Airworthiness directives: Boeing,
[Federal Register: May 28, 1999 (Volume 64, Number 103)]
[Rules and Regulations]
[Page 28901-28905]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr28my99-4]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-89-AD; Amendment 39-11183; AD 99-11-12]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-400 Series Airplanes Powered by Pratt & Whitney PW4000 Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that requires repetitive inspections to ensure proper installation of the engine thrust link components, and follow-on corrective action, if necessary; and replacement of the forward engine mount end cap assembly with an improved end cap assembly. Such replacement, when accomplished, will terminate the repetitive inspections. This amendment is prompted by a report of fatigue cracking of end cap bolts, caused by improper installation. Subsequent
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investigation revealed that properly installed end caps also are subject to early fatigue cracking. The actions specified by this AD are intended to prevent failure of the end cap assembly, which could lead to separation of the engine from the airplane in the event of a primary thrust linkage failure.
DATES: Effective July 2, 1999.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 2, 1999.
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: Tamara L. Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2771; 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 series airplanes was published in the Federal Register on May 20, 1998 (63 FR 27685). That action proposed to require repetitive inspections to detect improper installation and fatigue damage of the end cap of the forward engine mount, and replacement of the forward engine mount end cap assembly with an improved end cap assembly.
Clarification of the Rule
Since the issuance of the notice of proposed rulemaking (NPRM), the FAA has clarified certain wording in the final rule to more accurately describe the inspection requirements, which include the actions required and the components to be inspected. The Summary of the proposed AD states that repetitive inspections are required ``to detect improper installation and fatigue damage of the end cap of the forward engine mount. * * *'' However, the final rule states that repetitive inspections are required ``to ensure proper installation of the engine thrust link components, and follow-on corrective action, if necessary. * * *''
The FAA considers that such clarification of the inspection requirements is necessary for several reasons. First, the FAA has determined that requiring operators ``to ensure proper installation,'' rather than ``to detect improper installation,'' more accurately describes the action required for the inspection. Second, the FAA points out that ``fatigue damage of the end cap,'' which involves the secondary load path, could not be detected until the forward engine mount was disassembled. In addition, the inspections specified by Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996, are inspections of the ``engine thrust link components,'' not the ``end cap'' itself. This inspection requirement also was clear in the proposed rule, which correlated the corrective action to the presence or absence of damage to the engine thrust link components. Therefore, the FAA has deleted ``fatigue damage'' from the inspection requirements and has changed ``end cap'' to ``engine thrust link components.'' The FAA adds that the engine thrust link components, which involve the primary load path, can be inspected with no disassembly of the forward engine mount required. The Summary and paragraph (a)(1) of the final rule have been clarified accordingly.
In addition, although it is implied in the proposed AD that the FAA requires any discrepancy or damage to be repaired by taking corrective action, the FAA has clarified this requirement in the final rule. The first sentence of the Summary of this AD now includes ``and follow-on corrective action, if necessary.''
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 states that it is not affected by the proposal because it does not operate the affected airplanes. Another commenter generally supports the proposal.
Request to Withdraw the Proposed AD
One commenter states that ``regulatory action mandating incorporation of Boeing Alert Service Bulletin 747-71A2283 [dated October 10, 1996] is unwarranted for PW4000 powered 747 aircraft.'' That commenter also states that this alert service bulletin was issued on the basis of one report of a broken end cap bolt by one operator of a Model 747-400 series airplane. In addition, the commenter states that the discrepancy was revealed during engine overhaul and that the cause of the bolt failure was attributed to a personnel error when the end cap was installed backwards. The commenter adds that the redesigned end cap specified in the alert service bulletin does not prevent improper installation and does not address the original issue of misinstallation. Further, the commenter states that, during routine magnetic particle inspections of the end caps and bolts, no cracked end caps or bolts have been found. The commenter also states that such an incident should not lead to the conclusion that an unsafe condition exists or is likely to exist.
The FAA does not concur that the alert service bulletin is unwarranted or that the proposed AD should be withdrawn. The FAA points out that the current configuration of the end cap has been shown to fail if it is installed backwards because the end cap would contact the adjacent bearing, which is loaded during each flight. In addition, the end cap has insufficient fatigue life for such loading, and may not prevent separation of an engine in the event of failure of the primary thrust load path. However, the FAA has determined that the redesigned end cap specified in the alert service bulletin will prevent the end cap from contacting the adjacent bearing even if the redesigned end cap is installed backwards.
