AD Amdt-39-10931

[Federal Register Volume 63, Number 236 (Wednesday, December 9, 1998)]
[Rules and Regulations]
[Pages 67769-67771]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 98-32361]



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Federal Register / Vol. 63, No. 236 / Wednesday, December 9, 1998 / 
Rules and Regulations

[[Page 67769]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-291-AD; Amendment 39-10931; AD 98-25-06]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-200, -200C, -300, and 
-400 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 Boeing Model 737-200, -200C, -300, and -400 
series airplanes. This action requires repetitive inspections to detect 
cracking of the corners of the door frame and the cross beams of the 
aft cargo door, and corrective actions, if necessary. This action also 
provides an optional terminating action for the repetitive inspection 
requirement of this AD. This amendment is prompted by reports 
indicating that fatigue cracks have been detected in the corners of the 
door frame and the cross beams of the aft cargo door on several in-
service airplanes, and by another report indicating that rapid 
depressurization occurred during flight on one of those airplanes. The 
actions specified in this AD are intended to prevent fatigue cracking 
of the corners of the door frame and the cross beams of the aft cargo 
door, which could result in rapid depressurization of the airplane.

DATES: Effective December 24, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 24, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before February 8, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-291-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: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received reports indicating that 
fatigue cracks have been detected in the corners of the door frame and 
the cross beams of the aft cargo door on several in-service Boeing 
Model 737-200, -200C, -300, and -400 series airplanes. Such fatigue 
cracking results from cabin pressurization cycles. The FAA also has 
received a report indicating that an incident of rapid depressurization 
occurred during flight on one of the affected Boeing Model 737-200 
series airplanes. Investigation of that incident revealed fatigue 
cracks in the corners of the frame of the aft cargo door of the 
airplane. These conditions, if not corrected, could result in rapid 
depressurization of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-52-
1079, Revision 5, dated May 16, 1996. That service bulletin describes 
procedures for repetitive internal detailed visual inspections to 
detect cracking of the corners of the door frame and the upper and 
lower cross beams of the aft cargo door, and corrective actions, if 
necessary. Those corrective actions include repair, replacement of the 
damaged frame, and modification of the aft cargo door. The modification 
entails installation of a steel reinforcement angle at each corner of 
the door and installation of reinforcements on the upper and lower 
cross beams of the door. Accomplishment of such modification eliminates 
the need for the repetitive internal detailed visual inspections.

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 prevent fatigue cracking of the corners of the door 
frame and the cross beams of the aft cargo door, which could result in 
rapid depressurization of the airplane. This AD requires accomplishment 
of the actions specified in the service bulletin described previously, 
except as discussed below.

Other Relevant Rulemaking

    The FAA previously has issued AD 90-06-02, amendment 39-6489 (55 FR 
8372, March 7, 1990), applicable to certain Boeing Model 737 series 
airplanes. AD 90-06-02 requires accomplishment of certain structural 
modifications, which constitutes terminating action for the repetitive 
inspection requirements of this AD.

Differences Between Service Bulletin and This AD

    Operators should note that, unlike the procedures described in the 
service bulletin, this AD does not permit further flight with stop-
drilled cracks in the frame of the aft cargo door. The FAA has 
determined that, because of the safety implications and consequences 
associated with such cracking, any subject aft cargo door frame that is 
found to be cracked must be permanently repaired and modified prior to 
further flight.
    Operators also should note that, although the service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions, this AD requires the repair of those 
conditions to be accomplished in accordance with a method approved by 
the FAA.

Explanation of Applicability

    Operators should note that the effectivity listing of the service 
bulletin includes Boeing Model 737-200 and

[[Page 67770]]

-200C series airplanes having line numbers 6 through 873 inclusive. The 
applicability of this AD includes not only those airplanes listed in 
the effectivity listing of the service bulletin, but also Boeing Model 
737-200, -200C, -300, and -400 series airplanes; having line numbers 
874 through 1642 inclusive; that have certain replacement doors 
installed and that have not been modified in accordance with Boeing 
Service Bulletin 737-52-1079.

Explanation of Compliance Threshold

    Although the service bulletin recommends that the initial 
inspection be performed prior to the accumulation of 12,000 total 
flight cycles, this AD requires that the initial inspection be 
performed within 90 days or 700 flight cycles after the effective date 
of this AD, whichever occurs later. The FAA has determined that the 
number of total flight cycles for an airplane may not be a good 
indicator of the total cycle count for the subject aft cargo door, 
because a door may have been removed from an airplane with many total 
flight cycles and reinstalled on an airplane with relatively fewer 
total flight cycles. Also, the FAA finds that, in view of the reports 
indicating that rapid depressurization occurred on an airplane on which 
fatigue cracks were found in the frame of the aft cargo door, and 
because of the safety implications and consequences associated with 
such cracking, the initial compliance time specified in this AD is 
appropriate.

