[Federal Register Volume 66, Number 142 (Tuesday, July 24, 2001)]
[Rules and Regulations]
[Pages 38354-38357]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-18017]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-327-AD; Amendment 39-12331; AD 2001-14-20]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 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 and -200 series airplanes, 
that requires repetitive inspections to find fatigue cracking in the 
main deck floor beams located at certain body stations, and repair, if 
necessary. This AD also provides for optional terminating action for 
the repetitive inspections. This AD is prompted by reports of incidents 
involving fatigue cracking and corrosion in transport category 
airplanes that are approaching or have exceeded their design life goal. 
This AD relates to the recommendations of the Airworthiness Assurance 
Task Force assigned to review Model 737 series airplanes, which 
indicate that, to assure long term continued operational safety, 
various structural inspections should be accomplished. The actions 
specified by this AD are intended to prevent failure of the main deck 
floor beams at certain body stations due to fatigue cracking, which 
could result in rapid decompression and consequent reduced 
controllability of the airplane.

DATES: Effective August 28, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 28, 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 all Boeing Model 737-100 and -200 
series airplanes was published in the Federal Register on February 15, 
2001 (66 FR 10390). That action proposed to require repetitive 
inspections to find fatigue cracking in the main deck floor beams 
located at certain body stations, and repair, if necessary. That action 
also proposed to provide for optional terminating action for the 
repetitive inspections.

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.

Extend Compliance Time

    One commenter asks that the compliance time for the detailed visual 
inspection specified in paragraph (a) of the proposal be extended. The 
commenter states that the service bulletin specified in the proposed 
rule is listed in Boeing Document D6-38505, which is titled ``The Aging 
Airplane Service Bulletin Structural Modification and Inspection 
Program,'' hereinafter referred to as the ``Boeing Document.'' The 
commenter notes that previous ADs issued against bulletins included in 
this document contain provisions to minimize the impact of the ADs. To 
be consistent with previous ADs, the commenter suggests that a 15-month 
phase-in period be implemented before the issuance of this proposed 
rule.
    The FAA concurs. This final rule relates to the recommendations of 
the Airworthiness Assurance Task Force assigned to review Model 737 
series airplanes, which indicate that, to assure long term continued 
operational safety, various structural inspections should be 
accomplished per the Boeing Document. To be consistent with the other 
inspections required by the Aging Airplane Program, we have extended 
the compliance time in paragraph (a) of this AD to within 6,000 flight 
cycles or 15 months after the effective date of this AD, whichever 
occurs later.
    The same commenter asks that the initial inspection specified in 
paragraph (a) of the proposed rule be done within 10,000 flight cycles 
after the effective date of the AD, instead of within 6,000 flight 
cycles. The commenter states that, due to the fact that the proposed 
rule requires a repetitive inspection interval that must be 
accomplished at a `C' check

[[Page 38355]]

interval, and the inspection area is not readily available, most 
operators will do the terminating action instead of the repetitive 
inspections. The commenter suggests that an initial 10,000-flight-cycle 
threshold be added to the rule that would allow operators to modify the 
floor structure without the `C' check inspections. The commenter adds 
that it is doing the proposed inspections at a 4-year interval, and 
this interval is adequate to find and address cracks before they reach 
critical length. Additionally, at no time has the commenter found a 
crack that caused any risk of failure of the main deck floor beam. The 
commenter notes that the evident level of urgency of the proposed rule 
is unwarranted and adds that the referenced service bulletin has been a 
topic of the 737 Structures Task Group since 1993 with no significant 
findings presented to the industry to support an urgent, accelerated 
inspection program.
    The FAA does not concur. Insufficient data were submitted to 
support the commenter's request. We are unable to validate that the 
level of urgency for the unsafe condition as specified in the service 
bulletin is unwarranted, because the data submitted does not include 
all the airplanes affected by this final rule. Additionally, the 
necessity for the inspection was established by a review conducted by 
the 737 Structures Working Group. As the commenter shows no correlation 
between a 4-year interval or 10,000 flight cycles, we have determined 
that no change to the final rule is necessary in this regard.
    A second commenter, the manufacturer, asks that the repetitive 
inspection interval specified in paragraph (a)(2)(i) of the proposal be 
changed from every 3,000 flight cycles to every 6,000 flight cycles. 
The commenter states that the repetitive inspection interval specified 
in the referenced service bulletin was changed following an 
investigation by the manufacturer that showed that inspecting every 
6,000 flight cycles adequately addresses the unsafe condition.
    The FAA concurs. The commenter provided documentation from the 737 
Structures Working Group that supports an extension of the repetitive 
inspection interval. Paragraph (a)(2)(i) of the final rule has been 
changed accordingly.

