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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-307-AD; Amendment 39-11759; AD 2000-11-11] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Final rule. 

# SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 777-200 series airplanes, that requires one-time inspections to detect cracking of the aft wheel well bulkhead, corrective actions, if necessary, and modification of the aft wheel well bulkhead. For certain airplanes, this AD also requires a one-time visual inspection to detect excess sealant covering the outer flange of the side fitting and lower chord and splice area of the aft wheel well bulkhead, and corrective actions, if necessary. This amendment is prompted by a report indicating that numerous fatigue cracks were found in the aft wheel well bulkhead. The actions specified by this AD are intended to prevent fatigue cracking of the aft wheel well bulkhead, which could result in rapid in-flight decompression of the airplane. 

# DATES:

Effective July 10, 2000. 

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 10, 2000. 

# ADDRESSES:

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. 

# FOR FURTHER INFORMATION CONTACT:

Stan Wood, Aerospace Engineer,  Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2772; fax (425) 227-1181. 

# SUPPLEMENTARY INFORMATION:

                    A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes was published in the                     **Federal Register**                     on November 26, 1999 (64 FR 66426). That action proposed to require one-time inspections to detect cracking of the aft wheel well bulkhead, and corrective actions, if necessary. That action also proposed to require modification of the aft wheel well bulkhead. For certain airplanes, that action also proposed to require a one-time visual inspection to detect excess sealant covering the outer flange of the side fitting and lower chord and splice area of the aft wheel well bulkhead, and corrective actions, if necessary.                 

## Explanation of Relevant Service Information 

                    Since the issuance of the notice of proposed rulemaking (NPRM), the FAA has reviewed and approved Boeing Service Bulletin 777-53A0015, Revision 1, dated March 2, 2000. (The original issue of the service bulletin, dated June 17, 1999, is referenced in the NPRM as the appropriate source of service information for accomplishment of the proposed actions.) The procedures described in Revision 1 of the service bulletin are similar to those in the original issue, and Revision 1 adds no new airplanes to the effectivity listing. Therefore, paragraphs (a), (b), and (d) of                           ( print page 35564)                        this final rule have been revised to reference Revision 1 as the appropriate source of service information for accomplishment of the actions required by those paragraphs. In addition, a new “NOTE 3” has been added to this final rule to specify that actions accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 777-53A0015, dated June 17, 1999, are considered acceptable for compliance with this AD.                 

## Comments 

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. 

## Fleet Not Affected 

On behalf of one of its members, the Air Transport Association of America (ATA) comments that none of the airplanes operated by that member would be affected by the proposal. The ATA offers no further comment and makes no request. 

## Request To Revise Compliance Time: Paragraph (a)(2) 

One commenter requests that the FAA revise paragraph (a)(2) of the proposed rule to specify that removal of excess sealant from the aft wheel well bulkhead area is not required until accomplishment of the inspections specified in paragraph (b) of the proposed rule. [Paragraph (a)(2) of the proposed rule states that, if any excess sealant is found, it must be removed from the aft wheel well bulkhead area prior to further flight.] The commenter points out that the excess sealant is of concern because it can impede the inspections to detect fatigue cracking that are specified in paragraph (b) of the proposed rule, but the excess sealant on its own poses no threat to the continued safe operation of an airplane. 

The FAA does not concur with the commenter's request. The compliance time is the same for the requirements of both paragraphs (a) and (b). Therefore, the FAA expects the requirements of these paragraphs will be accomplished at the same time. No change to the final rule is necessary in this regard. 

## Request To Remove Airplane from Effectivity 

One commenter requests that the FAA revise the applicability of the proposed rule to delete the airplane having line number 1. The commenter states that this airplane is owned by the manufacturer and is operated in accordance with an experimental airworthiness certificate. The commenter asserts that this airplane does not accumulate enough flight cycles to develop significant fatigue cracking of the aft wheel well bulkhead. The commenter also states that, if the airplane is sold, the manufacturer will incorporate a design change equivalent to the requirements of this AD prior to delivery. The commenter claims that inclusion of the subject airplane in the applicability of this AD will “introduce additional unnecessary complications in obtaining certification of this airplane.” 

