E6-4620. Airworthiness Directives; Boeing Model 737-200C 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 all Boeing Model 737-200C series airplanes. The existing AD currently requires a one-time external detailed inspection for cracking of the fuselage skin in the lower lobe cargo compartment; repetitive internal detailed inspections for cracking of the frames in the lower lobe cargo compartment; repair of cracked parts; and terminating action for the repetitive internal detailed inspections. This proposed AD restates the requirements of the existing AD and adds a requirement to perform repetitive detailed inspections of the body station (BS) 360 and BS 500 fuselage frames, after accomplishing the terminating action, and repair if necessary. This proposed AD results from multiple reports that the existing AD is not fully effective in preventing cracks in the BS 360 and BS 500 fuselage frames. We are proposing this AD to detect and correct cracking of the fuselage frames from BS 360 to BS 500B, which, if not detected, could lead to loss of the cargo door during flight and consequent rapid decompression of the airplane.

DATES:

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

Howard Hall, 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-2006-24245; Directorate Identifier 2005-NM-166-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 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 June 4, 1999, we issued AD 99-12-08, amendment 39-11192 (64 FR 31488, June 11, 1999), for all Boeing Model 737-200C series airplanes. That AD requires a one-time external detailed inspection to detect and correct cracking of the fuselage skin in the lower lobe cargo compartment; repetitive internal detailed visual inspections for cracking of the frames in the lower lobe cargo compartment; repair of cracked parts; and a preventative modification that provides terminating action for the repetitive internal detailed inspections. That AD resulted from reports of cracking of the body frames between stringers 19 left and 25 left and at body station (BS) 360 to 500B. We issued that AD to prevent opening or loss of the cargo door during flight, and consequent rapid decompression of the airplane.

Actions Since Existing AD Was Issued

AD 99-12-08 states that modifying certain fuselage frames from BS 360 through BS 500B inclusive constitutes terminating action for the repetitive internal detailed inspections required for all specified fuselage frames. However, since we issued AD 99-12-08, we have received multiple reports indicating that the modification required by AD 99-12-08 is not fully effective in preventing cracking of the BS 360 and BS 500 fuselage frames. Consequently, to maintain airplane structural integrity, it is necessary to require new internal detailed inspections at the BS 360 and BS 500 fuselage frames on airplanes that have been modified as required by paragraph (c) of AD 99-12-08, and repair if necessary.

Changes to Existing AD

This proposed AD would retain certain requirements of AD 99-12-08. Since AD 99-12-08 was issued, the AD format has been revised; therefore, paragraphs (a), (b), and (c) of AD 99-12-08 have been re-identified as paragraphs (f), (g), and (h) in this proposed AD.

We have revised paragraph (g)(1) of this proposed AD to include a statement that repairs must be performed in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with the procedures specified in paragraph (k)(4) of this AD; and that the Boeing 737 Structural Repair Manual is one approved source of repair information for accomplishing the requirements of paragraph (g)(1) of this proposed AD.

Operators should be aware that paragraph (c) of AD 99-12-08 states that installing doublers on the fuselage frames between BS 360 to 500B constitutes terminating action for all inspections required by that AD, even though no doublers are installed on the fuselage frames at BS 360 and BS 500. Therefore, to maintain consistency with AD 99-12-08, paragraph (h) of this proposed AD continues to require installing doublers on the fuselage frames between BS 360 to 500B, which constitutes terminating action for the inspections required for those frames, while paragraph (i) of this proposed AD specifies a new requirement for repetitive inspections of the fuselage frames at BS 360 and BS 500 only.

AD 99-12-08 refers to a “detailed visual inspection.” However, since the issuance of AD 99-12-08, we have clarified the inspection terminology to refer to a “detailed inspection.” We have included a definition of this type of inspection in Note 1 of this proposed AD.

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 99-12-08 and retain the requirements of the existing AD. This proposed AD would also require repetitive internal detailed inspections for cracking of the BS 360 and BS 500 fuselage frames and repair if necessary. These inspections would be required to be done in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993; which were referenced as appropriate sources of service information by AD 99-12-08. That service information specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing 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.

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.

Costs of Compliance

There are about 90 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 18 airplanes of U.S. registry.

