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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-363-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 707, 727C, and 727-100C series airplanes, that currently requires repetitive inspections to detect cracking of the main cargo door skin and frames, and repair, if necessary. The existing AD also provides optional terminating modifications. This action would mandate follow-on repetitive inspections of repaired or modified areas for certain airplanes. This proposal is prompted by reports of cracking and/or tearing of the main cargo door outer skin and subsequent failure of the door frame. The actions specified by the proposed AD are intended to detect and correct such cracking and/or tearing, which could result in failure of the door frame and consequent rapid decompression of the airplane. 

# DATES:

Comments must be received by June 5, 2000. 

# ADDRESSES:

                        Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-363-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.                               ( print page 20925)                            Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.                     

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:

Walt Sippel, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2774; 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. 

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 99-NM-363-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. 99-NM-363-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On January 17, 1983, the FAA issued AD 83-02-09, amendment 39-4549 (48 FR 6953, February 17, 1983), applicable to certain Boeing Model 707, 727C, and 727-100C airplanes, to require inspection and repair, if necessary, of the main cargo door structure. That action was prompted by reports of skin cracking and door frame failures. The requirements of that AD are intended to detect cracking prior to reaching critical length, which could result in rapid decompression or loss of a portion of the main cargo door. 

## Actions Since Issuance of Previous Rule 

Since the issuance of that AD, the FAA has reviewed and approved Boeing Service Bulletin 727-52A0079, Revision 6, dated January 11, 1990. The service bulletin describes procedures for repetitive detailed visual, eddy current, and X-ray inspections of the main cargo door outer skin and the door frames between body stations (BS) 505 and 595 to detect cracking, and repair of any cracks. The service bulletin also describes procedures for modification of the main cargo door and detailed visual and eddy current inspections of the modified or repaired areas. Revisions 4 and 5 of the service bulletin were referenced in the existing AD as an appropriate source of service information for accomplishment of the inspections and modifications for the Model 727 series airplanes. 

The FAA also has reviewed and approved Revision 4 of Boeing Service Bulletin 2999, dated January 31, 1991. Revision 3 of the service bulletin was referenced in the existing AD as the appropriate source of service information for accomplishment of the inspections and modifications for the Model 707 series airplanes. The requirements for inspections and modifications of the Model 707 are unchanged in this proposed AD because the detailed visual and eddy current inspections of the modified or repaired areas are required by AD 85-12-01 R1, amendment 39-5439 (51 FR 36002, October 8, 1986). 

## 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 supersede AD 83-02-09 to continue to require repetitive inspections to detect cracking of the main cargo door outer skin and frames, and repair, if necessary. This proposed AD would mandate follow-on repetitive inspections of modified or repaired areas for certain airplanes. 

Paragraph (e) of the existing AD will not be restated in this proposal due to the FAA's determination that calculating the number of landings/flight cycles by fleet average would not allow for detection of cracks in a timely manner. 

Additionally, restatement of the requirements of the existing AD has been revised to remove all references to the use of “later FAA-approved revisions of the applicable service bulletin,” in order to be consistent with FAA policy in that regard. The FAA has determined that this change will not increase the economic burden on any operator, nor will it increase the scope of the AD, since later revisions of the service bulletin may be approved as an alternative method of compliance with this AD, as provided by paragraph (g)(1) of this AD. 

## Difference Between Proposed Rule and Service Bulletins 

Operators should note that, although the service bulletins specify that the manufacturer may be contacted for disposition of certain repair conditions, this proposed AD would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA, 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. 

## Cost Impact 

There are approximately 50 Model 707 and 308 Model 727 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 1 Model 707 and 81 Model 727 airplanes of U.S. registry would be affected by this proposed AD. 

                    The cost impact information in AD 83-02-09 inadvertently contained information relevant only to the X-ray inspection; however, since the detailed visual and eddy current inspections are also acceptable methods to detect cracking, this proposed AD includes the estimated number of work hours necessary to accomplish any one of the three inspection methods. Additionally, the FAA has recently reviewed the figures it has used over the past several years in calculating the economic impact of AD activity. In order to account for various inflationary costs in the airline industry, the FAA has determined that it is necessary to increase the labor rate used in these calculations from $40 per work hour to                           ( print page 20926)                        $60 per work hour. The cost impact information, below, has been revised to reflect these changes.                 

Should an operator elect to accomplish the detailed visual inspection that is currently required by AD 83-02-09, it would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the detailed visual inspection is estimated to be $60 per airplane. 

Should an operator elect to accomplish the eddy current inspection that is currently required by AD 83-02-09, it would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the eddy current inspection is estimated to be $60 per airplane. 

Should an operator elect to accomplish the X-ray inspection that is currently required by AD 83-02-09, it would take approximately 3 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 X-ray inspection is estimated to be $180 per airplane. 

The detailed visual inspection (for Model 727 series airplanes only) proposed by this AD would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the detailed visual inspection is estimated to be $4,860, or $60 per airplane. 

The eddy current inspection (for Model 727 series airplanes only) proposed by this AD would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the eddy current inspection is estimated to be $4,860, or $60 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. 

