[Federal Register Volume 66, Number 134 (Thursday, July 12, 2001)]
[Proposed Rules]
[Pages 36513-36515]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-17432]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-73-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200, -200C, -300, -
400, and -500 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 
directive (AD) that is applicable to certain Boeing Model 737-200, -
200C, -300, -400, and -500 series airplanes. This proposal would 
require the replacement of certain repairs in certain fuselage lap 
joints with improved repairs. This proposal also would require a high 
frequency eddy current inspection to find cracking of the repairs of 
the lower skin at the lower row of fasteners in the lap joints of the 
fuselage, and repair of any cracking found. This action is necessary to 
find and fix premature cracking of certain lap joint repairs, which 
could result in rapid decompression of the airplane. This action is 
intended to address the identified unsafe condition.

DATES: Comments must be received by August 27, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-73-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-73-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; 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-73-AD.'' The postcard will be date stamped and 
returned to the commenter.

[[Page 36514]]

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-73-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On October 21, 1997, the FAA issued AD 97-22-07, amendment 39-10179 
(62 FR 55732, October 28, 1997), applicable to certain Boeing Model 737 
series airplanes, which requires repetitive inspections to detect 
cracking of the lower skin at the lower row of fasteners in the lap 
joints of the fuselage, and repair of any cracking detected. That 
action also requires modification of the fuselage lap joints at certain 
locations.
    Since issuance of that AD, the manufacturer has informed the FAA 
that during fatigue testing of the skin panels on certain airplanes 
repaired in accordance with the existing AD, premature cracking in 
certain lap joint repairs was detected. Multiple cracks were detected 
underneath the repairs on airplanes that had accumulated between 10,000 
and 15,000 test cycles since repair per AD 97-22-07. These repairs were 
accomplished using the manufacturer's structural repair manual (SRM). 
Such repairs also may have been installed at times other than that 
required by AD 97-22-07. This condition, if not detected and corrected, 
could result in sudden decompression of the airplane.

Other Rulemaking

    At this time, the FAA is considering two other separate rulemaking 
actions to address the remaining potential unsafe conditions relating 
to the cracking of the lap joints of the fuselage. Those two other 
actions would address:
     Additional repetitive inspections to find cracking of the 
lower skin at the lower row of fasteners in the lap joints of the 
fuselage, and replacement of the preventive modification with an 
improved modification on Model 737 series airplanes, line numbers 292 
through 2565 inclusive. And
     Repetitive inspections to find cracking of certain 
fuselage lap joint areas and modification of those areas, which would 
constitute terminating action for the repetitive inspections. The 
actions would be applicable to Model 737 series airplanes, line numbers 
1 through 291 inclusive.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-
53A1177, Revision 6, dated May 31, 2001, which describes, among other 
things, procedures for replacement of certain SRM repairs in the 
fuselage lap joints with improved repairs. The service bulletin also 
describes a high frequency eddy current (HFEC) open-hole rotating probe 
inspection to find cracking of the lower skin at the lower row of 
fasteners in the lap joints of the fuselage, and repair of any cracking 
found. 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 the replacement of certain repairs in certain 
fuselage lap joints with improved repairs. This proposed AD also would 
require a high frequency eddy current inspection to find cracking of 
the lower skin at the lower row of fasteners in the lap joints of the 
fuselage, and repair of any cracking found. The actions would be 
required to be done per the service bulletin described previously, 
except as discussed below.

Differences Between Service Bulletin and Proposed Rule

    In light of the complexity of the service bulletin, three separate 
rulemaking actions are being issued to address the potential unsafe 
conditions relating to the cracking of the lap joints of the fuselage. 
This proposed rule will address only the sections in the service 
bulletin that pertain to inadequate lap joint repairs done per the SRM.
    Although the service bulletin specifies that the manufacturer may 
be contacted for disposition of certain repair/modification conditions, 
this proposed AD requires the repair/modification 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.

Cost Impact

    There are approximately 2,359 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 958 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 14 work hours per airplane to accomplish 
the proposed actions, 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 $804,720, or $840 per airplane.
    The cost impact figure discussed above is 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 proposed 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 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.

[[Page 36515]]

Sec. 39.13  [Amended]

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

Boeing: Docket 2000-NM-73-AD.
    Applicability: Model 737-200, -200C, -300, -400, and -500 series 
airplanes having line numbers 292 through 2565 inclusive, 
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 find and fix premature cracking of certain fuselage lap joint 
repairs, which could result in rapid decompression of the airplane, 
accomplish the following:

