E6-8006. 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 supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747 airplanes. The existing AD currently requires inspections to detect disbonding, corrosion, and cracking at the longitudinal rows of fasteners in the bonded skin panels in section 41 of the fuselage, and repair, if necessary. This proposed AD would add airplanes to the applicability, and require new inspections of airplanes that may have Alodine-coated rivets installed. This proposed AD results from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We are proposing this AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.

DATES:

We must receive comments on this proposed AD by July 10, 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:

Nicholas Kusz, 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-2006-24865; Directorate Identifier 2005-NM-194-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 October 28, 1996, we issued AD 96-23-02, amendment 39-9807 (61 FR 57994, November 12, 1996), for certain Boeing Model 747 airplanes. That AD requires inspections to detect disbonding, corrosion, and cracking at the longitudinal rows of fasteners in the bonded skin panels in section 41 of the fuselage, and repair, if necessary. That AD resulted from a report of skin cracking due to disbonding of the internal doubler of the cracked skin panels. We issued that AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.

Actions Since Existing AD Was Issued

Since 1985 Boeing has incorporated rivets coated with Alodine into production fuselage aluminum skins and post-production skin modification kits. Alodine coating on rivets provides a protective chemical conversion coating, but also increases electrical conductivity. Certain non-destructive inspection (NDI) methods rely on disruptions in the electromagnetic field around cracks in metallic structures to detect cracking. One such NDI method is the sliding probe eddy current inspection, which was one inspection method required by AD 96-23-02. Conductivity of the Alodine-coated rivet could be strong enough to mask cracking in the fastener hole during eddy current inspections.

Since we issued AD 96-23-02, cracking was discovered in a skin lap joint that was previously inspected using the eddy current method. Further investigation showed that the crack was not detected due to masking from Alodine rivets. The crack was discovered during a full-scale fatigue test on a Model 737 fuselage.

The manufacturer has accomplished a comprehensive study of the effect of Alodine-coated rivets on all Boeing Airplane models. Based on the critical nature of the sliding probe eddy current inspection method, this study indicates that two existing ADs, AD 96-23-02 and AD 90-26-10, require further rulemaking. We are proposing this NPRM to supersede AD 96-23-02, and Docket No. FAA-2006-24877 to supersede AD 90-26-10. In addition, based on this study, the FAA does not propose to issue other ADs related to Alodine-coated rivets.

Since we issued AD 96-23-02, we have also received reports of new crack findings on Model 747 airplanes that were not originally included in the applicability of AD 96-23-02.

Other Relevant Rulemaking

On December 3, 1990, we issued AD 90-26-10, amendment 39-6836 (55 FR 51401, December 14, 1990). That AD requires repetitive inspections to detect cracks at certain stringer fastener locations; and repair, if necessary. For certain airplanes, AD 90-26-10 requires a modification in certain areas where reports indicate that cracking was prevalent. This modification terminates the repetitive inspections only for those areas, and is also an option for other airplanes. Skin panels replaced in accordance with AD 90-26-10 are not susceptible to the disbonding and cracking that is the unsafe condition addressed by this proposed AD. That AD resulted from reports of multiple longitudinal skin cracks. We issued that AD to prevent rapid decompression of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005 (the original issue of Boeing Alert Service Bulletin 747-53A2409, dated September 26, 1996, was referenced as the appropriate source of service information for accomplishing the required actions in AD 96-23-02). Operators should note Revision 5 of the alert service bulletin revises the airplane group numbers that were referenced in AD 96-23-02.

Boeing Alert Service Bulletin 747-53A2409, Revision 5, describes procedures for initial inspections to detect disbonding, corrosion, and cracking of the longitudinal rows of fasteners in the bonded skin panels in section 41 of the fuselage, and repair if necessary. The alert service bulletin also describes procedures for related investigative actions if any discrepancy is found. These actions depend on the inspected area and the discrepancy and can include additional inspections using one of the methods described below.

The alert service bulletin identifies four affected skin areas:

• Area 1: The flat skin panel aft of the cockpit windows from body station (BS) 340 to BS 520 between S-6 and S-14.
• Area 2: The flat skin panels below the cockpit windows.
• Area 3: The large-radius skin panels in the main deck area (excluding Area 4).
• Area 4: The section of the large-radius skin panel aft of door 1 from BS 488 to BS 500 between S-16 and S-26.