## 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 39-4549 (48 FR 6953, February 17, 1983), and by adding a new airworthiness directive (AD), to read as follows: 

**Boeing:**                                 Docket 99-NM-363-AD. Supersedes AD 83-02-09, Amendment 39-4549.                            

*Applicability:*                                 Model 707, 727C, and 727-100C series airplanes; as listed in Boeing Service Bulletins 2999, Revision 3, dated January 12, 1972, and 727-52-79, Revision 4, dated June 19, 1981; 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 (g)(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 detect and correct cracking of the main cargo door skin and frames, which could result in failure of the door frame, and consequent rapid decompression of the airplane, accomplish the following: 

# Note 2:

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

## Restatement of Requirements of AD 83-02-09 

## Initial Inspection 

(a) Within 500 landings after March 3, 1983 (the effective date of AD 83-02-09, amendment 39-4549), or prior to the accumulation of 25,000 total landings after March 3, 1983, whichever occurs later: Perform an inspection (detailed visual, eddy current, or X-ray) to detect cracks of the main cargo door outer skin and frames between body stations (BS) 505 and 595, from the lower edge of the door hinge a minimum of 6 inches down, and 6 inches above, and 3 inches below the center line of stringer 10, in accordance with Boeing Service Bulletin 2999, Revision 3, dated January 12, 1972, or Revision 4, dated January 31, 1991 (for Model 707 series airplanes); or Boeing Service Bulletin 727-52-79, Revision 4, dated June 19, 1981, or Boeing Alert Service Bulletin 727-52A0079, Revision 5, dated June 17, 1983, or Revision 6, dated January 11, 1990 (for Model 727 series airplanes); as applicable.   

## Repetitive Inspections 

(b) Repeat the inspection required by paragraph (a) of this AD at the times specified in paragraph (b)(1), (b)(2) or (b)(3) of this AD; as applicable; until accomplishment of the modification required by paragraph (d) of this AD. 

(1) Repeat the detailed visual inspection at intervals not to exceed 500 landings. 

(2) Repeat the eddy current inspection at intervals not to exceed 750 landings. 

(3) Repeat the X-ray inspection at intervals not to exceed 1,000 landings. 

## Repair 

(c) If any cracking is detected during any inspection required by paragraph (a) or (b) of this AD: Prior to further flight, repair any cracks detected in accordance with Boeing Service Bulletin 2999, Revision 3, dated January 12, 1972, or Revision 4, dated January 31, 1991 (for Model 707 series airplanes); or Boeing Service Bulletin 727-52-79, Revision 4, dated June 19, 1981, or Boeing Alert Service Bulletin 727-52A0079, Revision 5, dated June 17, 1983, or Revision 6, dated January 11, 1990 (for Model 727 series airplanes), as applicable. 

## Optional Terminating Action 

                                (d) Modification of the main cargo door in accordance with Part II, Option 1 or Option                                       ( print page 20927)                                    2, as applicable, of the Accomplishment Instructions of Boeing Service Bulletin 2999, Revision 3, dated January 12, 1972, or Revision 4, dated January 31, 1991 (for Model 707 series airplanes); or Boeing Service Bulletin 727-52-79, Revision 4, dated June 19, 1981, or Boeing Alert Service Bulletin 727-52A0079, Revision 5, dated June 17, 1983, or Revision 6, dated January 11, 1990 (for Model 727 series airplanes); as applicable; constitutes terminating action for the requirements of paragraphs (a) and (b) of this AD.                             

## New Requirements of This AD 

## Post-Repair/Post-Mod Repetitive Inspections 

(e) For Model 727 series airplanes: Within 27,000 flight cycles after accomplishment of the repair specified in paragraph (c) of this AD, and/or the modification specified in paragraph (d) of this AD, as applicable; or within 1,000 flight cycles after the effective date of this AD; whichever occurs later; accomplish the requirements of paragraph (e)(1) or (e)(2) of this AD, as applicable. 

(1) For airplanes that have accomplished the modification specified in Part II, Option 1, of the Accomplishment Instructions of Boeing Service Bulletin 727-52-79, Revision 4, dated June 19, 1981, or Boeing Alert Service Bulletin 727-52A0079, Revision 5, dated June 17, 1983, or Revision 6, dated January 11, 1990: Perform a detailed visual and eddy current inspection of the modified area and/or any repaired area, to detect cracks, in accordance with the service bulletin. Repeat the inspections at intervals not to exceed 3,800 flight cycles. 

(2) For airplanes that have accomplished the modification specified in Part II, Option 2, of the Accomplishment Instructions of Boeing Service Bulletin 727-52-79, Revision 4, dated June 19, 1981, or Boeing Alert Service Bulletin 727-52A0079, Revision 5, dated June 17, 1983, or Revision 6, dated January 11, 1990: Perform an internal and external detailed visual and an eddy current inspection of the modified area to detect cracks in accordance with the service bulletin. Repeat the inspections at intervals not to exceed 3,800 flight cycles. 

## Repair 

(f) If any cracking is detected during any inspection required by paragraph (e)(1) or (e)(2) of this AD: Prior to further flight, repair any cracks detected in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; 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 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 Manager's approval letter must specifically reference this AD. 

## Alternative Methods of Compliance 

(g)(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 83-02-09, amendment 39-4549, are approved as alternative methods of compliance with this AD. 

# Note 3:

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

# Note 4:

Incorporation of the Boeing Model 707-720 Supplemental Structural Inspection Document (SSID) into the operator's approved airplane maintenance program constitutes an approved alternative method of compliance for Model 707 and 720 series airplanes. 

## Special Flight Permits 

(h) Special flight permits may be issued in accordance with 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 April 13, 2000. 

Charles D. Huber, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-9821 Filed 4-18-00; 8:45 am] 

BILLING CODE 4910-13-U