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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-208-AD; Amendment 39-11777; AD 2000-11-28] 
          - 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 747-400 and 767-200 and -300 series airplanes, that requires repetitive inspections to detect damage and wear of the auxiliary track assembly of the thrust reverser, and corrective actions, if necessary. This amendment also requires eventual repair of the auxiliary track assembly, or replacement of the slider and liner or the entire assembly, with new, improved parts, which, when accomplished, would terminate the repetitive inspections. This amendment is prompted by reports of damage and wear to the auxiliary track assembly. The actions specified by this AD are intended to prevent a slider disengaging from the auxiliary track assembly, which could lead to separation of a portion of the thrust reverser from the airplane during flight, possible impact of separated portions on airplane structure, and consequent possible rapid decompression of the airplane, reduced controllability of the airplane, or reduced structural integrity of the fuselage. 

# DATES:

Effective July 18, 2000. 

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 18, 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:

Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2686; 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 747-400 and 767-200 and -300 series airplanes was published in the                     **Federal Register**                     on October 19, 1999 (64 FR 56276). That action proposed to require repetitive inspections to detect damage and wear of the auxiliary track assembly of the thrust reverser, and corrective actions, if necessary. That action also proposed to require eventual replacement of the liner and slider, or the entire assembly, with new, improved parts, which, when accomplished, would terminate the repetitive inspections.                 

## 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. 

One commenter supports the proposed rule. 

## Request To Revise Certain Requirements in the Proposed AD 

Several commenters indicate that they disagree with the proposed replacement of the auxiliary track beam assembly, including installation of a new slider and liner, regardless of the amount of wear and/or damage to the track beam. The commenters request that repair of the track beam be allowed when the damage is within the allowable limits specified in the referenced service information. One commenter states that replacement of the track beam fitting is required only when the wear or damage is beyond repairable limits, as specified in Boeing Service Bulletin 747-78A2164, Revision 2, and Boeing Service Bulletin 767-78A0079, Revision 2. The commenter notes that replacement of the track beam fitting in and of itself does nothing to address the root cause of the excessive wear; however, the new design slider fitting and track liner do address and correct the root cause. A second commenter states that the service bulletins specify replacement of the track beam assembly if the track beam has any discrepancy AND the measurement of the gap is greater than 0.45 inch. If the track beam has any discrepancy and the gap measurement is less than 0.45 inch, only the slider and liner should be replaced. Another commenter states that replacement of the track beam assembly is necessary only when damage cannot be repaired by means of replacement of the liner, slider, and/or retainer bar. 

The FAA concurs with the commenters' requests. The FAA has coordinated this issue with the manufacturer, and has determined that if the damage to the track beam assembly is not beyond the repairable limits specified in the referenced service bulletins, a repair that involves replacement of the slider and liner and installation of a retainer bar, in lieu of replacement of the track beam assembly, is acceptable. Therefore, paragraphs (a) and (c) of this AD have been revised to specify measuring the auxiliary track beam dimensions in accordance with the Accomplishment Instructions of the referenced service bulletins, and to allow repair if the measurement is within the allowable limits. 

## Request To Revise Cost Impact Information 

One commenter states that the total number of U.S.-registered Model 747-400 series airplanes affected by the proposed AD should be higher than the 12 airplanes shown in the cost impact section. The commenter indicates that it has 10 affected airplanes in its fleet and assumes that other operators also have Model 747-400 series airplanes that are affected by the proposal. 

The FAA concurs. The referenced service bulletin specifies a total of 36 Model 747-400 series airplanes of U.S.-registry that are powered by Pratt & Whitney PW4000 series engines. In light of this information, the FAA has revised the cost impact information, below, to specify that 36 Model 747-400 series airplanes of U.S. registry will be affected by this AD. 

## Request for Credit for Previously Accomplished Work 

                    One commenter requests credit for prior accomplishment of work done in                           ( print page 37023)                        accordance with Boeing Service Bulletin 747-78A2164, dated June 19, 1997, including Revision 1, dated February 5, 1998; and 767-78A0079, dated June 19, 1997, including Revision 1, dated February 5, 1998; which were previously issued revisions of the service bulletins referenced in the proposed rule as the appropriate sources of service information for accomplishment of the actions in the proposal. The commenter states that it incorporated the inspection and terminating actions described in the above service bulletins on two-thirds of its fleet beginning in June 1997. Additionally, the commenter states that the proposed rule requires different terminating action than the original and Revision 1 of the service bulletins specify.                 

The FAA partially concurs with the commenter's request. The FAA has determined that there are significant differences between Revision 2 of the service bulletins and the original issue. The accomplishment instructions in Revision 2 provide more detailed information about how to perform the inspections, and are more specific regarding the extent of damage permitted before accomplishing repair work. Therefore, the FAA cannot give credit for work accomplished in accordance with the original issue of the service bulletin. However, for any procedure which an operator has accomplished previously, the operator may request approval of an alternative method of compliance in accordance with the provisions of paragraph (d) of this AD. 

