[Federal Register Volume 63, Number 207 (Tuesday, October 27, 1998)]
[Rules and Regulations]
[Pages 57240-57243]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-28540]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-245-AD; Amendment 39-10858; AD 98-22-10]
RIN 2120-AA64


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 supersedes an existing airworthiness directive 
(AD),

[[Page 57241]]

applicable to certain Boeing Model 737 series airplanes, that currently 
requires repetitive inspections for cracking of the aft frame and frame 
support structure of the forward service doorway, and repair, if 
necessary. This amendment reduces the compliance time for performing 
the initial inspection, and reduces the repetitive inspection 
intervals. This amendment also adds repetitive inspections for cracking 
of the aft frame web of the forward service doorway, and follow-on 
corrective actions, if necessary. This amendment also provides for an 
optional terminating action for the repetitive inspection requirements 
of this AD. This amendment is prompted by reports indicating that the 
repetitive inspections required by the existing AD may not detect 
cracking of the aft frame and frame support structure of the forward 
service doorway in a timely manner. The actions specified in this AD 
are intended to prevent fatigue cracking of the aft frame and frame 
support structure of the forward service doorway, which could result in 
loss of the door, and consequent rapid decompression of the fuselage.

DATES: Effective November 12, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of November 12, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before December 28, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-245-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: On January 11, 1988, the FAA issued AD 88-
03-03, amendment 39-5832 (53 FR 1609, January 21, 1988), applicable to 
certain Boeing Model 737 series airplanes, to require repetitive 
inspections for cracking of the aft frame and frame support structure 
of the forward service doorway, and repair, if necessary. That action 
was prompted by several reports of cracks of the doorstop support 
structure for the doorstops on the aft frame. The actions required by 
that AD are intended to prevent such cracking, which could result in 
loss of pressurization.

Actions Since Issuance of Previous Rule

    Since the issuance of that AD, the FAA has received reports 
indicating that cracked door frames and severed intercostals of the 
frame support structure have been found on several Boeing Model 737 
series airplanes.
    One operator reported two airplanes with two severed intercostals 
on each airplane. The severed intercostals were detected during a 
repetitive inspection of both airplanes that was performed in 
accordance with AD 88-03-03 at approximately 24,000 total landings. The 
same operator also reported another airplane with one severed 
intercostal and two additional airplanes with cracked frames. The 
severed intercostals were attributed to severe fatigue cracking. The 
initial inspection on each affected airplane was performed at 
approximately 18,000 total landings, and no cracking was detected 
during the initial inspections.
    These findings indicate that fatigue cracking could develop on the 
affected airplanes at a lower number of landings than the initial 
inspection threshold of 25,000 total landings that is mandated by the 
existing AD, and that such fatigue cracking could grow from 
undetectable to severe in fewer landings than the repetitive inspection 
interval of 9,000 landings that is mandated by the existing AD.
    Fatigue cracking of the aft frame and frame support structure of 
the forward service doorway, if not detected and corrected in a timely 
manner, could result in loss of the door, and consequent rapid 
decompression of the fuselage.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 737-
53A1108, Revision 5, dated October 26, 1989. That service bulletin 
describes procedures for a close visual inspection to detect cracking 
of the aft frame web of the forward service doorway around the doorstop 
fittings, an internal visual inspection to detect cracking of the 
intercostals and stringers of the frame support structure, and repair 
of any cracking that is detected. That service bulletin also describes 
a preventive modification that can be accomplished on any uncracked 
intercostals.

Explanation of Requirements of Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of this same type design, this AD 
supersedes AD 88-03-03 to continue to require repetitive internal 
visual inspections for cracking of the frame support structure of the 
forward service doorway, and repair, if necessary. This AD also 
requires repetitive close visual inspections for cracking of the aft 
frame web of the forward service doorway, and follow-on corrective 
actions, if necessary. This AD also provides for an optional 
terminating action for the repetitive inspection requirements of this 
AD. The actions are required to be accomplished in accordance with the 
service bulletin described previously, except as discussed below.

