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:

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 detailed and ultrasonic inspections of the thrust links of the rear engine mounts for any crack or fracture and corrective actions if necessary. This proposed AD would require repetitive replacement of the thrust links with new or overhauled thrust links, which ends the repetitive detailed and ultrasonic inspections. This proposed AD results from the finding of fractured and cracked forward lugs of the rear engine mount thrust link on the number one strut on two airplanes. We are proposing this AD to prevent 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:

We must receive comments on this proposed AD by February 27, 2006.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed 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 proposed 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:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “Docket No. FAA-2005-23441; Directorate Identifier 2005-NM-199-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

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 proposed 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 can visit http://dms.dot.gov.

Examining the Docket

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.

Discussion

On September 6, 2005, we issued AD 2005-19-06, amendment 39-14271 (70 FR 54474, September 15, 2005), for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. (A correction to AD 2005-19-06 was published in the Federal Register on September 30, 2005 (70 FR 57124).) That 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. That AD resulted from the finding of a fractured forward lug of the rear engine mount thrust link on the number one strut. We issued that 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.

Actions Since Existing AD Was Issued

In the preamble to AD 2005-19-06, we indicated that the actions required by that AD were considered “interim action.” We also indicated that we were considering further rulemaking action to require repetitive replacement of the thrust link with a new or overhauled thrust link. (The repetitive replacements are included as an optional terminating action in AD 2005-19-06.) However, the planned compliance time for that action was sufficiently long so that it was practicable to allow notice and opportunity for prior public comment. We have now determined that further rulemaking making action is indeed necessary, and this NPRM follows from that determination. We point out that this NPRM would require the repetitive replacements within a certain compliance time, regardless of any inspection results.

Comments

We have considered the following comments to AD 2005-19-06.

Request To Use an Alternative Method of Compliance (AMOC)

One commenter states that it can reduce the work required for replacing a thrust link by omitting the step for removing the engine to gain access to the thrust link. Part 2 of the accomplishment instructions of Boeing Alert Service Bulletin 747-71A2309, dated August 18, 2005, specifies removal of the engine. The commenter states, however, that there is no load on the thrust link at static condition, so the engine does not need to be removed. Instead, only the engine exhaust sleeve needs to be removed to replace the thrust link. The commenter also states that, in Boeing message No. 1-385158991-9, dated September 16, 2005, the manufacturer agreed that removing the sleeve would be an appropriate alternative procedure for replacing the thrust link. On October 26, 2005, the commenter submitted this request for approval as an AMOC.

We agree, since we have found the commenter's request for an AMOC to be acceptable. We have approved removing the side cowls, as an alternative to opening the side cowls as required by paragraph (g) of AD 2005-19-06. We have also approved removal of the turbine exhaust sleeve, as an alternative to removing the engine as required by paragraph (j) of AD 2005-19-06 (corresponding to paragraph (k) of this NPRM) provided that the engine is supported. We have included a provision in paragraph (l)(5) of this NPRM to account for the commenter's AMOC. Under the provisions of paragraph (l) of this NPRM, we may consider other requests for approval of an alternative method of compliance if sufficient data are submitted to substantiate that such a method would provide an acceptable level of safety.

Request To Clarify Inspection Requirements

One commenter requests that we clarify the required actions of AD 2005-19-06 for thrust links having part number (P/N) 65B90360-7. The commenter states that Boeing Alert Service Bulletin 747-71A2309 requires repetitive replacement of those thrust links, but that the repetitive replacement is identified as an optional action in AD 2005-19-06. The commenter would like to know if this means that there is no mandatory requirement for thrust links having P/N 65B90360-7.

As discussed previously, repetitive replacement of the thrust links as required by AD 2005-19-06 is considered an optional action because the planned compliance time for that action was sufficiently long enough to allow the public time to comment. This NPRM, however, would require the repetitive replacement of thrust links having P/N 65B90360-7 in agreement with the service bulletin. Also, we point out that AD 2005-19-06 does require the repetitive replacement of P/N 65B90360-7. Although that action is conditional in AD 2005-19-06, depending on whether P/N 65B90360-7 was installed while accomplishing the corrective action as applicable or the optional terminating action, as specified in paragraphs (h)(1)(ii) and (j)(2) of AD 2005-19-06, respectively.

Clarification of AMOC Paragraph

We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

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 2005-19-06. This proposed AD would continue to require 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 proposed AD would also require repetitive replacement of the thrust links with new or overhauled thrust links, which would end the repetitive inspections.

Costs of Compliance

There are about 274 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs, at an average labor rate of $65 per hour, for U.S. operators to comply with this proposed AD.

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 39—AIRWORTHINESS DIRECTIVES

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

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