Revision 1 of the service bulletin is essentially identical to Revision 2, which was cited in the proposed AD as the appropriate source of service information for accomplishment of the required actions. Revision 2 simply changes the recommended repetitive inspection interval for detection of no wear or damage. Therefore, this final rule has been revised to add a new NOTE 4 to include Revision 1 of the referenced service bulletins as an additional source of service information for accomplishment of the actions. 

## Request To Extend Compliance Time and Revise Proposed Inspection 

One commenter states that the results of a survey of operators of Model 747 and 767 series airplanes powered by Pratt & Whitney PW4000 series engines, which was conducted by the manufacturer in January 1998, revealed that the most significant wear occurs on the lower auxiliary track assembly. The commenter recommends that the inspection only pertain to that assembly. The commenter also requests that the FAA extend the grace period for inspection of the upper and lower auxiliary track assemblies from 90 days to 18 months for the reason stated previously. 

The FAA does not concur with the commenter's requests. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but accomplishment of the required inspection within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. However, under the provisions of paragraph (d) of the final rule, the FAA may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety. 

In addition, the inspection required by paragraph (a) of the final rule is required to be accomplished in accordance with the inspection procedures specified in Boeing Service Bulletin 747-78A2164, Revision 2, dated December 3, 1998; or Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3, 1998; as applicable. Inspection of only the lower auxiliary track assembly is inadequate, in light of the fact that service experience accumulated over time has shown that excessive wear and damage are present in both the upper and lower auxiliary track assemblies. Therefore, no change to the final rule is necessary in this regard. 

## Other Related Service Information 

One commenter recommends that the FAA include the actions specified in Boeing Service Bulletins 767-78-0005, 767-78-0037, and 767-78-0039 in the proposed rule as additional requirements. These service bulletins describe the replacement of the aluminum auxiliary slider fittings of the original design with new design steel fittings, on Model 767 series airplanes powered by General Electric CF6-80A and Pratt & Whitney JT9D-7R4D series engines. The commenter states that cracking of the aluminum fittings due to fatigue loading could result in breakage of the slider and subsequent separation of a portion of the thrust reverser from the airplane, which could lead to an unsafe condition similar to that addressed in the proposed AD. 

The FAA does not concur with the commenter's recommendation. The FAA has determined that since the suggested changes would alter the actions currently required by this AD, additional rulemaking would be required. The FAA finds that to delay this action would be inappropriate in light of the identified unsafe condition. However, the FAA will discuss this issue with the manufacturer at a later date; therefore, no change to the final rule is necessary. 

## 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 254 airplanes of the affected design in the worldwide fleet. The FAA estimates that 36 Model 747-400 series airplanes and 46 Model 767-200 and -300 series airplanes of U.S. registry will be affected by this AD. 

It will take approximately 4 work hours per engine to accomplish the required repetitive inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators of Model 747-400 series airplanes (4 engines per airplane) is estimated to be $34,560, or $960 per airplane, per inspection cycle. The cost impact of the AD on U.S. operators of Model 767 series airplanes (2 engines per airplane) is estimated to be $22,080, or $480 per airplane, per inspection cycle. 

Should an operator be required to accomplish the replacement of the auxiliary track assembly, it would take approximately 220 work hours per auxiliary track assembly to accomplish the replacement, at an average labor rate of $60 per work hour. Required parts would cost approximately $30,090. Based on these figures, the cost impact of this replacement is estimated to be $43,290 per assembly. There are four auxiliary track assemblies per engine. 

Should an operator be required to accomplish the replacement of the liner and slider, it would take approximately 8 work hours per auxiliary track assembly to accomplish the replacement, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of this replacement is estimated to be $480 per assembly. There are four auxiliary track assemblies per engine. 

                    The cost impact figures discussed above are based on assumptions that no                           ( print page 37024)                        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.                 

## 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 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: 

**2000-11-28 Boeing:**                                 Amendment 39-11777. Docket 99-NM-208-AD.                             

*Applicability:*                                 Model 747-400 series airplanes powered by Pratt & Whitney PW4000 series engines, line numbers 696 through 1100 inclusive; and Model 767-200 and -300 series airplanes powered by Pratt & Whitney PW4000 series engines, line numbers 1 through 646 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 (d) 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 a slider disengaging from the auxiliary track assembly, which could lead to separation of a portion of the thrust reverser from the airplane during flight, possible impact of separated portions on airplane structure, and consequent possible rapid decompression of the airplane, reduced controllability of the airplane, or reduced structural integrity of the fuselage, accomplish the following: 

## Initial Inspection 

(a) Prior to the accumulation of 3,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later, perform a detailed visual inspection of the upper and lower auxiliary track assemblies on each thrust reverser half of each engine to detect missing segments of the track lip; to detect signs that the slider has disengaged from the track; to detect cracks, gouges, and wear of the liner; and measure the auxiliary track beam dimensions; in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-78A2164, Revision 2, dated December 3, 1998 (for Model 747-400 series airplanes); or Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3, 1998 (for Model 767 series airplanes); as applicable. 

