[Federal Register Volume 66, Number 32 (Thursday, February 15, 2001)]
[Proposed Rules]
[Pages 10390-10393]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-3858]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-327-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

[[Page 10391]]

directive (AD) that is applicable to all Boeing Model 737-100 and -200 
series airplanes. This proposal would require repetitive inspections to 
find fatigue cracking in the main deck floor beams located at certain 
body stations, and repair, if necessary. This proposal also provides 
for optional terminating action for the repetitive inspections. This 
action is necessary 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. This action is intended to address the identified unsafe 
condition.

DATES: Comments must be received by April 2, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-327-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-327-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

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:

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 action may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    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 action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-327-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-327-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports from the manufacturer indicating 
several operators have found cracking in the body buttock line (BBL) 
0.07 floor beams. On airplanes having between 27,000 and 55,000 total 
flight cycles, cracks were found in the upper chord at body station 
(BS) 663. On airplanes having between 31,000 and 51,000 total flight 
cycles, cracks were found in the web at BS 663. On airplanes having 
between 18,000 and 54,000 total flight cycles, cracks were found in the 
lower chord at BS 727. On airplanes having between 23,000 and 39,000 
total flight cycles, cracks were found in the web at BS 706 through 
711. Investigation revealed that the cracks were caused by fatigue 
resulting from pressurization flexure. Failure of the main deck floor 
beams at certain body stations due to fatigue cracking could result in 
rapid decompression and consequent reduced controllability of the 
airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-57-
1210, dated April 4, 1991, which describes procedures for repetitive 
visual inspections of the main deck floor beams located between BS 650 
and BS 730, around BS 710 and BS 727, and at BS 650 through 675, to 
find cracking; and repair of any cracking found. If no cracking is 
found after doing the visual inspection, the service bulletin provides 
an option for a one-time eddy current inspection of the fastener holes. 
If no cracking is found during the eddy current inspection, doing the 
modification (change) of the applicable floor beams would end the 
repetitive visual inspections for that area. Accomplishment of the 
actions specified in the service bulletin is intended to adequately 
address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the service bulletin described previously, except as discussed below.

Difference Between Service Bulletin and This Proposed Rule

    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, this proposed AD requires the repair of those 
conditions to be done per a method approved by the 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.
    Operators also should note that the FAA has determined that the 
repetitive inspections proposed by this AD can be allowed to continue 
instead of doing a terminating action. In making this determination, 
the FAA considers that, in this case, long-term continued operational 
safety will be adequately assured by doing the repetitive inspections 
to find cracking before it represents a hazard to the airplane.

Cost Impact

    There are approximately 935 airplanes of the affected design in the

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worldwide fleet. The FAA estimates that 340 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
8 work hours per airplane to do the proposed inspection, and that the 
average labor rate is $60 per work hour. Based on these figures, the 
cost impact of the proposed 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 would take 
approximately 96 work hours per airplane to do the change, at an 
average labor rate of $60 per work hour. Required parts would 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 proposed herein would 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 proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' 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 2000-NM-327-AD.

    Applicability: All Model 737-100 and -200 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 per paragraph (d) 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 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 (BBL) 0.07] 
located between BS 650 and BS 730, per the 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 3,000 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)], specified in the Accomplishment 
Instructions of Boeing Service Bulletin 737-57-1210, dated April 4, 
1991, ends the repetitive inspections for that area.

Alternative Methods of Compliance

    (d) 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

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Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    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 Permit

    (e) Special flight permits may be issued per 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 done.


    Issued in Renton, Washington, on February 9, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-3858 Filed 2-14-01; 8:45 am]
BILLING CODE 4910-13-U