Clarify Terminating Action

    One commenter asks for clarification that repairs done per the 
referenced service bulletin terminate the repetitive inspections. The 
FAA concurs as this clarification is consistent with the referenced 
service bulletin. Paragraph (c) of the final rule has been revised 
accordingly.

Clarify Applicability

    One commenter, the manufacturer, asks that the Applicability 
section of the proposed rule be changed to, ``All Model 737-100 and 
``200 series passenger airplanes.''
    The FAA partially concurs. Model 737-200C series airplanes have a 
different structure in the areas specified in the proposed rule, and 
are not subject to the inspection requirements; however, 737-200C 
airplanes are not listed in the applicability of the proposed rule. The 
requested change is consistent with the effectivity specified in the 
referenced service bulletin; however, identifying the airplanes as 
``passenger'' is not sufficient. Some passenger airplanes have been 
converted to freighters per a supplemental type certificate, and are 
still subject to the unsafe condition. The Summary section of the final 
rule has been changed to ``certain'' Model 737-100 and -200 series 
airplanes, and the Applicability section has been changed to add, ``as 
listed in the referenced service bulletin,'' for clarification.

Revise Preamble Language

    One commenter asks that the Summary and Discussion sections of the 
proposed rule be changed to include information addressing the 
recommendations of the Airworthiness Assurance Task Force as published 
in the Boeing Document. The commenter states that, in AD 2000-07-12, 
amendment 39-11666 (65 FR 19310, May 16, 2000), the Discussion section 
gave significant detail explaining the purpose of the Aging Airplane 
Programs and why an AD was written against the service bulletin. The 
commenter adds that both sections should refer to the Boeing Document 
to reinforce the link between the proposal and the Aging Airplane 
Programs.
    While the FAA concurs with these comments in principle and 
acknowledges that the description of the Aging Airplane Programs could 
have been more specific in the Summary and Discussion sections, the 
Discussion section is not restated in this final rule. The intent of 
the Summary section of the final rule is to provide a brief explanation 
of the unsafe condition and the action necessary to prevent failure of 
the main deck floor beams at certain body stations due to fatigue 
cracking. However, we have included information addressing the 
recommendations of the Airworthiness Assurance Task Force in the 
Summary section of the final rule.

Allow Previously Approved Repairs

    One commenter asks that previously installed approved repairs 
exceeding the service bulletin repair size terminate the inspections 
specified in paragraph (a) of the proposed rule. The commenter states 
that many operators have already done the inspections and repairs per 
the Boeing Document instead of the referenced service bulletin. The 
commenter adds that the proposed AD requires that all repairs not 
installed per the service bulletin be submitted to the FAA for 
approval. To ease the burden of approving previously installed repairs, 
the commenter suggests that paragraph (b) of the proposal should be 
changed to add, ``* * * previously installed approved repairs exceeding 
the service bulletin repair size are considered terminating action for 
the inspections.''
    The FAA partially concurs. Previously approved repairs have been 
subject to analysis prior to acceptance as terminating action. Such 
repairs can be, in addition to the repairs described in the service 
bulletin, considered satisfactory and eliminate the need for 
reinspection in that area. The repairs do not have to be larger than 
the repairs described in the service bulletin to meet these conditions. 
However, installation of a local repair would eliminate the need for 
reinspection in the repaired area only. Paragraph (d) of this AD has 
been changed to add that the previously approved alternative methods of 
compliance (AMOC) of such repairs, issued for AD 90-06-02, amendment 
39-6489 (55 FR 8372, March 7, 1990), and AD 93-08-04, amendment 39-8551 
(58 FR 25546, April 27, 1993), are approved for this final rule.

