01-17432. Airworthiness Directives; Boeing Model 737-200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-200, -200C, -300, -400, and -500 series airplanes. This proposal would require the replacement of certain repairs in certain fuselage lap joints with improved repairs. This proposal also would require a high frequency eddy current inspection to find cracking of the repairs of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. This action is necessary to find and fix premature cracking of certain lap joint repairs, which could result in rapid decompression of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by August 27, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-73-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-73-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Scott Fung, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-73-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-73-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On October 21, 1997, the FAA issued AD 97-22-07, amendment 39-10179 (62 FR 55732, October 28, 1997), applicable to certain Boeing Model 737 series airplanes, which requires repetitive inspections to detect cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking detected. That action also requires modification of the fuselage lap joints at certain locations.

Since issuance of that AD, the manufacturer has informed the FAA that during fatigue testing of the skin panels on certain airplanes repaired in accordance with the existing AD, premature cracking in certain lap joint repairs was detected. Multiple cracks were detected underneath the repairs on airplanes that had accumulated between 10,000 and 15,000 test cycles since repair per AD 97-22-07. These repairs were accomplished using the manufacturer's structural repair manual (SRM). Such repairs also may have been installed at times other than that required by AD 97-22-07. This condition, if not detected and corrected, could result in sudden decompression of the airplane.

Other Rulemaking

At this time, the FAA is considering two other separate rulemaking actions to address the remaining potential unsafe conditions relating to the cracking of the lap joints of the fuselage. Those two other actions would address:

• Additional repetitive inspections to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and replacement of the preventive modification with an improved modification on Model 737 series airplanes, line numbers 292 through 2565 inclusive. And
• Repetitive inspections to find cracking of certain fuselage lap joint areas and modification of those areas, which would constitute terminating action for the repetitive inspections. The actions would be applicable to Model 737 series airplanes, line numbers 1 through 291 inclusive.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001, which describes, among other things, procedures for replacement of certain SRM repairs in the fuselage lap joints with improved repairs. The service bulletin also describes a high frequency eddy current (HFEC) open-hole rotating probe inspection to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require the replacement of certain repairs in certain fuselage lap joints with improved repairs. This proposed AD also would require a high frequency eddy current inspection to find cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking found. The actions would be required to be done per the service bulletin described previously, except as discussed below.

Differences Between Service Bulletin and Proposed Rule

In light of the complexity of the service bulletin, three separate rulemaking actions are being issued to address the potential unsafe conditions relating to the cracking of the lap joints of the fuselage. This proposed rule will address only the sections in the service bulletin that pertain to inadequate lap joint repairs done per the SRM.

Although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair/modification conditions, this proposed AD requires the repair/modification of those conditions to be done per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Cost Impact

There are approximately 2,359 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 958 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 14 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $804,720, or $840 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2000-NM-73-AD.

Applicability: Model 737-200, -200C, -300, -400, and -500 series airplanes having line numbers 292 through 2565 inclusive, certificated in any category.

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To find and fix premature cracking of certain fuselage lap joint repairs, which could result in rapid decompression of the airplane, accomplish the following:

Replacement of Structural Repair Manual (SRM) Lap Joint Repairs

(a) For Model 737-200, -200C, and -300 series airplanes: Within 5,000 flight cycles after the effective date of this AD, inspect all lap joints between body station (BS) 259.5 and BS 1016 to identify all repairs accomplished in accordance with 737-200 SRM, Subject 53-30-03, Figure 39 (for 737-200 series airplanes); or Boeing 737-300 SRM, Subject 53-00-01, Figure 227 (for 737-300 series airplanes).

