E6-3263. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-300, 747-400, 747-400D, and 747SR 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 and -200 series airplanes. The existing AD currently requires repetitive inspections for cracking of the station 800 frame assembly, and repair if necessary. This proposed AD would retain the repetitive inspection requirements of the existing AD, but would expand the area to be inspected. This proposed AD also would reduce the initial inspection threshold, remove the adjustment of the compliance threshold and repetitive interval based on cabin differential pressure, and add airplanes to the applicability. This proposed AD results from several reports of cracks of the station 800 frame assembly on airplanes that had accumulated fewer total flight cycles than the initial inspection threshold in the existing AD. We are proposing this AD to detect and correct fatigue cracks that could extend and fully sever the frame, which could result in development of skin cracks that could lead to rapid depressurization of the airplane.

DATES:

We must receive comments on this proposed AD by April 24, 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 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 [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 “Docket No. FAA-2006-24102; Directorate Identifier 2005-NM-244-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 may 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 [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

On July 12, 2001, we issued AD 2001-14-22, amendment 39-12333 (66 FR 38891, July 26, 2001), for certain Boeing Model 747-100 and -200 series airplanes. That AD requires repetitive detailed, surface high-frequency eddy current (HFEC), and open hole HFEC inspections for cracking of the station 800 frame assembly, and repair if necessary. That AD resulted from reports that operators had found fatigue cracks in the strap and inner chord angle at the station 800 frame, between stringers 14 and 18, on certain Boeing Model 747-100 and -200 series airplanes. We issued that AD to find and fix fatigue cracks that could extend and fully sever the frame, which could result in development of skin cracks that could lead to rapid depressurization of the airplane.

Actions Since Existing AD Was Issued

Since we issued AD 2001-14-22, we have received several reports of cracks of the station 800 frame assembly on airplanes that had accumulated fewer than 19,000 total flight cycles, which is the initial inspection threshold for AD 2001-14-22. Cracks between 0.4 and 0.8 inch in length were found at the inner chord angles on three airplanes that had accumulated between 15,735 and 16,428 total flight cycles. A crack indication was also found at the inner chord angle on an airplane that had accumulated 9,675 total flight cycles. In addition, Boeing found a crack at the aft inner chord angle on a Model 747-300 stretched upper deck airplane that had accumulated 23,475 total flight cycles. As a result of this finding, Boeing examined the Model 747-400 fatigue-test airplane and found significant damage in the affected area, including severed inner chord angles on both the left and right sides. The fatigue-test airplane had accumulated 54,000 test cycles.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2451, Revision 1, dated November 10, 2005. The procedures in this alert service bulletin are essentially the same as those in Boeing Alert Service Bulletin 747-53A2451, including Appendix A, dated October 5, 2000, which was referenced as the appropriate source of service information for accomplishing the required actions in AD 2001-14-22. However, Revision 1 of the alert service bulletin adds airplanes to the effectivity, and expands the inspection area for the detailed and surface HFEC inspections.

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

Explanation of Change to Adjustment Based on Cabin Differential Pressure

Paragraph (b) of AD 2001-14-22 allows for adjustment to the compliance threshold by not counting the flight cycles in which cabin differential pressure is at 2.0 pounds per square inch (psi) or less. This proposed AD would not allow that adjustment. However, this proposed AD states that operators may continue to adjust the repetitive inspection interval based on a lower cabin differential pressure until the next scheduled inspection. Thereafter, this proposed AD would not allow such adjustment. We have determined that an adjustment of flight cycles due to a lower cabin differential pressure is not substantiated and will not be allowed for use in determining the flight-cycle threshold for this proposed AD. There have been several instances on other in-service issues where analytical rationales have indicated that pressurization cycles of less than 2.0 psi should not be counted. However, when fleet records have been examined, the airplanes engaging in such operations have the same or greater occurrences of crack findings compared with those on which all pressurized flights are counted. As a result, we carefully consider such matters based on all available factors, including individual operators' specific maintenance programs, technical rationale, and fleet experience. We have found that such provisions are applicable only to a small number of operators that may not pressurize their airplanes above 2.0 psi in all their flights. We have determined that the best way to handle such circumstances is for operators to request an alternative method of compliance (AMOC) in accordance with the procedures in paragraph (l) of this proposed AD, rather than by increasing the complexity of the AD by addressing each operator's unique situation.

