E7-17283. Airworthiness Directives; Boeing Model 737-100, -200, and -200C 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 all Boeing Model 737-100, -200, and -200C series airplanes. This proposed AD would require revising the FAA-approved maintenance inspection program to include inspections that will give no less than the required damage tolerance rating for each structural significant item (SSI), doing repetitive inspections to detect cracks of all SSIs, and repairing cracked structure. This proposed AD results from a report of incidents involving fatigue cracking and corrosion in transport category airplanes that are approaching or have exceeded their design service goal. We are proposing this AD to ensure the continued structural integrity of the entire fleet of Model 737-100, -200, and -200C series airplanes.

DATES:

We must receive comments on this proposed AD by October 15, 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:

Nancy Marsh, 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 “FAA-2007-29069; Directorate Identifier 2007-NM-176-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 level 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

In the early 1980's, as part of its continuing work to maintain the structural integrity of older transport category airplanes, we concluded that the incidence of fatigue cracking may increase as these airplanes reach or exceed their design service objective (DSO). In light of this, and as a result of increased utilization, and longer operational lives, we determined that a supplemental structural inspection program (SSIP) was necessary to maintain the continued structural integrity for all airplanes in the transport fleet.

Issuance of Advisory Circular (AC)

As a follow-on from that determination, we issued AC No. 91-56, “Supplemental Structural Inspection Program for Large Transport Category Airplanes,” dated May 6, 1981. That AC provides guidance material to manufacturers and operators for use in developing a continuing structural integrity program to ensure safe operation of older airplanes throughout their operational lives. This guidance material applies to transport airplanes that were certified under the fail-safe requirements of part 4b (“Airplane Airworthiness, Transport Categories”) of the Civil Air Regulations or damage tolerance structural requirements of part 25 (“Airworthiness Standards: Transport Category Airplanes”) of the Federal Aviation Regulations (FAR) (14 CFR part 25), and that have a maximum gross weight greater than 75,000 pounds. The procedures set forth in that AC are applicable to transport category airplanes operated under subpart D (“Special Flight Operations”) of part 91 of the FAR (14 CFR part 91); part 121 (“Operating Requirements: Domestic, Flag, and Supplemental Operations”); part 125 (“Certification and Operations: Airplanes having a Seating Capacity of 20 or More Passengers or a Maximum Payload of 6,000 Pounds or More”); and part 135 (“Operating Requirements: Commuter and On-Demand Operations”) of the FAR (14 CFR parts 121, 125, and 135). The objective of the SSIP was to establish inspection programs to ensure timely detection of fatigue cracking.

Development of the SSIP

In order to evaluate the effect of increased fatigue cracking with respect to maintaining fail-safe design and damage tolerance of the structure of Boeing Model 737-100, -200, and -200C series airplanes, Boeing conducted a structural reassessment of those airplanes, using damage tolerance evaluation techniques. Boeing accomplished this reassessment using the criteria contained in AC No. 91-56, as well as Amendment 25-45 of section 25.571 (“Damage-tolerance and fatigue evaluation of structure”) of the FAR (14 CFR 25.571). During the reassessment, members of the airline industry participated with Boeing in working group sessions and developed the SSIP for Model 737-100, -200, and -200C series airplanes. Engineers and maintenance specialists from the FAA also supported these sessions. Subsequently, based on the working group's recommendations, Boeing developed the Supplemental Structural Inspection Document (SSID).

Other Related Rulemaking

We previously issued AD 98-11-04 R1, amendment 39-10984 (64 FR 987, January 7, 1999), applicable to all Boeing Model 737-100, -200, and -200C series airplanes (which refers to Boeing Document No. D6-37089, “Supplemental Structural Inspection Document” (SSID), Revision D, dated June 1995, as the appropriate source of service information for doing the required actions). That AD requires that the FAA-approved maintenance inspection program be revised to include inspections that will give no less than the required damage tolerance rating (DTR) for each structural significant item (SSI), and repair of cracked structure. The affected SSIs include, but are not limited to, the wing, fuselage, empennage, and strut. For Model 737-200C series airplanes, that AD requires inspecting SSIs affected by cargo configuration changes only.

Relevant Service Information

We have reviewed Boeing Document No. D6-37089, “Supplemental Structural Inspection Document for Model 737-100/200/200C Airplanes,” Revision E, dated May 2007 (hereafter “Revision E”); and “Appendix A Model 737-100/200/200C Airplanes,” Original Release, dated May 2007, of Revision E (hereafter “Appendix A”). Revision E and Appendix A describe procedures for revising the FAA-approved maintenance inspection program to include inspections that will give no less than the required DTR for each SSI, doing repetitive inspections to detect cracks of all SSIs, and repairing cracked structure. The inspections specified in Revision E are essentially identical to those in Revision D, except for Appendix A. Appendix A adds inspection procedures for SSIs on the wing trailing edge flap structure, which were not included previously in any revision of the SSID. Accomplishing the actions specified in Revision E and Appendix A 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 the following actions:

Paragraph (h) of the proposed AD would require incorporation of a revision into the FAA-approved maintenance inspection program that provides no less than the required DTR for each SSI listed in Appendix A.

Paragraph (i) of the proposed AD would require repetitive inspections to detect cracks of all SSIs.

Paragraph (j) of the proposed AD would require repairing any cracked structure in accordance with a method approved by the FAA or an Authorized Representative (AR) for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the FAA to make those findings.

Paragraph (k) of the proposed AD specifies the requirements of the inspection program for transferred airplanes. Before any airplane that is subject to this proposed AD can be added to an air carrier's operations specifications, a program for doing the inspections required by this proposed AD must be established.

