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Proposed Rule

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

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Information about this document as published in the Federal Register.

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AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

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 a one-time inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary. This proposed AD is prompted by reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines. Scribe line damage can also occur at many other locations, including butt joints, external doublers, door scuff plates, the wing-to-body fairing, and areas of the fuselage where decals have been applied or removed. We are proposing this AD to prevent rapid decompression of the airplane due to fatigue cracks resulting from scribe lines on pressurized fuselage structure.

DATES:

We must receive comments on this proposed AD by June 13, 2005.

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: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, Washington, DC 20590.
  • By fax: (202) 493-2251.
  • Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2005-20918; the directorate identifier for this docket is 2004-NM-269-AD.

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FOR FURTHER INFORMATION CONTACT:

Sue Lucier, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6438; fax (425) 917-6590.

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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 under ADDRESSES. Include “Docket No. FAA-2005-20918; Directorate Identifier 2004-NM-269-AD” in the subject line 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 submitted 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 can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

Examining the Docket

You can examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

We have received a report of scribe lines and fuselage skin cracks adjacent to the skin lap joints on two Boeing Model 737-200 series airplanes. Scribe lines are narrow, shallow, distinct lines of damage, usually associated with the removal of a fillet seal (from a lap joint) or gap seal (from a butt splice). Scribe lines have typically occurred during maintenance, including, for example, applying and removing graphic decals and stripping paint sealant from the lap joints, butt joints, certain external doublers, door scuff plates, and the wing-to-body fairing.

On one of the subject airplanes, a 5-inch crack was found at (body) station (STA) 827, just below the lap joint at stringer (S) S-4R. The airplane had accumulated 52,226 total flight cycles. On the second airplane, two cracks were found below the S-10R lap joint: a 10-inch crack between STA 757 and STA 767, and a 5-inch crack between STA 749 and STA 754. This airplane had accumulated 41,899 total flight cycles. Both airplanes had scribe lines along the lap joints and butt joints and around the wing-to-body fairing. The scribe lines appear to have been made on the skin when sealant was removed to prepare the airplane for repainting.

Analysis of the cracked skin areas confirmed that the cracks initiated at multiple sites along the scribe lines, which were 0.002 to 0.004 inch deep. The first airplane accumulated 5,500 flight cycles between crack initiation Start Printed Page 22273and a full-thickness crack; the second airplane accumulated 6,000 flight cycles during this period.

Scribe lines, if not corrected, could result in fatigue cracks that could grow large enough to allow rapid decompression of the airplane.

The configuration of the fuselage is the same on Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. Therefore, all these models may be subject to the identified unsafe condition.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004. The service bulletin describes procedures for a detailed inspection for scribe lines in the fuselage skin at certain lap joints, butt joints, external repair doublers, scuff plates and repairs in the restricted zones around the door cutouts, and, if affected, the skin around the wing-to-body fairing. The service bulletin specifies the following corrective actions:

  • Blending scribe lines that are within specified limits.
  • Repairing scribe lines or completing a limited return-to-service (LRTS) program for scribe lines that exceed specified limits. The LRTS includes various repetitive inspections (ultrasonic, eddy current, substructure, internal detailed stringer inspections) for cracks in the area of the scribe lines.
  • Contacting Boeing for crack repair instructions.

The inspection areas are divided into three zones, which specify locations and corresponding potential fatigue thresholds. Because of the complexity of the actions and the workload for affected operators, the service bulletin provides instructions for calculating separate inspection thresholds based on fatigue life of each zonal area. By defining criticality of location, the service bulletin addresses the most critical areas (i.e., Zone 1) first and provides longer compliance times for less critical areas (i.e., Zones 2 and 3). The service bulletin provides compliance charts, based on the zonal information, for determining the initial scribe line inspection thresholds. The initial inspection could be required as early as 4,500 flight cycles (for airplanes with modified lap splices) or 1,200 flight cycles (for airplanes with unmodified lap splices) after the effective date of the AD. The service bulletin also describes acceptable conditions for exemption from the inspection.

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. Therefore, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed below. The proposed AD would also require sending the inspection results of positive crack findings to Boeing.