# 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.” 

## Repetitive Inspections/Corrective Actions 

(1) If no discrepancy is detected, repeat the detailed visual inspection thereafter at intervals not to exceed 3,000 flight cycles or 7,000 flight hours, whichever occurs earlier, until paragraph (b) or (c), as applicable, has been accomplished. 

(2) If the auxiliary track lip has a missing segment of 3 inches or longer, or longitudinal cracks at the base of the lip, or other indications that the slider has disengaged from the track in the forward 4 inches, prior to further flight, repair in accordance with Part A of the Accomplishment Instructions of the applicable service bulletin. Repeat the detailed visual inspection thereafter at the applicable intervals specified in Part A of the Accomplishment Instructions of the applicable service bulletin, until paragraph (c) of this AD has been accomplished. 

(3) If the auxiliary track lip has a missing segment of 3 inches or longer, or longitudinal cracks at the base of the lip, or other indications that the slider has disengaged from the track AFT of the forward four inches, accomplish paragraphs (a)(3)(i) or (a)(3)(ii) of this AD. 

(i) Prior to further flight, repair in accordance with Part B of the Accomplishment Instructions of the applicable service bulletin. Repeat the detailed visual inspection thereafter at the applicable intervals specified in Part B of the Accomplishment Instructions of the applicable service bulletin, until paragraph (c) of this AD has been accomplished. 

(ii) Accomplish both paragraphs (a)(3)(ii)(A) and (a)(3)(ii)(B) of this AD: 

(A) Prior to further flight, deactivate the associated thrust reverser in accordance with Section 78-2 of Boeing Document D6U10151, “Boeing 747-400 Dispatch Deviations Guide,” Revision 11, dated March 31, 1998 (for Model 747-400 series airplanes); or Section 78-2 of Boeing Document D630T002, “Boeing 767 Dispatch Deviations Guide,” Revision 19, dated May 14, 1999 (for Model 767 series airplanes); as applicable. No more than one thrust reverser on any airplane may be deactivated under the provisions of the paragraph. 

# Note 3:

The airplane may be operated for up to 30 days in accordance with the provisions and limitations specified in the operator's FAA-approved Master Minimum Equipment List, provided that no more than one thrust reverser on the airplane is inoperative.

(B) Within 30 days after deactivation of any thrust reverser in accordance with paragraph (a)(3)(ii)(A) of this AD, the thrust reverser must be repaired in accordance with the Accomplishment Instructions of the applicable service bulletin; once this is accomplished, the thrust reverser may then be reactivated. Repeat the detailed visual inspection thereafter at the applicable intervals specified in the Accomplishment Instructions of the applicable service bulletin, until paragraph (c) of this AD has been accomplished. 

## Terminating Action 

                                (b) For any auxiliary track assembly on which no discrepancy is detected during any detailed visual inspection required by paragraph (a) of this AD: Replace the liner and slider of the auxiliary track assembly with a new, improved liner and slider, in accordance with Part A of the Accomplishment Instructions of Boeing Service Bulletin 747-78A2164, Revision 2, dated December 3, 1998 (for Model 747-400 series airplanes); or Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3, 1998 (for Model 767 series airplanes); as applicable; at the later of the times specified in paragraphs (b)(1) and (b)(2) of this AD. Such action constitutes terminating action for the requirements of this AD for that assembly.                                       ( print page 37025)    

(1) Within 6,000 flight cycles, 14,000 flight hours, or 5 years after the date of the first inspection, whichever occurs earliest; or 

(2) Within 4 years after the effective date of this AD. 

(c) For any auxiliary track assembly on which any discrepancy is detected during any detailed visual inspection required by paragraph (a) of this AD: Repair the auxiliary track assembly (replace the slider and liner and install a retainer bar), or replace with a new, improved assembly (including a new liner and slider), as applicable, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-78A2164, Revision 2, dated December 3, 1998 (for Model 747-400 series airplanes); or Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3, 1998 (for Model 767 series airplanes); as applicable; at the later of the times specified in paragraphs (c)(1) and (c)(2) of this AD. Such action constitutes terminating action for the requirements of this AD for that assembly. 

(1) Within 4,500 flight cycles, 10,000 flight hours, or 3 years after the date of the first repair, whichever occurs earliest; or 

(2) Within 2 years after the effective date of this AD. 

# Note 4:

Inspections and repairs accomplished prior to the effective date of this AD in accordance with Boeing Service Bulletin 747-78A2164, Revision 1, or Boeing Service Bulletin 767-78A0079, Revision 1, both dated February 5, 1998; are considered acceptable for compliance with the applicable actions specified in this AD. 

## Alternative Methods of Compliance 

(d) 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 Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. 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 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 

(e) 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 

(f) Except as provided by paragraph (a)(3)(ii)(A) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 747-78A2164, Revision 2, dated December 3, 1998; or Boeing Service Bulletin 767-78A0079, Revision 2, dated December 3, 1998; as applicable. 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. 

(g) This amendment becomes effective on July 18, 2000.

Issued in Renton, Washington, on June 2, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-14436 Filed 6-12-00; 8:45 am] 

BILLING CODE 4910-13-P