The FAA does not concur with the commenter's request. Though the airplane is operated in accordance with an experimental airworthiness certificate, the airplane is still subject to the unsafe condition addressed in this AD. Based on the current utilization of the airplane, the FAA acknowledges that it may be some time before the airplane will be required to be in compliance with this AD. However, eventually, the airplane must be inspected and modified in accordance with this AD, or modified with a design change that will provide an equivalent level of safety. Any design change that the manufacturer develops in lieu of the actions required by this AD must be approved as an alternative method of compliance in accordance with paragraph (e) of this AD. No change to the final rule is necessary in this regard. 

## Request To Revise Compliance Time:  Paragraph (d) 

One commenter requests that the compliance time stated for removal of excess sealant specified in paragraph (d) of the proposed rule be revised from “prior to further flight” to “prior to the threshold specified for fatigue inspections in Section 9 of the 777 Maintenance Planning Document [MPD]. . . .” The commenter states that the removal of the excess sealant in the area described in paragraph (d) of the proposed rule is intended to allow the fatigue inspections specified in Section 9 of the MPD to be properly conducted. The commenter states that the paragraph, as worded in the proposed rule, “can be interpreted to mean that the sealant must be removed to facilitate fatigue inspection of these areas at 11,000 flights.” Further, the commenter states, “There is no data to suggest that these areas would be subject to significant fatigue cracking earlier than the threshold specified in the MPD (currently 30,000 flights for all Structures items).” 

The FAA does not concur with the commenter's request. Excess sealant may impede detection of unexpected damage during general visual inspections performed as part of routine maintenance. Thus, the FAA finds it is necessary to require the sealant to be removed prior to further flight after accomplishment of the modification in accordance with paragraph (b) of this AD. No change to the final rule is necessary in this regard. 

## Conclusion 

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. 

## Cost Impact 

There are approximately 109 Boeing Model 777-200 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 35 airplanes of U.S. registry will be affected by this AD. 

For all airplanes, it will take approximately 2 work hours per airplane to accomplish the required general visual and HFEC inspections at an average labor rate of $60 per work hour. Based on these figures, the cost impact of these inspections on U.S. operators is estimated to be $4,200, or $120 per airplane. 

For all airplanes, it will take approximately 28 work hours per airplane to accomplish the required modification at an average labor rate of $60 per work hour. Required parts will cost approximately $6,013 per airplane. Based on these figures, the cost impact of the modification on U.S. operators is estimated to be $269,255, or $7,693 per airplane. 

For certain airplanes, it will take 3 work hours per airplane to accomplish the inspection to detect excess sealant at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection on U.S. operators is estimated to be $180 per airplane. 

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the 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 adopted herein will 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                           ( print page 35565)                        determined that this final rule does not have federalism implications under Executive Order 13132.                 

                    For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption                     **ADDRESSES**                    .                 

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - Safety

## Adoption of the Amendment 

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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: 

**2000-11-11 Boeing:**                             Amendment 39-11759. Docket 99-NM-307-AD.                         

*Applicability:*                            Model 777-200 series airplanes having line numbers 1 through 144; certificated in any category.                         

# 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 (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 prevent fatigue cracking of the aft wheel well bulkhead, which could result in rapid in-flight decompression of the airplane, accomplish the following: 

## General Visual Inspection 

(a) For Group 1 airplanes, as identified in Boeing Service Bulletin 777-53A0015, Revision 1, dated March 2, 2000: Prior to the accumulation of 11,000 total flight cycles, or within 4,000 flight cycles after the effective date of this AD, whichever occurs later, perform a one-time general visual inspection to detect excess sealant covering the outer flange of the side fitting and lower chord and splice of the aft wheel well bulkhead, in accordance with Part I of the Accomplishment Instructions of the service bulletin.

