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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-205-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes to revise an existing airworthiness directive (AD), applicable to certain Boeing Model 737-200, −200C, −300, and −400 series airplanes, that currently requires repetitive visual and high frequency eddy current (HFEC) inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. That amendment also mandates accomplishment of a modification to the aft cargo door, which would terminate the repetitive inspection requirements. This action would revise the compliance time of the terminating action. The actions specified by this proposal are intended to prevent fatigue cracking of the corners of the doorframe and the crossbeams of the aft cargo door, which could result in rapid depressurization of the airplane. 

# DATES:

Comments must be received by November 20, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-205-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via the Internet must contain “Docket No. 2000-NM-205-AD” in the subject line and need not be submitted in triplicate. 

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:

Nancy Marsh, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-2028; telephone (425) 227-2557; fax (425) 227-1181. 

# 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 notice 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-205-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-205-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On March 24, 2000, the FAA issued AD 2000-06-13, amendment 39-11654 (65 FR 17583, April 4, 2000), applicable to certain Boeing Model 737-200, −200C, −300, and −400 series airplanes, to require repetitive visual inspections and repetitive high frequency eddy current (HFEC) inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. That amendment also mandates accomplishment of a modification to the aft cargo door that terminates the repetitive inspection requirements. The actions specified by that AD are intended to prevent fatigue cracking of the corners of the door frame and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane. 

## Actions Since Issuance of Previous Rule 

                    Since the issuance of that AD, the FAA has reviewed AD 2000-06-13 and determined that the compliance times specified for the terminating action in paragraph (e) of that AD can be relaxed somewhat. Paragraph (e) of that AD states the compliance times as, “prior to the accumulation of 12,000 total flight cycles, or within 4 years after the effective date of this AD, whichever occurs later.” However, the FAA now has determined that the terminating action (modification of the aft cargo door) could be accomplished within “12,000 flight cycles or 4 years after the effective date of this AD, whichever occurs later.” The revision to the compliance time will permit a reasonable and adequate amount of time for operators to accomplish the                           ( print page 59382)                        terminating action, and will not adversely affect safety.                 

## Editorial Explanation 

                    The FAA also has noted that in paragraphs (a)(2), (a)(3), (a)(4), and Note 2 of AD 2000-06-13, reference is made to performing certain actions in accordance with certain paragraphs (                    *i.e.*, paragraph III.C., paragraph III.E., or paragraph III.F) of part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-52A1079, Revision 6, dated November 18, 1999. While those specific paragraph references are correct for references to Revision 5 of the Boeing Alert Service Bulletin, they are not the correct paragraph references of Revision 6 of the alert service bulletin. However, the correct reference section for both Revision 5 and Revision 6 is still in part 1 of the Accomplishment Instructions. Therefore, the FAA has deleted the references to specific paragraphs of part 1 of the Accomplishment Instructions of the alert service bulletin and retained reference only to part 1. Specifying that the actions must be accomplished in accordance with “Part 1 of the Accomplishment Instructions” of either revision will clarify and correct the appropriate references.                 

## 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 revise AD 2000-06-13 to continue to require repetitive visual and HFEC inspections to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions, if necessary. This proposal also would relieve the existing compliance time for the terminating action required by AD 2000-06-13 to modify the aft cargo door. 

## Cost Impact 

There are approximately 1,636 Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 707 airplanes of U.S. registry would be affected by this AD. 

The detailed visual inspections that currently are required by AD 2000-06-13, and retained in this AD, would take approximately 2 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be $84,840, or $120 per airplane, per inspection cycle. 

The high frequency eddy current inspections that would be required by this proposal would take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspections on U.S. operators is estimated to be $169,680, or $240 per airplane, per inspection cycle. 

The modification proposed in this action would take approximately 144 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $4,530 per airplane. Based on these figures, the estimated cost impact of the proposed modification on U.S. operators is estimated to be $9,311,190, or $13,170 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 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 

2. Section 39.13 is amended by removing amendment 39-11654 (65 FR 17583, April 4, 2000), and by adding a new airworthiness directive (AD), to read as follows: 

**Boeing:**                                 Docket 2000-NM-205-AD. Revises AD 2000-06-13, Amendment 39-11654.                             

*Applicability:*                                 The following airplane models, certificated in any category.                             
        - Model 737-200 and −200C series airplanes, line numbers 6 through 873 inclusive;
        - Model 737-200, −200C, −300, and −400 series airplanes; line numbers 874 through 1642 inclusive; equipped with an aft cargo door having Boeing part number (P/N) 65-47952-1 or P/N 65-47952-524; excluding:

1. Those airplanes on which that door has been modified in accordance with Boeing Service Bulletin 737-52-1079; or 

2. Those airplanes on which the door assembly having P/N 65-47952-524 includes four straps (P/N's 65-47952-139, 65-47952-140, 65-47952-141, and 65-47952-142) and a thicker lower cross beam web (P/N 65-47952-157). 

# Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (f)(1) 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 prevent fatigue cracking of the corners of the doorframe and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane, accomplish the following: 

## Restatement of the Requirements of AD 98-25-06 

### Inspections and Corrective Actions 

                                (a) Within 90 days or 700 flight cycles after December 24, 1998 (the effective date of AD                                       ( print page 59383)                                    98-25-06, amendment 39-10931), whichever occurs later, perform an internal detailed visual inspection to detect cracking of the corners of the door frame and the cross beams of the aft cargo door, in accordance with Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or Boeing Alert Service Bulletin 737-52A1079, Revision 6, dated November 18, 1999.                             

(1) If no cracking is detected, accomplish the requirements of either paragraph (a)(1)(i) or (a)(1)(ii) of this AD. 

(i) Repeat the internal visual inspection thereafter at intervals not to exceed 4,500 flight cycles. Or 

(ii) Prior to further flight, modify the corners of the doorframe and the crossbeams of the aft cargo door in accordance with the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD. 

(2) If any cracking is detected in the upper or lower cross beams, prior to further flight, modify the cracked beam in accordance with Part I of the Accomplishment Instructions of the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the repaired beam. 

(3) If any cracking is detected in the forward or aft upper door frame, prior to further flight, repair the frame and modify the corners of the door frame of the aft cargo door, in accordance with Part I of the Accomplishment Instructions of the service bulletin, except as provided by paragraph (b) of this AD. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the upper doorframe. 

# Note 2:

Cracks of the forward or aft upper door frame, regardless of length, must be repaired prior to further flight in accordance with Part I of the Accomplishment Instructions of the service bulletin.

(4) If any cracking is detected in the forward or aft lower door frame, prior to further flight, replace the damaged frame with a new frame, and modify the corners of the door frame of the aft cargo door, in accordance with Part I of the Accomplishment Instructions of the service bulletin. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1)(i) of this AD for the lower doorframe. 

(b) Where Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or Boeing Alert Service Bulletin, 737-52A1079, Revision 6, dated November 18, 1999, specifies that certain repairs are to be accomplished in accordance with instructions received from Boeing, this AD requires that, prior to further flight, such repairs be accomplished in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. 

## New Requirements of This AD

### Inspections and Corrective Actions 

(c) If any cracking of the outer chord of the upper or lower cross beams of the aft cargo door is detected as a result of any inspection required by paragraph (a) of this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle ACO; Boeing Alert Service Bulletin, 737-52A1079, Revision 6, dated November 18, 1999; or in accordance with 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. 

(d) Within 4,500 flight cycles or one year after the effective date of this AD, whichever occurs later: Perform a high frequency eddy current inspection (HFEC) to detect cracking of the four corners of the door frame of the aft cargo door, in accordance with the procedures specified in Boeing 737 Nondestructive Test Manual, Part 6, Chapter 51-00-00 (Figure 4 or Figure 23), or Boeing Alert Service Bulletin, 737-52A1079, Revision 6, dated November 18, 1999; 

(1) If no cracking of the corners of the doorframe of the aft cargo door is detected, repeat the HFEC inspections thereafter at intervals not to exceed 4,500 flight cycles until accomplishment of the modification specified in paragraph (e) of this AD. 

(2) If any cracking of the corners of the door frame of the aft cargo door is detected, prior to further flight, replace the damaged frame with a new frame, and modify the four corners of the door frame, in accordance with Parts II and III of the Accomplishment Instructions of Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or Boeing Alert Service Bulletin 737-52A1079, Revision 6, dated November 18, 1999. Accomplishment of such modification constitutes terminating action for the repetitive inspection requirements of paragraph (d)(1) of this AD for that doorframe. 

### Terminating Action 

(e) Within 4 years or 12,000 flight cycles after the effective date of this AD, whichever occurs later: Modify the four corners of the door frame and the cross beams of the aft cargo door, in accordance with Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or Boeing Alert Service Bulletin 737-52A1079, Revision 6, dated November 18, 1999. Accomplishment of that modification constitutes terminating action for the repetitive inspection requirements of this AD. 

# Note 3:

Accomplishment of the modification required by paragraph (a) of AD 90-06-02, amendment 39-6489, is considered acceptable for compliance with paragraph (e) of this AD.

# Note 4:

Modification of the corners of the door frame and the cross beams of the aft cargo door accomplished prior to the effective date of this AD in accordance with Boeing Service Bulletin 737-52-1079, dated December 16, 1983; Revision 1, dated December 15, 1988; Revision 2, dated July 20, 1989; Revision 3, dated May 17, 1990; Revision 4, dated February 21, 1991; is considered acceptable for compliance with paragraph (e) of this AD. 

### Alternative Methods of Compliance 

(f)(1) 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. 

(2) Alternative methods of compliance, approved previously in accordance with AD 98-25-06, amendment 39-10931, are approved as alternative methods of compliance with this AD. 

# Note 5:

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

### Special Flight Permits 

(g) Special flight permits may be issued in accordance with §§ 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 September 29, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-25534 Filed 10-4-00; 8:45 am] 

BILLING CODE 4910-13-P