Airworthiness directives: Boeing,
[Federal Register: November 24, 1998 (Volume 63, Number 226)]
[Proposed Rules]
[Page 64915-64918]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24no98-35]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-76-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
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 747 series airplanes, that currently requires a one-time inspection to detect cracking and corrosion of various areas at all four nacelle struts; and repair, if necessary. This action would require new repetitive inspections to detect fatigue cracking or loose or missing fasteners of the aft torque bulkheads of the outboard nacelle struts; and repair, if necessary. In addition, this action would expand the applicability of the existing AD to include additional airplanes. This proposal is prompted by the availability of new service instructions for detecting fatigue cracking that would not have been detected by the required actions of the existing AD. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking
[[Page 64916]]
and loose or missing fasteners, which could result in failure of an outboard nacelle strut, and consequent separation of the nacelle from the wing.
DATES: Comments must be received by January 8, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-76-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 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 98-NM-76-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. 98-NM-76-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
Discussion
On December 31, 1996, the FAA issued AD 96-26-51, amendment 39-9876 (62 FR 1038, January 8, 1997), applicable to certain Boeing 747 series airplanes, to require a one-time detailed visual inspection to detect cracking and corrosion of various areas at all four nacelle struts; and repair, if necessary. That action was prompted by reports of cracking of the aft torque bulkhead at the inboard and outboard nacelle struts. That action was applicable only to Model 747 series airplanes that were equipped with Rolls-Royce-type engines. The requirements of that AD were intended to detect and correct cracking of an inboard or outboard nacelle strut, which could result in failure of the nacelle strut and consequent separation of the nacelle from the wing.
Actions Since Issuance of Previous Rule
Since the issuance of that AD, the FAA has learned that the original report of fatigue cracking on the inboard strut was made in error. In fact, what was at first thought to be a fatigue crack on the inboard strut was later determined to be merely a surface scratch in the finish of the structure. Furthermore, the FAA has determined from the service history of the Model 747 airplane that only the outboard strut has proved to be susceptible to fatigue cracking of the aft torque bulkhead. Investigation has revealed that this is because the applied loading spectrum and design configuration of the outboard strut are significantly different from those of the inboard strut.
In addition, since the issuance of AD 96-26-51, the FAA has received an additional report of fatigue cracking found on another Model 747 airplane, which also was equipped with Rolls-Royce-type engines. The affected airplane had accumulated 18,663 total flight cycles. That airplane was found to have cracking on both the inboard and outboard vertical chords of the aft torque bulkhead on the number 4 nacelle strut. Specifically, two cracks of 0.53 inch and 0.34 inch in length were found on the inboard vertical chord of the aft torque bulkhead; and a single 0.12-inch crack was found on the outboard vertical chord of the aft torque bulkhead.
In addition, whereas the strut design configurations and applied loading spectra are significantly different for the inboard and outboard struts, analysis shows that this is not the case for many of the different engine types that can be installed on the outboard strut. Therefore, outboard struts equipped with Rolls-Royce Model RB211, General Electric Model CF6-45/50, or Pratt & Whitney Model JT9D-70 series engines also may be susceptible to fatigue cracking.
Also, the FAA has received reports of nine other nacelle struts that were found to have loose fasteners at the attachment between the vertical flange of the lower spar fitting and the aft torque bulkhead; there have been no reports of missing fasteners at this location. The cause of the fasteners becoming loose is not yet known.
These conditions (namely, fatigue cracking of the outboard nacelle strut aft torque bulkhead web, vertical chords, and side skin; or loose fasteners where the lower spar fitting attaches to the aft torque bulkhead), if not corrected, could result in failure of an outboard nacelle strut, and consequent separation of the nacelle from the wing.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997. The alert service bulletin describes procedures for repetitive detailed visual inspections to detect fatigue cracking of the web, vertical chords, and nacelle strut side skin of the aft torque bulkheads of the number 1 and 4 nacelle struts; and repair, if necessary. The repetitive inspections will also detect loose or missing fasteners on the lower spar fitting of the aft torque bulkhead. In addition, the alert service bulletin describes procedures for various repetitive non-destructive test (NDT) inspections to detect fatigue cracking of the aft torque bulkhead of the numbers 1 and 4 nacelle struts; and repair, if necessary. The NDT inspections consist of ultrasonic inspections, surface eddy current inspections, and open- hole eddy current inspections. The type of NDT inspection to be done depends upon the type of nacelle strut on the affected airplane. Accomplishment of the actions specified in the alert service bulletin is intended to adequately address the identified unsafe condition.
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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 all requirements of AD 96-26-51. This proposed AD would require repetitive detailed visual inspections and, for certain engine types, NDT inspections, to detect fatigue cracking or loose or missing fasteners of the aft torque bulkheads of the outboard nacelle struts; and repair, if necessary. This proposed AD also would revise the applicability of the existing AD to include additional airplanes having engine types in addition to those specified in the existing AD.
This proposed AD also provides for an optional terminating action for the repetitive inspections proposed for airplanes equipped with General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle struts.
[This same terminating action, although optional for this proposed AD, is required by another AD, namely, AD 95-13-07, amendment 39-9287 (60 FR 33336, June 28, 1995), as discussed below] . The FAA notes that there is, as yet, no terminating action for those airplanes equipped with Rolls-Royce RB-211 nacelle struts.
The actions above would be required to be accomplished in accordance with the alert service bulletin described previously, except as discussed below.
