06-3442. Airworthiness Directives; Boeing Model 737-600, -700, -700C, and -800 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 737-600, -700, -700C, and -800 series airplanes. The existing AD currently requires replacing the point “D” splice fitting between windows number 1 and 2 with a new splice fitting; performing an eddy current inspection for cracking of the holes in the structure common to the new splice fitting, including doing any related investigative actions; and performing corrective actions if necessary. This proposed AD would add repetitive inspections for cracking of the skin just below each splice fitting, and related corrective actions if necessary. This proposed AD results from full-scale fuselage fatigue testing on the splice fitting that failed prior to the design objective on Boeing Model 737-800 series airplanes, and a report of a cracked splice fitting on an operational airplane. We are proposing this AD to prevent cracking of the existing fitting, which may result in cracking through the skin and consequent decompression of the flight cabin.

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 service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Sue Lucier, 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-2006-24369; Directorate Identifier 2006-NM-001-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 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 November 25, 2005, we issued AD 2005-25-03, amendment 39-14396 (70 FR 72595, December 6, 2005), for certain Boeing Model 737-600, -700, -700C, and -800 series airplanes. That AD requires replacing the point “D” splice fitting between windows number 1 and 2 with a new splice fitting; performing an eddy current inspection for cracking of the holes in the structure common to the new splice fitting, including doing any related investigative actions; and performing corrective actions if necessary. That AD resulted from full-scale fuselage fatigue testing on the splice fitting that failed prior to the design objective on Boeing Model 737-800 series airplanes, and a report of a cracked splice fitting on an operational airplane. We issued that AD to prevent cracking of the existing fitting, which may result in cracking through the skin and consequent decompression of the flight cabin.

Since the Existing AD Was Issued

In the preamble to AD 2005-25-03, we indicated that the actions required by that AD were considered “interim action” and that further rulemaking action was being considered. We have determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination.

Relevant Service Information

We have previously reviewed Boeing Alert Service Bulletin (ASB) 737-53A1222, Revision 2, dated October 20, 2005, the appropriate service information referenced in AD 2005-25-03. The ASB describes procedures for replacing the splice fitting between windows number 1 and 2, at point “D” on the windowsill with a new splice fitting, and performing related investigative actions. Those investigative actions include performing an open hole eddy current inspection for cracking of the fastener holes, and a special detailed inspection for cracking of 12 fasteners in the adjacent structure. The ASB also describes procedures for repetitive detailed inspections of the skin near the six skin fasteners below the splice fitting. The ASB specifies that if cracking is detected, to contact Boeing for further instructions. 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 other airplanes of the same type design. For this reason, we are proposing this AD, which would supersede AD 2005-25-03 and retain the requirements of the existing AD. This proposed AD would also require accomplishing repetitive external detailed inspections of the skin near the six skin fasteners below the splice fitting, specified in the ASB described previously.

Differences Between the AD and the ASB

Where the ASB specifies contacting Boeing if any cracking is detected, this AD would require that repair of any cracking be accomplished before further flight, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO).

Costs of Compliance

There are about 563 airplanes of the affected design in the worldwide fleet. We estimate that about 243 airplanes are on the U.S. Register, and that the average labor rate is $80 per hour. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Fleet cost
Replacing splice fittings with new fittings (required by AD 2005-25-03)	36	$15,445	$18,325	$4,452,975
External detailed inspection (new proposed action)	1	0	80	*19,440
* 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 39-14396 (70 FR 72595, December 6, 2005) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24369; Directorate Identifier 2006-NM-001-AD.

Comments Due Date

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

Affected ADs

(b) This AD supersedes AD 2005-25-03.

Applicability

(c) This AD applies to Boeing Model 737-600, -700, -700C, and -800 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin (ASB) 737-53A1222, Revision 2, dated October 20, 2005.

Unsafe Condition

(d) This AD results from full-scale fuselage fatigue testing on a splice fitting that failed prior to the design objective on Boeing Model 737-800 series airplanes, and a report of a cracked splice fitting on an operational airplane. We are issuing this AD to prevent cracking of the existing fitting, which may result in cracking through the skin and consequent decompression of the flight cabin.

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 Certain Requirements of AD 2005-25-03

Replacing the Splice Fittings

(f) Replace the splice fittings with new splice fittings in accordance with the Accomplishment Instructions of Boeing ASB 737-53A1222, Revision 2, dated October 20, 2005, at the times specified in paragraph (f)(1) or (f)(2) of this AD, as applicable. Before further flight, do any related investigative actions by accomplishing all the applicable actions specified in the Accomplishment Instructions.

(1) For airplanes that have accumulated fewer than 13,500 total flight cycles as December 21, 2005 (the effective date of AD 2005-25-03): Replace prior to the accumulation of 13,500 total flight cycles, or within 1,000 flight cycles after December 21, 2005, whichever occurs later.

(2) For airplanes that have accumulated 13,500 or more total flight cycles as of December 21, 2005: Replace at the later of the times specified in paragraphs (f)(2)(i) and (f)(2)(ii) of this AD.

(i) Prior to the accumulation of 18,000 total flight cycles, or within 1,000 flight cycles after December 21, 2005, whichever occurs first.

(ii) Within 90 days after December 21, 2005.

New Requirements of This AD

Repetitive Inspections

(g) Within 24,000 flight cycles after accomplishing the actions specified in paragraph (f) of this AD, perform an external detailed inspection of the skin just below each splice fitting, in accordance with the Accomplishment Instructions of Boeing ASB 737-53A1222, Revision 2, dated October 20, 2005. Thereafter, repeat the external detailed inspections at intervals not to exceed 24,000 flight cycles.

Corrective Actions

(h) If any cracking is found during any inspection required by this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, or with a method approved in accordance with the procedures specified in paragraph (j) of this AD.

Acceptable Method of Compliance

(i) Replacing the splice fitting and any related investigative actions before December 21, 2005 (the effective date of AD 2005-25-03), in accordance with Boeing Service Bulletin 737-53-1222, dated June 6, 2002; or Boeing ASB 737-53A1222, Revision 1, dated January 30, 2003, is acceptable for compliance with the requirements of paragraph (f) of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle 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, and the approval must specifically refer to this AD.

(4) AMOCs approved previously in accordance with AD 2005-25-03, amendment 39-14396, are approved as AMOCs for the corresponding provisions of paragraphs (f) and (h) of this AD.

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

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.