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

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) for certain Boeing Model 747-100, -100B, -100B SUD, -200B, and -300 series airplanes; and Model 747SR and 747SP series airplanes. That AD currently requires repetitive inspections to detect fatigue cracking in the upper deck floor beams located at certain body stations, and repair, if necessary. This proposed AD would lower the threshold for the existing inspections and would require new repetitive inspections of previously repaired areas, and repair if necessary. This proposed AD is prompted by the results of an additional detailed analysis that indicate fatigue cracks can initiate sooner than has previously been observed. We are proposing this AD to prevent failure of the upper deck floor beams at certain body stations due to fatigue cracking, which could result in rapid decompression and reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by December 20, 2004.

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.

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

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov , or 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.

FOR FURTHER INFORMATION CONTACT:

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

Plain language information: Marcia Walters, marcia.walters@faa.gov.

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

Comments Invited

We invite you to submit any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-19495; Directorate Identifier 2003-NM-180-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 our docket 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 the 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.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/language and http://www.plainlanguage.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 (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 DMS receives them.

Discussion

On February 22, 2000, we issued AD 2000-04-17, amendment 39-11600 (65 FR 10695, February 29, 2000), for certain Boeing Model 747-100, -200, and -300 series airplanes. That AD requires repetitive inspections to detect fatigue cracking in the upper deck floor beams located at certain body stations, and repair, if necessary. That AD was prompted by a report from the manufacturer that, during a fatigue test at approximately 34,000 total flight cycles, the upper chord and web of the upper deck floor beams located at body stations (BS) 340 and 360 were found severed. Another report by an operator indicated that, at approximately 33,000 total flight cycles, a severed upper chord and web were found in the upper deck floor beam at BS 380. In addition, cracking was found at multiple fastener hole locations. We issued that AD to prevent failure of the upper deck floor beams at certain body stations due to fatigue cracking, which could result in rapid decompression and reduced controllability of the airplane.

Actions Since Existing AD Was Issued

Since we issued AD 2000-04-17, the results of an additional detailed analysis indicate that fatigue cracks can initiate sooner than has previously been observed. Subsequent to this analysis, the manufacturer issued, and we reviewed Revision 2 of Boeing Alert Service Bulletin 747-53A2431, dated June 13, 2002. (The original issue of the service bulletin was referred to in AD 2000-04-17 as the appropriate source of service information for the required actions). Revision 2 of the service bulletin changes the initial inspection threshold from 28,000 total flight cycles to 22,000 total flight cycles. It also adds new repetitive inspections of areas repaired per earlier issues of the service bulletin, and repair of any crack. Depending on the location of the repair, the inspections include:

• Open-hole HFEC inspections to detect cracks at the fastener holes of the floor panel attachment and the inboard and outboard end fastener locations common to the repair strap; and
• Surface HFEC inspections to detect cracks of the upper chord along the edge of the trimmed surface.

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 products of this same type design. Therefore, we are proposing this AD, which would supersede AD 2000-04-17. This proposed AD would continue to require repetitive inspections to detect fatigue cracking in the upper deck floor beams located at certain body stations, and repair, if necessary. The proposed AD also would require the existing repetitive inspections at a lower threshold. In addition, the proposed AD would require new repetitive inspections of previously repaired areas, and repair of any crack. This proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Differences Between the Proposed AD and Service Bulletin.”

Differences Between the Proposed AD and Service Bulletin

Although the service bulletin recommends accomplishing the initial inspection before the accumulation of 22,000 total flight cycles, we have determined that the inspection threshold would not address the identified unsafe condition soon enough to ensure an adequate level of safety for the affected fleet. As described in AD 2004-03-11, amendment 39-13455 (69 FR 5920, February 8, 2004), we have received a report indicating that cracks were found in the upper deck floor at BS 420 on a Boeing Model 747-200F series airplane with 19,598 total flight cycles. The upper chord and web of the floor beam were completely severed. AD 2004-03-11, applicable to certain Boeing Model 747-200C and -200F series airplanes, requires repetitive inspections to find fatigue cracking in the upper chord of the upper deck floor beams, and repair if necessary. For certain airplanes, that AD also provides an optional repair/modification, which extends certain repetitive inspection intervals. That AD is intended to find and fix cracking in certain upper deck floor beams, which extend and sever floor beams at a floor panel attachment hole location and could result in rapid decompression and consequent loss of controllability of the airplane.