Differences Between Service Bulletin and This AD

    Operators should note that, although the service bulletin describes 
procedures for a close visual inspection of the aft frame web of the 
forward service doorway around the doorstop fittings, this AD does not 
permit that inspection to be accomplished in lieu of the internal 
visual inspection. The FAA has determined that, because cracking in the 
frame may be masked by the doorstop fittings, the close visual 
inspection is not an adequate indicator of the condition of the 
intercostals and stringers of the frame support structure. Therefore, 
if any cracking is found, this AD requires removal of the doorstop 
fittings and a detailed visual inspection to detect further cracking of 
the frame, prior to the repair of any cracking.
    Operators also should note that, although the service bulletin 
recommends accomplishing the initial inspection prior to the 
accumulation of 25,000 total flight cycles (landings) or within the 
next 4,500 flight cycles (after receipt of the service bulletin), 
whichever occurs later, the FAA has determined that such a threshold 
does not address the identified unsafe condition in a timely manner. In 
addition, the FAA has determined that the repetitive inspection 
interval of 9,000 landings, as specified in the service bulletin, does 
not address the identified unsafe condition in a timely manner. The 
FAA's determination is based upon the case of two airplanes, described 
previously, on which no cracking was detected during internal visual 
inspections of the intercostals at

[[Page 57242]]

18,000 total landings; but, during repetitive inspections conducted at 
approximately 24,000 total landings, two severed intercostals were 
found. This evidence reveals that cracking may appear earlier than 
25,000 total landings and grow from being undetectable to severe in 
fewer than 6,000 flight cycles. In light of these factors, the FAA 
finds a compliance time of 18,000 total landings (or within 700 
landings or 90 days after the effective date of this AD, whichever 
occurs later) for initiating the required inspections, and a repetitive 
interval of 4,500 landings, is warranted, in that those times represent 
an appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.
    Operators also should note that, although the service bulletin 
specifies Boeing 737 Structural Repair Manual Items (SRM) 51-40-2 and 
51-40-3 as optional sources of service information for repairing 
cracked intercostals, this AD requires that all future repairs of 
cracked intercostals be accomplished in accordance with Figure 3 of the 
service bulletin. The FAA has determined that SRM's 51-40-2 and 51-40-3 
may not provide an acceptable source of service information for repair 
of the intercostals.
    Additionally, although the service bulletin specifies that SRM 53-
10-4 is an appropriate source of service information for repairing 
cracked frames, and that SRM 53-10-3 is an appropriate source of 
service information for repairing cracked stringers, this AD requires 
that all future repairs of cracked frames or stringers be accomplished 
in accordance with a method approved by the FAA. The FAA has determined 
that SRM's 53-10-4 and 53-10-3 may not provide structurally acceptable 
methods of repair for frames and stringers.
    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, this proposal would require the repair of those 
conditions to be accomplished in accordance with a method approved by 
the FAA.

Explanation of Revision to Applicability

    AD 88-03-03 applies to certain Boeing Model 737 series airplanes, 
as listed in Boeing Service Bulletin 737-53A1108, Revision 2, dated 
August 13, 1987. This AD is applicable to certain Boeing Model 737 
series airplanes, as listed in Boeing Service Bulletin 737-53A1108, 
Revision 5, dated October 26, 1989. Revision 5 of the service bulletin 
updates the effectivity listing of the service bulletin only to reflect 
current airplane ownership but adds no new airplanes.

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. That AD requires accomplishment of certain structural 
modifications, which constitutes terminating action for the repetitive 
inspection requirements of this AD.

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-245-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 removing amendment 39-5832 (53 FR 
1609, January 21, 1988), and by adding a new airworthiness directive 
(AD), amendment 39-10858, to read as follows:

98-22-10  BOEING: Amendment 39-10858. Docket 98-NM-245-AD. 
Supersedes AD 88-03-03, amendment 39-5832.

    Applicability: Model 737 series airplanes, as listed in Boeing 
Service Bulletin 737-

[[Page 57243]]

53A1108, Revision 5, dated October 26, 1989; 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 (f)(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. 3
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fatigue cracking of the aft frame and frame support 
structure of the forward service doorway, which could result in loss 
of the door, and consequent rapid decompression of the fuselage, 
accomplish the following:

Restatement of the Requirements of AD 88-03-03

    (a) Prior to the accumulation of 25,000 total landings or within 
4,500 landings after February 28, 1988 (the effective date of AD 88-
03-03, amendment 39-5832), whichever occurs later, perform an 
internal visual inspection for cracking in the intercostals and 
stringers, which support the doorstop fittings of the aft frame of 
the service doorway, in accordance with Boeing Service Bulletin 737-
53A1108, Revision 1, dated March 12, 1987; Revision 2, dated August 
13, 1987; Revision 3, dated March 3, 1988; Revision 4, dated 
November 17, 1988; or Revision 5, dated October 26, 1989.
    (1) If no cracking is found during any inspection performed in 
accordance with paragraph (a) of this AD, repeat the inspection 
thereafter at intervals not to exceed 9,000 landings, until the 
inspection required by paragraph (b) of this AD is accomplished.
    (2) If any cracking is found during any inspection performed in 
accordance with paragraph (a) of this AD, prior to further flight, 
repair in accordance with the service bulletin. Thereafter, repeat 
the inspection at intervals not to exceed 9,000 landings, until the 
inspection required by paragraph (b) of this AD is accomplished.