The alert service bulletin also specifies four methods of inspection, with related corrective actions:

• Method 1: One-time external ultrasonic inspections of the skin for disbonded doublers; and an external inspection of the skin for cracks, and repair, if necessary;
• Method 2: One-time internal detailed inspections of the skin for disbonded doublers, corrosion, or cracks; and repair, or an external inspection of the skin for cracks, if necessary;
• Method 3: Repetitive external detailed inspections of the skin for cracks, and repair, if necessary; and
• Method 4: Repetitive external high frequency eddy current (HFEC) inspections of the skin for cracks, and repair, if necessary.

Figures 1, 2, 3, 17, 18, 19, 20, 21, and 22 of the alert service bulletin provide the compliance times for all inspections. The compliance times for doing the initial and repetitive inspections depend on previous installation of rivets coated with Alodine, and on previous inspections, modifications, and repairs. The thresholds for initial inspections are the latest of 150 flight cycles after the date of the service bulletin or 3,000 flight cycles after a previous inspection. The repetitive intervals also depend on certain previous repairs and range from 150 flight cycles to 3,000 flight cycles. The compliance time for all applicable repairs is before further flight.

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 develop on airplanes of the same type design. For this reason, we are proposing this AD, which would supersede AD 96-23-02 and would retain the requirements of the existing AD. This proposed AD would also require accomplishing the actions specified in the alert service bulletin described previously, except as discussed under “Differences Between the Proposed AD and the Alert Service Bulletin.”

Differences Between the Proposed AD and the Alert Service Bulletin

Operators should note that, although the referenced alert service bulletin describes procedures for submitting an inspection report to the manufacturer, this proposed AD would not require that action.

The alert service bulletin specifies compliance times relative to the date of issuance or receipt of the service bulletin; however, this proposed AD would require compliance before the specified compliance time after the effective date of this AD or another applicable AD, as specified.

While the alert service bulletin describes procedures for inspections of four particular areas of the airplane, this proposed AD would require inspections of only two of those areas.

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions or do certain actions, but this proposed AD would require repairing those conditions or doing those actions 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.

The service bulletin specifies that it is not necessary to count flight cycles at 2.0 psi or less cabin differential pressure. We find that insufficient data exist to support this adjustment to flight cycles. Consequently, this AD does not allow for this adjustment factor.

These differences have been coordinated with Boeing.

Clarification of Alternative Method of Compliance (AMOC) Paragraph

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.

Explanation of Change in Applicability

We have revised the applicability of the AD to identify the model designations as published in the most recent type certificate data sheet for the affected model.

Costs of Compliance

There are about 623 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. The average labor rate is $80 per work hour.

Estimated Costs

Action	Work hours	Cost per airplane, per inspection cycle	U.S.-registered airplanes	Fleet cost, per inspection cycle
Inspections (required by AD 96-23-02, and continued in this proposed AD)	308	$24,640	79	$1,946,460.
New inspections (for airplanes with alodine-coated rivets)	42	3,360	96	Up to $322,560.

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 39-9807 (61 FR 57994, November 12, 1996) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24865; Directorate Identifier 2005-NM-194-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by July 10, 2006.

Affected ADs

(b) This AD supersedes AD 96-23-02.

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 747-53A2409, Revision 5, dated August 18, 2005.

Unsafe Condition

(d) This AD results from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We are issuing this AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.

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.

Requirements of AD 96-23-02

Actions for Groups 1 Through 10, and 17 Through 36, as Specified in Boeing Alert Service Bulletin 747-53A2409, Revision 5

(f) For airplanes identified as Groups 1 through 10 inclusive, and 17 through 36 inclusive, in Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005: Do the inspections in paragraphs (f)(1); and do the corrective action in paragraph (f)(2) of this AD as applicable. Except as provided by paragraph (i) of this AD, do all actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2409, dated September 26, 1996; or Revision 5, dated August 18, 2005. After the effective date of this AD, only Revision 5 may be used.

(1) At the applicable time in Figures 1, 2, 18, and 20 of Revision 5 of the service bulletin, do initial and repetitive inspections of Areas 1 and 4, as applicable, to detect disbonding, corrosion, and cracking of the skin; except any inspection using Method 1 or 2 must not be accomplished before the latest of the following, as applicable: Before the accumulation of 2,000 total flight cycles; 2,000 flight cycles since modification to the stretched upper deck (SUD) configuration; or 2,000 flight cycles since skin panel replacement in accordance with AD 90-26-10, amendment 6836 (55 FR 51401, December 14, 1990). If inspection Method 1 or 2 is used and no disbonded doubler is found, no further action is required by this AD.

(2) If any corrosion or cracking is found during any inspection required by paragraph (f)(1) of this AD: Before further flight, except as provided by paragraph (i) of this AD, repair and do any applicable related investigative actions in accordance with the Accomplishment Instructions of the service bulletin.

