05-2762. 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 repetitive inspections of the dual side braces (DSBs), underwing midspar fittings, and associated parts; other specified actions; and corrective actions if necessary. This proposed AD also provides an optional terminating action for the inspections and other specified actions. This proposed AD is prompted by reports of corroded, migrated, and rotated bearings for the DSBs in the inboard and outboard struts, a report of a fractured retainer for the eccentric bushing for one of the side links of a DSB, and reports of wear and damage to the underwing midspar fitting on the outboard strut. We are proposing this AD to prevent the loss of a DSB or underwing midspar fitting load path, which could result in the transfer of loads and motion to other areas of a strut, and possible separation of a strut and engine from the airplane during flight.

DATES:

We must receive comments on this proposed AD by March 31, 2005.

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.
• By fax: [phone].
• 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.

For service information identified in this proposed AD, contact Boeing Commercial Airplanes, PO Box 3707, Seattle, Washington 98124-2207.

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2005-20364; the directorate identifier for this docket is 2004-NM-186-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 [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 under ADDRESSES. Include “Docket No. FAA-2005-20364; Directorate Identifier 2004-NM-186-AD” in the subject line 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 submitted 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 can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

Examining the Docket

You can 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 [phone]) 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 DMS receives them.

Discussion

We have received reports of corroded, migrated, and rotated bearings for the dual side braces (DSBs) in the inboard and outboard struts, a report of a fractured retainer for the eccentric bushing for one of the side links of a DSB, and reports of wear and damage to the underwing midspar fitting on the outboard strut on Boeing Model 747-400 and Model 747SP series airplanes. These conditions, if not corrected, could result in the loss of the DSB or underwing midspar fitting load path, which could result in the transfer of loads and motion to other areas of a strut, and possible separation of a strut and engine from the airplane during flight.

The subject area on certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400D, 747-400F, and 747SR series airplanes is of a similar type design to those on the affected Model 747-400 and 747SP series airplanes. Therefore, all of these models may be subject to the same unsafe condition.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004. The service bulletin describes procedures for repetitive inspections of the DSBs, underwing midspar fittings, and associated parts; other specified actions; and corrective actions if necessary. This proposed AD also provides an optional terminating action for the repetitive actions.

The service bulletin specifies that the initial inspections of the DSBs and of the underwing midspar fitting be done within 24 months after the release date of the service bulletin. The service bulletin also specifies that the initial corrosion removal and re-lubrication of the DSB bearings be done within 72 months after the release date of the service bulletin (unless directed by the findings of the initial inspections of the DSBs to be done earlier). The service bulletin specifies that repetitive intervals range between 24 months and 72 months for the aforementioned actions. The service bulletin also specifies that the corrective actions be done before further flight or within 24 months of finding certain conditions.

The service bulletin specifies that the following actions for the inboard and outboard struts are applicable to Groups 1-3 airplanes, and that only the actions for the inboard struts are applicable to Group 4 airplanes:

Part 1—Dual Side Brace Inspections

The service bulletin describes the following DSB inspections:

• Do a detailed inspection of the bearing spherical ball for corrosion, corrosion pitting, and corrosion products.
• Do a detailed inspection for migration and rotation of the bearing outer race.
• Do a detailed inspection for cracks or fracture of the eccentric bushing retainer.

The service bulletin specifies that if no discrepancies are found during the inspections, either repeat Part 1 and Part 4, or do Part 4 and Part 3 (terminating action).

The service bulletin specifies that if any discrepancies are found during the inspections, the corrective actions include doing Part 4 and Part 2; or doing Part 4 and Part 3 (terminating action); as applicable.

The service bulletin also specifies that Part 2 may be done instead of Part 1.

Part 2—Bearing Corrosion Removal and Re-Lubrication

The service bulletin describes the following inspections and rework of the DSB bearings and associated parts, and other specified actions.

• Do a detailed inspection of the bearing for migration and rotation.
• Do a detailed inspection for cracks or fracture of the swaged lips.
• Do a detailed inspection for cracks or fracture of the eccentric bushing retainer.
• Do a detailed inspection of the eccentric bushing for damage.
• Do a detailed inspection of the bushing and fuse pin for damage.
• Do a detailed inspection of the bolt for damage.
• The other specified actions include determining if the amount of play in the bearing exceeds specified limits, determining if corrosion exceeds specified limits, and removing corrosion, as applicable; and lubricating the spherical ball and inside of the outer race.

The service bulletin specifies that if no discrepancies are found during the actions specified in Part 2: Either repeat both Part 1 and Part 4, and Part 4 and Part 2; or do Part 4 and Part 3 (terminating action).

The service bulletin specifies that if any discrepancies are found during the actions specified in Part 2, the corrective actions include repeating both Part 1 and Part 4, and Part 4 and Part 2; or doing Part 4 and Part 3 (terminating action); as applicable. The corrective actions also include replacing any damaged bushings/eccentric bushings/fuse pins/bolts with new or serviceable bushings/eccentric bushings/fuse pins/bolts; and contacting Boeing for additional instructions.

Part 3—Dual Side Brace Bearing Replacement and Side Link Modification

The service bulletin describes procedures for replacing the strut and wing side DSB bearings with new or serviceable strut and wing side bearings (includes, for Groups 3 and 4, installing cups per Part 7), modifying side links, and doing related investigative and corrective actions.