# Note 2:

For the purposes of this AD, a general visual inspection is defined as: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or drop-light, and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.” 

# Note 3:

Inspections and modifications accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 777-53A0015, dated June 17, 1999, are considered acceptable for compliance with paragraphs (a), (b), and (d) of this AD. 

(1) If no excess sealant is detected, no further action is required by this paragraph. 

(2) If any excess sealant is detected, prior to further flight, remove the excess sealant from the aft wheel well bulkhead area in accordance with the service bulletin. 

## Inspections/Modification 

(b) For Groups 1 and 2 airplanes, as identified in Boeing Service Bulletin 777-53A0015, Revision 1, dated March 2, 2000: Prior to the accumulation of 11,000 total flight cycles, or within 4,000 flight cycles after the effective date of this AD, whichever occurs later, perform a one-time general visual inspection to detect cracking of the adjacent structure of the aft wheel well bulkhead and perform a one-time high frequency eddy current (HFEC) inspection to detect cracking of the fastener holes in the web, side fitting, and outer chord of the aft wheel well bulkhead, in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

(1) If no cracking is detected during the general visual and HFEC inspections, prior to further flight, modify the aft wheel well bulkhead (including cold working; replacing the fairing support bracket and splice plates with revised fairing support brackets and splice plates; and installing new web doublers and, if necessary, shims), in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

(2) If any cracking is detected during the general visual inspection, prior to further flight, accomplish the requirements of paragraph (c) of this AD. 

(3) If any cracking is detected during the one-time HFEC inspection, prior to further flight, remove additional fasteners, and perform a second HFEC inspection to detect cracking of the fastener holes, in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

(i) If no cracking is detected during the second HFEC inspection, prior to further flight, oversize all the holes to the diameter specified in the service bulletin, and perform a third HFEC inspection to detect cracking of the fastener holes, in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

(A) If no cracking is detected during the third HFEC inspection, prior to further flight, replace the fasteners with new fasteners and modify the aft wheel well bulkhead (including cold working; replacing the fairing support bracket and splice plates with revised fairing support brackets and splice plates; and installing new web doublers and, if necessary, shims), in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

(B) If any cracking is detected during the third HFEC inspection, prior to further flight, accomplish the requirements of paragraph (c) of this AD. 

(ii) If any cracking is detected during the second HFEC inspection, prior to further flight, accomplish the requirements of paragraph (c) of this AD. 

## Repair 

(c) For airplanes on which cracking has been detected during any inspection required by paragraph (b)(2), (b)(3)(i)(B), or (b)(3)(ii) of this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Airplane 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. 

## Removal of Excess Sealant 

(d) For Group 1 airplanes, as identified in Boeing Service Bulletin 777-53A0015, Revision 1, dated March 2, 2000, on which excess sealant was detected and removed in accordance with paragraph (a) of this AD: Prior to further flight following the accomplishment of the modification required by paragraph (b) of this AD, remove any excess sealant in the remaining area of the lower lobe of the aft wheel well bulkhead between stringers S-27L and S-27R, in accordance with the service bulletin. 

## Alternative Methods of Compliance 

                            (e) 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                                   ( print page 35566)                                comments and then send it to the Manager, Seattle ACO.                         

# Note 4:

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 

(f) 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. 

## Incorporation by Reference 

                            (g) Except as provided by paragraph (c) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 777-53A0015, Revision 1, dated March 2, 2000. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the                             **Federal Register**                            , 800 North Capitol Street, NW., suite 700, Washington, DC.                         

(h) This amendment becomes effective on July 10, 2000. 

Issued in Renton, Washington, on May 24, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-13565 Filed 6-2-00; 8:45 am] 

BILLING CODE 4910-13-U