
[Federal Register: December 5, 2008 (Volume 73, Number 235)]
[Proposed Rules]               
[Page 74080-74082]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr05de08-21]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-1275; Directorate Identifier 2007-NM-167-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 certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes. This proposed AD would require repetitive detailed 
and high frequency eddy current inspections to detect cracks of the 
backup intercostals and the upper sill of the forward airstair doorway, 
and applicable corrective actions. This proposed AD would also provide 
for an optional terminating

[[Page 74081]]

action, which would eliminate the need for repetitive inspections. This 
proposed AD results from a report indicating that cracks were found in 
the backup intercostals and upper sill web of the forward airstair 
doorway. We are proposing this AD to detect and correct fatigue 
cracking of the backup intercostals and upper sill web of the forward 
airstair doorway, which could result in a rapid loss of cabin pressure.

DATES: We must receive comments on this proposed AD by January 20, 
2009.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     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.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Boeing 
Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207; 
telephone 206-544-9990; fax 206-766-5682; e-mail DDCS@boeing.com; 
Internet https://www.myboeingfleet.com. You may review copies of the 
referenced service information at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information 
on the availability of this material at the FAA, call 425-227-1221 or 
425-227-1152.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://
www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this AD, the regulatory evaluation, 
any comments received, and other information. The street address for 
the Docket Office (telephone 800-647-5527) is in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

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 send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-1275; 
Directorate Identifier 2007-NM-167-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We have received a report indicating that cracks were found in the 
backup intercostals and upper sill web of the forward airstair doorway 
on a Boeing Model 737-200 series airplane. The cracks were found in the 
upper sill web at the stop fitting at station (STA) 312 and in the two 
backup intercostals of the stop support structure at STA 322.7 and STA 
333.3. Investigation revealed the cracks are due to fatigue caused by 
cyclic loads acting on the upper sill web, which is stabilized by the 
backup intercostals. Fatigue cracking of the backup intercostals and 
upper sill web of the forward airstair doorway, if not detected and 
corrected, could result in a rapid loss of cabin pressure.
    The configuration of the subject area on certain Boeing Model 737-
100, -200C, -300, -400, and -500 series airplanes is almost identical 
to that on the affected Boeing Model 737-200 series airplanes. 
Therefore, those Boeing Model 737-100, -200C, -300, -400, and -500 
series airplanes are subject to the unsafe condition revealed on the 
Boeing Model 737-200 series airplanes.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1269, dated 
May 17, 2007. The service bulletin describes procedures for repetitive 
detailed and high frequency eddy current inspections to detect fatigue 
cracking of the backup intercostals and the upper sill web of the 
forward airstair doorway, and applicable corrective actions. The 
service bulletin also describes procedures for an optional terminating 
action, which would eliminate the need for the repetitive inspections.
    The corrective and optional terminating actions include doing a 
repair/preventive modification to install new backup intercostals with 
radius fillers, installing the preventive modification filler and 
doubler plate, and repairing any cracked upper sill web.
    The service information also specifies the following compliance 
times:
     For the initial inspections: The threshold is prior to 
45,000 or 49,500 total flight cycles depending on the flight cycles on 
the airplane. The grace period is 1,000 or 4,500 flight cycles 
depending on the flight cycles on the airplane.
     For the applicable repetitive inspections: The compliance 
time is at intervals of 4,500 flight cycles.
     For the applicable corrective actions: The compliance time 
is before further flight.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition.

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 certain actions specified in the 
service information described previously. The proposed AD also provides 
for an optional terminating action, as specified in the service 
bulletin, for the repetitive inspection requirements.

Costs of Compliance

    There are about 1,712 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 509 airplanes of 
U.S. registry. The proposed inspections would take about 2 work hours 
per airplane, at an average labor rate of $80 per work hour. Based on 
these figures, the estimated cost of the proposed AD for U.S. operators 
would be $81,440, or $160 per airplane, per inspection cycle.
    The optional terminating action, if done, would take about 9 work 
hours, at an average labor rate of $80 per work hour. Required parts 
would cost between $533 and $566 per airplane, depending on the 
airplane configuration. Based on these figures, the estimated cost of 
the optional terminating action would range between $1,253 and $1,286 
per airplane, depending on the airplane configuration.

[[Page 74082]]

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 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, Incorporation by 
reference, 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-2008-1275; Directorate Identifier 2007-NM-
167-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by January 
20, 2009.

Affected ADs

    (b) None

Applicability

    (c) This AD applies to Boeing Model 737-100, -200, -200C, -300, 
-400, and -500 series airplanes, certificated in any category; as 
identified in Boeing Alert Service Bulletin 737-53A1269, dated May 
17, 2007.

Unsafe Condition

    (d) This AD results from a report indicating that cracks were 
found in the backup intercostals and upper sill web of the forward 
airstair doorway. We are issuing this AD to detect and correct 
fatigue cracking of the backup intercostals and upper sill web of 
the forward airstair doorway, which could result in a rapid loss of 
cabin pressure.

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.

Inspections

    (f) At the applicable compliance times and repeat intervals 
listed in the tables of paragraph 1.E., ``Compliance,'' of Boeing 
Alert Service Bulletin 737-53A1269, dated May 17, 2007 (hereafter 
``the service bulletin''), except as provided by paragraphs (f)(1), 
(f)(2), and (f)(3) of this AD: Do repetitive detailed and high 
frequency eddy current inspections to detect cracks of the backup 
intercostals and the upper sill of the forward airstair doorway, and 
applicable corrective actions by accomplishing all the applicable 
actions specified in the Accomplishment Instructions of the service 
bulletin. Do the applicable corrective actions before further 
flight.
    (1) Where the service bulletin specifies a compliance time from 
the release date of the service bulletin, this AD requires 
compliance within the specified compliance time after the effective 
date of this AD.
    (2) Where the columns identified as ``Airplane Flight Cycles'' 
in the tables of the service bulletin specify less than 45,000 total 
flight cycles for certain actions, this AD affects airplanes having 
less than or equal to 45,000 total flight cycles.
    (3) Where the columns identified as ``Repeat Interval'' in the 
tables of the service bulletin specify an interval of 4,500 flight 
cycles for all conditions, this AD requires repetitive inspections 
only if no crack is found during any inspection required by 
paragraph (f) of this AD.

Optional Terminating Action

    (g) Accomplishing the backup intercostal repair/preventative 
modification and/or the upper door sill web repair, in accordance 
with the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-53A1269, dated May 17, 2007, ends all the corresponding 
repetitive inspection requirements of paragraph (f) of this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, ATTN: Howard Hall, Aerospace Engineer, Airframe Branch, ANM-
120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 
98057-3356; telephone (917) 917-6430; fax (425) 917-6590; has the 
authority to approve AMOCs for this AD, if requested using 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, FAA, 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 November 26, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E8-28819 Filed 12-4-08; 8:45 am]

BILLING CODE 4910-13-P
