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-2008-0107; Directorate Identifier 2007-NM-087-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 747 Airplanes

DATES: We must receive comments on this proposed AD by March 17, 2008.

DOCUMENT SUMMARY: We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 747 airplanes. This proposed AD would require inspections for scribe lines in affected lap and butt splices, wingto body fairing locations, and external repair and cutout reinforcement areas; and related investigative and corrective actions if necessary. This proposed AD results from reports of scribe lines found at lap joints and butt joints, around external doublers and antennas, and at locations where external decals had been cut. We are proposing this AD to detect and correct scribe lines, which can develop into fatigue cracks in the skin and cause sudden decompression of the airplane.

SUMMARY: Boeing Model 747 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. FAA20080107; Directorate Identifier 2007NM087AD'' 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 scribe lines have been found by 8 operators on 15 Model 747 airplanes. Scribe lines were found at lap joints and butt joints, around external doublers and antennas, and at locations where external decals had been cut. Many of the scribe lines appear to have been made when sealant was removed as part of preparation of the airplane for repainting. Although fatigue cracks can develop in the skin at scribe line locationsand have been found on some airplane models, no such cracking has been found on Model 747 airplanes. Such fatigue cracks, if not corrected, could grow large and cause sudden decompression of the airplane.

Related ADs

This proposed AD is similar to two existing ADs. AD 20060712, amendment 3914539 (71 FR 16211, March 31, 2006), applies to all Boeing Model 737100, 200, 200C, 300, 400, and 500 series airplanes. AD 20071907, amendment 3915198 (72 FR 60244, October 24, 2007), applies to all Boeing Model 757200, 200PF, and 200CB series airplanes. Those ADs require inspections to detect scribe lines in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary. Those actions resulted from reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines.

Relevant Service Information

We have reviewed Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008. The service bulletin describes procedures for exploratory detailed inspections to detect scribe lines in affected lap and butt splices, wingtobody fairing locations, and external repair and cutout reinforcement areas. The service bulletin specifies removing paint and sealant from affected areas before the initial exploratory inspection. The compliance time for the exploratory inspections is 15,000 or 25,000 total flight cycles (depending on the inspection location), with a grace period between 500 and 1,500 flight cycles depending on the age of the airplane and the location of the inspection.

The service bulletin specifies conditional actions, depending on the size, depth, and location of the damage. These actions include performing eddy current or ultrasonic inspections of the scribe lines to detect cracks, and either repairing scribe lines and cracks or contacting Boeing for repair instructions.

The service bulletin specifies repairing scribe lines before further flight, except when a limited return to service (LRTS) program for qualifying scribe lines would allow return to service for a limited period before scribe lines are repaired. The LRTS program includes repetitive inspections to detect cracks where scribe lines are found. To
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qualify for an LRTS program, scribe lines must meet certain criteria based on their depth and location. The service bulletin specifies contacting Boeing for final repair instructions, which would eliminate the need for the repetitive inspections of the LRTS program. The repetitive intervals for the LRTS program range from 250 to 10,000 flight cycles, depending on the depth and location of the scribe lines and the configuration of the airplane.

The service bulletin notes that certain inspections would not be required under the following conditions:

The airplane had never been stripped or repainted.

The wingtobody fairings had never been removed.

The airplane had never been stripped or repainted under the wingtobody fairings.

For each repair, the airplane had never been stripped or repainted since the repair was installed.

No sealant had been removed except in accordance with the specified sealant removal processes as given in Appendix A of the service bulletin.

The service bulletin specifies submitting the initial inspection results to Boeing. The service bulletin also provides procedures for addressing scribe lines detected before the initial inspection threshold.

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) same type design(s). This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed below. This proposed AD would also require sending the results of the exploratory inspections to Boeing.

Difference Between the Proposed AD and Service Bulletin

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require 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. Clarification of Proposed Requirements Beyond Specified Inspection Areas and Threshold

Although the service bulletin provides procedures for addressing scribe lines that are found outside the inspection areas and before the initial inspection threshold, this proposed AD would not include such requirements.

Interim Action

This proposed AD is considered to be interim action. The inspection reports that would be required by this proposed AD will enable the manufacturer to obtain better insight into the nature, cause, and extent of the cracking, and eventually to develop final action to address the unsafe condition. Once final action has been identified, we may consider further rulemaking.

Costs of Compliance

There are about 1,038 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 Number of U.S. Action Work hours Average labor Cost per airplane registered Fleet cost rate per hour airplanes Exploratory inspections.......... 1,020 to 1,140........... $80 $81,600 to $91,200.......... 219 $17,870,400 to $19,972,800. Report........................... 1........................ 80 $80......................... 219 $17,520. 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: [[Page 5770]]
Boeing: Docket No. FAA20080107; Directorate Identifier 2007NM 087AD.
Comments Due Date
(a) We must receive comments by March 17, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Boeing Model 747100, 747100B, 747100B SUD, 747200B, 747200C, 747200F, 747300, 747400, 747400D, 747 400F, 747SP, and 747SR series airplanes, certificated in any category; as identified in Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008.
Unsafe Condition
(d) This AD results from reports of scribe lines found at lap joints and butt joints, around external doublers and antennas, and at locations where external decals had been cut. We are issuing this AD to detect and correct scribe lines, which can develop into fatigue cracks in the skin and cause sudden 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.
Inspection
(f) At the applicable times specified in paragraph 1.E., ``Compliance,'' of Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008, except as provided in paragraph (g) of this AD, do detailed exploratory inspections for scribe lines of affected lap and butt splices, wingtobody fairing locations, and external repair and cutout reinforcement areas, and do all applicable related investigative and corrective actions, by accomplishing all actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraph (h) of this AD.

Note 1: The inspection exemptions noted in paragraph 1.E. of Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008, apply to this AD.
Exceptions to Service Bulletin Specifications
(g) Where Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008, 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.
(h) Where Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008, specifies to contact Boeing for appropriate action, accomplish applicable actions before further flight using a method approved in accordance with the procedures specified in paragraph (k) of this AD.
Report
(i) At the applicable time specified in paragraph (i)(1) or (i)(2) of this AD: Submit a report of the findings (both positive and negative) of the inspections required by paragraph (f)(1) of this AD. One approved method for reporting is Appendixes B and C as applicable of Boeing Service Bulletin 74753A2563, Revision 2, dated January 3, 2008. Send the report to Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 981242207. The report must contain, at a minimum, the inspection results, a description of any discrepancies found, the airplane serial number, and the number of flight cycles and flight hours on the airplane. Under the provisions of the Paperwork Reduction Act (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 21200056.
(1) If the inspection was done after the effective date of this

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.