The FAA acknowledges that, if the redesigned end cap was installed backwards, several problems could occur. First, only a portion of the threads of the fasteners would engage and the few engaged threads could strip, resulting in inadequate torque of the fasteners. Second, if the installation procedure was continued, a mechanical interference could occur between the fan case and the fastener heads. However, the FAA points out that, because inadequate torque of the fasteners could be easily detected, installation of the engine would not be continued until corrective action was taken. The new design also would prevent inadvertent loading of the secondary thrust load path, which is reserved for use in the event of a failure in the primary thrust load path.
In light of this information, the FAA has determined that the redesigned end cap would significantly reduce the probability of inadvertent error in engine installation. In addition, the FAA was informed by the manufacturer that the original end cap assembly, if installed correctly, has insufficient fatigue life to prevent separation of an engine in case of a primary thrust link failure.
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Request To Correct the Name of the Component To Be Inspected
One commenter, the manufacturer, requests that the inspection described in the ``Explanation of Relevant Service Information'' and in paragraph (a)(1) of the proposed AD be changed from ``end cap of the forward engine mount'' to ``engine thrust link components'' in the final rule.
The FAA concurs with this request. As described earlier in the ``Clarification of the Rule'' paragraph, the FAA agrees that the ``engine thrust link components'' are the correct components to be inspected. The FAA points out that, although the alert service bulletin specifies an inspection of the ``forward engine mount,'' the FAA agrees with the manufacturer that the ``engine thrust link components'' are the appropriate components to be inspected. The FAA has made this change throughout the final rule, including the Summary and paragraph (a)(1). No change was made in the ``Explanation of Relevant Service Information'' because this paragraph does not appear in the final rule.
Request To Change a Reference to the Airplane Maintenance Manual
One commenter suggests changing a reference in the ``Differences Between Proposed Rule and Service Bulletin'' of the proposed AD from ``Chapter 71-00-00 of the Boeing 747 Airplane Maintenance Manual (AMM)'' to ``paragraph (a)(2) of this AD.''
The FAA concurs. The FAA acknowledges that the reference to Chapter 71-00-00 of the AMM in the ``Differences Between Proposed Rule and Service Bulletin'' of the proposed AD is incorrect because that chapter of the AMM does not include procedures for replacing the end cap and bolts. The FAA agrees that paragraph (a)(2) correctly references the appropriate work package of the alert service bulletin for such replacement procedures. However, the FAA has determined that further clarification is necessary, and has placed such clarification in the paragraph titled ``Additional Differences Between This AD and the Service Information,'' below. In that paragraph, the FAA has deleted the reference to the AMM and added that the end cap and bolts be replaced ``in accordance with the alert service bulletin referenced in paragraph (a)(2) of this AD.''
Request To Add a Statement Regarding Repair
One commenter requests adding ``repair all discrepancies or damage found in accordance with an approved FAA procedure* * *'' to the requirements of paragraph (a)(1)(ii) of the proposed AD.
The FAA acknowledges that adding a statement regarding the repair requirement is necessary for clarification of the final rule. As discussed earlier in the ``Clarification of the Rule'' paragraph, the FAA considers that the repair requirement was inherent in the proposed rule. The FAA agrees with the commenter that the repair requirement should be more explicit and has added this requirement to the final rule.
However, the FAA has determined that it is unnecessary to add that the repair must be ``in accordance with an approved FAA procedure.'' The FAA points out that because the repairs required by this AD are considered common industry practice, it is unnecessary to require that such repairs must be accomplished in accordance with an approved FAA procedure. Since the suggested change would increase the burden to the operator and require issuance of further rulemaking to allow opportunity for public comment, the FAA has determined that such a change would be inappropriate in light of the identified unsafe condition.
In light of this information, the FAA has added the repair requirement to paragraph (a)(1)(ii)(A) of the final rule, but has not added the requirement that the repair be accomplished ``in accordance with an approved FAA procedure.''
Request To Allow an Operator's Equivalent Procedure for Certain Tasks
One commenter states that it objects to paragraph (c) of the proposed AD because it eliminates the option to perform certain tasks in accordance with an operator's equivalent procedure. The commenter also states that operators often incorporate changes to maintenance manual procedures and work cards by resequencing or improving the work steps to improve efficiency. The commenter maintains that its operator's procedures are equivalent to those specified in the AMM and will ensure accomplishment of the work specified in the AMM. For these reasons, the commenter requests that paragraph (c) of the proposed AD be deleted.
