For the onetime general visual inspection, onetime detailed inspection, onetime openhole HFEC inspection, and the initial external HFEC inspection, the service bulletin specifies a compliance time of 16,000 or 25,000 total flight cycles depending on the airplane configuration, or 2,000 flight cycles after the date on the service bulletin, whichever occurs later. The service bulletin also specifies that if a skin panel was replaced, the inspection threshold for the affected area can be calculated from the time it was replaced. For the repetitive external HFEC inspections, the service bulletin specifies a repeat interval of 3,000 flight cycles.

The corrective actions include repairing any crack found in an inspection area, and installing a new external doubler where any external doubler has been removed from the inspection area. The service bulletin specifies accomplishing the corrective actions 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) same type design(s). This proposed AD would require accomplishing the actions specified in the service
[[Page 7487]]
information described previously, except as discussed under ``Differences Between the Proposed AD and Service Bulletin.'' Differences Between Proposed AD and Service Bulletin

Although Figure 19 of the service bulletin specifies doing a ``detailed visual inspection'' of the fastener holes, this proposed AD would require doing a ``detailed inspection.''

This proposed AD expands the inspection area at certain skinto stringer attachments. In Figure 3 of the service bulletin, S5 and S5A from STA 340 to STA 360 should be bold in the illustration to include those areas as part of the recommended inspection (similar to Figure 8 for the right side). Also, in Figure 15 of the service bulletin, S14A from STA 200 to STA 220 should be bold in the illustration to include that area as part of the recommended inspection (similar to Figure 17 for the right side). Boeing is aware of these discrepancies, concurs with the changes, and has issued Information Notice (IN) 74753A2704 IN 01, dated December 19, 2007, to inform operators of the errors. We have included this information in paragraph (g) of this proposed AD. Clarification of Proposed Requirements

The service bulletin notes that, at locations where external doublers exist that do not end on a stringer in the inspection area, repetitive inspections of the skin for cracking at critical rows of fasteners are required in accordance with Boeing Document Number D6 36181, ``Repair Assessment GuidelinesModel 747.'' These inspections would not be required by this AD, since compliance is already required by sections 91.410, 121.370, 125.248, and 129.32 of the Federal Aviation Regulations (14 CFR 91.410, 121.370, 125.248, and 129.32). Costs of Compliance

We estimate that this proposed AD would affect 165 airplanes of U.S. registry. We also estimate that it would take up to 64 workhours per product to comply with this proposed AD. The average labor rate is $80 per workhour. Based on these figures, we estimate the cost of this proposed AD to the U.S. operators to be $844,800 or $5,120 per product. 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. FAA20080148; Directorate Identifier 2007NM 299AD.
Comments Due Date
(a) We must receive comments by March 24, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to all Boeing Model 747100, 747100B, 747 100B SUD, 747200B, 747200C, 747200F, 747300, 747400, 747400D, 747400F, 747SR, and 747SP series airplanes, certificated in any category.
Unsafe Condition
(d) This AD results from reports of cracks found at fastener locations in the fuselage skins at section 41. We are issuing this AD to detect and correct fuselage skin cracks at fastener locations along the skintostringer attachments, which could join together and become large and consequently result in rapid decompression of the cabin.
Compliance
(e) Comply with this AD within the compliance times specified, unless already done.
Repetitive Inspections and Related Investigative/Corrective Actions (f) At the applicable compliance times specified in Tables 1 and 2 of paragraph 1.E. of Boeing Alert Service Bulletin 74753A2704, dated October 4, 2007: Do a general visual inspection of the fuselage skins at section 41 to find any external doublers that cover the inspection area and to identify the external doublers that end on a stringer in the inspection area and those that do not, and do all the related investigative and corrective actions as applicable, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraph (g) of this AD. Repeat the related investigative actions thereafter at the interval specified in Tables 1 and 2 of the service bulletin, as applicable.
Exceptions to the Service Bulletin
(g) Where Tables 1 and 2 of paragraph 1.E. of Boeing Alert Service Bulletin 74753A2704, dated October 4, 2007, specify counting the compliance time from ``* * * after the date on this service bulletin,'' this AD requires counting the compliance time from the effective date of this AD. Where Figure 19 of the service bulletin specifies doing a ``detailed visual inspection'' for any crack at fastener holes common to the stringer, this AD would require doing a detailed inspection. In Figure 3 of the service bulletin, also inspect the areas at stringer 5 (S5) and S5A between station (STA) 340 and STA 360 (similar to Figure 8 for the right side). In Figure 15 of the service bulletin, also inspect the area at S14A between STA 200 and STA 220 (similar to Figure 17 for the right side).
Alternative Methods of Compliance (AMOCs)
(h)(1) The Manager, Seattle Aircraft Certification Office, FAA,

FOR FURTHER INFORMATION CONTACT Ivan Li, Aerospace Engineer, Airframe Branch, ANM120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980573356; telephone (425) 9176437; fax (425) 9176590.