from 6,000 to 9,000 flight 
cycles as the commenter requests. The commenter's crack findings (or 
lack thereof) in its own fleet cannot be generalized to all affected 
airplanes. No change to the AD is necessary in this regard.
    However, as previously explained relative to paragraph (a) of this 
AD, the FAA finds it appropriate to add a new compliance time 
alternative of 15 months after the effective date of this AD for the 
initial inspection required by paragraph (b) of this AD. For certain 
operators, this may extend the compliance time for the initial 
inspection required by paragraph (b) of this AD. The FAA has revised 
paragraph (b) of this AD accordingly.

Approve Existing Repairs as Terminating Action

    One commenter requests that the FAA allow existing repairs as 
terminating action for both the initial and repetitive inspections as 
well as the repairs specified in the proposed rule. The commenter 
states that identifying previous repairs as terminating action for 
actions in the proposed rule would ease the burden of gaining 
reapproval for existing approved repairs.
    The FAA partially concurs with the commenter's request. The FAA 
finds that previously approved repairs (as well as repairs according to 
the procedures in the service bulletin) may be considered acceptable 
and eliminate the need for repetitive inspections of the repaired area 
according to this AD. Operators should note that this applies only to 
inspections of repaired structure: Any unrepaired areas continue to be 
subject to the inspection and repair requirements of this AD. 
Accordingly, the FAA has revised paragraph (c)(1) of this AD to state, 
``For airplanes in Groups 1, 2, and 5; as listed in the service 
bulletin: Modification of the LBL and RBL 24.8 floor beams in the area 
of the aileron control quadrant cutout in accordance with Part I of the 
Accomplishment Instructions of the service bulletin constitutes 
terminating action for the initial and repetitive inspection 
requirements of paragraph (a) of this AD.'' Also, the FAA has added a 
new paragraph (d)(2) which states, ``Repairs approved previously as 
alternative methods of compliance in accordance with AD 90-06-02, 
amendment 39-6489, and AD 93-17-08, amendment 39-8679, are approved as 
alternative methods of compliance with this AD for the AREA OF REPAIR 
ONLY.''

Modifications Required By Previous AD

    One commenter notes that the modifications in Boeing Service 
Bulletin 737-57-1139, Revision 4, are already required by AD 90-06-02, 
amendment 39-6489 (55 FR 8372, March 7, 1990). The commenter requests 
additional recent documentation to substantiate the need for the 
proposed inspections.
    The FAA infers that the commenter is requesting that the FAA 
withdraw the proposed rule. The FAA does not concur with the 
commenter's request. The modifications in the referenced service 
bulletin are already required as part of AD 90-06-02, but that AD 
requires these modifications at 75,000 flight cycles. Cracking has been 
found on in-service airplanes much earlier than this threshold. 
Therefore, the FAA considers it necessary to mandate the inspections in 
this AD, in addition to the modifications required by AD 90-06-02, to 
ensure the continued safety of the airplane fleet. No change to the AD 
is necessary in this regard.

New Service Information

    The airplane manufacturer requests that the FAA revise the proposed 
rule to refer to a new revision of the referenced service bulletin. The 
commenter states that it will issue Revision 5 of the service bulletin 
at an unspecified later date. The commenter notes that this new 
revision will revise a certain compliance time and repetitive interval.
    The FAA does not concur with the commenter's request. The FAA 
cannot approve a document that we have not reviewed. Once the airplane 
manufacturer issues a new revision of the service bulletin, the FAA 
will review the service bulletin and approve it, if appropriate. At 
that point, the FAA will consider allowing Revision 5 of the service 
bulletin to be used as an alternative method of compliance for the 
actions required by this AD. With regard to the extended compliance 
time and repetitive interval, as explained previously, the FAA has 
extended the grace period for the requirements of paragraph (a) and the 
repetitive interval for the requirements of paragraph (a)(1) from 3,000 
to 6,000 flight cycles, which corresponds to the times that the 
airplane manufacturer will identify in Revision 5 of the service 
bulletin. No further change to this AD is necessary.

Statement of Unsafe Condition

    One commenter asks the FAA to revise the statement of unsafe 
condition to remove the statement that cracking at the aileron control 
quadrant cutouts and in the cabin floor beams and pressure web 
transverse beams above the main wheel well could result in rapid loss 
of cabin pressure and reduced structural integrity of the airframe. The 
commenter states that the redundancy in the floor beam structure over 
the wing center section significantly reduces the potential for rapid 
decompression due to fatigue cracking at a certain location of one 
floor beam.
    The FAA does not concur with the commenter's request. Because the 
commenter provides no technical data to justify its request, the FAA 
cannot validate the commenter's claim. No change to the AD is necessary 
in this regard.

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 971 Model 737-100, -200, and -200C series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 333 airplanes of U.S. registry will be affected by this 
AD, and that it will take approximately 10 work hours per airplane to 
accomplish the required

[[Page 44949]]

inspections, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of these inspections on U.S. operators 
is estimated to be $199,800, or $600 per airplane, per inspection 
cycle.
    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. The cost impact figures discussed 
in AD rulemaking actions represent only the time necessary to perform 
the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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:

    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:

2001-17-18  Boeing: Amendment 39-12409. Docket 99-NM-310-AD.

