E6-3559. 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 mid- and low-frequency eddy current inspections for cracks in the overlapped skin panels in the fuselage skin lap joints in sections 41, 42, 44, and 46, and corrective actions if necessary. This proposed AD is prompted by a report indicating that an operator found multiple small cracks in the overlapped skin panels in the fuselage skin lap joints. We are proposing this AD to detect and correct cracks in the overlapped skin panels, which could join together and result in reduced structural capability in the skin and consequent rapid decompression of the airplane.

DATES:

We must receive comments on this proposed AD by April 28, 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.
• 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, 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 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-2006-24119; the directorate identifier for this docket is 2005-NM-100-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 under ADDRESSES. Include “Docket No. FAA-2006-24119; Directorate Identifier 2005-NM-100-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 Docket Management System (DMS) receives them.

Discussion

We have received a report indicating that an operator found multiple small cracks in the overlapped skin panels in the fuselage skin lap joints at stringer (S)-44L between station (STA) 440 and 460, and at S-12R between STA 1870 and STA 1910, on a Boeing Model 747SR series airplane. The operator trimmed out the cracked skins and repaired them in accordance with the structural repair manual. The manufacturer analyzed the trimmed-out skins and found that the cracks were caused by fatigue from cyclic pressurization, flight loads, and ground handling loads. Multiple cracks in the overlapped skin panels could join together. This condition, if not corrected, could result in reduced structural capability in the skin and consequent rapid decompression of the airplane.

The subject area on certain Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, and 747SP series airplanes is almost identical to that on the affected Model 747SR series airplanes. Therefore, those airplanes may be subject to the unsafe condition revealed on the Model 747SR series airplane.

Other Relevant Rulemaking

We have previously issued AD 2004-13-02, amendment 39-13682 (69 FR 35237, June 24, 2004). That AD applies to certain Boeing Model 747-100, -200B, and -200F series airplanes. That AD requires initial and repetitive inspections to find discrepancies in the upper and lower skins of the fuselage lap joints, and repair if necessary. Accomplishing the actions in AD 2004-13-02 terminates certain inspections in this proposed AD for those airplanes.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2501, dated March 24, 2005. The service bulletin describes procedures for doing inspections for cracks in the overlapped skin panels in the fuselage skin lap joints in sections 41, 42, 44, and 46. For all airplanes, at most affected lap joint locations, the service bulletin describes procedures for doing repetitive mid-frequency eddy current inspections of the internal surface at the overlapped skin around the bottom row of fasteners in the lap joint.

For airplanes having line numbers 201 and after, the service bulletin describes procedures for doing additional repetitive external surface low-frequency eddy current inspections of the overlapped skin around the bottom row of fasteners at any section 41 lap joint with four rows of fasteners. If cracks are found, the service bulletin states that operators should repair them before further flight. The service bulletin recommends that operators repair the cracks in accordance with the structural repair manual, or get repair data from Boeing. In addition, if the damaged area is more than certain specified limits, the service bulletin recommends that operators write to Boeing for repair instructions, and that the letter include sketches, photographs, and information about any corrosion damage.

For airplanes identified in the service bulletin as Groups 1, 2, 4, and 11 that have line numbers 1 through 200 inclusive, the service bulletin states that the procedures apply only to airplanes that have accumulated between 25,000 and 30,000 total flight cycles. When the airplane has accumulated 30,000 total flight cycles, the service bulletin states that the airplane is subject to the inspection requirements of AD 2004-13-02. The service bulletin recommends that operators of these airplanes that have accumulated 29,000 total flight cycles as of the effective date of the service bulletin do the inspections in accordance with AD 2004-13-02 rather than the inspections in this service bulletin.

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 Proposed AD and the Service Bulletin.”

Differences Between the Proposed AD and the Service Bulletin

Although the service bulletin referenced in this proposed AD specifies to submit certain information to the manufacturer, this proposed AD does not include that requirement.

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 Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

These differences have been coordinated with Boeing.

