Federal Register: PROPOSED RULES Airworthiness Directives: [14 CFR Part 39]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

CFR Citation: 14 CFR Part 39

Docket ID: [Docket No. FAA-2008-0671; Directorate Identifier 2008-NM-017-AD]

RIN ID: RIN 2120-AA64

NOTICE: PROPOSED RULES

ACTION: Airworthiness Directives:

DOCUMENT ACTION: Notice of proposed rulemaking (NPRM).

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

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

DOCUMENT SUMMARY: We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 737300, 400, and 500 series airplanes. This proposed AD would require repetitive high frequency eddy current (HFEC) inspections for cracking of the 1.04inch nominal diameter wire penetration hole in the
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frame and frame reinforcement, between stringers S20 and S21, 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 1.04inch 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.

SUMMARY: Boeing Model 737 300, 400, and 500 Series Airplanes,

SUPPLEMENTAL 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. FAA20080671; Directorate Identifier 2008NM017AD'' 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 1.04inch nominal diameter wire penetration hole intended for wire routing, between stringers S20 and S21, 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 737500 series airplanes. The cracks at the 1.04inch nominal diameter wire penetration hole are due to the effect of operating loads in combination with the stress concentration at the 1.04inch nominal hole. The cracking initiated at the 1.04inch nominal diameter wire penetration hole and grew towards the inner chord.

We have since received reports of more than fifty cracked frames at the 1.04inch nominal diameter wire penetration hole on more than 20 airplanes, all either Model 737300 or 737500 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 737300 series airplanes, at one frame station on Model 737400 series airplanes, and at four stations on Model 737500 series airplanes. Sixteen airplanes had cracking at multiple frames, and 10 frames had cracking at adjacent frames. Fortythree frames had cracking only at the inboard side of the 1.04inch 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 1.04inch 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 0.50inch diameter hole positioned below the 1.04inch 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 73753A1279, 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 1.04inch nominal diameter wire penetration hole in the frame and frame reinforcement, between stringers S20 and S21, 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 0.50inch diameter hole and all standoff/tooling holes in the frame and frame reinforcement, between stringers S19 and S22. 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)
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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 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.

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 39AIRWORTHINESS 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. FAA20080671; Directorate Identifier 2008NM 017AD.
Comments Due Date
(a) We must receive comments by August 8, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 737300, 400, and 500 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 73753A1279, 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 1.04inch 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 1.04inch nominal diameter wire penetration hole in the frame and frame reinforcement, between stringer S20 and S21; and do all applicable related investigative and corrective actions; by accomplishing all
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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 980573356; telephone (425) 9176447; fax (425) 9176590; 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. E814183 Filed 62308; 8:45 am]
BILLING CODE 491013P

FOR FURTHER INFORMATION CONTACT Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980573356; telephone (425) 9176447; fax (425) 9176590.