[Federal Register Volume 59, Number 236 (Friday, December 9, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-30143]


[[Page Unknown]]

[Federal Register: December 9, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-205-AD; Amendment 39-9089; AD 94-25-05]

 

Airworthiness Directives; Boeing Model 737 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 certain Model 737 series airplanes. This action 
requires 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. This amendment is prompted by reports of cracking in 
the lap joints of the fuselage skin. The actions specified in this AD 
are intended to prevent sudden decompression of the airplane due to 
undetected cracking of the fuselage skin.

DATES: Effective December 27, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 27, 1994.
    Comments for inclusion in the Rules Docket must be received on or 
before February 7, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-205-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    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 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.

FOR FURTHER INFORMATION CONTACT: Thomas Rodriguez, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2779; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: Recently, the FAA has received reports of 
cracking in the lap joints of the fuselage skin on Boeing Model 737 
series airplanes that had accumulated between 52,000 and 77,000 total 
flight cycles. These cracks were located in the lower skin at the lower 
row of fasteners in the lap joints of the fuselage at the tear straps 
locations. Further cracking was found between the tear straps that are 
installed at the frames and halfway between the frames. The longest 
crack was 0.52 inch long, but when linked with adjacent cracks, the 
total length of this crack was 2.0 inches. The cause of this cracking 
has been attributed to fatigue. Such cracking, if not detected and 
corrected in a timely manner, could result in sudden decompression of 
the airplane.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-53A1177, dated November 8, 1994, which describes procedures for 
repetitive eddy current inspections to detect cracking of the lower 
skin at the lower row of fasteners in the lap joints between body 
stations 259.50 and 1016, and repair of any cracking detected. The 
alert service bulletin also describes procedures for close visual 
inspections to detect corrosion and bulging in the lap joints, and 
repair of any corrosion or bulging detected. [Visual inspections to 
detect corrosion are required by AD 90-25-01, amendment 39-6789 (55 FR 
49263, November 27, 1990), which requires the implementation of a 
corrosion control program.]
    Since an unsafe condition has been identified that is likely to 
exist or develop on other Model 737 series airplanes of the same type 
design, this AD is being issued to detect and correct fatigue cracking 
that could lead to sudden decompression of the airplane. This AD 
requires repetitive eddy current inspections to detect cracking of the 
lower skin at the lower row of fasteners in the lap joints of the 
fuselage between body stations 259.50 and 1016, and repair of any 
cracking detected. The actions are required to be accomplished in 
accordance with the alert service bulletin described previously.
    The compliance time for accomplishment of the initial action 
required by this AD is 120 days. That number of days is usually 
sufficient to allow for prior notice to the public and a brief comment 
period before adoption of a final rule. In this AD, however, that 
compliance time was selected because of (1) the large number of 
aircraft affected by the AD (2,274 airplanes worldwide, of which 
approximately 815 are U.S.-registered); (2) the large number of work 
hours (approximately 40) required to accomplish the inspection; (3) the 
availability of an adequate number of maintenance facilities able to 
accommodate scheduling the fleet for inspection; and (4) a foreseeable 
short-term problem with availability of repair parts and procedures if 
cracks are found. A shorter compliance time might have resulted in the 
unnecessary removal of airplanes from service pending scheduling and 
delivery of repair parts. Nevertheless, the FAA has determined that 
immediate adoption is necessary in this case because of the importance 
of initiating the required inspections as soon as possible.
    This is considered to be interim action. The manufacturer has 
advised that it currently is developing a modification that will 
positively address the unsafe condition addressed by this AD. Once this 
modification is developed, approved, and available, the FAA may 
consider additional rulemaking.
    As a result of recent communications with the Air Transport 
Association (ATA) of America, the FAA has learned that, in general, 
some operators may misunderstand the legal effect of AD's on airplanes 
that are identified in the applicability provision of the AD, but that 
have been altered or repaired in the area addressed by the AD. Under 
these circumstances, at least one operator appears to have incorrectly 
assumed that its airplane was not subject to an AD. On the contrary, 
all airplanes identified in the applicability provision of an AD are 
legally subject to the AD. If an airplane has been altered or repaired 
in the affected area in such a way as to affect compliance with the AD, 
the owner or operator is required to obtain FAA approval for an 
alternative method of compliance with the AD, in accordance with the 
paragraph of each AD that provides for such approvals. A note has been 
included in this rule to clarify this requirement.
    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 94-NM-205-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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.
    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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

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

94-25-05 Boeing: Amendment 39-9089. Docket 94-NM-205-AD.

    Applicability: Model 737 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 use the authority 
provided in paragraph (d) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition; or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent sudden decompression of the airplane, accomplish the 
following:
    (a) Prior to the accumulation of 60,000 total flight cycles or 
within the next 120 days after the effective date of this AD, 
whichever occurs later, unless accomplished previously within the 
last 120 days prior to the effective date of this AD, perform a low 
frequency eddy current inspection to detect cracking of the lower 
skin at the lower row of fasteners in the lap joints of the fuselage 
between body stations 259.50 and 1016, in accordance with Boeing 
Alert Service Bulletin 737-53A1177, dated November 8, 1994.
    (1) If no cracking is detected, repeat the inspection thereafter 
at the times specified in paragraph (b) of this AD.
    (2) If any cracking is detected, prior to further flight, repair 
in accordance with the alert service bulletin, or in accordance with 
a method approved by the Manager, FAA, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate.
    (b) Repeat the low frequency eddy current inspection required by 
paragraph (a) of this AD at the times specified in paragraphs (b)(1) 
and (b)(2) of this AD.
    (1) If, at the time of the most recent inspection required by 
paragraph (a) of this AD, the airplane had accumulated 60,000 or 
more total flight cycles, but fewer than 69,999 total flight cycles, 
perform the next inspection within 3,500 flight cycles. Repeat the 
inspection thereafter at intervals not to exceed 3,500 flight cycles 
until the airplane accumulates 70,000 total flight cycles; then 
perform the inspections required by paragraph (b)(2) of this AD.
    (2) If, at the time of the most recent inspection, the airplane 
had accumulated 70,000 or more total flight cycles, perform the next 
inspection within 1,500 flight cycles. Repeat the inspection 
thereafter at intervals not to exceed 1,500 flight cycles.
    (c) Within 20 days after the airplane is returned to service 
subsequent to the completion of the inspection required by paragraph 
(a) of this AD, submit a report of the findings of that inspection 
to the FAA, Transport Airplane Directorate, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056; or fax the report to (206) 227-1181. The report should 
include, as a minimum, the information in paragraphs (c)(1), (c)(2), 
and (c)(3) if this AD.
    (1) Aircraft ID (N number, serial number, etc.).
    (2) Total number of cracks detected, including size and location 
of crack(s).
    (3) Negative reports must be submitted (findings of no 
cracking). Information collection requirements contained in this 
regulation have been approved by the Office of Management and Budget 
(OMB) under the provisions of the Paperwork Reduction Act of 1980 
(44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 
2120-0056.
    (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 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.

    (e) 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.
    (f) The inspections shall be done in accordance with Boeing 
Alert Service Bulletin 737-53A1177, dated November 8, 1994. 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.
    (g) This amendment becomes effective on December 27, 1994.

    Issued in Renton, Washington, on December 2, 1994.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-30143 Filed 12-8-94; 8:45 am]
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