[Federal Register Volume 66, Number 223 (Monday, November 19, 2001)]
[Proposed Rules]
[Pages 57908-57910]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-28798]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-359-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -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 supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 737 
series airplanes. The existing AD currently requires repetitive 
inspections for cracking and corrosion of the pressure bulkhead at body 
station (BS) 1016, and follow-on actions. This action would expand the 
applicability of the existing AD to include additional airplanes and 
require new repetitive inspections to detect cracking and corrosion of 
the aft pressure bulkhead at BS 1016, and follow-on actions. This 
action is necessary to detect and correct corrosion or cracking of the 
aft pressure bulkhead at BS 1016, which could result in loss of the aft 
pressure bulkhead web and stiffeners and consequent rapid decompression 
of the fuselage. This action is intended to address the identified 
unsafe condition.

DATES: Comments must be received by January 3, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-359-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. 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-359-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-359-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-359-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On December 6, 1985, the FAA issued AD 84-20-03 R1, amendment 39-
5183 (50 FR 51235, December 16, 1985), applicable to certain Boeing 
Model 737 series airplanes, to require repetitive inspections for 
cracking and corrosion of the pressure bulkhead at body station (BS) 
1016, and follow-on actions. That action was prompted by reports 
indicating that cracking or corrosion and cracking had been found on 
several Boeing Model 737-200 series airplanes at the lower central web 
and stiffeners of the pressure bulkhead at BS 1016. The requirements of 
that AD are intended to detect and correct such corrosion and cracking, 
which could result in reduced structural integrity of the aft pressure 
bulkhead.

Actions Since Issuance of Previous Rule

    Since the issuance of that AD, we have received reports of severe 
corrosion in the area affected by the existing AD on other Model 737 
series airplanes which are not included in the applicability of the 
existing AD. In addition, we have determined that the instructions for 
the inspections required by the existing AD are not adequate in 
defining the inspection level and area, nor are the instructions 
adequate for gaining access and preparing for the inspection.

Explanation of Relevant Service Information

    We have reviewed and approved Boeing Alert Service Bulletin 737-
53A1075, Revision 3, dated June 8, 2000. (The existing AD shows Boeing 
Service Bulletin 737-53-1075, Revision 1, dated September 2, 1983, as 
the appropriate source of service information for accomplishment of the 
actions required by that AD.) Revision 3 of the service bulletin 
describes procedures for repetitive detailed visual inspections for 
cracking and corrosion of the aft pressure bulkhead at BS 1016, 
including inspections of the following items: Forward and aft sides of 
the pressure web, forward and aft sides of the pressure chord, pressure 
chord radius, forward and aft sides of the angle stiffener, forward and 
aft chord, stringer end fitting, system penetration doublers, channel 
stiffeners and fasteners, ``Z'' stiffeners and fasteners, and fasteners 
common to the pressure

[[Page 57909]]

chord and pressure web. The service bulletin also describes follow-on 
actions to these inspections, which involve repair, if necessary, as 
well as clearing the drain path to ensure that it is free of debris, 
enlarging the drain hole, and replacing existing leveling compound, if 
necessary. Accomplishment of the actions shown 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 supersede AD 84-20-03 R1 to continue to require 
repetitive detailed visual inspections for cracking and corrosion of 
the pressure bulkhead at BS 1016, and follow-on actions. This action 
would require new repetitive inspections to detect cracking and 
corrosion of the aft pressure bulkhead at BS 1016 and follow-on 
actions, and would require these inspections to be accomplished on 
airplanes not subject to the existing AD. The actions would be required 
to be accomplished according to Revision 3 of the service bulletin 
described previously, except as discussed below.

Differences Between Proposed AD and Service Bulletin

    This proposed AD differs from Revision 3 of the service bulletin in 
this way: The service bulletin states that the manufacturer must be 
contacted for disposition of certain repair conditions, but this 
proposed AD would require the repair of those conditions to be 
accomplished 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 
Manager, Seattle Aircraft Certification Office, to make such findings.