New Requirements of This AD

Actions for Groups 11 Through 16 as Specified in Boeing Alert Service Bulletin 747-53A2409, Revision 5 (Airplanes Added To the Applicability of This AD)

(g) For airplanes identified as Groups 11 through 16 inclusive in Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005: Do the inspections in paragraph (g)(1); and do the corrective action in paragraph (g)(2) of this AD as applicable. Except as provided by paragraph (i) of this AD, do all actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005.

(1) At the applicable time in Figures 18 and 20 of the service bulletin, do initial inspections of Area 4 and repetitive inspections, as applicable, to detect disbonding, corrosion, and cracking of the skin; except any inspection using Method 1 or 2 must not be accomplished before the latest of the following, as applicable: Before the accumulation of 2,000 total flight cycles; 2,000 flight cycles since modification to the SUD configuration; or 2,000 flight cycles since skin panel replacement in accordance with AD 90-26-10, amendment 6836 (55 FR 51401, December 14, 1990). If inspection Method 1 or 2 is used and no disbonded doubler is found, no further action is required by this AD.

(2) If any corrosion, disbonding, or cracking is found during any inspection required by paragraph (g)(1) of this AD, before further flight: Repair and do any applicable related investigative actions in accordance with the Accomplishment Instructions of the service bulletin.

Actions for Airplanes With Alodine-Coated Rivets for Groups 1 Through 10, and 17 Through 36 as Specified in Boeing Alert Service Bulletin 747-53A2409, Revision 5

(h) For airplanes identified as Groups 1 through 10 inclusive, and 17 through 36 inclusive, in Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005: Do the inspections in paragraph (h)(1); and do the corrective action in paragraph (h)(2) of this AD if necessary. Except as provided by paragraph (i) of this AD, do all actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005.

(1) At the applicable time in Figures 21 and 22 of the service bulletin: Do initial and repetitive inspections of Areas 1 and 4, as applicable, to detect cracking of the skin.

(2) If any cracking is found during any inspection required by paragraph (h)(1) of this AD, before further flight: Repair in accordance with the Accomplishment Instructions of the service bulletin.

Exceptions

(i) Do all actions in accordance with the applicable service bulletin except as provided by paragraphs (i)(1), (i)(2), (i)(3), (i)(4), and (i)(5) of this AD.

(1) For the action in paragraph (f)(1) of this AD: Where Boeing Alert Service Bulletin 747-53A2409, dated September 26, 1996; and Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005; specify a compliance time after the issuance of any revision of the service bulletin, this paragraph requires compliance before the specified compliance time after November 27, 1996, the effective date of AD 96-23-02.

(2) For the actions in paragraphs (g)(1) and (h)(1) of this AD: Where Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005, specifies a compliance time after the issuance or receipt of any revision of the service bulletin, this paragraph requires a compliance time after the effective date of this AD.

(3) For any repair or any inspection where Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005, specifies to contact the manufacturer for further instructions: Before further flight, repair or inspect using a method approved in accordance with the procedures specified in paragraph (k) of this AD.

(4) If corrosion is found during any inspection required by this AD, before further flight: Repair in accordance with an FAA-approved method.

(5) Where Boeing Alert Service Bulletin 747-53A2409, Revision 5, dated August 18, 2005, specifies that it is not necessary to count flight cycles at 2.0 psi or less cabin differential pressure, this AD does not allow for that adjustment factor.

Credit for Actions Accomplished Previously

(j) Actions done before the effective date of this AD in accordance with the service bulletins specified in Table 1 of this AD are acceptable for compliance with the corresponding requirements of paragraphs (f) and (g) of this AD.

Table 1.—Credit Service Bulletins

Service bulletin	Revision level	Date
Boeing Alert Service Bulletin 747-53A2409	1	May 29, 1997.
Boeing Alert Service Bulletin 747-53A2409	2	August 6, 1998.
Boeing Alert Service Bulletin 747-53A2409	3	October 22, 1998.
Boeing Alert Service Bulletin 747-53A2409	4	February 17, 2000.

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) 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) AMOCs approved previously in accordance with AD 96-23-02, amendment 39-9807, are approved as AMOCs for the corresponding provisions of paragraph (f) of this AD, except AMOCs for terminating action based upon inspection results using a sliding probe low frequency eddy current (LFEC), sliding probe high frequency eddy current (HFEC), or mid frequency surface eddy current (MFEC) inspection methods; and provided that any alternative method for future inspections did not incorporate a sliding probe LFEC, sliding probe HFEC, or MFEC inspection methods.

(4) 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 and the approval must specifically refer to this AD.

Issued in Renton, Washington, on May 16, 2006.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.