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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-377-AD] 
          - RIN 2120-AA64 

# 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 747 series airplanes. This proposal would require inspections to detect cracking of the frame web, doubler, and inner chord of the forward edge frame of main entry door number 1, and various follow-on actions. This proposal is prompted by reports of cracking in the frame web, doubler, inner chord, and strap of the forward edge frame of main entry door number 1. The actions specified by the proposed AD are intended to prevent cracks in the frame web and doubler of the forward edge frame of main entry door number 1, which could result in inability of the edge frame to react door stop loads, and consequent rapid depressurization of the airplane. 

# DATES:

Comments must be received by July 31, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-377-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. 

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:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; 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-377-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-377-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

                    The FAA has received reports indicating that cracking has been detected in the frame web, doubler,                           ( print page 37498)                        inner chord, and strap of the forward edge frame of main entry door number 1 on several Boeing Model 747 series airplanes. One operator reported that the frame web, doubler, inner chord, and strap were severed at the lower sill. Cracks initiated in the frame web at the fastener holes where the sill attach clip attaches to the frame web. Other operators have reported small cracks in the frame web and doubler at the cable penetration just below the lower sill. On certain Boeing Model 747 series airplanes, the subject frame web, doubler, and inner chord are made from 7075 aluminum. Fatigue cracks in the frame web and doubler of the forward edge frame of main entry door number 1, if not detected, could extend to the inner chord of the frame and cause the inner chord to break, leading to failure of the outer chord and adjacent fuselage skin. This condition, if not corrected, could result in inability of the edge frame to react door stop loads, and consequent rapid depressurization of the airplane.                 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Service Bulletin 747-53A2417, Revision 1, dated July 23, 1998, which describes procedures for detailed visual and high frequency eddy current (HFEC) inspections to detect cracking of the frame web, doubler, and inner chord of the forward edge frame of main entry door number 1, and various follow-on actions. If no cracking is detected, follow-on actions include repetitive detailed visual and HFEC inspections, reinforcement of the forward edge frame and repetitive detailed visual inspections, and eventual repair of the door frame. If any cracking is detected, the repair is required prior to further flight. The repair includes replacement of the existing frame web and doubler with a new frame web, doubler, and splice doubler made of 2024-T3 aluminum, which is a more fatigue-resistant material than 7075 aluminum. Accomplishment of the repair eliminates the need for the repetitive inspections described by the service bulletin. 

## 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 accomplishment of the actions specified in the service bulletin described previously, except as discussed below. 

## Difference Between This Proposed AD and Service Information 

As described previously, the service bulletin describes procedures for detailed visual and HFEC inspections to detect cracking of the frame web, doubler, and inner chord of the forward edge frame of main entry door number 1. Operators should note that paragraph (c) of this proposed AD also would require certain repetitive detailed visual inspections not described in the service bulletin. These additional inspections are prompted by two reports that cracking was detected outside the area covered by the service bulletin. As a result of the reports, the FAA has determined that it is necessary to propose additional repetitive inspections. These additional inspections involve removal of the cover assembly for the body torque tube located between the door hinge attachments, and accomplishment of a detailed visual inspection to detect cracking of the aft side of the forward edge door frame web of main entry door number 1. The area to be inspected includes the exposed area from doorstop #2 [approximately water line (WL) 218] to doorstop #5 (approximately WL 245) at body station 434. 

## Cost Impact 

There are approximately 685 airplanes of the affected design in the worldwide fleet. The FAA estimates that 211 airplanes of U.S. registry would be affected by this proposed AD. 

For Group 1 airplanes (approximately 191 U.S.-registered airplanes), it would take approximately 3 work hours per airplane to accomplish the proposed inspections, 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 of Group 1 airplanes is estimated to be $34,380, or $180 per airplane, per inspection cycle. 

For Group 2 airplanes (approximately 20 U.S.-registered airplanes), it would take approximately 2 work hours per airplane to accomplish the proposed inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators of Group 2 airplanes is estimated to be $2,400, or $120 per airplane, per inspection cycle. 

For Group 1 airplanes (approximately 191 U.S.-registered airplanes), it would take approximately 128 work hours per airplane to accomplish the proposed repair, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed repair on U.S. operators of Group 1 airplanes is estimated to be $1,466,880, or $7,680 per airplane. 

For Group 2 airplanes (approximately 20 U.S.-registered airplanes), it would take approximately 64 work hours per airplane to accomplish the proposed repair, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators of Group 2 airplanes is estimated to be $76,800, or $3,840 per airplane. 

The cost impact figures discussed above are 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. 

Should an operator elect to accomplish the reinforcement of the door frame on a Group 1 airplane, it would take approximately 9 work hours per airplane to accomplish the reinforcement, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the reinforcement on a Group 1 airplane is estimated to be $540 per airplane. 

Should an operator elect to accomplish the reinforcement of the door frame on a Group 2 airplane, it would take approximately 5 work hours per airplane to accomplish the reinforcement, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the reinforcement on a Group 2 airplane is estimated to be $300 per airplane. 