Costs of Compliance

There are about 1,081 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	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Inspection for Model 747SP series airplanes	48	$80	$3,840, per inspection cycle	10	$38,400, per inspection cycle.
Inspection for all other Model 747 series airplanes	68	80	$5,440, per inspection cycle	196	$1,066,240, 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. 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-2006-24119; Directorate Identifier 2005-NM-100-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by April 28, 2006.

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 747-53A2501, dated March 24, 2005.

Unsafe Condition

(d) This AD was prompted by a report indicating that an operator found multiple small cracks in the overlapped skin panels in the fuselage skin lap joints. We are issuing this AD to detect and correct cracks in the overlapped skin panels, which could join together and result in reduced structural capability in the skin and consequent rapid decompression 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.

Inspections and Corrective Actions: For Airplanes With Line Numbers 1 Through 200 Inclusive

(f) For airplanes with line numbers 1 through 200 inclusive, at the applicable time in paragraph (f)(1) or (f)(2) of this AD: Do the applicable eddy current inspection or inspections for cracks in the overlapped skin panels in the fuselage skin lap joints in sections 41, 42, 44, and 46; and do any applicable corrective actions before further flight. Except as provided by paragraph (f)(1)(ii) of this AD, repeat the applicable inspection or inspections thereafter at intervals not to exceed 3,000 flight cycles. Except as provided by paragraph (h) of this AD, do all actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2501, dated March 24, 2005.

(1) Except as provided by paragraph (f)(2) of this AD, do the applicable action in paragraph (f)(1)(i) or (f)(1)(ii) of this AD.

(i) For airplanes that have accumulated fewer than 29,000 total flight cycles as of the effective date of this AD: Before the accumulation of 25,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, do a mid-frequency eddy current inspection for cracks of the internal surface at the overlapped skin around the bottom row of fasteners in the lap joint.

(ii) For airplanes that have accumulated 29,000 or more total flight cycles, do the inspections in accordance with the requirements of AD 2004-13-02, amendment 39-13682, at the applicable threshold and intervals in that AD. Doing the repeat inspections in accordance with AD 2004-13-02, terminates the repetitive inspection requirements of this AD only for airplanes with line numbers 1 through 200 inclusive.

(2) For airplanes that have had skin panels replaced: Do the eddy current inspections of the replaced overlapped panel prior to the accumulation of 25,000 total flight cycles since panel replacement, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later. Skin panel replacement, along with ongoing inspections in accordance with paragraph (f) of this AD terminates the requirements of paragraphs (a) and (d) of AD 2004-13-02, only for the skin lap sections where the overlapped panel has been replaced.

Inspections and Corrective Actions: For Airplanes With Line Numbers 201 and After

(g) For airplanes with line numbers 201 and after: Before the accumulation of 25,000 total flight cycles, within 1,000 flight cycles after the effective date of this AD, or within 25,000 flight cycles after the time when the overlapped skin was replaced, whichever occurs later, do the applicable inspection in paragraphs (g)(1) and (g)(2) of this AD for cracks in the overlapped skin panels in the fuselage skin lap joints in sections 41, 42, 44, and 46; and do any applicable corrective actions before further flight. Repeat the applicable inspection thereafter at intervals not to exceed 3,000 flight cycles. Except as provided by paragraph (h) of this AD, do all actions in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2501, dated March 24, 2005.

(1) Do a mid-frequency eddy current inspection for cracks of the internal surface at the overlapped skin around the bottom row of fasteners in the lap joint.

(2) Do a low-frequency eddy current inspection for cracks of the overlapped skin around the bottom row of fasteners at the Section 41 lap joints with four rows of fasteners.

Repair Instructions

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

No Reporting Required

(i) Although Boeing Alert Service Bulletin 747-53A2501, dated March 24, 2005, specifies to submit certain information to the manufacturer, this AD does not include that requirement.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle Aircraft Certification Office (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 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.

(3) 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 3, 2006.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.