E7-16104. Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series 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 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD would require repetitive detailed and high-frequency eddy current inspections for cracking around the heads of the fasteners on the forward fastener row of certain areas of the station (STA) 259.5 circumferential butt splice, and repair if necessary. This proposed AD would also require a preventive modification, which would eliminate the need for the repetitive inspections. This proposed AD results from a report that an operator found multiple cracks in the fuselage skin of a Model 737-200 airplane, at the forward fastener row of the STA 259.5 circumferential butt splice between stringers 19 and 24. We are proposing this AD to prevent cracking of the STA 259.5 circumferential butt splice, which could result in loss of structural integrity of the fuselage skin and possible loss of cabin pressure.

DATES:

We must receive comments on this proposed AD by October 1, 2007.

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: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room W12-140 on the ground floor of the West Building, 1200 New Jersey Avenue, SE., 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 the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; 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-2007-28942; Directorate Identifier 2007-NM-093-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 DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may 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 Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located on the ground floor of the West 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

We have received a report indicating that an operator found multiple cracks in the fuselage skin of a Model 737-200 airplane that had accumulated 69,350 total flight cycles. The cracking was found at the forward fastener row of the station (STA) 259.5 circumferential butt splice between stringers 19 and 24, and some cracks had joined into one large crack. This condition, if not corrected, could result in loss of structural integrity of the fuselage skin and possible loss of cabin pressure.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006. The service bulletin describes procedures for doing repetitive detailed and high-frequency eddy current (HFEC) surface inspections for cracking around the heads of the fasteners on the forward fastener row of certain areas of the STA 259.5 circumferential butt splice, and applicable repair if necessary. Certain areas of the circumferential butt splice are those described in the Accomplishment Instructions of Service Bulletin 737-53-1267 as areas that have not had a preventive modification installed in accordance with Boeing Service Bulletin 737-53-1076, or have not had a Boeing, FAA-approved repair accomplished.

The service bulletin also describes procedures for doing a preventive modification of certain areas of the STA 259.5 circumferential butt splice, including removing the existing fasteners, doing an HFEC rotary probe inspection of the fastener holes, and, if no crack is found, oversizing the holes and installing new protruding head fasteners. The preventive modification eliminates the need for the repetitive inspections.

The service bulletin specifies compliance times that depend upon the number of total flight cycles accumulated by the airplane. Compliance times for doing the initial inspections begin at or before the accumulation of 50,000 total flight cycles, with grace periods ranging between 500 and 4,500 flight cycles after the release date of the service bulletin. The service bulletin specifies that repetitive inspections shall be done thereafter at intervals of 9,000 flight cycles, until the preventive modification is done. The service bulletin specifies that all repairs are to be done before further flight and that the preventive modification is to be done before the accumulation of 75,000 total flight cycles or within 6,000 flight cycles after the release date of the service bulletin, whichever comes later.

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. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Costs of Compliance

There are about 2,150 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, at an average labor rate of $80 per work hour. Required parts would be supplied by the operator.

Estimated Costs

Action	Work hours	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Inspection	5	$400, per inspection cycle	654	$261,600, per inspection cycle.
Preventive modification	24	$1,920	654	$1,255,680.

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 adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-28942; Directorate Identifier 2007-NM-093-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 1, 2007.

Affected ADs

(b) Accomplishing repairs and modifications described in paragraphs (f) and (g) of this AD is considered acceptable for compliance with repair requirements of paragraphs (f) and (g) of AD 92-25-09, amendment 39-8424, for the areas of the station (STA) 259.5 circumferential butt splice only.

Applicability

(c) This AD applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes, certificated in any category, as identified in Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006.

Unsafe Condition

(d) This AD results from a report that an operator found multiple cracks in the fuselage skin of a Model 737-200 airplane, at the forward fastener row of the STA 259.5 circumferential butt splice between stringers 19 and 24. We are issuing this AD to prevent cracking of the STA 259.5 circumferential butt splice, which could result in loss of structural integrity of the fuselage skin and possible loss of cabin pressure.

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

(f) At the applicable initial compliance time specified in paragraph 1.E. “Compliance” of Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006, except as provided by paragraph (j) of this AD: Do detailed and high-frequency eddy current inspections for cracking around the heads of the fasteners on the forward fastener row of certain areas of the station (STA) 259.5 circumferential butt splice, by doing all of the actions specified in Part 1 of the Accomplishment Instructions of the service bulletin, except as provided by paragraph (i) of this AD. Repeat the inspections thereafter at the intervals specified in paragraph 1.E. of the service bulletin. Doing the preventive modification specified in paragraph (h) of this AD terminates the repetitive inspection requirements of this paragraph.

Repair

(g) If any crack is found during any inspection required by this AD, before further flight, repair in accordance with Part 1 of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006.

Preventive Modification

(h) At the compliance time specified in paragraph 1.E. of Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006, except as provided by paragraph (j) of this AD: Do the preventive modification in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006. Doing the preventive modification terminates the repetitive inspections required by paragraph (f) of this AD.

Modification or Repair Done in Accordance with AD 92-25-09

(i) Inspections described by paragraph (f) of this AD are not required for areas of the STA 259.5 circumferential butt splice that have been modified in accordance with the service information specified in Table 1 of this AD. (Boeing Service Bulletin 737-53-1076, Revision 4, dated September 26, 1991, is cited as an appropriate source of service information for doing certain requirements of AD 92-25-09.)

Table 1.—Service Information

Boeing Service Bulletin	Revision level	Date
737-53-1076	4	September 26, 1991.
737-53-1076	3	September 20, 1990.
737-53-1076	2	February 8, 1990.
737-53-1076	1	November 23, 1988.
737-53-1076	Original Issue	October 30, 1986.

Compliance Times

(j) Where the service bulletin specifies compliance times relative to the release date of Boeing Special Attention Service Bulletin 737-53-1267, dated November 28, 2006, this AD requires compliance at compliance times relative to the effective date of this AD.

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) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

(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.

Issued in Renton, Washington, on July 30, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.