## 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.**

      ( print page 37499)    

# 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 adding the following new airworthiness directive: 

**Boeing:**                                 Docket 99-NM-377-AD.                             

*Applicability:*                                Model 747 series airplanes, line numbers 1 through 685 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 (g) 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 frame web and doubler of the forward edge frame of main entry door number 1, which could result in inability of the edge frame to react door stop loads, and consequent rapid depressurization of the airplane, accomplish the following: 

## Initial Inspection: Compliance Time 

(a) At the time specified in paragraph (a)(1), (a)(2), (a)(3), or (a)(4); as applicable; accomplish the requirements of paragraphs (b) and (c) of this AD. 

(1) For airplanes that have accumulated fewer than 13,000 total flight cycles as of the effective date of this AD: Inspect prior to the accumulation of 13,000 total flight cycles, or within 1,500 flight cycles after the effective date of this AD, whichever occurs later. 

(2) For airplanes that have accumulated 13,000 or more total flight cycles but fewer than 20,000 total flight cycles as of the effective date of this AD: Inspect prior to the accumulation of 21,000 total flight cycles, or within 1,500 flight cycles after the effective date of this AD, whichever occurs first. 

(3) For airplanes that have accumulated 20,000 or more total flight cycles but fewer than 25,000 total flight cycles as of the effective date of this AD: Inspect prior to the accumulation of 25,500 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs first. 

(4) For airplanes that have accumulated 25,000 or more total flight cycles as of the effective date of this AD: Inspect within 500 flight cycles after the effective date of this AD. 

## Initial Detailed Visual and High Frequency Eddy Current Inspections 

(b) Perform a detailed visual inspection and a high frequency eddy current inspection of the frame web, doubler, and inner chord of the forward edge door frame to detect cracking of main entry door number 1, in accordance with Boeing Service Bulletin 747-53A2417, Revision 1, dated July 23, 1998. For Group 1 airplanes (as identified in the service bulletin), accomplish the inspections on the left and right sides of the airplane. For Group 2 airplanes (as identified in the service bulletin), accomplish the inspections on the left side of the airplane only. 

# Note 2: 

For the purposes of this AD, it is not necessary to count flight cycles accumulated at 2.0 pounds per square inch or less differential pressure.

# Note 3: 

Inspections, reinforcements, and repairs accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-53A2417, dated June 25, 1998, are considered acceptable for compliance with paragraph (b) of this AD. 

# Note 4: 

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.” 

## Repetitive Detailed Visual Inspections (No Terminating Action) 

(c) Remove the cover assembly for the body torque tube located between the door hinge attachments. Perform a detailed visual inspection to detect cracking of the aft side of the forward edge door frame web of main entry door number 1 in the exposed area from doorstop #2 [approximately water line (WL) 218] to doorstop #2 (approximately WL 245) at body station 434. Pay particular attention to the row of fasteners that attach the frame web to the frame outer chord. After completing inspections, replace the cover assembly. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles. 

# Note 5: 

The inspections required by paragraph (c) of this AD are not described in Boeing Service Bulletin 747-53A2417, Revision 1, dated July 23, 1998.

# Note 6: 

There is no terminating action currently available for the inspections required by paragraph (c) of this AD.

## Repetitive Inspections/Reinforcement/Repair (No Cracks Detected) 

(d) If no crack is detected during the inspection required by paragraph (b) of this AD, prior to further flight, oversize fastener holes in accordance with Boeing Service Bulletin 747-53A2417, Revision 1, dated July 23, 1998, and accomplish the requirements of paragraph (d)(1), (d)(2), or (d)(3) of this AD. 

(1) Repeat the inspections specified in paragraph (b) of this AD one time within 3,000 flight cycles. Within 3,000 flight cycles after accomplishment of the repeat inspection, accomplish paragraph (d)(2) or (d)(3) of this AD. 

(2) Reinforce the door frame, in accordance with Figure 5 of the service bulletin. Thereafter, at intervals not to exceed 3,000 flight cycles, perform a detailed visual inspection to detect cracks of the forward and aft side of the frame, in accordance with Figure 6 of the service bulletin. Within 10,000 flight cycles after the reinforcement, accomplish the requirements of paragraph (d)(3) of this AD. 

(3) Accomplish the web replacement repair (“Terminating Action”) in accordance with the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of paragraphs (d)(1) and (d)(2) of this AD. 

## Repair (Cracks Detected) 

(e) If any crack is detected during any inspection required by paragraph (b), (d)(1), or (d)(2) of this AD, prior to further flight, accomplish the repair (“Terminating Action”) in accordance with Boeing Service Bulletin 747-53A2417, Revision 1, dated July 23, 1998. Such repair constitutes terminating action for the repetitive inspection requirements of paragraphs (d)(1) and (d)(2) of this AD. 

## Repair 

(f) If any cracking is detected during the inspection required by paragraph (c) of this AD, prior to further flight, repair 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 (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 7: 

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
      ( print page 37500)    

## 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 June 9, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-15190 Filed 6-14-00; 8:45 am] 

BILLING CODE 4910-13-U