[Federal Register Volume 64, Number 78 (Friday, April 23, 1999)]
[Rules and Regulations]
[Pages 19879-19881]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-9739]



[[Page 19879]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-337-AD; Amendment 39-11132; AD 99-08-23]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
300, -400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to all Boeing Model 737-100, -200, -200C, -300, -400, and 
-500 series airplanes. This action requires repetitive inspections to 
detect cracking in the web of the aft pressure bulkhead at body station 
1016 at the aft fastener row attachment to the ``Y'' chord; and 
corrective actions, if necessary. This amendment is prompted by several 
reports of fatigue cracking found at that location on Model 737 series 
airplanes. The actions specified in this AD are intended to detect and 
correct such fatigue cracking, which could result in rapid 
decompression of the fuselage.

DATES: Effective May 10, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 10, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before June 22, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-337-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.

FOR FURTHER INFORMATION CONTACT: Nenita Odesa, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2557; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received reports of fatigue 
cracking found on Boeing Model 737-200 series airplanes in the web of 
the aft pressure bulkhead at body station 1016 at the aft fastener row 
attachment to the ``Y'' chord. An 11-inch crack was found on an 
airplane with 40,000 total flight cycles, and a 3.5-inch crack was 
found on an airplane with 28,000 total flight cycles. Investigation 
revealed 43 fasteners installed in improperly drilled holes at the web-
to-``Y'' chord attachment in the area of the 11-inch crack. Such 
fatigue cracking, if not detected and corrected, could result in rapid 
decompression of the fuselage.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to detect and correct fatigue cracking at certain fastener 
holes of the aft pressure bulkhead, which could result in rapid 
decompression of the fuselage. This AD requires repetitive inspections 
of the web of the aft pressure bulkhead at body station 1016 at the aft 
fastener row attachment to the ``Y'' chord, and corrective actions, if 
necessary. For compliance with this inspection requirement, operators 
may perform either a low frequency eddy current (LFEC) inspection from 
the aft side of the bulkhead or a detailed visual inspection from the 
forward side of the bulkhead. Corrective actions include a high 
frequency eddy current inspection to detect cracking of the web at the 
``Y'' chord attachment; a detailed visual inspection of the bulkhead, 
if necessary; and repair in accordance with a method approved by the 
FAA.

Differences Between AD and Relevant Service Information

    This AD refers to Boeing 737 Nondestructive Test (NDT) Manual D6-
37239, Part 6, Subject 53-10-54, as the appropriate source of service 
information for accomplishment of the LFEC inspection. Operators should 
note that, unlike the procedures described in the NDT manual, which 
specifies that the web be inspected only from stringer 9 left to 
stringer 9 right, this AD expands the area to be inspected. Because of 
the safety implications and consequences associated with fatigue 
cracking and because of the unknown nature of the source of the subject 
cracking, the FAA has determined that an LFEC inspection, if 
accomplished, must be performed from stringer 15 left to stringer 15 
right of the upper section of the bulkhead at body station 1016.

Interim Action

    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-337-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will not have substantial direct 
effects 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, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.

[[Page 19880]]

    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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:

99-08-23  Boeing: Amendment 39-11132. Docket 98-NM-337-AD.

    Applicability: All Model 737-100, -200, -200C, -300, -400, and -
500 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 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 detect and correct fatigue cracking at certain fastener holes 
of the aft pressure bulkhead, which could result in rapid 
decompresssion of the fuselage, accomplish the following:

