Airworthiness directives: Boeing,

[Federal Register: December 21, 1999 (Volume 64, Number 244)]

[Proposed Rules]

[Page 71336-71339]

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

[DOCID:fr21de99-23]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-30-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747-200, -300, and -400 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 Model 747- 200, -300, -400 series airplanes, that currently requires repetitive high frequency eddy current (HFEC) inspections to detect cracking of

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the front spar web of the center section of the wing, and repair, if necessary. This action would require that the existing inspection be accomplished at a reduced threshold. This action also would add a requirement that the existing HFEC inspection be accomplished on repaired areas. This proposal is prompted by reports of cracking in repaired areas of the front spar web and cracking of the front spar web on an airplane that had accumulated fewer flight cycles than the inspection threshold of the existing AD. The actions specified by the proposed AD are intended to prevent the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard.

DATES: Comments must be received by February 4, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-30-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 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 Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 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 99-NM-30-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. 99-NM-30-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On February 19, 1997, the FAA issued AD 97-05-01, amendment 39-9945 (62 FR 8613, February 26, 1997), applicable to certain Boeing Model 747-200, -300, and -400 series airplanes, to require repetitive high frequency eddy current (HFEC) inspections to detect cracking of the front spar web of the center section of the wing, and repair, if necessary. That action was prompted by reports of fatigue cracking found in the front spar web. The requirements of that AD are intended to prevent the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard.

Actions Since Issuance of Previous Rule

Since the issuance of AD 97-05-01, the FAA has received reports of cracking in repaired areas of the front spar web on Model 747SR series airplanes. Also, the FAA has received a report for the first time of cracking in the front spar web on a Model 747-200 series airplane. The Model 747-200 series airplane had accumulated 13,309 total flight cycles, which is less than the 18,000 total landing compliance time specified in AD 97-05-01 for certain airplanes.

The front spar web on Model 747SR series airplanes is identical to that on the affected Model 747-200 series airplanes, except there is no fuel located behind the front spar web on Model 747SR series airplanes. In addition, if the subject fatigue cracking were to occur on these airplanes, the cabin pressure would vent through the front spar web and then the limiting access holes of the front spar; this would result in a loss of pressurization, but not sudden decompression. This would also not result in damage to unpressurized areas. Therefore, no unsafe condition exists on Model 747SR series airplanes.

Explanation of Relevant Service Information

Subsequent to the finding of this new cracking, the manufacturer issued and the FAA reviewed and approved Boeing Service Bulletin 747- 57A2298, Revision 2, dated October 2, 1997, and Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999.

The method of inspection in Revision 2 of the service bulletin is identical to that described in Revision 1 of the service bulletin (which was referenced in AD 97-05-01 as the appropriate source of service information). However, Revision 2 revises the inspection procedures to include instructions for repetitive HFEC inspections of the aft side of the front spar web to detect cracking. These instructions were added to allow inspection when a prior repair precludes access to the forward side of the front spar web.

The inspection procedures in Revision 3 of the service bulletin are identical to those described in Revision 2 of the service bulletin. Revision 3 reduces the inspection threshold and revises the listing of current operators of affected airplanes.

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 97-05-01 to continue to require accomplishment of the requirements of the existing AD and to require accomplishment of the actions specified in the service bulletins described previously, except as discussed below.

Differences Between Proposed Rule and the Service Bulletins

Operators should note that, although the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposed AD would require the repair of those 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

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approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Cost Impact

There are approximately 485 airplanes of the affected design in the worldwide fleet. The FAA estimates that 105 airplanes of U.S. registry would be affected by this proposed AD.

The inspections that are currently required by AD 97-05-01 and retained in this AD, take approximately 8 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 currently required actions on U.S. operators is estimated to be $50,400, or $480 per airplane, per inspection cycle.

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 39-9945 (62 FR 8613, February 26, 1997), and by adding a new airworthiness directive (AD), to read as follows:

   BOEING: Docket 99-NM-30-AD. Supersedes AD 97-05-01, amendment 39- 9945.

   Applicability: Model 747-200, -300, -400 series airplanes, up to and including line number 744, 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 the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard, accomplish the following:

   Restatement of Requirement of AD 97-05-01, Amendment 39-9945

   Repetitive Inspections

   (a) Perform a high frequency eddy current (HFEC) inspection to detect cracking of the front spar web of the center section of the wing, in accordance with Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996; Boeing Service Bulletin 747- 57A2298, Revision 2, dated October 2, 1997; or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999; at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable, until accomplishment of the requirements of paragraph (b) of this AD.

   (1) For airplanes that have accumulated 12,000 to 17,999 total landings as of April 2, 1997 (the effective date of AD 97-05-01, amendment 39-9945): Perform the initial inspection within 12 months after April 2, 1997, unless previously accomplished within the last 12 months prior to April 2, 1997. Perform this inspection again prior to the accumulation of 18,000 total landings or within 1,400 landings, whichever occurs later; after accomplishing the initial inspection, and thereafter at intervals not to exceed 1,400 landings.

   (2) For all other airplanes: Perform the initial inspection prior to the accumulation of 18,000 total landings or within 12 months after April 2, 1997, whichever occurs later. Repeat this inspection thereafter at intervals not to exceed 1,400 landings.

   New Requirements of This AD

   Repetitive Inspections

   (b) Prior to accumulation of 12,000 total landings, or within 12 months after the effective date of this AD, whichever occurs later, perform an HFEC inspection to detect cracking of the front spar web of the center section of the wing, in accordance with Boeing Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997; or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999. Repeat the HFEC inspection thereafter at intervals not to exceed 1,400 landings. Accomplishment of the HFEC inspection constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD.

   Repair

   (c) If any cracking is detected during any inspection required by paragraph (a) or (b) of this AD, prior to further flight, confirm the cracking with secondary procedures in accordance with Boeing Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997, or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999. Thereafter repeat the HFEC inspection required by paragraph (a) or (b) of this AD at intervals not to exceed 1,400 landings.

   (1) If any vertical crack is found that is less than 10 inches in length and has not extended in a diagonal direction, prior to further flight, repair in accordance with the service bulletin.

   (2) If any vertical crack is found that is 10 inches or greater in length; or if any crack is found that has extended in a diagonal direction (regardless of the length); or if any crack is found that would affect an existing repair, prior to further flight, 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 Designated Engineering Representative who has been authorized by the FAA to make such findings. For a repair method to be approved by the Manager, Seattle ACO, or a Boeing DER, as required by this paragraph, the approval letter must specifically reference 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 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

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   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.

   Issued in Renton, Washington, on December 15, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 99-32982Filed12-20-99; 8:45 am]

   BILLING CODE 4910-13-U