Since the issuance of AD 2004-03-11, we have received two reports of multiple-floor beam cracking on two Model 747-200F series airplanes with 19,687 and 23,561 total flight cycles. Numerous cracks up to 0.75 inches long were found at the floor beams. Some of the cracks exceeded the repairable limits specified in Boeing Alert Service Bulletin 747-53A2439, dated July 5, 2001 (cited in AD 2004-03-11 as the appropriate source of service information for the required actions). We are considering further rulemaking action to address these new findings.

The upper deck floor beams at BS 340, 360, and 380 on Model 747-100, -100B, -100B SUD, -200B, and -300 series airplanes, and Model 747SR and 747SP series airplanes are a similar type design to those on Model 747-200C and -200F series airplanes. Therefore, we find that a 18,000 flight-cycle compliance time represents an appropriate interval of time for affected airplanes to continue to operate without compromising safety.

For locations that have been repaired by oversizing the fastener holes only (i.e., repair strap and/or clip not installed) as specified in Table 1 of Part 3 of the Accomplishment Instructions of the service bulletin, Part 4 of the Accomplishment Instructions of the service bulletin does not specify an inspection method or compliance time for that type of repaired location. Therefore, this proposed AD would require an open-hole HFEC inspection to detect cracks of the upper floor beams in accordance with Part 1 of the Accomplishment Instructions of the service bulletin. The compliance time for that inspection is before the accumulation of the applicable threshold specified in the “New Inspection Threshold” column in Table 1 of Part 3 of the Accomplishment Instructions of the service bulletin, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later.

The service bulletin specifies not to count flight cycles with a cabin pressure differential of 2.0 pounds per square inch (psi) or less, and that any flight cycles with momentary spikes in cabin pressure differential above 2.0 psi must be included as a full-pressure flight cycle. We find that insufficient data exist to support this adjustment to flight cycles. In fact, data are available which indicate that the use of a 2.0 adjustment factor provides inaccurate data and unjustified relief for inspection intervals. Consequently, this AD does not allow for this adjustment factor.

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 type certification basis of the airplane, and that have been approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make those findings.

Although the service bulletin does not list a grace period in the compliance time for the post-repair inspection, this proposed AD adds a grace period to the compliance times. We find that a grace period will keep airplanes from being grounded unnecessarily.

In addition, the effectivity of service bulletin incorrectly specifies “747-300B” as an affected airplane model. The correct model designation is 747-300, as specified in type certificate data sheet, A20WE, May 10, 2004. As explained further below, this AD specifies model designations in the applicability of this proposed AD as published in the most recent type certificate data sheet.

Certain Changes to Existing AD

We find that certain affected Model 747-100, -100B, -100B SUD, -200B, and -300 series airplanes, and Model 747SR and 747SP series airplanes were not specifically identified by model name in the applicability of AD 2000-04-17. However, all of those airplanes were identified by manufacturer's fuselage numbers in the effectivity listing of Boeing Alert Service Bulletin 747-53A2431, dated February 10, 2000, which was referenced in that AD as the appropriate source of service information for the required actions. Therefore, we have specified model designations in the applicability of this proposed AD as published in the most recent type certificate data sheet and Revision 2 of the referenced service bulletin for the affected models.

This proposed AD would retain all requirements of AD 2000-04-17. Since AD 2000-04-17 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, paragraph (a) of AD 2000-04-17 has been redesignated as paragraph (g) in this proposed AD.

Costs of Compliance

There are about 539 Model 747-100, -100B, -100B SUD, -200B, and -300 series airplanes; and Model 747SR and 747SP series airplanes worldwide of the affected design. This proposed AD would affect about 168 airplanes of U.S. registry.

The actions that are currently required by AD 2000-04-17 and retained in this proposed AD take about 15 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, estimated cost of the currently required actions is $163,800, or $975 per airplane.

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.