06-3433. 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 all Boeing Model 747 airplanes. This proposed AD would require repetitive inspections for cracking of the web of the station (STA) 2360 aft pressure bulkhead around the fastener heads in the critical fastener rows in the web lap joints, from the Y-chord to the inner ring; and repair if necessary. This proposed AD also would require a modification, which would terminate the repetitive inspections. This proposed AD results from analysis by the manufacturer that the radial lap splices of the STA 2360 aft pressure bulkhead are subject to widespread fatigue damage. We are proposing this AD to detect and correct cracking of the bulkhead web at multiple sites along the radial lap splice, which could join together to form cracks of critical length, and result in rapid decompression and loss of control of the airplane.

DATES:

We must receive comments on this proposed AD by May 26, 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: [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.

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:

Nicholas Kusz, Aerospace Engineer, Airframe Branch, ANM-120S, Seattle Aircraft Certification Office, FAA, 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 in the ADDRESSES section. Include the docket number “FAA-2006-24410; Directorate Identifier 2005-NM-261-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 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 Docket Management System receives them.

Discussion

We have received a report indicating that the radial lap splices of the station (STA) 2360 aft pressure bulkhead are subject to widespread fatigue damage (WFD), on all Boeing Model 747 airplanes that have exceeded the original Design Service Object of 20,000 total flight cycles. This WFD, if not detected and corrected, could result in cracking of the bulkhead web at multiple sites along the radial lap splice, which could join together to form cracks of critical length, and result in rapid decompression and loss of control of the airplane.

Other Relevant Rulemaking

On July 26, 2000, we issued AD 2000-15-08, amendment 39-11840 (65 FR 74255, August 2, 2000), for certain Boeing Model 747 airplanes. That AD requires repetitive inspections for damage or cracking of the aft pressure bulkhead, and cracking of the web-to-Y-ring lap joint area and the upper segment of the bulkhead web; certain follow-on actions if necessary; and repetitive inspections to detect cracking of the upper and lower segments of the aft bulkhead web, including radial lap joints. That AD was prompted by a report of a crack in the upper portion of the web of the pressure bulkhead at STA 2360 on a Boeing Model 747 airplane. We issued that AD to detect and correct fatigue cracking of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane. Among other actions, AD 2000-15-08 requires inspecting the radial lap joints, which are the subject of this proposed AD; however, this proposed AD would require repetitive inspections at reduced intervals.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2561, dated September 22, 2005. The service bulletin describes procedures for doing repetitive high-frequency eddy current inspections for cracking of the web of the STA 2360 aft pressure bulkhead around the fastener heads in the critical fastener rows in the web lap joints, from the Y-chord to the inner ring. The service bulletin specifies that it is not necessary to inspect areas where production doublers cover the lap joint. If any cracking is found, the service bulletin specifies repairing in accordance with the Structural Repair Manual (SRM), or asking Boeing for repair data. The service bulletin also specifies that if the length of the crack is more than certain specified limits defined in the SRM to contact Boeing for repair instructions. The service bulletin also recommends that a modification be installed when the airplane has flown 35,000 total flight cycles, but does not give procedures for doing that modification. The modification is intended to terminate the repetitive inspections. 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. For this reason, 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 Proposed AD and the Service Bulletin.”

Differences Between the Proposed AD and the Service Bulletin

Although the service bulletin does not specify a compliance grace period for modifying the airplanes that have accumulated more than 35,000 total flight cycles, this proposed AD would include an 18-month grace period for modifying those airplanes.

Although the service bulletin specifies to contact Boeing for repair data if a damaged area is more than certain specified limits, or if the damage includes corrosion; and although the service bulletin does not specify procedures for installing the modification when the airplane has accumulated 35,000 total flight cycles; this proposed AD would require operators to do the repairs and modification using a method approved by the FAA.

Costs of Compliance

There are about 949 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 153 airplanes of U.S. registry. The proposed inspections would take about 11 work hours per airplane, at an average labor rate of $680 per work hour. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $134,640, or $880 per airplane, per inspection cycle.

Because the manufacturer has not yet developed a modification that matches the actions specified by this proposed AD, we cannot provide specific information regarding the required number of work hours or the cost of parts to do the proposed modification. In addition, modification costs will likely vary depending on the operator and the 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
• 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-2006-24410; Directorate Identifier 2005-NM-261-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by May 26, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all 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.

Unsafe Condition

(d) This AD results from analysis by the manufacturer that the radial lap splices of the station (STA) 2360 aft pressure bulkhead are subject to widespread fatigue damage. We are issuing this AD to detect and correct cracking of the bulkhead web at multiple sites along the radial lap splice, which could join together to form cracks of critical length, and result in rapid decompression and 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.

Repetitive Inspections

(f) Before the airplane accumulates 28,000 total flight cycles, or within 18 months after the effective date of this AD, whichever occurs later: Do a high-frequency eddy current inspection for cracking of the web of the STA 2360 aft pressure bulkhead around the fastener heads in the critical fastener rows in the web lap joints, from the Y-chord to the inner ring; in accordance with Part 2, “Access and Inspection,” of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2561, dated September 22, 2005. Repeat the inspection thereafter at intervals not to exceed 2,000 flight cycles until the modification in paragraph (h) of this AD is done.

Repair

(g) If any cracking is found during any inspection required by paragraph (f) of this AD: Before further flight, do the applicable action in paragraph (g)(1) or (g)(2) of this AD.

(1) If the cracking is within certain limits specified in Boeing Alert Service Bulletin 747-53A2561, dated September 22, 2005, (referencing the structural repair manual) do the repair in accordance with the Accomplishment Instructions of the alert service bulletin.

(2) If the cracking is more than certain limits specified in Boeing Alert Service Bulletin 747-53A2561, dated September 22, 2005, or if the alert service bulletin specifies to ask Boeing for repair data: Repair the cracking using a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically refer to this AD.

Modification

(h) Before the airplane accumulates 35,000 total flight cycles or within 18 months after the effective date of this AD, whichever occurs later: Modify the aft pressure bulkhead using a method approved by the Manager, Seattle ACO. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically refer to this AD. Doing this modification terminates the repetitive inspection requirements of paragraph (f) of 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) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Issued in Renton, Washington, on March 31, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.