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 2001-14-22 and retain the requirements of the existing AD. This proposed AD would reduce the initial inspection threshold, remove the adjustment of the compliance threshold and repetitive interval based on cabin differential pressure, and add airplanes to the applicability. This proposed AD would require accomplishing the actions specified in the service bulletin described previously, except as discussed under “Differences Between the Proposed AD and the Service Bulletin.”

Differences Between the Proposed AD and the Service Bulletin

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing 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 Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Although the service bulletin specifies to send Boeing a report of any structural damage found while doing the inspections, this proposed AD would not include that requirement.

Explanation of Additional Changes to Existing AD

Boeing has received a Delegation Option Authorization (DOA). We have revised this proposed AD to delegate the authority to approve an alternative method of compliance for any repair that would be required by this proposed AD to the Authorized Representative for the Boeing DOA Organization rather than the Designated Engineering Representative (DER).

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.

We have revised the applicability to reflect the model designations as published in the most recent type certificate data sheets.

This proposed AD would retain the repetitive inspection requirements of AD 2001-14-22. Since AD 2001-14-22 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result of this change, the corresponding paragraph identifiers have changed in this proposed AD, as listed in the following table:

Revised Paragraph Identifiers

Requirement in AD 2001-14-22	Corresponding requirement in this proposed AD
Paragraph (a)	Paragraph (f).
Paragraph (b)	Paragraph (g).
Paragraph (c)	Paragraph (h).

Clarification of Inspections

We have changed all references to a “detailed visual inspection” in the existing AD to “detailed inspection” in this proposed AD. A definition of a detailed inspection is included in the service bulletin.

Costs of Compliance

There are about 900 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 156 airplanes of U.S. registry.

The inspections that are specified in AD 2001-14-22, and retained in this proposed AD, take between 12 and 14 work hours per airplane, depending on the airplane configuration. The average labor rate is $65 per work hour. Based on these figures, the estimated cost of the currently required actions is between $121,680 and $141,960, or between $780 and $910 per airplane, per inspection cycle.

The new proposed actions would take between 18 and 20 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, the estimated cost of the new actions specified in this proposed AD for U.S. operators is between $182,520 and $202,800, or between $1,170 and $1,300 per airplane, per inspection cycle.

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 removing amendment 39-12333 (66 FR 38891, July 26, 2001) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24102; Directorate Identifier 2005-NM-244-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by April 24, 2006.

Affected ADs

(b) This AD supersedes AD 2001-14-22.

Applicability

(c) This AD applies to all Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-300, 747-400, 747-400D, and 747SR series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from several reports of cracks of the station 800 frame assembly on airplanes that had accumulated fewer total flight cycles than the initial inspection threshold in the existing AD. We are issuing this AD to detect and correct fatigue cracks that could extend and fully sever the frame, which could result in development of skin cracks that could lead to rapid depressurization 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.

Restatement of the Requirements of AD 2001-14-22

Repetitive Inspections

(f) For Boeing Model 747-100, 747-100B, 747-100B SUD, -200B, 747-200C, and 747-200F series airplanes, as identified in Boeing Alert Service Bulletin 747-53A2451, including Appendix A, dated October 5, 2000: Do detailed, surface high-frequency eddy current (HFEC), and open-hole HFEC inspections, as applicable, for cracking of the station 800 frame assembly (including the inner chord strap, angles, and exposed web) between stringers 14 and 18, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2451, including Appendix A, dated October 5, 2000; or Boeing Alert Service Bulletin 747-53A2451, Revision 1, dated November 10, 2005; after the effective date of this AD, only Revision 1 of the service bulletin may be used. Except as provided by paragraph (g) of this AD, do the inspection at the applicable time specified in Table 1 of this AD, and repeat the inspections thereafter at intervals not to exceed 3,000 flight cycles until the initial inspections required by paragraph (h) of this AD are accomplished.

