[Federal Register Volume 73, Number 122 (Tuesday, June 24, 2008)]
[Proposed Rules]
[Pages 35598-35601]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-14183]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0671; Directorate Identifier 2008-NM-017-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Boeing Model 737-300, -400, and -500 series airplanes. This 
proposed AD would require repetitive high frequency eddy current (HFEC) 
inspections for cracking of the 1.04-inch nominal diameter wire 
penetration hole in the

[[Page 35599]]

frame and frame reinforcement, between stringers S-20 and S-21, on both 
the left and right sides of the airplane, and related investigative/
corrective actions if necessary. This proposed AD results from reports 
of cracking in the frame, or in the frame and frame reinforcement, 
common to the 1.04-inch nominal diameter wire penetration hole intended 
for wire routing. We are proposing this AD to detect and correct 
cracking in the fuselage frames and frame reinforcements, which could 
reduce the structural capability of the frames to sustain limit loads, 
and result in cracking in the fuselage skin and subsequent rapid 
depressurization of the airplane.

DATES: We must receive comments on this proposed AD by August 8, 2008.

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.

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 proposed 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: Wayne Lockett, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6447; 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-2008-0671; 
Directorate Identifier 2008-NM-017-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 reports of cracking in the frame, or in the frame 
and frame reinforcement, common to the 1.04-inch nominal diameter wire 
penetration hole intended for wire routing, between stringers S-20 and 
S-21, on both the left and right sides of the airplane. The cracked 
frames are located between station (STA) 500B and STA 520 on Model 737-
300 and -400 series airplanes and between STA 482 and STA 520 on Model 
737-500 series airplanes. The cracks at the 1.04-inch nominal diameter 
wire penetration hole are due to the effect of operating loads in 
combination with the stress concentration at the 1.04-inch nominal 
hole. The cracking initiated at the 1.04-inch nominal diameter wire 
penetration hole and grew towards the inner chord.
    We have since received reports of more than fifty cracked frames at 
the 1.04-inch nominal diameter wire penetration hole on more than 20 
airplanes, all either Model 737-300 or 737-500 series airplanes. The 
airplanes had accumulated between 35,832 and 66,694 total flight 
cycles.
    This type of cracking has occurred at three frame stations on Model 
737-300 series airplanes, at one frame station on Model 737-400 series 
airplanes, and at four stations on Model 737-500 series airplanes. 
Sixteen airplanes had cracking at multiple frames, and 10 frames had 
cracking at adjacent frames. Forty-three frames had cracking only at 
the inboard side of the 1.04-inch nominal diameter wire penetration 
hole in the frame inner chord or in the frames and frame reinforcement 
inner chord. Three of the frames had cracking in the outboard side of 
the 1.04-inch nominal diameter wire penetration hole in the frame and 
the frame reinforcement. Two of the frames were severed. Some of the 
frames had additional cracking at either the standoff/tooling holes or 
at the 0.50-inch diameter hole positioned below the 1.04-inch nominal 
diameter wire penetration hole.
    Cracking in the fuselage frames at the wire penetration hole 
intended for wire routing will reduce the structural capability of the 
frames to sustain limit loads. Cracking in the frames could result in 
cracking in the fuselage skin and subsequent rapid depressurization of 
the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 737-53A1279, dated 
December 18, 2007. The service bulletin describes procedures for doing 
either a high frequency eddy current (HFEC) surface inspection or HFEC 
hole/edge inspection for cracking of the 1.04-inch nominal diameter 
wire penetration hole in the frame and frame reinforcement, between 
stringers S-20 and S-21, on both the left and right sides of the 
airplane. If cracking is found, the service bulletin also describes 
procedures for related investigative and corrective actions. The 
related investigative action is doing an HFEC inspection for cracking 
in the 0.50-inch diameter hole and all standoff/tooling holes in the 
frame and frame reinforcement, between stringers S-19 and S-22. The 
corrective action is repairing any cracking found and repeating the 
HFEC inspections. If additional cracking is found, the service bulletin 
specifies contacting Boeing for repair instructions. The service 
bulletin further describes procedures for a preventative modification 
for frames on which either the initial or repetitive inspections have 
been done. The preventative modification terminates the repetitive 
inspections.
    The initial compliance time for the initial inspection is either 
within 3,000 or 6,000 (but not to exceed 53,000 total flight cycles) 
flight cycles after release of the service bulletin, depending on the 
number of total flight cycles on the airplane. The repetitive interval 
for the HFEC inspection is 14,000 flight cycles. Corrective actions 
must be done before further flight.