    Applicability: Model 737-100, -200, and ``200C series airplanes; 
as listed in Boeing Service Bulletin 737-57-1139, Revision 4, dated 
April 16, 1992; 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 (d)(1) 
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 detect and correct cracks in the floor beams at the aileron 
control quadrant cutout and in the floor beams and pressure web 
transverse beams above the main wheel well, which could result in 
rapid loss of cabin pressure and reduced structural integrity of the 
airplane, accomplish the following:

Initial Inspection and Follow-On Actions: Groups 1, 2, and 5

    (a) For airplanes in Groups 1, 2, and 5; as listed in Boeing 
Service Bulletin 737-57-1139, Revision 4, dated April 16, 1992: 
Prior to the accumulation of 12,000 total flight cycles, within 
6,000 flight cycles after the effective date of this AD, or within 
15 months after the effective date of this AD, whichever occurs 
latest, perform a detailed visual inspection to detect cracking of 
the left and right buttock line (LBL and RBL) 24.8 floor beams in 
the area of the aileron control quadrant cutout, in accordance with 
Part II of the Accomplishment Instructions of the service bulletin.

    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 appropriated by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc. may be used. Surface cleaning and 
elaborate access procedures may be required

    (1) If no cracking is detected, repeat the inspection thereafter 
at intervals not to exceed 6,000 flight cycles, until the 
modification in paragraph (c)(1) of this AD is done.
    (2) If cracking is detected that is within the limits specified 
in Part II, Paragraphs C.1. and C.2., of the Accomplishment 
Instructions of the service bulletin, prior to further flight, 
repair the crack per the service bulletin, and accomplish the 
modification specified in paragraph (c)(1) of this AD.
    (3) If cracking is detected that is outside the limits 
identified in Part II, Paragraphs C.1. and C.2., of the 
Accomplishment Instructions of the service bulletin, prior to 
further flight, repair in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA; or in 
accordance with a method approved by a Boeing Company Designated 
Engineering Representative (DER) who has been authorized by the 
Manager, Seattle ACO, to make such findings. For the repair method 
to be approved by the Manager, Seattle ACO, as required by this 
paragraph, the approval letter must specifically reference this AD.

Initial Inspection and Follow-On Actions: Groups 1, 2, 3, and 4

    (b) For airplanes in Groups 1, 2, 3, and 4; as listed in Boeing 
Service Bulletin 737-57-1139, Revision 4, dated April 16, 1992: 
Prior to the accumulation of 20,000 total flight cycles, within 
6,000 flight cycles after the effective date of this AD, or within 
15 months after the effective date of this AD, whichever occurs 
latest, perform a detailed visual inspection to detect cracking of 
the transverse beams and floor beams at the beam intersections in 
accordance with Part II of the Accomplishment Instructions of the 
service bulletin.
    (1) If no cracking is detected, repeat the inspection thereafter 
at intervals not to exceed 6,000 flight cycles, until the 
modification in paragraph (c)(2) of this AD is done.
    (2) If any cracking is detected, prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle ACO, or 
in accordance with a method approved by a Boeing Company DER who has 
been authorized by the Manager, Seattle ACO, to make such findings. 
For the repair method to be approved by the Manager, Seattle ACO, as 
required by this paragraph, the approval letter must specifically 
reference this AD.

Modifications (Terminating Action)

    (c) The following modifications in accordance with Boeing 
Service Bulletin 737-57-1139, Revision 4, dated April 16, 1992, 
constitute terminating action for certain requirements of this AD.
    (1) For airplanes in Groups 1, 2, and 5; as listed in the 
service bulletin: Modification of the LBL and RBL 24.8 floor beams 
in the area of the aileron control quadrant cutout in accordance 
with Part I of the Accomplishment Instructions of the service 
bulletin constitutes terminating action for the initial and 
repetitive inspection requirements of paragraph (a) of this AD.
    (2) For airplanes in Groups 1, 2, 3, and 4; as listed in the 
service bulletin: Modification of the transverse beams and floor 
beams at the beam intersections in accordance with Part III or Part 
I, as applicable, of the Accomplishment Instructions of the service 
bulletin constitutes terminating action for the repetitive 
inspections required by paragraph (b) of this AD.


[[Page 44950]]


    Note 3: The modifications specified in Boeing Service Bulletin 
737-57-1139, Revision 4, dated April 16, 1992, are required by AD 
90-06-02, amendment 39-6489, and AD 93-17-08, amendment 39-8679.

Alternative Methods of Compliance

    (d)(1) 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.
    (2) Repairs approved previously as alternative methods of 
compliance in accordance with AD 90-06-02, amendment 39-6489, and AD 
93-17-08, amendment 39-8679, are approved as alternative methods of 
compliance with this AD for the AREA OF REPAIR ONLY.

    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

    (e) 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

    (f) Except as provided in paragraphs (a)(3) and (b)(2) of this 
AD, the actions shall be done in accordance with Boeing Service 
Bulletin 737-57-1139, Revision 4, dated April 16, 1992. 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.

Effective Date

    (g) This amendment becomes effective on October 1, 2001.

    Issued in Renton, Washington, on August 17, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-21393 Filed 8-24-01; 8:45 am]
BILLING CODE 4910-13-U