E9-22577. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP Series Airplanes Equipped With General Electric CF6-45 or -50 Series Engines, or Equipped With Pratt & Whitney ...

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. The existing AD currently requires repetitive inspections to detect cracks and fractures of the strut front spar chord assembly (including the forward side) at each strut location, and repair if necessary. This proposed AD would add a one-time inspection for cracking of the forward side of the front spar chord assembly on the inboard and outboard struts, installation of a cap skin doublers for certain airplanes, and repair if necessary. These actions would terminate the repetitive inspections of the forward side of the strut front spar chord assembly; the inspections of the aft side assembly continue as specified in the existing AD. This proposed AD results from a report of a fractured front spar assembly for strut No. 3, which resulted in the loss of the strut upper link load path. We are proposing this AD to detect and correct cracks and fractures of the nacelle strut front spar chord assembly. Fracture of the front spar chord assembly could lead to loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane.

DATES:

We must receive comments on this proposed AD by November 2, 2009.

ADDRESSES:

You may send comments by any of the following methods:

• Federal rulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, 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, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; e-mail [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Ken Paoletti, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY 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. FAA-2009-0865; Directorate Identifier 2009-NM-023-AD” 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

On December 26, 2006, we issued AD 2007-01-15, amendment 39-14887 (72 FR 1427, January 12, 2007), for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. That AD requires repetitive inspections to detect cracks and fractures of the strut front spar chord assembly, including the forward side, at each strut location, and repair if necessary. That AD resulted from a strut front spar chord assembly that was found fractured, forward of the inspections that are required by AD 2004-25-05, amendment 39-13893 (69 FR 71349), which was superseded by AD 2007-01-15. We issued AD 2007-01-05 to detect and correct cracks and fractures of the nacelle strut front spar chord assembly. Fracture of the front spar chord assembly could lead to loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane.

Actions Since Existing AD Was Issued

The preamble to AD 2007-01-15 specifies that we consider the requirements “interim action” and that the manufacturer is developing a modification to address the unsafe condition. That AD explains that we might consider further rulemaking if a modification is developed, approved, and available. The manufacturer now has developed such a modification only for the front spar chord assembly forward of the upper link attachment. Therefore, we have determined that further rulemaking is indeed necessary; this proposed AD follows from that determination.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-54A2230, dated October 30, 2008. The service bulletin describes the following procedures:

• A one-time open-hole high frequency eddy current (HFEC) inspection for cracking of the forward side of the front spar chord assembly on the inboard and outboard struts. For airplanes on which the cap skin doubler is not installed, the service bulletin also includes procedures for installing the cap skin doubler.
• For airplanes on which no crack is found, the service bulletin states that no further action is required.
• For airplanes on which any crack is found, the service bulletin specifies the corrective action of contacting Boeing for additional instructions and doing the repair before further flight. The service bulletin specifies that doing the repair ends the need for the repetitive inspections of the forward side of the strut front spar chord assembly.

The service bulletin specifies doing the inspection, and the installation of the cap skin doubler for certain airplanes, within 48 months after the date on the service bulletin for the outboard strut, and within 36 months after the date on the service bulletin for the inboard strut.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to develop on other airplanes of the same type design. For this reason, we are proposing this AD, which would supersede AD 2007-01-15 and retain the requirements of the existing AD. This proposed AD would also require accomplishing the actions specified in the service bulletin described previously, except as discussed under “Difference Between the Proposed AD and the Service Bulletin.”

Difference Between the Proposed AD and the Service Bulletin

Boeing Alert Service Bulletin 747-54A2230, dated October 30, 2008, 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 has been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Changes to Existing AD

This proposed AD would retain all requirements of AD 2007-01-15. Since AD 2007-01-15 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, the corresponding paragraph identifiers have changed in this proposed AD, as listed in the following table:

Revised Paragraph Identifiers

Requirement in AD 2007-01-15	Corresponding requirement in this proposed AD
Paragraph (f)	paragraph (g).
Paragraph (g)	paragraph (h).
Paragraph (h)	paragraph (i).
Paragraph (i)	paragraph (j).
Paragraph (j)	paragraph (k).
Paragraph (k)	paragraph (l).
Paragraph (l)	paragraph (m).
Paragraph (m)	paragraph (q).

Interim Action

We consider the actions in this proposed AD to be interim actions for the strut front spar chord assembly at each strut location, excluding the forward side (the terminating action for the forward side is included in this proposed AD). If the manufacturer develops a modification for the remainder of the front spar chord assembly, we might consider additional rulemaking.

Costs of Compliance

There are about 411 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

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Inspections (required by AD 2007-01-15)	17	$80	$0	$1,360 per inspection cycle	85	$115,600 per inspection cycle.
One-time inspection and cap skin doubler installation (new proposed action)	30 to 116 1	80	$893 to $36,737 1	$3,293 to $46,017 1	85	$279,905 to $3,911,445.1
1 Depending on airplane configuration.

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
• Incorporation by reference
• 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 39—AIRWORTHINESS DIRECTIVES

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

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

§ 39.13

[Amended]

2. The FAA amends § 39.13 by removing amendment 39-14887 (72 FR 1427, January 12, 2007) and adding the following new AD:

Boeing: Docket No. FAA-2009-0865; Directorate Identifier 2009-NM-023-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by November 2, 2009.

Affected ADs

(b) This AD supersedes AD 2007-01-15.

