Document ID: FAA-2007-0024-0001
Agency: faa
Document Type: Notice
Title: Airworthiness Directives; Boeing Model 737-100, -200, -200C, - 300, -400, and -500 Series Airplanes
Posted Date: 2007-10-11T04:00Z

[Federal Register: October 11, 2007 (Volume 72, Number 196)]
[Proposed Rules]               
[Page 57890-57892]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr11oc07-19]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0024; Directorate Identifier 2007-NM-086-AD]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes. This proposed AD would require repetitive inspections for 
cracking in and around the upper and lower hinge cutouts of the forward 
entry and forward galley service doorways, and corrective actions if 
necessary. This proposed AD results from multiple reports of cracks 
found in the skin, bearstrap, and/or frame outer chord in the hinge 
cutout areas of the forward entry and forward galley service doorways. 
We are proposing this AD to detect and correct such cracking, which 
could result in rapid decompression of the airplane.

DATES: We must receive comments on this proposed AD by November 26, 
2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 

the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://www.regulations.gov
 and follow the instructions for sending your 

comments electronically.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue, SE., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Howard Hall, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6430; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2007-
0024; Directorate Identifier 2007-NM-086-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov
, including any personal information you provide. We will 

also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that Web site, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov
, or in person at the Docket Operations office between 9 

a.m. and 5 p.m., Monday through Friday, except Federal holidays. The 
Docket Operations office (telephone (800) 647-5527) is located on the 
ground floor of the West Building at the DOT street address stated in 
the ADDRESSES section. Comments will be available in the AD docket 
shortly after the Docket Management System receives them.

Discussion

    We have received multiple reports of cracks found in the skin, 
bearstrap, and/or frame outer chord in the hinge cutout areas of the 
forward entry and forward galley service doorways. Cracks in the 
forward entry door bearstrap were reported on an airplane with as few 
as

[[Page 57891]]

24,538 total flight cycles. Cracks in the forward galley service door 
bearstrap were reported on an airplane with as few as 44,938 total 
flight cycles. One operator reported a severed bearstrap, a severed 
station (STA) 291.5 frame, and a 14.5-inch crack in the skin at the 
lower hinge cutout of the forward galley service doorway. The airplane 
had accumulated 61,297 total flight cycles. Such cracking, if not 
corrected, could result in rapid decompression of the airplane.
    The fatigue cracks are caused by cyclic cabin pressure loads and 
are not due to manufacturing defects in the bearstrap. The unsafe 
condition is unrelated to any previous investigation related to 
suspected unapproved parts.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1200, dated 
April 13, 2006. The service bulletin describes procedures for 
repetitive inspections for cracking in and around the upper and lower 
hinge cutouts of the forward entry and forward galley service doorways. 
The service bulletin describes the following inspections:
     External detailed inspection of the skin;
     High frequency eddy current (HFEC) hole probe inspection 
of the skin, bonded doubler, bearstrap, and frame chord at specified 
fastener locations;
     HFEC hole probe inspection of the skin, bonded doubler, 
and bearstrap at specified fastener locations aft of the frame chord;
     HFEC inspection of the skin hinge cutout trim;
     Low frequency eddy current (LFEC) hole probe inspection of 
the skin, bonded doubler, and bearstrap at specific fastener locations 
aft of the frame chord;
     LFEC hole probe inspection of the skin, bonded doubler, 
bearstrap, and frame chord at specific fastener locations.
    The service bulletin provides two options for the inspections, as 
follows:

                                                Compliance Times
----------------------------------------------------------------------------------------------------------------
                                                                                                   Repetitive
        Option                  Inspections            Threshold, in total    Grace period, in    interval, in
                                                          flight  cycles        flight cycles     flight cycles
----------------------------------------------------------------------------------------------------------------
A \1\................  External detailed             Entry door: 20,000.....             3,000            18,000
                        inspection; HFEC inspection  Service door: 40,000...
                        of the skin hinge cutout
                        trim; and HFEC rotary probe
                        inspection of the entire
                        zone.
B....................  External detailed             Entry door: 20,000.....             3,000             3,000
                        inspection; HFEC inspection  Service door: 40,000...
                        of the skin hinge cutout
                        trim; and LFEC inspection
                        of the entire zone.
¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
                       HFEC rotary probe inspection  Entry door: 20,000.....             6,000            18,000
                        of the aft zone (required    Service door: 40,000...
                        only for Group 1,
                        Configuration 1, and only
                        for the entry door).
----------------------------------------------------------------------------------------------------------------
\1\ Option A is mandatory for the forward entry door, upper and lower hinge cutouts, on Model 737-200C
  airplanes.

    The service bulletin specifies contacting Boeing for crack repair 
instructions.
    The service bulletin also states that the service bulletin might in 
the future be revised to include a preventive modification that will 
eliminate the need for the repetitive inspections. The service bulletin 
specifies contacting Boeing for information about this modification.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously, except as discussed below.

Difference Between the Proposed AD and the Service Bulletin

    The service bulletin specifies contacting the manufacturer for 
instructions for crack repair and for an optional modification that 
would terminate the repetitive inspections. But this proposed AD would 
require doing the repair and optional modification in one of the 
following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.

Costs of Compliance

    There are about 2,437 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD, per inspection cycle.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                           Number of U.S.-
            Work hours               Average hourly    Cost per airplane      registered         Fleet cost
                                       labor rate                             airplanes
----------------------------------------------------------------------------------------------------------------
13 to 14..........................             $80   $1,040 to $1,120....           1,055   $1,097,200 to
                                                                                             $1,181,600
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for

[[Page 57892]]

safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    We have determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify that the 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. 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0024; Directorate Identifier 2007-NM-
086-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by November 
26, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all Boeing Model 737-100, -200, -200C, -
300, -400, and -500 series airplanes, certificated in any category.

Unsafe Condition

    (d) This AD results from multiple reports of cracks found in the 
skin, bearstrap, and/or frame outer chord in the hinge cutout areas 
of the forward entry and forward galley service doorways. We are 
issuing this AD to detect and correct such cracking, which could 
result in rapid decompression of the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Repetitive Inspections

    (f) Except as provided by paragraph (g) of this AD, at the 
applicable times specified in paragraph 1.E. of Boeing Alert Service 
Bulletin 737-53A1200, dated April 13, 2006, do external detailed, 
low frequency eddy current, high frequency eddy current, and high 
frequency eddy current rotary probe inspections, as applicable, for 
cracks in and around the upper and lower hinge cutouts of the 
forward entry and forward galley service doorways, in accordance 
with the Accomplishment Instructions of the service bulletin, except 
as provided by paragraph (h) of this AD. Do not exceed the 
applicable repetitive interval for the previous inspection, as 
specified in the service bulletin as Option A or Option B. Repair 
any crack before further flight using a method approved in 
accordance with the procedures specified in paragraph (i) of this 
AD.

Exceptions to Service Bulletin Specifications

    (g) Where the service bulletin specifies a compliance time after 
the release date of the service bulletin, this AD requires 
compliance within the specified compliance time after the effective 
date of this AD.
    (h) Although the service bulletin specifies contacting Boeing 
for information about installing an optional preventive modification 
that would terminate the repetitive inspections specified in this 
AD, this AD requires that any terminating action be done by using a 
method approved in accordance with the procedures specified in 
paragraph (i) of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the certification basis 
of the airplane, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on October 1, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-20048 Filed 10-10-07; 8:45 am]

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