Initial Inspection

    (a) Perform either inspection specified by paragraph (a)(1) or 
(a)(2) of this AD at the time specified in paragraph (b) of this AD.
    (1) Perform a low frequency eddy current inspection from the aft 
side of the aft pressure bulkhead to detect discrepancies (including 
cracking, misdrilled fastener holes, and corrosion) of the web of 
the upper section of the aft pressure bulkhead at body station 1016 
at the aft fastener row attachment to the ``Y'' chord, from stringer 
15 left to stringer 15 right, in accordance with Boeing 737 
Nondestructive Test Manual D6-37239, Part 6, Section 53-10-54, dated 
December 5, 1998.
    (2) Perform a detailed visual inspection of the aft fastener row 
attachment to the ``Y'' chord from the forward side of the aft 
pressure bulkhead to detect discrepancies (including cracking, 
misdrilled fastener holes, and corrosion) of the entire web of the 
aft pressure bulkhead at body station 1016.
    (b) Perform the inspection required by paragraph (a) of this AD 
at the time specified by paragraph (b)(1), (b)(2), or (b)(3) of this 
AD, as applicable.
    (1) For airplanes that have accumulated 40,000 or more total 
flight cycles as of the effective date of this AD: Inspect within 
375 flight cycles or 60 days after the effective date of this AD, 
whichever occurs later.
    (2) For airplanes that have accumulated 25,000 or more total 
flight cycles and fewer than 40,000 total flight cycles as of the 
effective date of this AD: Inspect within 750 flight cycles or 90 
days after the effective date of this AD, whichever occurs later.
    (3) For airplanes that have accumulated fewer than 25,000 total 
flight cycles as of the effective date of this AD: Inspect prior to 
the accumulation of 25,750 total flight cycles.

Repetitive Inspections

    (c) Within 1,200 flight cycles after performing the initial 
inspection required by paragraph (a) of this AD, and thereafter at 
intervals not to exceed 1,200 flight cycles: Perform either 
inspection specified by paragraph (a)(1) or (a)(2) of this AD.

Corrective Actions

    (d) If any discrepancy is detected during any inspection 
required by this AD: Prior to further flight, accomplish the actions 
specified by paragraphs (d)(1) and (d)(3), and paragraph (d)(2) if 
applicable, of this AD.
    (1) Perform a high frequency eddy current inspection from the 
forward side of the bulkhead to detect cracking of the web at the 
``Y'' chord attachment, around the entire periphery of the ``Y'' 
chord, in accordance with Boeing 737 Nondestructive Test Manual D6-
37239, Part 6, Section 51-00-00, Figure 23, dated November 5, 1997.
    (2) If the most recent inspection performed in accordance with 
paragraph (a) of this AD was not a detailed visual inspection: 
Accomplish the actions specified by paragraph (a)(2) of this AD. If 
the inspection was a detailed visual inspection, it is not necessary 
to repeat that inspection prior to further flight.
    (3) Repair any discrepancy such as cracking or corrosion or 
misdrilled fastener holes in accordance with a method approved by 
the Manager, Seattle Aircraft Certification Office (ACO), FAA, 
Transport Airplane Directorate; or in accordance with 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 ACO, to make such findings.

Alternative Methods of Compliance

    (e) 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 Permits

    (f) Special flight permits may be issued in accordance with 
Secs. 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

    (g) The eddy current inspections shall be done in accordance 
with Boeing 737 Nondestructive Test Manual D6-37239, Part 6, Section 
53-10-54, dated December 5, 1998; or Boeing 737 Nondestructive Test 
Manual D6-37239, Part 6, Section 51-00-00, Figure 23, dated November 
5, 1995; as applicable. These references contain the specified list 
of effective pages:

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                Page No.                     Revision level shown on page             Date shown on page
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Title Page.............................  Not Shown..........................  February 5, 1995.
List of Effective Pages--Pages 1, 6-12.  Not Shown..........................  December 5, 1998.
List of Effective Pages--Page 2........  Not Shown..........................  August 5, 1998.
List of Effective Pages--Pages 2A, 3...  Not Shown..........................  November 5, 1997.
List of Effective Pages--Page 4........  Not Shown..........................  November 5, 1995.

[[Page 19881]]

 
List of Effective Pages--Page 5........  Not Shown..........................  May 5, 1997.
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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.
    (h) This amendment becomes effective on May 10, 1999. .

    Issued in Renton, Washington, on April 9, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-9739 Filed 4-22-99; 8:45 am]
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