Revised Service Bulletin/Withdraw Proposed Rule

    Three commenters ask that a revised service bulletin be used for 
doing the actions specified in the proposed rule. One commenter asks 
that Boeing Service Bulletin 737-57-1210, Revision 1, be referenced in 
the proposed rule as the appropriate source of service information for 
doing of the specified actions, instead of the original issue that is 
now referenced. A second commenter states that it has done the 
modification specified in the proposed rule on approximately half of 
its fleet and at least eight of its airplanes have factory production 
changes which should negate the requirement to install modifications. 
The commenter adds that these changes are not identified in the service 
bulletin and notes that issuing an AD would be premature until the 
service bulletin can be revised. A third commenter asks that the 
proposed rule

[[Page 38356]]

be put on hold until the manufacturer has updated the referenced 
service bulletin to include repairs to address the new conditions.
    The FAA does not concur with the commenters. The AD will not be 
revised to reference Revision 1 of the service bulletin because we 
cannot approve the use of a document that does not yet exist. Due to 
the urgency of the unsafe condition, the final rule will be issued 
using the original issue of the service bulletin as the appropriate 
source of service information for doing the specified actions. However, 
operators may submit a request for an AMOC to use a later service 
bulletin through an appropriate FAA Principal Maintenance Inspector, as 
provided for by paragraph (d)(1) of this AD.

Cost Impact

    One commenter states that the cost and time impacts for the 
inspection are unrealistic. The commenter notes that, although the FAA 
does not consider time necessary to gain access and return the area to 
the previous condition, this would constitute the majority of the time 
required to accomplish the inspections. The commenter adds that 
repetitive inspections would be required every 3,000 flight cycles, 
which would necessitate accomplishing the inspections on a special 
schedule when access to the area is not normally available. The 
commenter estimates that it would take 16 hours to gain access and 
close up, so the time and cost estimate for the inspection should be 
greatly increased. Also, if the cost data utilized by the FAA for 
procurement of parts is based upon the referenced service bulletin, 
then the data is approximately 10 years old and should be reviewed for 
accuracy.
    The FAA does not concur with what it infers is a request to revise 
the cost estimate. We stated in the Cost Impact section of the proposed 
rule that, ``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.'' Our position on this matter has not changed since issuance 
of the proposed rule. No change to the final rule 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 935 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 340 airplanes of U.S. registry 
will be affected by this AD, that it will take approximately 8 work 
hours per airplane to do the required inspection, and that the average 
labor rate is $60 per work hour. Based on these figures, the cost 
impact of the AD on U.S. operators is estimated to be $163,200, or $480 
per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet done any of the proposed requirements of this AD 
action, and that no operator would do those actions in the future if 
this proposed AD were not adopted. The cost impact figures discussed in 
AD rulemaking actions represent only the time necessary to do 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.
    Should an operator elect to do the optional terminating action 
rather than continue the repetitive inspections, it will take 
approximately 96 work hours per airplane to do the change, at an 
average labor rate of $60 per work hour. Required parts will cost 
between $218 and $1,426 per airplane. Based on these figures, the cost 
impact of this optional terminating action is estimated to be between 
$5,978 and $7,186 per airplane.

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:

2001-14-20  Boeing: Amendment 39-12331. Docket 2000-NM-327-AD.