Applicability

(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes, certificated in any category, equipped with General Electric CF6-45 or -50 series engines, or equipped with Pratt & Whitney JT9D-3 or -7 (excluding -70) series engines, as identified in Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006.

Subject

(d) Air Transport Association (ATA) of America Code 54: Nacelles/Pylons.

Unsafe Condition

(e) This AD results from a report of a fractured front spar assembly for strut No. 3, which resulted in the loss of the strut upper link load path. The Federal Aviation Administration is issuing this AD to detect and correct cracks and fractures of the nacelle strut front spar chord assembly. Fracture of the front spar chord assembly could lead to loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane.

Compliance

(f) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Restatement of Requirements of AD 2004-25-05, Amendment 39-13893

Aft Side Detailed and High Frequency Eddy Current (HFEC) Inspections With New Service Information

(g) Within 90 days after December 27, 2004 (the effective date of AD 2004-25-05, which was superseded by AD 2007-01-15), perform detailed and HFEC inspections to detect any cracks or fractures of the front spar chord assembly for strut numbers 1 through 4 inclusive, in accordance with Boeing Alert Service Bulletin 747-54A2224, dated September 30, 2004; or in accordance with Part 1—Aft Side Inspection of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006. As of January 29, 2007 (the effective date of AD 2007-01-15), only Part 1—Aft Side Inspection of the Accomplishment Instructions of Revision 1 of Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006, may be used.

(h) Accomplishment of the detailed and HFEC inspections in accordance with Boeing 747 Fleet Team Digest 747-FTD-54-04002, dated April 15, 2004, May 4, 2004, June 1, 2004, July 12, 2004, or July 28, 2004; or Boeing Message 1-C6ELC (Service Request ID No.: 218724992), dated April 14, 2004; before December 27, 2004, is considered acceptable for compliance with the requirements of paragraph (g) of this AD.

Repetitive Inspections

(i) For airplanes on which no crack or fracture is detected during the inspections required by paragraph (g) of this AD: At the applicable times specified in Table 1—Repetitive Intervals of this AD, repeat the detailed and HFEC inspections required by paragraph (g) of this AD.

Table 1—Repetitive Intervals

For airplanes identified in Boeing Alert Service Bulletin 747-54A2224, dated September 30, 2004; or Revision 1, dated November 16, 2006; as—	Repeat the inspections at intervals not to exceed—
Group 1	1,000 flight cycles or 18 months, whichever occurs first.
Group 2 and Group 3	1,200 flight cycles or 18 months, whichever occurs first.
Group 4 and Group 6	1,500 flight cycles or 18 months, whichever occurs first.
Group 5	2,000 flight cycles or 18 months, whichever occurs first.

Corrective Action

(j) If any crack or fracture is found during any inspection required by paragraphs (g) and (i) of this AD, and Boeing Alert Service Bulletin 747-54A2224, dated September 30, 2004; or Revision 1, dated November 16, 2006; specifies contacting Boeing for appropriate action: Before further flight, repair the crack or fracture using a method approved in accordance with the procedures specified in paragraph (q) of this AD.

Restatement of Requirements of AD 2007-01-15

Forward Side Detailed and HFEC Inspections

(k) Within 90 days after January 29, 2007, do detailed and HFEC inspections for any cracks or fracture of the front spar chord assembly for strut numbers 1, 2, 3, and 4, in accordance with Part 2—Forward Side Inspection of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006. If no crack or fracture is found, repeat the inspections thereafter at the applicable interval specified in Table 1 of this AD. Doing the inspections required by paragraph (n) of this AD terminates the forward side detailed and HFEC inspection requirements of this paragraph.

Corrective Action for Forward Side Inspection

(l) If any crack or fracture is found during any inspection required by paragraph (k) of this AD, and Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006, specifies to contact Boeing for appropriate action: Before further flight, repair the crack or fracture using a method approved in accordance with the procedures specified in paragraph (q) of this AD.

Credit for Inspections Done According to Boeing 747 Fleet Team Digest

(m) Detailed and HFEC inspections done before January 29, 2007, in accordance with Boeing 747 Fleet Team Digest 747-FTD-54-06002, dated June 29, 2006; or October 16, 2006; are acceptable for compliance with the initial inspection required by paragraph (k) of this AD.

New Requirements of This AD

Inspection and Corrective Actions

(n) At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-54A2230, dated October 30, 2008; except that 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: Do an open-hole high frequency eddy current (HFEC) inspection for cracking of the of the forward side of the front spar chord assembly on the inboard and outboard struts; and, for airplanes on which the cap skin doubler is not installed, install the cap skin doubler; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2230, dated October 30, 2008.

(o) If any crack is found during the inspection required by paragraph (n) of this AD: Before further flight, repair the crack using a method approved in accordance with the procedures specified in paragraph (q) of this AD.

(p) Doing all applicable actions required by paragraphs (n) and (o) of this AD terminates the repetitive forward side detailed and HFEC inspection requirements of paragraph (k) of this AD. All aft side inspection requirements of this AD remain in effect.

Alternative Methods of Compliance (AMOCs)

(q)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Ken Paoletti, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Or, e-mail information to [e-mail].

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(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.

(4) AMOCs approved previously in accordance with AD 2007-01-15, are approved as AMOCs for the corresponding provisions of this AD.

Issued in Renton, Washington, on September 11, 2009.

Stephen P. Boyd,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.