Explanation of Changes to Requirements of Existing AD

    We have revised the requirements of the existing AD, as restated in 
this proposed AD, to remove all references to the use of ``later FAA-
approved revisions of the applicable service bulletin.'' This change is 
consistent with FAA policy in that regard. In place of this language, 
we have revised the existing requirements restated in this proposed AD 
to provide for accomplishment of actions per Revision 1, Revision 2, or 
Revision 3 of the service bulletin. We have determined that this change 
will not increase the economic burden on any operator, nor will it 
increase the scope of the proposed AD.

Explanation of Repetitive Interval

    For certain airplanes, the proposed AD would require repetitive 
inspections at least every two years. For other airplanes, the 
repetitive interval is four years. This difference is due to design 
changes to improve corrosion resistance in the subject area. For 
example, airplanes with line numbers 1 through 929 inclusive have a 
single 0.25-inch drain hole (which the existing AD requires to be 
expanded to 0.5 inch), and airplanes with line numbers 930 through 1042 
inclusive have a single 0.5-inch drain hole. This proposed AD would 
require repetitive inspections on these airplanes at least every two 
years. However, airplanes with line numbers 1043 through 3132 have TWO 
0.5-inch drain holes. We find that the addition of a second drain hole 
on these airplanes, as well as improvements to the leveling compound 
and finishes that are present on airplanes with line numbers 930 
through 3132 inclusive provides additional corrosion resistance. Thus, 
this proposed AD would require repetitive inspections on these 
airplanes at least every four years.

Cost Impact

    There are approximately 2,920 airplanes of the affected design in 
the worldwide fleet.
    We estimate that 337 airplanes of U.S. registry are subject to the 
existing AD. The inspections that are currently required by AD 84-20-03 
R1 take approximately 2 work hours per airplane to accomplish, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the currently required inspections on U.S. operators is 
estimated to be $40,440, or $120 per airplane, per inspection cycle.
    The drain hole enlargement that is currently required by AD 84-20-
03 R1 takes approximately 2 work hours per airplane to accomplish, at 
an average labor rate of $60 per work hour. Based on these figures, the 
cost impact of this currently required action on U.S. operators is 
estimated to be $40,440, or $120 per airplane.
    We estimate that 1,143 airplanes of U.S. registry would be affected 
by this proposed AD. The new inspections that are proposed in this AD 
action would take approximately 4 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of these new proposed requirements on 
U.S. operators is estimated to be $274,320, or $240 per airplane, per 
inspection cycle.
    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 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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-5183 (50 FR

[[Page 57910]]

51235, December 16, 1985), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 2000-NM-359-AD. Supersedes AD 84-20-03 R1, Amendment 
39-5183.

    Applicability: Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes; line numbers (L/N) 1 through 3132 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 (h)(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 corrosion or cracking of the aft pressure 
bulkhead at Body Station (BS) 1016, which could result in loss of 
the aft pressure bulkhead web and stiffeners and consequent rapid 
decompression of the fuselage, accomplish the following:

Restatement of Requirements of AD 84-20-03 R1

Initial Inspection

    (a) For Model 737 series airplanes with L/N 1 through 929 
inclusive, with more than 20,000 hours time-in-service or 7 years 
since date of manufacture, whichever occurs first: Within 120 days 
after January 20, 1986 (the effective date of AD 84-20-03 R1, 
amendment 39-5183), unless already accomplished within the 21 months 
before January 20, 1986, visually inspect the BS 1016 pressure 
bulkhead for cracking and corrosion; according to Boeing Alert 
Service Bulletin 737-53A1075, Revision 1, dated September 2, 1983; 
Revision 2, dated July 13, 1984; or Revision 3, dated June 8, 2000. 
Remove any obstruction to the drain hole in the frame chord and 
replace any deteriorated leveling compound as noted in the service 
bulletin. Treat the area of inspection with corrosion inhibitor BMS 
3-23, or equivalent.

