Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP Series Airplanes

AGENCY:

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

ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. This AD requires repetitive detailed and ultrasonic inspections of the thrust links of the rear engine mounts for any crack or fracture and corrective actions if necessary. This AD results from the finding of a fractured forward lug of the rear engine mount thrust link on the number one strut. We are issuing this AD to detect and correct cracked or fractured thrust links that could lead to the loss of the load path for the rear engine mount bulkhead and damage to other primary engine mount structure, which could result in the in-flight separation of the engine from the airplane and consequent loss of control of the airplane.

DATES:

This AD becomes effective September 30, 2005.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of September 30, 2005.

We must receive comments on this AD by November 14, 2005.

ADDRESSES:

Use one of the following addresses to submit comments on this 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.
• 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.

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

FOR FURTHER INFORMATION CONTACT:

Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6437; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Discussion

We have received a report indicating that one operator found a fractured forward lug of the rear engine mount thrust link on the number one strut. The fractured thrust link was found on a Model 747-200B series airplane equipped with Pratt & Whitney JT9D-7Q engines. The fractured thrust link had accumulated 91,173 total flight hours (and 27,931 total flight cycles). The fracture occurred about 65,000 flight hours (and 14,000 flight cycles) after the thrust link had been overhauled to replace a worn spherical bearing. The same operator also reported finding a cracked thrust link on the number one strut of a Model 747-200B series airplane equipped with Pratt & Whitney JT9D-7Q engines. That cracked thrust link had accumulated about 66,000 total flight hours (and about 19,000 total flight cycles) and about 55,700 flight hours (and about 11,100 flight cycles) since it was last overhauled. Metallurgical analysis by the airplane manufacturer indicates that cracking of the high-strength steel thrust links resulted from fatigue. In both of the reported incidents, cracking could have occurred before the overhaul. Continued airplane operation with a cracked or fractured thrust link could lead to the loss of the load path for the rear engine mount bulkhead and damage to other primary engine mount structure. This condition, if not detected and corrected, could result in the in-flight separation of the engine from the airplane and consequent loss of control of the airplane.

The rear engine mount thrust links on the Model 747-200B series airplanes equipped with Pratt & Whitney JT9D-7Q engines are similar to those on the affected Model 747-100, 747-100B, 747-100B SUD, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes, equipped with Pratt & Whitney JT9D-3 and -7 series engines, except JT9D-70 engines. Therefore, all of these models may be subject to the same unsafe condition.

Other Related Rulemaking

On July 19, 2001, we issued AD 2001-15-15, amendment 39-12349 (66 FR 39425, dated July 31, 2001), applicable to certain Boeing Model 747 airplanes powered by Pratt & Whitney JT9D-7 series engines. That AD requires detailed visual inspections of the lugs on the bulkhead fitting of the rear engine mounts, and corrective action if necessary. That AD also requires ultrasonic inspections and, for certain airplanes, rework of the bulkhead fitting of the rear engine mounts. Reworking the lugs on the bulkhead fitting of the rear engine mounts (in accordance with “Part 5—Rework” of the Accomplishment Instructions of Boeing Service Bulletin 747-54A2200, Revision 1, dated February 15, 2001) as specified in paragraphs (b)(2), (e), and (f) of AD 2001-15-15 is acceptable for compliance with “Part 3—Rear Engine Mount Bulkhead Inspection and Lug Overhaul and Upper Fitting Overhaul and Bolt Replacement” of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005 (which is referenced as the appropriate source of service information for doing the actions required by this AD).

On March 24, 2004, we issued AD 2004-07-22, amendment 39-13566 (69 FR 18250, April 7, 2004), applicable to all Boeing Model 747 airplanes. (A correction to AD 2004-07-22 was published in the Federal Register on May 3, 2004 (69 FR 24063).) That AD requires that the FAA-approved maintenance inspection program be revised to include inspections that will give no less than the required damage tolerance rating for each structural significant item (SSI), and repair of cracked structure. Accomplishing the inspections and repetitive overhaul or replacement specified in paragraphs (g) and (j) of this AD are approved as an alternative method of compliance to paragraphs (c) and (d) of AD 2004-07-22 for the inspections of SSI S-2, for the thrust links only, of the Boeing Supplemental Structural Inspection Document D6-35022, Revision G, dated December 2000.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005. The service bulletin describes procedures for doing detailed and ultrasonic inspections of the thrust link lugs of the rear engine mount of struts 1, 2, 3, and 4 for any crack or fracture and other specified and corrective actions as applicable.