(b) For Model 737-200, -200C, and -300 series airplanes that have a lap joint repair installed at stringers S-4L and S-4R, located between BS 259.5 and BS 1016; and installed at S-10L and S-10R, or at S-14L and S-14R, located between BS 259.5 and BS 540, and between BS 727 and BS 1016; that was previously done per the procedures specified in Boeing 737-200 SRM, Subject 53-30-3, Figure 39 repair (for 737-200 series airplanes); or Boeing 737-300 SRM, Subject 53-00-01, Figure 227 repair (for 737-300 series airplanes): Before the accumulation of 15,000 flight cycles since repair installation, or within 5,000 flight cycles after the effective date of this AD, whichever is later, do the requirements of paragraph (b)(1) or (b)(2) of this AD, as applicable, per Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001. If the area of damage that required the existing repair is outside the lap joint lower row, before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

(1) If the lap joints are being cut out when replacing the SRM repair: Replace the Figure 39 repair of the lower skin at the lower row of fasteners in the lap joints of the fuselage per Figures 16, 17, and 18 of the Accomplishment Instructions of the service bulletin.

(2) If the lap joints are not being cut out when replacing the SRM repair: Do a high frequency eddy current (HFEC) open-hole rotating probe inspection to find cracking of the SRM repair of the lower skin at the lower row of fasteners in the lap joints of the fuselage, per the Figure 20 inspection procedures of the Accomplishment Instructions of the service bulletin. Before further flight after doing the inspection, replace a Boeing 737-200 SRM, Subject 53-30-3, Figure 39 repair with a Boeing 737-200 SRM, Subject 53-30-3, Figure 42 repair (for 737-200 series airplanes); or replace a Boeing 737-300 SRM, Subject 53-00-01, Figure 227 repair with a Boeing 737-300 SRM, Subject 53-00-01, Figure 228 repair (for 737-300 series airplanes); as applicable; per Part II.D. (“Crack Repair”) of the Accomplishment Instructions of the service bulletin.

(c) For Model 737-200, -200C, and -300 series airplanes that have a lap joint repair installed in any area between BS 259.5 and BS 1016, other than those specified in paragraph (b) of this AD, that was previously done per the procedures specified in Boeing 737-200 SRM, Subject 53-30-3, Figure 39 repair (for 737-200 series airplanes); or Boeing 737-300 SRM Subject 53-00-01, Figure 227 repair (for 737-300 series airplanes): Before the accumulation of 20,000 flight cycles since repair installation, or within 5,000 flight cycles after the effective date of this AD, whichever is later, do the requirements of paragraph (b)(1) or (b)(2) of this AD, as applicable, per Boeing Service Bulletin 737-53A1177, Revision 6, dated May 31, 2001.

(d) For Model 737-400 and -500 series airplanes: Within 5,000 flight cycles after the effective date of this AD, inspect all lap joints between BS 259.5 and BS 1016 to identify all repairs accomplished in accordance with 737-400 SRM, Subject 53-00-01, Figure 229 (for 737-400 series airplanes); or Boeing 737-500 SRM, Subject 53-00-01, Figure 227 (for 737-500 series airplanes).

(e) For Model 737-400 and -500 series airplanes that have a lap joint repair installed at S-4L and S-4R, located between BS 259.5 and BS 1016; and installed at S-10L and S-10R, or S-14L and S-14R, located between BS 259.5 and BS 540, and between BS 727 and BS 1016; that was previously done per the procedures specified in Boeing 737-400 SRM, Subject 53-00-01, Figure 229 repair (for 737-400 series airplanes); or Boeing 737-500 SRM, Figure 227 repair (for 737-500 series airplanes): Before the accumulation of 15,000 flight cycles since repair installation, or within 5,000 flight cycles after the effective date of this AD, whichever is later, cut out and replace the repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

(f) For Model 737-400, and -500 series airplanes that have a lap joint repair installed in any area between BS 259.5 and BS 1016, other than those specified in paragraph (d) of this AD, that was previously done per the procedures specified in Boeing 737-400 SRM, Subject 53-00-01, Figure 229 repair (for 737-400 series airplanes); or Boeing 737-500 SRM, Figure 227 repair (for 737-500 series airplanes): Before the accumulation of 20,000 flight cycles since repair installation, or within 5,000 flight cycles after the effective date of this AD, whichever is later, cut out and replace the repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

Alternative Methods of Compliance

(g) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permit

(h) Special flight permits may be issued per sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Issued in Renton, Washington, on July 6, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.