The FAA concurs with the commenter's request to delete paragraph (c) of the proposed AD and to allow the use of an operator's equivalent procedure for accomplishment of certain actions required by the final rule. The FAA points out that it did not intend to require the accomplishment of access procedures prior to inspection and closure procedures after inspection in accordance with only the AMM. The FAA also intended to allow the accomplishment of access and closure procedures in accordance with an operator's equivalent procedure. The FAA has determined that accomplishment of the access and closure procedures, in accordance with an operator's equivalent procedure, and accomplishment of the inspection requirements, in accordance with Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996, will adequately address the identified unsafe condition and provide an acceptable level of safety.
In light of this, the FAA has deleted paragraph (c) that was included in the proposed AD, which did not allow the actions required by the proposed AD to be accomplished in accordance with an operator's equivalent procedure. In addition, the reference to paragraph (c) has been deleted from paragraphs (a) and (b) of the final rule.
Additional Differences Between This AD and the Service Information
Boeing Alert Service Bulletin 747-71A2283 divides the affected airplanes into two groups depending upon the particular engine configuration of the affected airplane, and provides different procedures depending upon group classification and engine on-wing flight cycles. Operators should note that, whereas the alert service bulletin specifies that operators of Group 1 airplanes should contact the manufacturer for disposition of the terminating action, this AD requires that the end cap and bolts be replaced in accordance with the alert service bulletin referenced in paragraph (a)(2) of this AD as terminating action.
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 133 Model 747-400 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 36 airplanes of U.S. registry will be affected by this AD: 35 Group 1 airplanes, and 1 Group 2 airplane.
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It will take approximately 36 work hours per Group 1 airplanes (9 work hours per engine) to accomplish the required inspection 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 $75,600, or $2,160 per airplane, per inspection cycle.
It will take approximately 272 work hours per airplane (68 work hours per engine) for both Group 1 and Group 2 airplanes to accomplish the required replacement of the forward engine mount end cap and/or end cap bolts at an average labor rate of $60 per work hour. Required parts will cost approximately $1,000 per airplane. Based on these figures, the cost impact of this replacement on U.S. operators is estimated to be $623,520, or $17,320 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 substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
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
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
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Section 39.13 is amended by adding the following new airworthiness directive:
99-11-12 Boeing: Amendment 39-11183. Docket 97-NM-89-AD.
Applicability: Model 747-400 series airplanes powered by Pratt & Whitney PW4000 engines, as listed in Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996; 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 possible separation of the engine from the airplane in the event of a primary thrust linkage failure, accomplish the following:
Initial Inspection and Corrective Actions
(a) For Group 1 airplanes, as identified in Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996: Accomplish paragraphs (a)(1) and (a)(2), of this AD, as applicable.
(1) Within 500 hours time-in-service after the effective date of this AD, perform a detailed visual inspection (Work Package 1) to ensure proper installation of the engine thrust link components, in accordance with the alert service bulletin.
(i) If no attachment hardware is found loose or missing, and if no part shows signs of damage, repeat the inspection thereafter at intervals not to exceed 5,000 hours time-in-service or 15 months, whichever occurs first, until the requirements of paragraph (a)(2) of this AD have been accomplished.
(ii) If any attachment hardware is found loose or missing, or if any part shows signs of damage, prior to further flight, accomplish the actions required by paragraphs (a)(1)(ii)(A) and (a)(1)(ii)(B).
(A) Repair any discrepancy or damage.
(B) Replace the existing end cap and end cap bolts of the forward engine mount end cap assembly with an improved end cap and end cap bolts (Work Package 2) in accordance with the alert service bulletin.
Terminating Action
(2) Replace the existing end cap and end cap bolts of the forward engine mount end cap assembly with an improved end cap and end cap bolts (Work Package 2), in accordance with Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996, at the earlier of the times specified in paragraphs (a)(2)(i) and (a)(2)(ii) of this AD. Accomplishment of the replacement constitutes terminating action for the requirements of this AD for Group 1 airplanes.
(i) Prior to the accumulation of 16,000 total flight cycles on any engine, or within 500 hours time-in-service after the effective date of this AD, whichever occurs later; or
(ii) Within 3 years after the effective date of this AD.
(b) For Group 2 airplanes, as identified in Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996: Within 3 years after the effective date of this AD, replace the existing end cap bolts of the forward engine mount with improved end cap bolts (Work Package 3), in accordance with the alert service bulletin.
Spares
(c) As of the effective date of this AD, no person shall install on any airplane a forward engine mount end cap having part number 310T3026-1.
Alternative Method 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 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 2: 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) The inspections and replacement shall be done in accordance with Boeing Alert Service Bulletin 747-71A2283, dated October 10, 1996. 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.
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(g) This amendment becomes effective on July 2, 1999.
Issued in Renton, Washington, on May 20, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-13483Filed5-27-99; 8:45 am]
BILLING CODE 4910-13-P