The modification required by AD 99-12-08, and retained in this proposed AD, takes approximately 160 work hours per airplane to accomplish, at an average labor rate of $80 per work hour. Required parts cost about $5,500 per airplane. Based on these figures, the estimated cost of the currently required modification for U.S. operators is $329,400, or $18,300 per airplane.

The new proposed inspections would take about 3 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the new inspections specified in this proposed AD for U.S. operators is $4,320, or $240 per airplane, 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 39-11192 (64 FR 31488, June 11, 1999), and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24245; Directorate Identifier 2005-NM-166-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by May 15, 2006.

Affected ADs

(b) This AD supersedes AD 99-12-08.

Applicability

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

Unsafe Condition

(d) This AD results from multiple reports that the modification required by AD 99-12-08 is not fully effective in preventing cracks in the BS 360 and BS 500 fuselage frames. We are issuing this AD to detect and correct cracking of the fuselage frames from BS 360 to BS 500B, which, if not detected, could lead to loss of the cargo door during flight 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.

Restatement of Requirements of AD 99-12-08

One-Time External Detailed Inspection

(f) Prior to the accumulation of 29,000 total flight cycles or within 250 flight cycles after August 9, 1993 (the effective date AD 93-13-02, amendment 39-8615, which was superseded by AD 99-12-08), whichever occurs later, accomplish an external detailed inspection to detect cracks of the fuselage skin between stringers 19 left and 25 left and at body stations 360 to 540, in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. If any crack is found, prior to further flight, accomplish the requirements of paragraphs (f)(1) and (f)(2) of this AD.

(1) Perform an internal detailed inspection to detect cracks of the frames between stringers 19 left and 25 left and at body stations 360 to 500B, in accordance with either service bulletin.

(2) Repair all cracks in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

Internal Detailed Inspections

(g) Within 3,000 flight cycles after completing the requirements of paragraph (f) of this AD, unless accomplished within the last 6,000 flight cycles prior to August 9, 1993, perform an internal detailed inspection to detect cracks of the frames between stringers 19 left and 25 left and at body stations 360 to 500B, in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. Thereafter, repeat the internal detailed inspection at intervals not to exceed 9,000 flight cycles. If any crack is found during any inspection required by this paragraph, before further flight, repair as specified in paragraph (g)(1) or (g)(2) of this AD, as applicable.

(1) If any crack is found that does not exceed the limits specified in the Boeing 737 Structural Repair Manual (SRM), repair the crack in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with the procedures specified in paragraph (k)(4) of this AD. The SRM is one approved source of information for accomplishing the requirements of this paragraph. Repeat the internal detailed inspection thereafter at intervals not to exceed 9,000 flight cycles.

(2) If any crack is found that exceeds the limits specified in the SRM, repair the crack in accordance with a method approved by the Manager, Seattle ACO; or in accordance with the procedures specified in paragraph (k)(4) of this AD. Repeat the internal detailed visual inspection thereafter at intervals not to exceed 9,000 flight cycles.

Install Doublers

(h) Prior to the accumulation of 75,000 total flight cycles, or within 3,000 flight cycles after July 16, 1999 (the effective date of AD 99-12-08), whichever occurs later, install doublers on the specified frames located between stringers 19 left and 25 left from BS 360 to BS 500B, in accordance with Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. Installing these doublers on the specified fuselage frames ends the repetitive inspections required by paragraphs (f) and (g) of this AD.

New Requirements of This AD

Repetitive Inspection of Certain Frames

(i) Within 9,000 flight cycles after accomplishing the modification required by paragraph (h) of this AD, or within 4,500 flight cycles after the effective date of this AD, whichever occurs later, perform an internal detailed inspection to detect cracking in the fuselage frame at BS 360 and the fuselage frame at BS 500, between stringers 19 left and 25 left, in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. Thereafter, repeat the internal detailed inspection of the BS 360 and BS 500 frames at intervals not to exceed 9,000 flight cycles.

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

Note 1:

For the purposes of this AD, a detailed inspection is: “An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.”

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle ACO, 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 14 CFR 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 99-12-08, including AMOCs approved previously in accordance with AD 93-13-02, are approved as AMOCs for the corresponding provisions specified in paragraphs (f), (g), and (h) of this AD.

(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 March 17, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.