Airworthiness directives: Boeing,

[Federal Register: September 2, 1999 (Volume 64, Number 170)]

[Proposed Rules]

[Page 48120-48123]

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

[DOCID:fr02se99-25]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-56-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

[[Page 48121]]

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This proposal would require repetitive inspections or checks to detect broken H-11 steel bolts at the wing rear spar side-of-body on the lower chord splice plate and kick fitting; and corrective actions, if necessary. This proposal also would require eventual replacement of the existing bolts with new inconel bolts, which would constitute terminating action for the repetitive inspections. This proposal is prompted by a report of broken bolts at the wing rear spar side-of-body on the lower chord splice plate. The actions specified by the proposed AD are intended to prevent cracking of the bolts due to stress corrosion, which could result in reduced structural integrity of the wing-to-body joint structure.

DATES: Comments must be received by October 18, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-56-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. 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 99-NM-56-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-56-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report indicating that an operator found four broken high strength H-11 steel bolts on a Boeing Model 747 series airplane. The broken bolts were on one side of the wing rear spar side- of-body on the lower chord splice plate. The broken bolts were attributed to stress corrosion cracking. This condition, if not detected, could result in reduced structural integrity of the wing-to- body joint structure.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999. The service bulletin describes procedures for repetitive detailed visual inspections, or alternatively, ultrasonic inspections or torque checks, to detect broken H-11 steel bolts common to the rear spar lower chord splice plate and H-11 steel bolts on the wing rear spar lower kick fitting; and corrective actions, if necessary. The corrective actions involve performing either an ultrasonic inspection or torque check for broken bolts, if necessary; an open hole high frequency eddy current (HFEC) inspection to detect cracks at the broken bolt hole location; and installing an inconel bolt, which would eliminate the need for the repetitive inspections at this bolt location, as applicable. The service bulletin also describes procedures for an optional terminating action for the repetitive inspections. Accomplishment of the actions specified in the service bulletin 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 require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

Operators should note that, although incorporation of the terminating action specified in the referenced service bulletin is optional, this AD proposes to mandate, within 48 months after the effective date of this AD, the open hole inspection and replacement specified in the referenced service bulletin as terminating action for the repetitive inspections.

The FAA has determined that long-term continued operational safety would be better assured by design changes to remove the source of the problem, rather than by repetitive inspections. Long-term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous continual inspections, has led the FAA to consider placing less emphasis on inspections and more emphasis on design improvements. The proposed replacement requirement is in consonance with these conditions.

In addition, operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposal 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 approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. For a repair method to be approved, the approval letter must specifically reference this AD.

Cost Impact

There are approximately 523 airplanes of the affected design in the worldwide fleet. The FAA estimates that

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115 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection of the wing rear spar side-of-body lower chord splice plate and kick fitting high strength H-11 steel bolts proposed by this AD on U.S. operators is estimated to be $6,900, or $60 per airplane, per inspection cycle.

It would take approximately 13 (Groups 1, 3, 4, and 5 airplanes) and 10 (Group 2 airplanes) work hours per airplane to accomplish the proposed open hole HFEC inspection and replacement, at an average labor rate of $60 per work hour. Required parts would cost approximately $4,500 per airplane. Based on these figures, the cost impact of the open hole HFEC inspection and replacement proposed by this AD on U.S. operators is estimated to be $5,280 (Groups 1, 3, 4, and 5 airplanes) and $5,100 (Group 2 airplanes) per airplane.

The cost impact figures discussed above are based on assumptions that no 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 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 adding the following new airworthiness directive:

   Boeing: Docket 99-NM-56-AD.

   Applicability: Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999, 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 detect and prevent cracking of the high strength H-11 steel bolts on the wing rear spar side-of-body on the lower chord splice plate and kick fitting due to stress corrosion, which could result in reduced structural integrity of the wing-to-body joint structure, accomplish the following:

   Repetitive Inspections

   (a) Within 12 months after the effective date of this AD, perform a detailed visual inspection, or alternatively, an ultrasonic inspection or torque check, to detect broken H-11 steel bolts common to the rear spar lower chord splice plate and the H-11 steel bolts common to the wing rear spar lower chord kick fitting, in accordance with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999. Thereafter, repeat the applicable inspection or torque check at intervals not to exceed 18 months, until accomplishment of the actions specified in paragraph (d) of this AD.

   Note 2: For the purposes of this AD, a detailed 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.''

   Corrective Actions

   (b) If there is any detection or indication that any bolt is broken during the inspection required by paragraph (a) of this AD, prior to further flight, perform the applicable corrective action

   [i.e., ultrasonic inspection, torque check, high frequency eddy current (HFEC) inspection, repair, and replacement] in accordance with Boeing Alert Service Bulletin 747-57A2309, dated February 25, 1999; except as provided in paragraph (c) of this AD. Replacement of a broken bolt with a new inconel bolt in accordance with the service bulletin constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD for that bolt only.

   (c) If any crack is detected during any corrective action required by paragraph (b) of this AD; and the service bulletin specifies to contact Boeing for appropriate action: 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 Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.

   Terminating Action

   (d) Within 48 months after the effective date of this AD, accomplish the actions required by paragraphs (d)(1) and (d)(2) of this AD in accordance with Boeing Alert Service Bulletin 747- 57A2309, dated February 25, 1999. Accomplishment of the actions specified in this paragraph constitutes terminating action for the repetitive inspection requirements of this AD.

   (1) Prior to accomplishing the replacement required by paragraph (d)(2) of this AD, perform an open hole HFEC inspection to detect cracks at the bolt hole location for the eight high strength H-11 steel bolts common to the rear spar lower chord splice plate and the four high strength H-11 steel bolts common to the wing rear spar lower chord kick fitting. If any crack is detected, prior to further flight, perform applicable corrective actions in accordance with paragraph (c) of this AD.

   (2) Replace all eight high strength H-11 steel bolts common to the rear spar lower chord splice plate and all four high strength H- 11 steel bolts common to the wing rear spar lower chord kick fitting with new inconel bolts.

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   Spares

   (e) As of the effective date of this AD, no person shall install an H-11 steel bolt having part number (P/N) BACB30MT ( ) * ( ) or BACB30TR ( ) * ( ), or any other H-11 steel bolt in the locations specified in this AD, on any airplane.

   Alternative Methods of Compliance

   (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 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 3: 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

   (g) Special flight permits may be issued in accordance with 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 August 27, 1999. Vi L. Lipski, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 99-22921Filed9-1-99; 8:45 am]

   BILLING CODE 4910-13-P