The compliance times listed in the Part A Inspections, as specified in the service bulletin, are as follows: The compliance time for airplanes on which the detailed visual and high frequency eddy current (HFEC) inspections of the inboard and outboard strut rear engine mount bulkheads in the original issue of the service bulletin have been done ranges from 180 days to 18 months from the release date of Revision 1 of the service bulletin or 350 flight cycles to 1,200 flight cycles, whichever occurs earlier; the repetitive interval ranges from 350 flight cycles to 1,200 flight cycles or 18 months, whichever occurs earlier.

The compliance time for airplanes on which the inspections in the original issue of the service bulletin have not been done is within 90 days from the release date of Revision 1 of the service bulletin to within 18 months or 1,200 flight cycles, whichever occurs earlier; the repetitive interval ranges from 350 flight cycles to 1,200 flight cycles or 18 months, whichever occurs earlier. The compliance times depend on airplane configuration and nacelle strut position.

The compliance times listed in the Part B InspectionsPost Modification, as specified in the service bulletin, are as follows: The compliance time for airplanes on which the repairs have been done ranges from 600 flight cycles to 7,200 flight cycles or 18 months after repair; the repetitive interval ranges from 600 flight cycles to 1,200 flight cycles or 18 months, whichever occurs earlier. At 7,200 flight cycles after repair the repetitive interval changes from doing a detailed visual inspection every 1,200 flight cycles or 18 months, to doing detailed visual and HFEC inspections every 1,200 flight cycles or 18 months.

Depending on the group, the service bulletin specifies doing the following repairs, related investigative actions, and corrective actions:

Repair 2 includes the following related investigative and corrective actions: Detailed visual and HFEC inspections for cracks of the bulkhead frame, repair or replacement of cracked frames, inspection of holes in frames for cracks, inspection of holes in chords for cracks, replacement of cracked chords, inspection of holes on aft left hand and righthand sides of bulkhead in frame and skin for cracks, inspection of frame edge for cracks, and inspection of the holes on the forward side of bulkhead in frame and skin for cracks.

Repair 3 includes the following related investigative and corrective actions: Inspection of holes in frames for cracks, replacement of cracked frames, inspection of frame edge for cracks, and replacement of cracked frames.

The procedures in the service bulletin specify doing the following modifications for Groups 1, 2, and 5 airplanes, depending on airplane configuration:

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. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed below. Differences Between the Alert Service Bulletin and This Proposed AD

The alert 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:

In this NPRM, the ``detailed visual inspection'' specified in Boeing Alert Service Bulletin 74754A2202, Revision 1, is referred to as a ``detailed inspection.''

Costs of Compliance

There are about 460 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 135 airplanes of U.S. registry.

It would take about 4 work hours per airplane to accomplish the proposed detailed inspection, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the proposed inspection is $43,200, or $320 per airplane, per inspection cycle.

It would take about 32 work hours per airplane to accomplish the proposed high frequency eddy current inspection, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the proposed high frequency eddy current inspection is $345,600, or $2,560 per airplane, per inspection cycle.

For Groups 1, 2, and 5 airplanes, it would take between approximately 10 and 95 work hours per strut (four struts per airplane) to accomplish the proposed modification, depending on airplane configuration, at an average labor rate of $80 per work hour. Parts cost for the fasteners only would be between $269 and $897 per strut. Based on these figures, the cost impact of the proposed modification would be between $4,276 and $33,988 per airplane. We are unable to provide specific information as to the cost of the actual parts other than the fasteners that would be required to accomplish the proposed modification since the parts would be supplied from operator stock. 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 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 and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation. 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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):
Boeing: Docket No. FAA20070204; Directorate Identifier 2007NM 083AD.
Comments Due Date
(a) The FAA must receive comments on this AD action by January 3, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to Model 747100, 100B, 100B SUD, 200B, 200C, 200F, 300, 747SP, and 747SR series airplanes; certificated in any category; powered by General Electric (GE) CF645/50 and Pratt & Whitney (P&W) JT9D70, JT9D3 or JT9D7 series engines; as identified in Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006.
[[Page 64964]]
Unsafe Condition
(d) This AD results from reports of web and frame cracks and sheared attachment fasteners on the inboard and outboard nacelle strut. We are issuing this AD to detect and correct cracks and broken fasteners of the inboard and outboard nacelle struts, which could result in possible loss of the rear engine mount bulkhead load path and consequent separation of the engine from 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.
Compliance Times
(f) Do all applicable actions specified in paragraphs (g), (h), and (i) of this AD at the applicable times specified in paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006, except that where paragraph 1.E. of the service bulletin specifies starting the compliance time from ``* * * the release date of Revision 1 of this service bulletin,'' this AD requires starting the compliance time from the effective date of this AD.
Initial and Repetitive Inspections/Corrective Actions
(g) For all airplanes: Perform detailed and high frequency eddy current inspections for cracks and broken fasteners of the rear engine mount bulkhead of the inboard and outboard nacelle struts, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006. Repeat the applicable inspection and actions thereafter at the applicable interval specified in paragraph 1.E., ``Compliance,'' of the service bulletin. Accomplishing the applicable repair (Repair 1, 2, 3, or 4, or repair per the 747 structural repair manual, section 541103 or 541203) terminates the requirements in this paragraph for that nacelle strut only.
Modification
(h) For Groups 1, 2, and 5 airplanes: Do the applicable modification (Repair 2, 3, or 4) of the rear engine mount bulkhead of the inboard and outboard nacelle struts, and all the applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747 54A2202, Revision 1, dated June 22, 2006. Accomplishing this modification terminates the requirements in paragraph (g) of this AD for that nacelle strut only.
PostModification Inspection/Corrective Actions
(i) For Groups 1, 2, and 5 airplanes on which the applicable corrective actions (Repair 1, 2, 3, or 4) required by paragraph (g) of this AD have been accomplished; or the applicable modification (Repair 2, 3, or 4) required by paragraph (h) of this AD has been accomplished: At the applicable time specified in paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006, or within 6 months after the effective date of this AD, whichever occurs later, perform detailed and high frequency eddy current inspections for cracks and broken fasteners of the rear engine mount bulkhead of the inboard and outboard nacelle struts, and do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006. Repeat the applicable inspections and actions thereafter at the applicable interval specified in paragraph 1.E., ``Compliance,'' of the service bulletin.
Exception to Service Bulletin
(j) If any crack or any broken fastener is found during any inspection required by this AD, and Boeing Alert Service Bulletin 74754A2202, Revision 1, dated June 22, 2006, specifies to contact Boeing for appropriate action: Before further flight, repair the discrepancy using a method approved in accordance with the procedures specified in paragraph (k) of this AD.
Alternative Methods of Compliance (AMOCs)
(k)(1) The Manager, Seattle Aircraft Certification Office (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) 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 November 7, 2007. Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. E722542 Filed 111607; 8:45 am]
BILLING CODE 491013P

FOR FURTHER INFORMATION CONTACT Tamara Anderson, Aerospace Engineer, Airframe Branch, ANM120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 980573356; telephone (425) 9176421; fax (425) 9176590.