Replacement of Structural Repair Manual (SRM) Lap Joint Repairs

    (a) For Model 737-200, -200C, and -300 series airplanes: Within 
5,000 flight cycles after the effective date of this AD, inspect all 
lap joints between body station (BS) 259.5 and BS 1016 to identify 
all repairs accomplished in accordance with 737-200 SRM, Subject 53-
30-03, Figure 39 (for 737-200 series airplanes); or Boeing 737-300 
SRM, Subject 53-00-01, Figure 227 (for 737-300 series airplanes).
    (b) For Model 737-200, -200C, and -300 series airplanes that 
have a lap joint repair installed at stringers S-4L and S-4R, 
located between BS 259.5 and BS 1016; and installed at S-10L and S-
10R, or at S-14L and S-14R, located between BS 259.5 and BS 540, and 
between BS 727 and BS 1016; that was previously done per the 
procedures specified in Boeing 737-200 SRM, Subject 53-30-3, Figure 
39 repair (for 737-200 series airplanes); or Boeing 737-300 SRM, 
Subject 53-00-01, Figure 227 repair (for 737-300 series airplanes): 
Before the accumulation of 15,000 flight cycles since repair 
installation, or within 5,000 flight cycles after the effective date 
of this AD, whichever is later, do the requirements of paragraph 
(b)(1) or (b)(2) of this AD, as applicable, per Boeing Service 
Bulletin 737-53A1177, Revision 6, dated May 31, 2001. If the area of 
damage that required the existing repair is outside the lap joint 
lower row, 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 
(DER) who has been authorized by the Manager, Seattle ACO, to make 
such findings. For a repair method to be approved by the Manager, 
Seattle ACO, as required by this paragraph, the approval letter must 
specifically reference this AD.
    (1) If the lap joints are being cut out when replacing the SRM 
repair: Replace the Figure 39 repair of the lower skin at the lower 
row of fasteners in the lap joints of the fuselage per Figures 16, 
17, and 18 of the Accomplishment Instructions of the service 
bulletin.
    (2) If the lap joints are not being cut out when replacing the 
SRM repair: Do a high frequency eddy current (HFEC) open-hole 
rotating probe inspection to find cracking of the SRM repair of the 
lower skin at the lower row of fasteners in the lap joints of the 
fuselage, per the Figure 20 inspection procedures of the 
Accomplishment Instructions of the service bulletin. Before further 
flight after doing the inspection, replace a Boeing 737-200 SRM, 
Subject 53-30-3, Figure 39 repair with a Boeing 737-200 SRM, Subject 
53-30-3, Figure 42 repair (for 737-200 series airplanes); or replace 
a Boeing 737-300 SRM, Subject 53-00-01, Figure 227 repair with a 
Boeing 737-300 SRM, Subject 53-00-01, Figure 228 repair (for 737-300 
series airplanes); as applicable; per Part II.D. (``Crack Repair'') 
of the Accomplishment Instructions of the service bulletin.
    (c) For Model 737-200, -200C, and -300 series airplanes that 
have a lap joint repair installed in any area between BS 259.5 and 
BS 1016, other than those specified in paragraph (b) of this AD, 
that was previously done per the procedures specified in Boeing 737-
200 SRM, Subject 53-30-3, Figure 39 repair (for 737-200 series 
airplanes); or Boeing 737-300 SRM Subject 53-00-01, Figure 227 
repair (for 737-300 series airplanes): Before the accumulation of 
20,000 flight cycles since repair installation, or within 5,000 
flight cycles after the effective date of this AD, whichever is 
later, do the requirements of paragraph (b)(1) or (b)(2) of this AD, 
as applicable, per Boeing Service Bulletin 737-53A1177, Revision 6, 
dated May 31, 2001.
    (d) For Model 737-400 and -500 series airplanes: Within 5,000 
flight cycles after the effective date of this AD, inspect all lap 
joints between BS 259.5 and BS 1016 to identify all repairs 
accomplished in accordance with 737-400 SRM, Subject 53-00-01, 
Figure 229 (for 737-400 series airplanes); or Boeing 737-500 SRM, 
Subject 53-00-01, Figure 227 (for 737-500 series airplanes).
    (e) For Model 737-400 and -500 series airplanes that have a lap 
joint repair installed at S-4L and S-4R, located between BS 259.5 
and BS 1016; and installed at S-10L and S-10R, or S-14L and S-14R, 
located between BS 259.5 and BS 540, and between BS 727 and BS 1016; 
that was previously done per the procedures specified in Boeing 737-
400 SRM, Subject 53-00-01, Figure 229 repair (for 737-400 series 
airplanes); or Boeing 737-500 SRM, Figure 227 repair (for 737-500 
series airplanes): Before the accumulation of 15,000 flight cycles 
since repair installation, or within 5,000 flight cycles after the 
effective date of this AD, whichever is later, cut out and replace 
the repair per a method approved by the Manager, Seattle ACO; or per 
data meeting the type certification basis of the airplane approved 
by a Boeing Company DER who has been authorized by the Manager, 
Seattle ACO, to make such findings. For a repair method to be 
approved by the Manager, Seattle ACO, as required by this paragraph, 
the approval letter must specifically reference this AD.
    (f) For Model 737-400, and -500 series airplanes that have a lap 
joint repair installed in any area between BS 259.5 and BS 1016, 
other than those specified in paragraph (d) of this AD, that was 
previously done per the procedures specified in Boeing 737-400 SRM, 
Subject 53-00-01, Figure 229 repair (for 737-400 series airplanes); 
or Boeing 737-500 SRM, Figure 227 repair (for 737-500 series 
airplanes): Before the accumulation of 20,000 flight cycles since 
repair installation, or within 5,000 flight cycles after the 
effective date of this AD, whichever is later, cut out and replace 
the repair per a method approved by the Manager, Seattle ACO; or per 
data meeting the type certification basis of the airplane approved 
by a Boeing Company DER who has been authorized by the Manager, 
Seattle ACO, to make such findings. For a repair method to be 
approved by the Manager, Seattle ACO, as required by this paragraph, 
the approval letter must specifically reference this AD.

Alternative Methods of Compliance

    (g) 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.

    Note 2: 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

    (h) 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 accomplished.

    Issued in Renton, Washington, on July 6, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-17432 Filed 7-11-01; 8:45 am]
BILLING CODE 4910-13-P