If a thrust link is not cracked or fractured, the service bulletin specifies repeating the detailed and ultrasonic inspections and doing other specified actions. The other specified actions are to repetitively replace the thrust link with a new or overhauled thrust link, which ends the repetitive inspections of the thrust link lugs.

If a thrust link is cracked, the corrective action is to repetitively replace the cracked thrust link with a new or overhauled thrust link. If the thrust link is fractured, the corrective actions include the following:

• Repetitively replacing the fractured thrust link with a new or overhauled thrust link (Part 2 of the Accomplishment Instructions of the service bulletin).
• Inspecting the upper fitting assembly of the rear engine mount for cracks and material deformation and repairing if necessary; doing a detailed inspection of the bulkhead assembly of the rear engine mount for cracks, fracture, and material deformation and contacting the manufacturer for additional instructions if necessary; overhauling the lugs of the rear engine mount bulkhead and upper fitting assembly and contacting the manufacturer for additional instructions if necessary; and replacing the bolts that attach the upper fitting to the rear engine mount bulkhead with new bolts (Part 3 of the Accomplishment Instructions of the service bulletin).
• Doing the inspection of the engine nacelle for damage, as specified in Chapter 05-51-06 of the Boeing 747-100/-200/-300 Airplane Maintenance Manual, and contacting the manufacturer for additional instructions if necessary (Part 4 of the Accomplishment Instructions of the service bulletin).
• Doing a detailed inspection of the forward engine mount for material deformation and contacting the manufacturer for additional instructions if necessary (Part 5 of the Accomplishment Instructions of the service bulletin).

FAA's Determination and Requirements of This AD

The unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. For this reason, we are issuing this AD to detect and correct cracked or fractured thrust links of the rear engine mount that could lead to the loss of the load path for the rear engine mount bulkhead and damage to other primary engine mount structure, which could result in the in-flight separation of the engine from the airplane and consequent loss of control of the airplane. This AD requires repetitive detailed and ultrasonic inspections of the thrust link lugs of the rear engine mount of struts 1, 2, 3, and 4 for any crack or fracture and corrective actions as applicable in accordance with the service information described above, except as discussed under “Differences Between the AD and Service Bulletin.”

Differences Between the AD and Service Bulletin

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this AD requires 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.

The service bulletin specifies doing corrective actions if a fractured thrust link is found during any required inspections, but does not specify what action to take if one is found during any replacement or overhaul of the thrust link. This AD requires accomplishing those same corrective actions before further flight, whether the fractured thrust link is found during an inspection, replacement, or overhaul. (Those corrective actions are defined in the “Relevant Service Information” section of this AD.) This difference has been coordinated with the manufacturer.

Although the service bulletin recommends repetitively replacing the thrust links of the rear engine mounts with new or overhauled thrust links at an initial threshold of within 36 months after issuance of the service bulletin, this AD is not mandating those replacements in this rulemaking action. Instead, we have included those replacements as an optional terminating action in this AD.

Interim Action

This is considered to be interim action. The FAA is currently considering requiring the repetitive replacement or overhaul of the thrust links of the rear engine mounts, which will constitute terminating action for the repetitive inspections required by this AD action. However, the planned compliance time for the other specified actions is sufficiently long so that notice and opportunity for prior public comment will be practicable.

FAA's Determination of the Effective Date

Since an unsafe condition exists that requires the immediate adoption of this AD, we have found that notice and opportunity for public comment before issuing this AD are impracticable, and that good cause exists to make this AD effective in less than 30 days.

Comments Invited

This AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed in the ADDRESSES section. Include “Docket No. FAA-2005-22413; Directorate Identifier 2005-NM-167-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD that might suggest a need to modify it.

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 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 may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Dockets

You may 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 Docket Management System receives them.

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 AD will not have federalism implications under Executive Order 13132. This AD will 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 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 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

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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.

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

2005-19-06 Boeing: Amendment 39-14271. Docket No. FAA-2005-22413; Directorate Identifier 2005-NM-167-AD.

Effective Date

(a) This AD becomes effective September 30, 2005.

Affected ADs

(b) None.

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 Pratt & Whitney JT9D-3 and -7 series engines, except JT9D-70 engines; as identified in Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005.