Related investigative actions include the following inspections:

• Detailed inspection of the fuse pin for damage.
• Detailed inspection for damage of the strut fitting lug bore and chamfers.
• Fluorescent penetrant inspection (FPI) or high frequency eddy current inspection for cracks of the strut fitting lug bore and chamfers.
• Detailed inspection for cracking of the swaged lip of the bearing.
• FPI of the eccentric bushing bore in the link for cracks, corrosion, and damage.
• Detailed inspection of the bushing for damage.

Corrective actions include replacing any damaged fuse pin with a new or serviceable fuse pin; contacting Boeing for additional instructions; oversizing the lug bore; and replacing any damaged bearing with a new or serviceable bearing.

Part 4—Underwing Midspar Fitting Inspection

The service bulletin describes an inspection to determine the gap between the underwing midspar fitting and strut midspar fitting.

The service bulletin specifies that if the gap is within limits specified in the service bulletin no further action is required.

The service bulletin specifies that if the gap is not within limits specified in the service bulletin, the corrective action includes doing Part 4 and Part 3 (terminating action) or doing Part 3, Part 5, and Part 6 (terminating action), as applicable.

Part 5—Underwing Midspar Fitting Inspection and Rework

The service bulletin describes procedures to do a detailed inspection of the underwing midspar fitting lugs, strut spring beam lugs and bushings, and strut fitting lugs for damage, and corrective action if necessary.

The corrective action includes reworking the underwing midspar fitting, spring beams, and strut fitting; and contacting Boeing for additional instructions.

Part 6—Dual Side Brace Fitting and Underwing Midspar Fitting Tension Bolt Inspection

The service bulletin describes procedures to do a detailed inspection of the dual side brace fitting and underwing fittings for missing or fractured tension bolts or for broken sealant around the fasteners; and do a detailed inspection of the visible areas of the underwing fitting lugs and strut fitting lugs or spring beam lugs for damage; and corrective action if necessary. The corrective action is repairing any damage and contacting Boeing for additional instructions.

Part 7—Vapor Seal Web Cup Installation

The service bulletin describes procedures for Groups 3 and 4 to install cups for the vapor seal web.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

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. Therefore, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the AD and the Service Bulletin.”

The FAA is not proposing to mandate the optional terminating action for several reasons:

1. Accessing the areas for inspection at the intervals is easily accomplished.

2. The inspection items are easily performed by means of a detailed inspection.

3. Long-term continued operational safety in this case will be adequately ensured by repetitive inspections to prevent the loss of a DSB or underwing midspar fitting load path.

Differences Between the Proposed AD and the Service Bulletin

The service bulletin specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require you to repair 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 Delegation Option Authorization Organization who has been authorized by the FAA to make those findings.

Costs of Compliance

There are about 1,091 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
Part 1
Inspections, per inspection cycle	8	$65	None	$520	229	$119,080, per inspection cycle.
Part 2
Inspections, per inspection cycle	48	65	None	3,120	229	714,480, per inspection cycle.
Part 4
Inspections, per inspection cycle	4	65	None	260	229	59,540, per inspection cycle.

Authority for this Rulemaking

The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. 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.

This rulemaking is promulgated 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. 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 FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2005-20364; Directorate Identifier 2004-NM-186-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by March 31, 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, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes; certificated in any category; as identified in Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004.

Unsafe Condition

(d) This AD was prompted by reports of corroded, migrated, and rotated bearings for the dual side braces (DSB) in the inboard and outboard struts, a report of a fractured retainer for the eccentric bushing for one of the side links of a DSB, and reports of wear and damage to the underwing midspar fitting on the outboard strut. We are issuing this AD to prevent the loss of a DSB or underwing midspar fitting load path, which could result in the transfer of loads and motion to other areas of a strut, and possible separation of a strut and engine from the airplane during flight.

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.

Inspections and Corrective Action

(f) At the times specified in Figure 1 of Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004, except as provided by paragraph (g) of this AD: Do the various inspections and other specified actions in the figure to detect discrepancies of the dual side braces, underwing midspar fittings, and associated parts, by doing all of the actions specified in Parts 1, 2, and 4; and the applicable corrective actions specified in Parts 3, 5, 6, and 7; of the Accomplishment Instructions of the service bulletin, except as provided by paragraph (h) of this AD. Repeat the inspections and other specified actions thereafter at the intervals specified in Figure 1 of the service bulletin. Accomplishment of any terminating action specified in Figure 1 of the service bulletin terminates the inspections and other specified actions.

(g) Where Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004, recommends an initial compliance threshold of “within 24 months after the original issue date on this service bulletin” for Parts 1 and 4 of the service bulletin, and of “within 72 months after the original issue date on this service bulletin” for Part 2 of the service bulletin, this AD requires an initial compliance threshold of “within 24 months after the effective date of this AD” for Parts 1 and 4 of the service bulletin and of “within 72 months after the effective date of this AD” for Part 2 of the service bulletin.

(h) If any damage or crack is found during any inspection or corrective action required by this AD, before further flight, repair in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004; except, where the service bulletin specifies to contact Boeing, before further flight, repair according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or according to data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing 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 approval must specifically refer to this AD.

Alternative Methods of Compliance (AMOCs)

(i)(1) The Manager, Seattle ACO, 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 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 approval must specifically refer to this AD.

Issued in Renton, Washington, on February 7, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.