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-291-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.
    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:

98-25-06  Boeing: Amendment 39-10931. Docket 98-NM-291-AD.

    Applicability: The following airplane models, certificated in 
any category:
    <bullet> Model 737-200 and -200C series airplanes, line numbers 
6 through 873 inclusive;
    <bullet> Model 737-200, -200C, -300, and -400 series airplanes; 
line numbers 874 through 1642 inclusive; equipped with an aft cargo 
door having Boeing part number (P/N) 65-47952-1 or P/N 65-47952-524; 
except:
    1. Those airplanes on which that door has been modified in 
accordance with Boeing Service Bulletin 737-52-1079; or,
    2. Those airplanes on which the door assembly having P/N 65-
47952-524 includes four straps (P/N's 65-47952-139, 65-47952-140, 
65-47952-141, and 65-47952-142) and a thicker lower cross beam web 
(P/N 65-47952-157).

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (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 fatigue cracking of the corners of the door frame and 
the cross beams of the aft cargo door, which could result in rapid 
depressurization of the airplane, accomplish the following:
    (a) Within 90 days or 700 flight cycles after the effective date 
of this AD, whichever occurs later, perform an internal detailed 
visual inspection to detect cracking of the

[[Page 67771]]

corners of the door frame and the cross beams of the aft cargo door, 
in accordance with Boeing Service Bulletin 737-52-1079, Revision 5, 
dated May 16, 1996.
    (1) If no cracking is detected, accomplish the requirements of 
either paragraph (a)(1)(i) or (a)(1)(ii) of this AD.
    (i) Repeat the internal visual inspection thereafter at 
intervals not to exceed 4,500 flight cycles. Or,
    (ii) Prior to further flight, modify the corners of the door 
frame and the cross beams of the aft cargo door in accordance with 
the service bulletin. Accomplishment of such modification 
constitutes terminating action for the repetitive inspection 
requirements of this AD.
    (2) If any cracking is detected in the upper or lower cross 
beams, prior to further flight, modify the cracked beam in 
accordance with paragraph III.C. of Part I of the Accomplishment 
Instructions of the service bulletin. Accomplishment of such 
modification constitutes terminating action for the repetitive 
inspection requirements of this AD for the repaired beam.
    (3) If any cracking is detected in the forward or aft upper door 
frame, prior to further flight, repair the frame and modify the 
corners of the door frame of the aft cargo door, in accordance with 
paragraph III.E. of Part I of the Accomplishment Instructions of the 
service bulletin, except as provided by paragraph (b) of this AD. 
Accomplishment of such modification constitutes terminating action 
for the repetitive inspection requirements of this AD for the upper 
door frame.

    Note 2: Cracks of the forward or aft upper door frame, 
regardless of length, must be repaired prior to further flight in 
accordance with paragraph III.E. of Part I of the Accomplishment 
Instructions of the service bulletin.

    (4) If any cracking is detected in the forward or aft lower door 
frame, prior to further flight, replace the damaged frame with a new 
frame, and modify the corners of the door frame of the aft cargo 
door, in accordance with paragraph III.F. of Part I of the 
Accomplishment Instructions of the service bulletin. Accomplishment 
of such modification constitutes terminating action for the 
repetitive inspection requirements of this AD for the lower door 
frame.
    (b) Where Boeing Service Bulletin 737-52-1079, Revision 5, dated 
May 16, 1996, specifies that certain repairs are to be accomplished 
in accordance with instructions received from Boeing, this AD 
requires that, prior to further flight, such repairs be accomplished 
in accordance with a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.
    (c) Modification of the corners of the door frame and the cross 
beams of the aft cargo door in accordance with Boeing Service 
Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or in 
accordance with the requirements of AD 90-06-02, amendment 39-6489, 
constitutes terminating action for the repetitive inspection 
requirements of this AD.

    Note 3: Modification of the corners of the door frame and the 
cross beams of the aft cargo door accomplished prior to the 
effective date of this AD in accordance with Boeing Service Bulletin 
737-52-1079, dated December 16, 1983; Revision 1, dated December 15, 
1988; Revision 2, dated July 20, 1989; Revision 3, dated May 17, 
1990; or Revision 4, dated February 21, 1991; are considered 
acceptable for compliance with paragraph (c) of this AD.

    (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 4: 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 
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.
    (f) Except as provided by paragraph (b) of this AD, the 
inspections, repair, replacement, and modification (if 
accomplished), shall be done in accordance with Boeing Service 
Bulletin 737-52-1079, Revision 5, dated May 16, 1996. 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 24, 1998.

    Issued in Renton, Washington, on November 30, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-32361 Filed 12-8-98; 8:45 am]
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