Unsafe Condition

(d) This AD results from the finding of a fractured forward lug of the rear engine mount thrust link on the number one strut. We are issuing this AD to detect and correct cracked or fractured thrust links that could lead to the loss of the load path for the rear engine mount bulkhead and damage to other primary engine mount structure, which could result in the in-flight separation of the engine from the airplane and consequent loss of control 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.

Service Bulletin References

(f) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005.

Repetitive Inspections of Thrust Links

(g) Within 90 days after the effective date of this AD, do a detailed inspection and ultrasonic inspection of thrust link lugs having part number (P/N) 65B90360-1 or -4 of the rear engine mount of struts 1, 2, 3, and 4 for any crack or fracture, in accordance with Part 1 of the service bulletin. If the thrust link is not found cracked or fractured: Repeat the inspections thereafter at intervals not to exceed 1,200 flight cycles or 18 months, whichever is first, until the optional repetitive replacement or overhaul of the thrust link as specified in paragraph (j) of this AD is accomplished. Accomplishing the repetitive replacement or overhaul of a thrust link specified in paragraph (h) or (j) of this AD terminates the repetitive inspections for that thrust link only.

Corrective Actions

(h) If a cracked thrust link is found during any inspection required by paragraph (g) of this AD or during any replacement or overhaul done in accordance with the service bulletin: Before further flight, do the actions specified in paragraph (h)(1) of this AD. If a fractured thrust link is found during any inspection required by paragraph (g) of this AD or during any replacement or overhaul done in accordance with the service bulletin: Before further flight, do the actions specified in paragraphs (h)(1) and (h)(2) of this AD.

(1) Replace the cracked thrust link with a new or overhauled thrust link in accordance with Part 2 of the service bulletin; except as provided by paragraph (i) of this AD. Repeat the replacement at the applicable compliance time specified in paragraph (h)(1)(i) or (h)(2)(ii) of this AD.

(i) For replacement with a thrust link assembly having P/N 65B90360-1 or -4: Thereafter at intervals not to exceed 6,000 flight cycles.

(ii) For replacement with a thrust link assembly having P/N 65B90360-7: Thereafter at intervals not to exceed 12,000 flight cycles.

(2) Do the corrective actions in accordance with Parts 3, 4, and 5 of the service bulletin; except as provided by paragraph (i) of this AD.

(i) Where the service bulletin specifies to contact Boeing for appropriate action, do the corrective action using a method approved in accordance with paragraph (l) of this AD.

Optional Repetitive Replacement or Overhaul of a Thrust Link

(j) For a thrust link that is not found cracked or fractured during the inspections required by paragraph (g) of this AD: Repetitive replacement of the thrust link with a new or overhauled thrust link at the applicable compliance time specified in paragraph (j)(1) or (j)(2) of this AD, in accordance with Part 2 of the service bulletin, terminates the repetitive inspections required by paragraph (g) of this AD for that thrust link only. If a cracked or fractured thrust link is found during any replacement or overhaul done in accordance with the service bulletin: Before further flight, do the applicable corrective actions specified in paragraph (h) of this AD at the applicable compliance time specified in that paragraph.

(1) For a thrust link assembly having P/N 65B90360-1 or -4: Within 36 months after the effective date of this AD. Thereafter at intervals not to exceed 6,000 flight cycles.

(2) For a thrust link assembly having P/N 65B90360-7: Within 12,000 flight cycles after the new or overhauled thrust link has been installed. Thereafter at intervals not to exceed 12,000 flight cycles.

Credit for Certain Corrective Actions

(k) Reworking the lugs on the bulkhead fitting of the rear engine mount as specified in paragraphs (b)(2), (e), and (f) of AD 2001-15-15, amendment 39-12349, is acceptable for compliance with accomplishing the corrective action specified in “Part 3—Rear Engine Mount Bulkhead Inspection and Lug Overhaul and Upper Fitting Overhaul and Bolt Replacement” of the service bulletin.

Alternative Methods of Compliance (AMOCs)

(l)(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) 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.

(3) The actions identified in paragraphs (g) and (j) of this AD are approved as an AMOC to paragraphs (c) and (d) of AD 2004-07-22, amendment 39-13566, for the inspections of structural significant item S-2, for the thrust links only, of Boeing Supplemental Structural Inspection Document D6-35022, Revision G, dated December 2000. All provisions of AD 2004-07-22 that are not specifically referenced in this paragraph, including the initial inspection threshold required by paragraph (d) of AD 2004-07-22, remain fully applicable and must be complied with.

Material Incorporated by Reference

(m) You must use Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov;; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.