E7-17284. Airworthiness Directives; Boeing Model 747 Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747 airplanes. This proposed AD would require inspecting the trunnion fork assembly of the wing landing gears to determine the part number and serial number and to determine the category of the trunnion fork assemblies. For certain airplanes, this proposed AD also would require, if necessary, various inspections to detect discrepancies of the trunnion fork assemblies, related investigative/corrective actions, and a terminating action. This proposed AD results from a report of a fractured trunnion fork assembly. We are proposing this AD to prevent a fractured trunnion fork assembly, which could result in the collapse of a wing landing gear on the ground and possible damage to hydraulic equipment and the aileron and spoiler cables. Such damage could result in reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by October 15, 2007.

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: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room W12-140 on the ground floor of the West Building, 1200 New Jersey Avenue, SE., 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 the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Berhane Alazar, 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 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 “FAA-2007-29065; Directorate Identifier 2007-NM-142-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 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 Docket

You may examine the AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located on the ground level of the West 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

We have received a report indicating that a fractured trunnion fork assembly was found during push back and tow of an airplane. Analysis showed that a crack was initiated by fatigue on the inner surface and eventually fractured by ductile rupture. The analysis also showed that the crack most likely initiated as a result of two manufacturing anomalies. A fractured trunnion fork assembly could result in the collapse of a wing landing gear on the ground and possible damage to hydraulic equipment and the aileron and spoiler cables. Such damage could result in reduced controllability of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-32A2482, dated June 14, 2007. The service information describes procedures for inspecting the pad-up area on the forward upper inboard surface of the trunnion fork assembly of both the left and right wing landing gears to determine the part number and serial number and to determine the category of the trunnion fork assemblies. For certain airplanes, the service information describes the following procedures, as applicable:

• Doing an initial detailed inspection for damage to the protective finish and for corrosion of the trunnion fork assembly, and an initial high frequency eddy current (HFEC) inspection to detect cracks of the trunnion fork assembly (Part 2).
• Doing an ultrasonic inspection to determine the wall thickness in the area forward of the outer cylinder attach lugs in 8 zones, and a hardness measurement if the wall thickness is less than the specified value (Part 3).
• Doing related investigative/corrective actions if necessary. The related investigative actions include repetitive detailed and HFEC inspections (Part 2). The corrective actions include overhauling the trunnion fork assembly (Part 4), and replacing the trunnion fork assembly (Part 5); as applicable.
• Replacing the trunnion fork assembly of the wing landing gear with a certain trunnion fork assembly (Part 5). Accomplishing the replacement ends the need for the actions specified in the service information.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. The compliance time for the initial detailed, HFEC, and ultrasonic inspections and replacement specified in the service information is either 18 months or 6 years, depending on the category of the trunnion fork assembly. The compliance time for the related investigative/corrective actions specified in the service information ranges between before further flight and 10 years, depending on the condition of the trunnion fork assembly.

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.

Costs of Compliance

There are about 1,055 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 215 airplanes of U.S. registry. The proposed inspection for part number, serial number, and category would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of this inspection proposed by this AD for U.S. operators is $17,200, or $80 per airplane.

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.

§ 39.13

[Amended]

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

Boeing: Docket No. FAA-2007-29065; Directorate Identifier 2007-NM-142-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 15, 2007.

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, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 747-32A2482, dated June 14, 2007.

Unsafe Condition

(d) This AD results from a report of a fractured trunnion fork assembly. We are issuing this AD to prevent a fractured trunnion fork assembly, which could result in the collapse of a wing landing gear on the ground and possible damage to hydraulic equipment and the aileron and spoiler cables. Such damage could result in reduced controllability 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

(f) The term “service bulletin,” as used in this AD, means Boeing Alert Service Bulletin 747-32A2482, dated June 14, 2007.

Initial Inspection for Part Number, Serial Number, and Category

(g) Within 18 months after the effective date of this AD, inspect the pad-up area on the forward upper inboard surface of the trunnion fork assembly of both the left and right wing landing gears to determine the part number and serial number and to determine the category of the trunnion fork assemblies, in accordance with the Accomplishment Instructions of the service bulletin.

Follow-On Actions for Category A, B, C, or D Trunnion Fork Assemblies

(h) If any part number and serial number identified as Category A, B, C, or D in Tables 2 and 3 of paragraph 1.E., “Compliance,” of the service bulletin is found installed during the inspection required by paragraph (g) of this AD: At the applicable compliance time(s) listed in Table 4 or 5 of paragraph 1.E., “Compliance,” of the service bulletin, except as provided by paragraph (i) of this AD, do the applicable action(s) in Table 1 of this AD and applicable related investigative/corrective actions, in accordance with the Accomplishment Instructions of the service bulletin.

Table 1.—Requirements for Category A, B, C, or D Trunnion Fork Assemblies

For—	Do—	And—	Or—
(1) Categories A and D trunnion fork assemblies	A detailed inspection for damage to the protective finish and for corrosion of the trunnion fork assembly and a high frequency eddy current (HFEC) inspection to detect cracks (Part 2)	An ultrasonic inspection to determine the wall thickness in the area forward of the outer cylinder attach lugs in 8 zones, and a hardness measurement if applicable (Part 3)	Do the terminating action (Part 5).
(2) Categories B and C trunnion fork assemblies	An ultrasonic inspection to determine the wall thickness in the area forward of the outer cylinder attach lugs in 8 zones, and a hardness measurement (Part 3)	None	None.

(i) Where paragraph 1.E., “Compliance,” of 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.

Terminating Action

(j) Replacing the trunnion fork assembly of the wing landing gear with a trunnion fork assembly identified in Part 5 of the service bulletin, in accordance with and at the applicable time specified in Table 4 or 5 of paragraph 1.E., “Compliance,” of the service bulletin, constitutes terminating action for the requirements of this AD for that side only.

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.

Issued in Renton, Washington, on August 17, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.