Airworthiness directives: Boeing,

[Federal Register: July 7, 1998 (Volume 63, Number 129)]

[Proposed Rules]

[Page 36628-36630]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr07jy98-21]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-185-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747 Series Airplanes Equipped with Pratt & Whitney Model JT9D-70 Engines

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 747 series airplanes, that currently requires repetitive inspections to detect fatigue cracking of the spring beams on the outboard struts; replacement of cracked spring beams with new or serviceable spring beams; and follow-on actions. That action also provides an optional terminating action for the repetitive inspections. This action would remove that optional terminating action, and would require a new terminating action. This proposal is prompted by the development of an improved process for manufacturing titanium spring beams that will eliminate the embedded porosity flaws in the existing spring beams from which fatigue cracking can originate. The actions specified by this proposal are intended to prevent fatigue cracking of the spring beam, which could result in loss of an outboard strut.

DATES: Comments must be received by August 21, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-185-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: 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:

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

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summarizing each FAA-public contact concerned with the substance of this proposal will be filedin 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 97-NM-185-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. 97-NM-185-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On November 30, 1994, the FAA issued AD 94-25-01, amendment 39-9085 (59 FR 63003, December 7, 1994), applicable to certain Boeing Model 747 series airplanes, to require repetitive detailed visual inspections to detect fatigue cracking of the spring beams on the outboard struts; replacement of cracked spring beams with new or serviceable spring beams; and follow-on actions. That action also provides an optional terminating action for the repetitive inspections.

AD 94-25-01 was prompted by a report of failure of a spring beam due to cracking that was propagated by fatigue. The requirements of that AD are intended to prevent failure of the spring beam, which could result in loss of an outboard strut.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the FAA has determined that the specified optional terminating action, if accomplished, would not adequately address the unsafe condition. Neither the fluorescent dye penetrant inspection nor the zero-time overhaul, which are part of the optional terminating action, would detect the porosity flaws that are embedded within the titanium material of the existing spring beams. In addition, an improved process for manufacturing titanium spring beams has been developed that will eliminate the embedded porosity flaws in the existing spring beams from which fatigue cracking can originate. Such fatigue cracking, if not corrected, could result in loss of an outboard strut.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-54- 2177, dated June 27, 1996, which describes procedures for replacement of the spring beams on the outboard struts with new, improved spring beams, which would eliminate the need for the repetitive inspections of the spring beams.

In addition, the FAA has reviewed and approved Boeing Service Bulletin 747-54A2171, Revision 1, dated June 27, 1996, which changes the original issue of the alert service bulletin (which was referenced in AD 94-25-01 as the appropriate source of service information). This revision changes the repetitive inspection intervals and the terminating action. Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition.

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 94-25-01 to continue to require the repetitive inspections to detect fatigue cracking of the spring beams on the outboard struts, and to remove the follow-on actions. For certain airplanes, this proposed AD would reinstate the repetitive inspections of AD 94-25-01 to detect fatigue cracking of the spring beams on the outboard struts. In addition, the proposed AD would remove the current optional terminating action, and would require a new terminating action for the repetitive inspections. The actions would be required to be accomplished in accordance with Boeing Service Bulletin 747-54-2177 and Boeing Alert Service Bulletin 747-54A2171.

Cost Impact

There are approximately 7 airplanes of the affected design in the worldwide fleet. The FAA estimates that 5 airplanes of U.S. registry would be affected by this proposed AD.

The inspections that are currently required by AD 94-25-01, and retained in this proposed AD, take approximately 40 work hours per airplane, per inspection cycle, to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be$12,000, or $2,400 per airplane, per inspection cycle.

The new replacement proposed by this AD would take approximately 376 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $105,000 per airplane. Based on these figures, the cost impact of the replacement proposed by this AD on U.S. operators is estimated to be$637,800, or $127,560 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 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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.

   Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-9085 (59 FR 63003, December 7, 1994), and by

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   adding a new airworthiness directive (AD), to read as follows:

   Boeing: Docket 97-NM-185-AD. Supersedes AD 94-25-01, Amendment 39- 9085.

   Applicability: Model 747 series airplanes, line numbers 202 through 396 inclusive, equipped with Pratt & Whitney Model JT9D-70 engines; 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 (f) 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 spring beam, which could result in loss of an outboard strut, accomplish the following:

   (a) Prior to the accumulation of 10,000 total flight cycles, or within 30 days after December 22, 1994 (the effective date of AD 94- 25-01), whichever occurs later, perform a detailed visual inspection to detect fatigue cracking of the spring beams on the outboard struts, in accordance with Boeing Alert Service Bulletin 747- 54A2171, dated October 31, 1994, or Revision 1, dated June 27, 1996. (Remove the gap covers and fairing access panels to perform this inspection.)

   (1) If no cracking is detected, repeat the visual inspection thereafter at intervals not to exceed 300 flight cycles until the requirements of paragraph (d) of this AD have been accomplished.

   (2) If any cracking is detected, prior to further flight, accomplish the replacement actions specified in paragraph (d) of this AD.

   Note: 2: Accomplishment of the optional terminating action specified in paragraph (b) of AD 94-25-01 does not constitute terminating action for the requirements of this AD.

   (b) For airplanes that have accomplished terminating action in accordance with paragraph (b) of AD 94-25-01: Within 1,000 flight cycles after accomplishment of the terminating action specified by AD 94-25-01, or within 90 days after the effective date of this AD, whichever occurs later, perform a detailed visual inspection to detect fatigue cracking of the spring beams on the outboard struts, in accordance with Boeing Alert Service Bulletin 747-54A2171, dated October 31, 1994, or Revision 1, dated June 27, 1996.

   (1) If no cracking is detected, repeat the detailed visual inspection thereafter at intervals not to exceed 300 flight cycles until the requirements of paragraph (d) of thisAD have been accomplished.

   (2) If any cracking is detected, prior to further flight, accomplish the replacement actions specified in paragraph (d) of this AD.

   (c) For airplanes that have accomplished installation of the Boeing-inspected spare titanium spring beams in accordance with Boeing Service Bulletin 747-54A2171,Revision 1, dated June 27, 1996: Within 3,000 flight cycles after accomplishment of the installation of the spare spring beams, or within 90 days after the effective date of thisAD, whichever occurs later, perform a detailed visual inspection to detect fatigue cracking of the spring beams on the outboard struts, in accordance with Boeing AlertService Bulletin 747-54A2171, dated October 31, 1994, or Revision 1, dated June 27, 1996.

   (1) If no cracking is detected, repeat the detailed visual inspection thereafter at intervals not to exceed 300 flight cycles until the requirements of paragraph (d) of thisAD have been accomplished.

   (2) If any cracking is detected, prior to further flight, accomplish the replacement actions specified in paragraph (d) of this AD.

   (d) For all airplanes: Prior to the accumulation of 10,000 total flight cycles, or within 18 months after the effective date of this AD, whichever occurs later, replace the spring beams on the outboard struts with new, improved spring beams, in accordance with Boeing Service Bulletin 747-54-2177, dated June 27, 1996. Accomplishment of this replacement constitutes terminating action for the repetitive inspection requirements of this AD.

   (e) As of the effective date of this AD, no person shall install a spring beam assembly, part numbers 65B89175-5, -6, -9, -10, -13, - 14, -19, and -20, on any airplane.

   (f) 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 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

   (g) Special flight permits may be issued in accordance with sections Secs. 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 30, 1998. Vi L. Lipski, Acting Manager, Transport Airplane Directorate,Aircraft Certification Service.

   [FR Doc. 98-17947Filed7-6-98; 8:45 am]

   BILLING CODE 4910-13-U