FAA's Determination and Requirements of this Proposed AD

    We are proposing this AD because we evaluated all relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the(se)

[[Page 35600]]

same type design(s). This proposed AD would require accomplishing the 
actions specified in the service information described previously, 
except as discussed under ``Differences Between the Proposed AD and the 
Service Bulletin.''

Differences Between the Proposed AD and the Service Bulletin

    The service bulletin specifies to contact the manufacturer for 
instructions on how to remove damage and repair certain conditions, but 
this proposed AD would require removing damage and repairing those 
conditions 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

    We estimate that this proposed AD would affect 616 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD. The average labor rate 
is $80 per work hour.

                                                 Estimated Costs
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                                                                                    Number of
                                                                                      U.S.-
            Action                  Work hours        Parts      Cost per product   registered     Fleet cost
                                                                                    airplanes
----------------------------------------------------------------------------------------------------------------
Inspection....................  Between 6 and 8             $0  Between $480 and           616  Between $295,680
                                 (depending on                   $640, per                       and $394,240,
                                 airplane                        inspection cycle.               per inspection
                                 configuration),                                                 cycle.
                                 per inspection
                                 cycle.
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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 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 this 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

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 FAA amends Sec.  39.13 by adding the following new AD:

Boeing: Docket No. FAA-2008-0671; Directorate Identifier 2008-NM-
017-AD.

Comments Due Date

    (a) We must receive comments by August 8, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300, -400, and -500 
series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 737-53A1279, dated December 18, 2007.

Unsafe Condition

    (d) This AD results from reports of cracking in the frame, or in 
the frame and frame reinforcement, common to the 1.04-inch nominal 
diameter wire penetration hole intended for wire routing. We are 
issuing this AD to detect and correct cracking in the fuselage 
frames and frame reinforcements, which could reduce the structural 
capability of the frames to sustain limit loads, and result in 
cracking in the fuselage skin and subsequent rapid depressurization 
of the airplane.

Compliance

    (e) Comply with this AD within the compliance times specified, 
unless already done.

Service Bulletin Reference Paragraph

    (f) The term ``service bulletin,'' as used in this AD, means the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1279, dated December 18, 2007.
    (1) Where the service bulletin specifies a compliance time after 
the date on the service bulletin, this AD requires compliance within 
the specified compliance time after the effective date of this AD.
    (2) Where the service bulletin specifies to contact Boeing for 
instructions for removing damage and repairing cracking: Before 
further flight, remove the damage or repair the cracking using a 
method approved in accordance with the procedures specified in 
paragraph (i) of this AD.
    (3) Although the service bulletin referenced in this AD 
specifies to submit information to the manufacturer, this AD does 
not include that requirement.

Inspections, Related Investigative and Corrective Actions

    (g) At the applicable time specified in paragraph 1.E., 
``Compliance,'' of the service bulletin, except as specified by 
paragraph (f)(1) of this AD: Do a high frequency eddy current (HFEC) 
surface inspection or an HFEC hole/edge inspection for cracking of 
the 1.04-inch nominal diameter wire penetration hole in the frame 
and frame reinforcement, between stringer S-20 and S-21; and do all 
applicable related investigative and corrective actions; by 
accomplishing all

[[Page 35601]]

the actions specified in the Accomplishment Instructions of the 
service bulletin, except as specified by paragraphs (f)(2) and 
(f)(3) of this AD. Do all applicable related investigative and 
corrective actions before further flight. Thereafter, repeat the 
inspections at the applicable intervals specified in paragraph 1.E. 
of the service bulletin.

Terminating Action

    (h) Doing the repair in Part 3 or the preventative modification 
in Part 4 of the service bulletin terminates the repetitive 
inspection requirements of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, ATTN: Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-
120S, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; 
telephone (425) 917-6447; 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, 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 June 8, 2008.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-14183 Filed 6-23-08; 8:45 am]
BILLING CODE 4910-13-P