Differences Between the Proposed AD and Service Information

For Model 737-100 and -200 series airplanes, and Model 737-200C series airplanes on which details are not affected by the cargo configuration, Section 3.0, “Structural Significant Items (SSIs),” of Revision E specifies a threshold of 66,000 flight cycles for accomplishing the initial inspections; however, it does not specify a grace period for airplanes that are near or exceeded that threshold. This proposed AD would allow a grace period of 12 months after the effective date of the AD to incorporate Appendix A into the FAA-approved maintenance inspection program. This proposed AD also would allow a grace period of 4,000 flight cycles measured from 12 months after the effective date of the AD to initiate the applicable inspections to detect cracks of all SSIs.

Revision E does not specify instructions on how to repair certain conditions. This proposed AD would require repairing those conditions in one of the following ways:

• Using a method that we approve; or
• Using data that have been approved by an AR for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Costs of Compliance

There are about 676 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	Number of U.S.-registered airplanes	Fleet cost
Revision of maintenance inspection program	200 per operator (23 U.S. operators)	$80	$16,000 per operator	118	$368,000.
Inspections	150 per airplane	80	$12,000, per airplane, per inspection cycle	118	$1,416,000 per inspection cycle.

The number of work hours, as indicated above, is presented as if the accomplishment of the actions in this proposed AD is to be conducted as “stand alone” actions. However, in actual practice, these actions for the most part will be done coincidentally or in combination with normally scheduled airplane inspections and other maintenance program tasks. Therefore, the actual number of necessary additional work hours will be minimal in many instances. Additionally, any costs associated with special airplane scheduling will be minimal.

Further, compliance with this proposed AD would be a means of compliance with the aging airplane safety final rule (AASFR) for the baseline structure of Model 737-100, -200, and -200C series airplanes. The AASFR final rule requires certain operators to incorporate damage tolerance inspections into their maintenance inspection programs. These requirements are described in 14 CFR 121.370(a) and 129.16. Accomplishment of the actions required by this proposed AD will meet the requirements of these CFR sections for the baseline structure. The costs for accomplishing the inspection portion of this proposed AD were accounted for in the regulatory evaluation of the AASFR final rule.

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-2007-29069; Directorate Identifier 2007-NM-176-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 15, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Boeing Model 737-100, -200, and -200C series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from a report of incidents involving fatigue cracking and corrosion in transport category airplanes that are approaching or have exceeded their design service objective. We are issuing this AD to maintain the continued structural integrity of the entire fleet of Model 737-100, -200, and -200C series airplanes.

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.

Service Information

(f) The term “Revision E,” as used in this AD, means Boeing Document No. D6-37089, “Supplemental Structural Inspection Document for Model 737-100/200/200C Airplanes,” Revision E, dated May 2007.

(g) The term “Appendix,” as used in this AD, means “Appendix A Model 737-100/200/200C Airplanes,” Original Release, dated May 2007, of Revision E.

Revision of the FAA-Approved Maintenance Inspection Program

(h) Before the accumulation of 66,000 total flight cycles, or within 12 months after the effective date of this AD, whichever occurs later, incorporate a revision into the FAA-approved maintenance inspection program that provides no less than the required damage tolerance rating (DTR) for each structural significant item (SSI) listed in Section 3.0, “Flap and Support Structure (Flap Structure) SSI Information,” of Appendix A. (The required DTR value for each SSI is listed in the Appendix.) The revision to the maintenance inspection program must include and must be implemented in accordance with the procedures in Section 3.0 of the Appendix, and in accordance with the procedures in Section 5.0, “Damage Tolerance Rating (DTR) System Application,” and Section 6.0, “SSI Discrepancy Reporting” of Revision E. Under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection requirements contained in this AD and has assigned OMB Control Number 2120-0056.

Initial and Repetitive Inspections

(i) Before the accumulation of 66,000 total flight cycles, or within 4,000 flight cycles measured from 12 months after the effective date of this AD, whichever occurs later, do the applicable initial inspections to detect cracks of all SSIs, in accordance with Appendix A. Repeat the applicable inspections thereafter at the intervals necessary to obtain the required DTR specified in Appendix A.

Repair

(j) If any cracked structure is found during any inspection required by paragraph (i) of this AD, before further flight, repair the cracked structure using a method approved in accordance with the procedures specified in paragraph (l) of this AD.

Inspection Program for Transferred Airplanes

(k) Before any airplane that is subject to this AD and that has exceeded the applicable compliance times specified in paragraph (i) of this AD can be added to an air carrier's operations specifications, a program for the accomplishment of the inspections required by this AD must be established in accordance with paragraph (k)(1) or (k)(2) of this AD, as applicable.

(1) For airplanes that have been inspected in accordance with this AD: The inspection of each SSI must be done by the new operator in accordance with the previous operator's schedule and inspection method, or the new operator's schedule and inspection method, at whichever time would result in the earlier accomplishment for that SSI inspection. The compliance time for accomplishment of this inspection must be measured from the last inspection accomplished by the previous operator. After each inspection has been done once, each subsequent inspection must be performed in accordance with the new operator's schedule and inspection method.

(2) For airplanes that have not been inspected in accordance with this AD: The inspection of each SSI required by this AD must be done either before adding the airplane to the air carrier's operations specification, or in accordance with a schedule and an inspection method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. After each inspection has been done once, each subsequent inspection must be done in accordance with the new operator's schedule.

Alternative Methods of Compliance (AMOCs)

(l)(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) 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 approval must specifically refer to this AD.

Issued in Renton, Washington, on August 17, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.