New Requirements of This AD

    (b) Perform a close visual inspection for cracking of the aft 
frame web and an internal visual inspection for cracking of the 
intercostals and stringers of the frame support structure of the 
forward service doorway, in accordance with Boeing Service Bulletin 
737-53A1108, Revision 1, dated March 12, 1987; Revision 2, dated 
August 13, 1987; Revision 3, dated March 3, 1988; Revision 4, dated 
November 17, 1988; or Revision 5, dated October 26, 1989; at the 
latest of the times specified in paragraphs (b)(1), (b)(2), (b)(3), 
and (b)(4) of this AD. Accomplishment of these inspections 
constitutes terminating action for the repetitive inspection 
requirements of paragraphs (a)(1) and (a)(2) of this AD.
    (1) Prior to the accumulation of 18,000 total landings.
    (2) If an internal visual inspection was performed in accordance 
with paragraph (b) of AD 88-03-03: Within 4,500 landings after the 
last inspection performed in accordance with paragraph (b) of AD 88-
03-03.
    (3) Within 700 landings after the effective date of this AD.
    (4) Within 90 days after the effective date of this AD.
    (c) If no cracking of the aft frame web, intercostals, or 
stringers is detected during any inspection required by paragraph 
(b) of this AD, repeat the inspection thereafter at intervals not to 
exceed 4,500 landings, until the actions specified by paragraph (e) 
of this AD are accomplished.
    (d) If any cracking of the aft frame web, intercostals, or 
stringers is detected during any inspection required by paragraph 
(b) of this AD, prior to further flight, remove the six doorstop 
fittings, and perform a detailed visual inspection to detect further 
cracking of the frame web. Prior to further flight, repair any 
cracked intercostal in accordance with Figure 3 of Boeing Service 
Bulletin 737-53A1108, Revision 1, dated March 12, 1987; Revision 2, 
dated August 13, 1987; Revision 3, dated March 3, 1988; Revision 4, 
dated November 17, 1988; or Revision 5, dated October 26, 1989. 
Prior to further flight, repair any cracked frame web or stringer 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. Thereafter, repeat the inspection specified 
in paragraph (b) of this AD at intervals not to exceed 4,500 
landings, until the actions specified by paragraph (e) of this AD 
are accomplished.
    (e) Repair of all intercostals in accordance with Figure 3 of 
Boeing Service Bulletin 737-53A1108, Revision 1, dated March 12, 
1987; Revision 2, dated August 13, 1987; Revision 3, dated March 3, 
1988; Revision 4, dated November 17, 1988; or Revision 5, dated 
October 26, 1989; or modification of all intercostals accomplished 
in accordance with the requirements of AD 90-06-02, amendment 39-
6489; constitutes terminating action for the repetitive inspection 
requirements of this AD.
    (f)(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.
    (f)(2) Alternative methods of compliance pertaining to 
inspection methods, approved previously in accordance with AD 88-03-
03, amendment 39-5832, are not considered to be approved as 
alternative methods of compliance with this AD.
    (f)(3) Alternative methods of compliance pertaining to repairs 
or modifications, approved previously in accordance with AD 88-03-
03, amendment 39-5832, are considered to be approved as alternative 
methods of compliance with this AD.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (g) 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.
    (h) The internal visual inspection for cracking in the 
intercostals and stringers, close visual inspection for cracking of 
the aft frame web, and repair of intercostals, if necessary, shall 
be done in accordance with Boeing Service Bulletin 737-53A1108, 
Revision 1, dated March 12, 1987; Boeing Service Bulletin 737-
53A1108, Revision 2, dated August 13, 1987; Boeing Service Bulletin 
737-53A1108, Revision 3, dated March 3, 1988; Boeing Service 
Bulletin 737-53A1108, Revision 4, dated November 17, 1988; or Boeing 
Service Bulletin 737-53A1108, Revision 5, dated October 26, 1989. 
Boeing Service Bulletin 737-53A1108, Revision 3, dated March 3, 
1988, contains the following list of effective pages:

------------------------------------------------------------------------
                                    Revision
                                      level
     Page number shown on page      shown on      Date shown on page
                                      page
------------------------------------------------------------------------
1-14, 22..........................         3  March 3, 1988.
15-21, 23-27......................         2  August 13, 1987.
------------------------------------------------------------------------

    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.

    (i) This amendment becomes effective on November 12, 1998.

    Issued in Renton, Washington, on October 19, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-28540 Filed 10-26-98; 8:45 am]
BILLING CODE 4910-13-P