    Applicability: Model 737-100 and -200 series airplanes as listed 
in Boeing Service Bulletin 737-57-1210, dated April 4, 1991, 
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 prevent failure of the main deck floor beams at certain body 
stations (BS) due to fatigue cracking, which could result in rapid 
decompression and consequent reduced controllability of the 
airplane, do the following:

Inspections

    (a) Before the accumulation of 20,000 total flight cycles, or 
within 6,000 flight cycles or 15 months after the effective date of 
this AD, whichever occurs later: Do a detailed visual inspection to 
find cracking of the main deck floor beams (body buttock line 0.07) 
located between BS 650 and BS 730, per the

[[Page 38357]]

Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, 
dated April 4, 1991. If no cracking is found, do the requirements in 
paragraph (a)(1) or (a)(2) of this AD at the applicable times 
specified.

    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 find 
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.''

    (1) If no cracking is found around BS 710 (Figure 1) or BS 727 
(Figure 2), do the requirements in either paragraph (a)(1)(i) or 
(a)(1)(ii) of this AD.
    (i) Repeat the detailed visual inspection at intervals not to 
exceed 6,000 flight cycles until accomplishment of the change 
specified in paragraph (c) of this AD. Or
    (ii) Before further flight, do a one-time eddy current 
inspection for cracking of the fastener holes. If no cracking is 
found, before further flight, install the change at BS 710 (Figure 
6) or BS 727 (Figure 7), as applicable, per the Accomplishment 
Instructions of the service bulletin. Doing the change ends the 
repetitive inspections for that area.
    (2) If no cracking is found at BS 650 through BS 675 (Figure 8), 
do the requirements in either paragraph (a)(2)(i) or (a)(2)(ii) of 
this AD.
    (i) Repeat the detailed visual inspection at intervals not to 
exceed 6,000 flight cycles until accomplishment of the change 
specified in paragraph (c) of this AD. Or
    (ii) Before further flight, do a one-time eddy current 
inspection for cracking of the fastener holes. If no cracking is 
found, before further flight, install the change at BS 663 (Figure 
9) per the Accomplishment Instructions of the service bulletin. 
Doing the change ends the repetitive inspections for that area.

Repair

    (b) If any cracking is found during any inspection required by 
paragraph (a) of this AD, before further flight, either do the 
repair per the Accomplishment Instructions of Boeing Service 
Bulletin 737-57-1210, dated April 4, 1991, or do the change 
specified in paragraph (c) of this AD. Where the service bulletin 
specifies to contact Boeing for repair instructions: Before further 
flight, repair per a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA; or per data meeting the 
type certification basis of the airplane approved by a Boeing 
Company Designated Engineering Representative who has been 
authorized by the FAA to make such findings. For a repair method to 
be approved by the Manager, Seattle ACO, as required by this 
paragraph, the Manager's approval letter must specifically reference 
this AD.

Optional Terminating Action

    (c) Accomplishment of the main deck floor beam change in the 
applicable areas (BS 710 (Figure 6), BS 727 (Figure 7), or BS 650 
through 675 (Figure 9)), as specified in the Accomplishment 
Instructions of Boeing Service Bulletin 737-57-1210, dated April 4, 
1991; or repair of the applicable area per the service bulletin; 
ends the repetitive inspections for that area.

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) Alternative methods of compliance, approved previously in 
accordance with AD 90-06-02, amendment 39-6489 (55 FR 8372, March 7, 
1990), and AD 93-08-04, amendment 39-8551 (58 FR 25546, April 27, 
1993), are approved as alternative methods of compliance with this 
AD.

    Note 3: 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 by paragraph (b) of this AD, the actions 
shall be done in accordance with Boeing Service Bulletin 737-57-
1210, dated April 4, 1991. 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 August 28, 2001.

    Issued in Renton, Washington, on July 12, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-18017 Filed 7-23-01; 8:45 am]
BILLING CODE 4910-13-P