Differences Between Proposed Rule and Alert Service Bulletin
Operators should note that, although the alert service bulletin provides for certain repair actions and specifies that the manufacturer may be contacted for disposition of other repair conditions, this proposal would require the repair of all conditions to be accomplished in accordance with a method approved by the FAA, 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 FAA to make such findings.
In addition, operators should note that there is a typographical error on Sheet 3 of Figure 1 of the alert service bulletin. The logic block that contains a reference to ``Group 1 airplanes'' should have read ``Groups 1 and 2 airplanes.''
Other Relevant Rulemaking
The FAA has previously issued AD 95-13-07, which requires modification of airplanes equipped with General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle struts. Accomplishment of the modification required by that AD constitutes terminating action for the requirements of this proposed AD. However, this proposed AD would not affect the current requirements of AD 95-13-07.
Cost Impact
There are approximately 273 airplanes of the affected design in the worldwide fleet. The FAA estimates that 24 airplanes of U.S. registry would be affected by this proposed AD.
The new inspections that are proposed in this AD action for airplane Groups 3 and 4 would take approximately 24 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators of airplanes in Groups 3 and 4 is estimated to be $34,560, or $1,440 per airplane, per inspection cycle.
The cost impact figure discussed above is 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.
There currently are no affected airplanes on the U.S. Register identified as Group 1 or 2 in the referenced alert service bulletin. The airplanes included in Groups 1 and 2 of the applicability of this rule currently are operated by non-U.S. operators under foreign registry; therefore, they are not directly affected by this AD action. However, the FAA considers that this rule is necessary to ensure that the unsafe condition is addressed in the event that any of these subject airplanes are imported and placed on the U.S. Register in the future.
Should an affected Group 1 or 2 airplane be imported and placed on the U.S. Register in the future, it would require approximately 78 work hours to accomplish the new inspections proposed in this AD, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this proposed AD on airplane Groups 1 and 2 would be $4,680 per airplane, per inspection cycle.
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
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
-
Section 39.13 is amended by removing amendment 39-9876 (62 FR 1038, January 8, 1997), and by adding a new airworthiness directive (AD), to read as follows:
Boeing: Docket 98-NM-76-AD. Supersedes AD 96-26-51, Amendment 39- 9876.
Applicability: Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997, 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 (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.
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To detect and correct fatigue cracking and loose or missing fasteners of the aft torque bulkheads of the outboard nacelle struts, which could result in failure of an outboard nacelle strut, and consequent separation of the nacelle from the wing, accomplish the following:
(a) For airplanes identified as Groups 1 and 2 airplanes in Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior to the accumulation of 12,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later, perform a detailed visual inspection of the aft torque bulkheads of the number 1 and number 4 nacelle struts to detect fatigue cracking and loose or missing fasteners. The inspection shall be accomplished in accordance with Part I of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997.
Note 2: There is a typographical error on Sheet 3 of Figure 1 of the alert service bulletin. The words ``Group 1 airplanes'' should read ``Groups 1 and 2 airplanes.''
(1) If no cracking, and if no loose or missing fastener is found, repeat the inspection thereafter at the intervals specified in Figure 1 of the alert service bulletin.
(2) If any cracking, or if any loose or missing fastener is found, prior to further flight, repair in accordance with Part III of the alert service bulletin. Repeat the inspection thereafter at the intervals specified in Figure 1 of the alert service bulletin. Where the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, 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.
(b) For airplanes identified as Groups 1 and 2 airplanes in Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior to the accumulation of 12,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later, perform a non-destructive test (NDT) inspection of the aft torque bulkheads of the number 1 and number 4 nacelle struts to detect fatigue cracking. The NDT inspection shall be accomplished in accordance with Part II of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997.
Note 3: The alert service bulletin refers to a variety of NDT inspections, consisting of ultrasonic inspections, surface eddy current inspections, and open-hole eddy current inspections. The logic diagram in Figure 1 of the alert service bulletin states the conditions under which each of these inspections is to be performed.
(1) If no cracking is found, repeat the inspection thereafter at the intervals specified in Figure 1 of the alert service bulletin.
(2) If any cracking is found, prior to further flight, repair in accordance with Part III of the alert service bulletin. Repeat the inspection thereafter at the intervals specified in Figure 1 of the alert service bulletin. Where the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, repair in accordance with a method approved by the Manager, Seattle ACO; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(c) For airplanes identified as Groups 3 and 4 airplanes in Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Prior to the accumulation of 12,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later, perform a detailed visual inspection of the aft torque bulkheads of the number 1 and number 4 nacelle struts to detect fatigue cracking and loose or missing fasteners. The inspection shall be accomplished in accordance with Part I of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997.
(1) If no cracking, and if no loose or missing fastener is found, repeat the inspection thereafter at the intervals specified in Figure 1 of the alert service bulletin, until the applicable requirements of paragraph (d) are accomplished.
(2) If any cracking, or if any loose or missing fastener is found, prior to further flight, repair in accordance with Part III of the alert service bulletin. Where the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, repair in accordance with a method approved by the Manager, Seattle ACO; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings.
(d) For airplanes identified as Groups 3 and 4 airplanes in Boeing Alert Service Bulletin 747-54A2184, dated July 3, 1997: Accomplishment of the nacelle strut modifications required in AD 95- 13-07, amendment 39-9287 (applicable to airplanes equipped with either General Electric CF6-45/50 or Pratt & Whitney JT9D-70 nacelle struts), constitutes terminating action for the requirements of this AD.
(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 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.
(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.
Issued in Renton, Washington, on November 18, 1998. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-31326Filed11-23-98; 8:45 am]
BILLING CODE 4910-13-U