Table 1.—Compliance Times

Total flight cycles as of August 30, 2001 (the effective date of AD 2001-14-22)	Do the inspection in paragraph (f) of this AD at this time
(1) Fewer than 19,000	Before the accumulation of 19,000 total flight cycles, or within 1,500 flight cycles after August 30, 2001, whichever comes later.
(2) 19,000 or more, but 21,250 or fewer	Within 1,500 flight cycles or 12 months after August 30, 2001, whichever comes first.
(3) 21,251 or more	Within 750 flight cycles or 12 months after August 30, 2001, whichever comes first.

Adjustments to Compliance Time: Cabin Differential Pressure

(g) For Boeing Model 747-100, 747-100B, 747-100B SUD, -200B, 747-200C, and 747-200F series airplanes, as identified in Boeing Alert Service Bulletin 747-53A2451, including Appendix A, dated October 5, 2000, that are inspected before the effective date of this AD: Except as provided by paragraph (i) of this AD, for the purposes of calculating the compliance threshold and repetitive interval for the actions required by paragraph (f) of this AD, the number of flight cycles in which cabin differential pressure is at 2.0 pounds per square inch (psi) or less need not be counted when determining the number of flight cycles that have occurred on the airplane, provided that the flight cycles with momentary spikes in cabin differential pressure above 2.0 psi are included as full pressure cycles. For this provision to apply, all cabin pressure records must be maintained for each airplane: NO fleet-averaging of cabin pressure is allowed.

New Requirements of This Ad

Repetitive Inspections of Expanded Area at a New Reduced Threshold

(h) For all airplanes, at the applicable time specified in Table 2 of this AD, except as provided by paragraph (i) of this AD, do the following inspections of the station 800 frame assembly in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2451, Revision 1, dated November 10, 2005: A detailed inspection for cracking of the inner chord strap, angles, and exposed web adjacent to the inner chords on the station 800 frame between stringer 14 and stringer 18; and surface HFEC and open-hole HFEC inspections for cracking of the inner chord strap and angles. Do the initial inspections at the applicable time specified in Table 2 of this AD, and repeat the inspections thereafter at intervals not to exceed 3,000 flight cycles. Accomplishing the initial inspections required by this paragraph terminates the inspection requirements of paragraph (f) of this AD.

Table 2.—Revised Compliance Times

Total flight cycles as of the effective date of this AD	Do the inspections in paragraph (h) of this AD at this time
(1) Fewer than 16,000	Before the accumulation of 16,000 total flight cycles, or within 1,500 flight cycles after the effective date of this AD, whichever comes later.
(2) 16,000 or more, but 24,250 or fewer	Within 1,500 flight cycles or 12 months after the effective date of this AD, whichever comes first.
(3) 24,251 or more	Within 750 flight cycles or 12 months after the effective date of this AD, whichever comes first.

Adjustments to Compliance Time: Cabin Differential Pressure

(i) For the purposes of calculating the compliance threshold and repetitive interval for actions required by paragraphs (f) and (h) of this AD, on or after the effective date of this AD: All flight cycles, including the number of flight cycles in which cabin differential pressure is at 2.0 psi or less, must be counted when determining the number of flight cycles that have occurred on the airplane. However, for airplanes on which the repetitive interval for the actions required by paragraph (f) of this AD have been calculated in accordance with paragraph (g) of this AD by excluding the number of flight cycles in which cabin differential pressure is at 2.0 pounds psi or less: Continue to adjust the repetitive inspection interval in accordance with paragraph (g) of this AD until the initial inspections required by paragraph (h) of this AD are accomplished. Thereafter, no adjustment to compliance times based on paragraph (g) of this AD is allowed.

Repair

(j) If any cracking is detected during any inspection required by paragraph (f) or (h) of this AD, and the service bulletin specifies to contact Boeing for appropriate action: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (l) of this AD.

No Report Required

(k) Although the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2451, including Appendix A, dated October 5, 2000; and Boeing Alert Service Bulletin 747-53A2451, Revision 1, dated November 10, 2005; describe procedures for reporting certain information to the manufacturer, this AD does not require that report.

Alternative Methods of Compliance (AMOCs)

(l)(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) 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.

(3) 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 Commercial Airplanes 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 repair must meet the certification basis of the airplane.

(4) AMOCs approved previously in accordance with AD 2001-14-22, are approved as AMOCs for the corresponding provisions of paragraphs (f) and (j) of this AD.

Issued in Renton, Washington, on February 28, 2006.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.