Drain Hole Enlargement

    (b) For airplanes identified in paragraph (a) of this AD: Within 
1 year after January 20, 1986, accomplish the drain hole enlargement 
as shown in Boeing Alert Service Bulletin 737-53A1075, Revision 1, 
dated September 2, 1983; Revision 2, dated July 13, 1984; or 
Revision 3, dated June 8, 2000.

Corrective Action

    (c) If cracking or corrosion is found during any inspection 
required by paragraph (a) or (d) of this AD, before further flight, 
repair according to paragraph (c)(1) or (c)(2) of this AD.
    (1) According to Boeing Alert Service Bulletin 737-53A1075, 
Revision 1, dated September 2, 1983; Revision 2, dated July 13, 
1984; or Revision 3, dated June 8, 2000.
    (2) According to 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 Manager's approval letter must 
specifically reference this AD.

Repetitive Inspections

    (d) For airplanes identified in paragraph (a) of this AD: Repeat 
the visual inspections and corrosion inhibitor treatment in 
paragraph (a) at intervals not to exceed 2 years, until paragraph 
(e) of this AD has been done.

New Requirements of This AD

Initial Inspection

    (e) Do a detailed visual inspection for cracking or corrosion of 
the aft pressure bulkhead at BS 1016 (including the forward and aft 
sides of the pressure web, forward and aft sides of the pressure 
chord, pressure chord radius, forward and aft sides of the angle 
stiffener, forward and aft chord, stringer end fitting, system 
penetration doublers, channel stiffeners and fasteners, ``Z'' 
stiffeners and fasteners, and fasteners common to the pressure chord 
and pressure web), according to Boeing Alert Service Bulletin 737-
53A1075, Revision 3, dated June 8, 2000. Do this inspection at the 
applicable time shown in paragraph (e)(1), (e)(2), or (e)(3) of this 
AD.

    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 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) For airplanes on which an inspection has previously been 
done according to the requirements of paragraph (a) of this AD: Do 
the inspection within 2 years since the most recent inspection 
according to paragraph (a) or (d) of this AD, as applicable. 
Inspection according to paragraph (e) of this AD ends the 
requirement for inspections according to paragraph (d) of this AD.
    (2) For airplanes having L/N 930 through 1042 inclusive, on 
which an inspection has not previously been done according to 
paragraph (a) of this AD: Do the inspection within 2 years after the 
effective date of this AD.
    (3) For airplanes having L/N 1043 through 3132 inclusive, on 
which an inspection has not previously been done according to 
paragraph (a) of this AD: Do the inspection within 6 years since the 
airplane's date of manufacture, or within 2 years after the 
effective date of this AD, whichever occurs later.

Repetitive Inspections

    (f) Repeat the inspection in paragraph (e) of this AD at the 
applicable time shown in paragraph (f)(1) or (f)(2) of this AD.
    (1) For airplanes having L/N 1 through 1042 inclusive: Repeat 
the inspection at least every 2 years.
    (2) For airplanes having L/N 1043 through 3132 inclusive: Repeat 
the inspection at least every 4 years.

Repair

    (g) If any corrosion or cracking is found during any inspection 
according to paragraph (e) or (f) of this AD: Before further flight, 
repair according to Boeing Alert Service Bulletin 737-53A1075, 
Revision 3, dated June 8, 2000. EXCEPTION: If corrosion or cracking 
of the web and stiffeners is outside the limits specified in the 
service bulletin, or if corrosion or cracking is found in any 
structure not covered by the repair instructions in the service 
bulletin, before further flight, repair according to 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 Manager's approval letter 
must specifically reference this AD.

Alternative Methods of Compliance

    (h)(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 84-20-03 R1, amendment 39-5183, 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

    (i) 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 November 9, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-28798 Filed 11-16-01; 8:45 am]
BILLING CODE 4910-13-P