Differences Between the Proposed AD and the Service Bulletin

The service bulletin (in Part 14) provides procedures for scribe lines found before the initial inspection threshold. This proposed AD would not require those procedures but would require only the directed inspection program (Parts 1 through 11). This proposed AD would allow the optional accomplishment of an LRTS program (in Parts 12 and 13), under certain conditions, to allow temporary return to service.

This proposed AD would require operators to report cracks found during the inspections. While the service bulletin does not explicitly direct operators to provide such a report, Boeing advises that the data from these reports will help in the ongoing efforts to improve the scribe line inspection program.

The service bulletin specifies compliance times relative to the date of issuance of the service bulletin; however, this proposed AD would require compliance before the specified compliance time relative to the effective date of the AD.

The service bulletin specifies that operators may contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repair 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 Delegation Option Authorization Organization whom we have authorized to make those findings.

We have coordinated these different requirements with Boeing.

Costs of Compliance

There are about 3,132 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.

Estimated Costs

ZoneActionWork hoursAverage labor rate/hourCost per airplaneNumber of U.S.- registered airplanesFleet cost
1Sealant removal Inspection66 4$65 65$4,290 2601,384 1,384$5,937,360 359,840
2Sealant removal Inspection38 2965 652,470 1,8851,384 1,3843,418,480 2,608,840
3Sealant removal Inspection88 3865 655,720 2,4701,384 1,3847,916,480 3,418,480

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 Start Printed Page 22274products 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. See the ADDRESSES section for a location to examine the regulatory evaluation.

Start List of Subjects

List of Subjects in 14 CFR Part 39

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The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2005-20918; Directorate Identifier 2004-NM-269-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by June 13, 2005.

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 was prompted by reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines. Scribe line damage can also occur at many other locations, including butt joints, external doublers, door scuff plates, the wing-to-body fairing, and areas of the fuselage where decals have been applied or removed. We are issuing this AD to prevent rapid decompression of the airplane due to fatigue cracks resulting from scribe lines on pressurized fuselage structure.

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.

Inspection

(f) Do a detailed inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1262, dated December 9, 2004, except as provided by paragraph (g) of this AD. Do the actions at the time specified in paragraph 1.E., “Compliance,” of the service bulletin, except as required by paragraph (i) of this AD. Acceptable inspection exemptions are described in paragraph 1.E.1. of Boeing Alert Service Bulletin 737-53A1262.

(1) If no scribe line is found, no further work is required by this AD.

(2) If any scribe line is found: Do all applicable investigative and corrective actions at the time specified by doing all applicable actions specified in the Accomplishment Instructions of the service bulletin, except as required by paragraph (h) of this AD.

Note 1:

A detailed inspection is defined in Note 10 of Boeing Alert Service Bulletin 737-53A1262 under 3.A., “General Information.” Specific magnification requirements may be specified in the steps of the Work Instructions.

Exceptions to Service Bulletin Procedures

(g) This AD requires accomplishment of Parts 1 through 11 of Boeing Alert Service Bulletin 737-53A1262. Parts 12 and 13 of the service bulletin may be accomplished, if applicable, to allow temporary return to service. This AD does not require accomplishment of Part 14 of the service bulletin.

(h) If any scribe line or crack is found during any inspection required by this AD, and the service bulletin specifies to contact Boeing for appropriate action: Before further flight, repair according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or according to data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing 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 approval must specifically refer to this AD.

(i) Where the service bulletin specifies a compliance time after the issuance of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.

Reporting Requirement

(j) At the applicable time specified in paragraph (j)(1) or (j)(2) of this AD, submit a report of positive findings of cracks found during the inspection required by paragraph (f) of this AD to the Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Alternatively, operators may submit reports to their Boeing field service representatives. The report shall contain, as a minimum, the following information: airplane serial number, flight cycles at time of discovery, location(s) and extent of positive crack findings. Under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection requirements contained in this AD and has assigned OMB Control Number 2120-0056.

(1) If the inspection was done before the effective date of this AD: Send the report within 30 days after the effective date of this AD.

(2) If the inspection was done after the effective date of this AD: Send the report within 30 days after the inspection is done.

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle 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) 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 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 approval must specifically refer to this AD.

Start Signature

Issued in Renton, Washington, on April 19, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 05-8578 Filed 4-28-05; 8:45 am]

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