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Proposed Rule

Airworthiness Directives; Boeing Model 747 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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Start Preamble

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 inspection of the flap tracks of the wing trailing edge flaps for adequate cadmium plating and for corrosion of certain bolt holes of the fail-safe bar, and plating of such holes, if necessary. This new action would require post-modification inspections of certain bolt holes of the fail-safe bar of the flap tracks of the wing trailing edge flaps for discrepancies, and corrective actions, if necessary. This proposal is prompted by reports of corrosion and cracks found in certain bolt holes reworked according to the existing AD. The actions specified by the proposed AD are intended to find and fix discrepancies of the bolt holes, which could result in fracture of the flap track, separation of the flap, and consequent loss of control of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by August 15, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-24-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. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-24-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Start Printed Page 44117Boeing 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.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Tamara Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425) 227-1181.

End Further Info End Preamble Start Supplemental Information

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 action may be changed in light of the comments received.

Submit comments using the following format:

  • Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
  • For each issue, state what specific change to the proposed AD is being requested.
  • Include justification (e.g., reasons or data) for each request.

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 filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-24-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. 2002-NM-24-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On January 24, 1991, the FAA issued AD 91-03-17, amendment 39-6884 (56 FR 4534, February 5, 1991), applicable to certain Boeing Model 747 series airplanes, to require inspection of the flap tracks of the trailing edge for adequate cadmium plating and to find corrosion of certain bolt holes of the fail-safe bar, and plating of such holes, if necessary. That action was prompted by reports of missing cadmium plating and corrosion in certain flap track fail-safe bar bolt holes. The requirements of that AD are intended to prevent fracture of the trailing edge flap track, separation of the flap supported by the track, and resultant reduction of the controllability of the airplane and/or damage to other structure from impact with the departing debris.

Actions Since Issuance of Previous Rule

Since the issuance of AD 91-03-17, there have been reports of additional corrosion and cracks found in certain forward bolt holes of the fail-safe bar of the flap tracks of the wing trailing edge flaps on certain Boeing Model 747 series airplanes. The corrosion and cracks were found AFTER the bolt holes were reworked or replated with cadmium, as required by that AD. Boeing Service Bulletins 747-57-2256, dated March 8, 1990, and Revision 1, dated November 15, 1990, were the sources of service information specified in that AD for accomplishment of those actions. Boeing Service Bulletin 747-57-2256, Revision 2, dated March 5, 1992, was approved by the FAA after that AD was issued and has since been revised. In light of these findings, the terminating actions (replating with cadmium and rework of the bolt holes), and the option to defer bolt rework if corrosion is found, as specified in that AD, are no longer valid and have not been included in this proposed AD. In addition, although the effectivity specified in the most recently revised service bulletin (below) has not changed from the applicability of the existing AD, the applicability section in this proposed AD has been changed to specify Revision 3 of the service bulletin instead of the original issue.

Explanation of Revised Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-57-2256, Revision 3, dated June 21, 2001, which describes procedures for post-modification inspections of certain bolt holes of the fail-safe bar of the flap tracks of the trailing edge for discrepancies (corrosion, cracks, damaged cadmium plating), and corrective actions (rework, repair, or replate with cadmium the affected bolt holes), if necessary. The service bulletin revises the procedures specified in the original issue, Revision 1, and Revision 2 of the service bulletin as follows: changes the post-modification inspection; adds separate post-modification and rework instructions in Part 2; changes the type of bolts in Figure 4, Table II, to “K” material-type bolts (corrosion-resistant); and eliminates the option to defer bolt hole rework if corrosion is found. The service bulletin specifies that no more work is necessary on airplanes that had cadmium plating installed during production and on which no corrosion was found after doing the initial inspection specified in the service bulletin. 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 supersede AD 91-03-17 to continue to require inspection of the flap tracks of the trailing edge for adequate cadmium plating of certain bolt holes of the fail-safe bar, and plating of such holes, if necessary. This new action would require post-modification inspections of certain bolt holes of the fail-safe bar of the flap tracks of the trailing edge for discrepancies, and corrective action, if necessary. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below.

Difference Between Service Bulletin and Proposed AD

The service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions. This proposed AD requires the repair of those conditions to be accomplished per a method approved by the FAA, or per 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 Aircraft Certification Office, to make such findings. Start Printed Page 44118

Cost Impact

There are approximately 553 airplanes of the affected design in the worldwide fleet. The FAA estimates that 169 airplanes of U.S. registry would be affected by this proposed AD.

The actions that are currently required by AD 91-03-17 take approximately 50 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 is estimated to $3,000 per airplane.

The borescope inspection proposed in this AD action would take approximately 32 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 is estimated to be $324,480, or $1,920 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Should an operator be required to accomplish the eddy current inspection, it would take approximately 40 work hours per airplane to accomplish the inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection is estimated to be $2,400 per airplane.

Should an operator be required to accomplish the modification of the bolt holes, it would take approximately 256 work hours per airplane to accomplish the modification, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the modification is estimated to be $15,360 per airplane.

Regulatory Impact

The regulations proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

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.

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List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
[Amended]

2. Section 39.13 is amended by removing amendment 39-6884 (56 FR 4534, February 5, 1991), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2002-NM-24-AD. Supersedes AD 91-03-17, Amendment 39-6884.

Applicability: Model 747 series airplanes, as listed in Boeing Service Bulletin 747-57-2256, Revision 3, dated June 21, 2001, 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)(1) 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 find and fix discrepancies of certain bolt holes of the fail-safe bar of the flap tracks of the wing trailing edge flaps, which could result in separation of the flap and consequent loss of control of the airplane, accomplish the following:

Restatement of Certain Requirements of AD 91-03-17

Inspections

(a) Prior to the accumulation of 30,000 total flight hours, or 8 years time-in-service on current production flap tracks, whichever is first; or within 2,000 flight cycles after March 11, 1991 (the effective date of AD 91-03-17, amendment 39-6884); whichever is later: Perform a borescope inspection of the forward four bolt holes on each side of the affected trailing edge flap tracks for corrosion and adequate cadmium plating, in accordance with the procedures specified in Boeing Service Bulletin 747-57-2256, dated March 8, 1990; Revision 1, dated November 15, 1990; Revision 2, dated March 5, 1992; or Revision 3, dated June 21, 2001. If the cadmium plating is adequate, as specified in the service bulletin, and no corrosion or cracks are found, no further action is required for this paragraph. If the cadmium plating is not adequate, or if corrosion exists in any bolt hole, prior to further flight, conduct an eddy current inspection of the bolt hole for cracks, in accordance with the service bulletin. After the effective date of this AD only Revision 3 of the service bulletin may be used.

Corrective Actions

(b) If the cadmium plating is not adequate and no corrosion or cracks are found during the inspection required by paragraph (a) of this AD: Within 1,000 flight cycles after accomplishment of the inspection required by paragraph (a) of this AD, cadmium plate the affected bolt holes in accordance with Boeing Service Bulletin 747-57-2256, dated March 8, 1990; Revision 1, dated November 15, 1990; Revision 2, dated March 5, 1992; or Revision 3, dated June 21, 2001; and conduct the inspections of the affected track as specified in paragraphs (b)(1), (b)(2), and (b)(3) of this AD, in accordance with the service bulletin. Restoration of the cadmium plating terminates the inspections required by this paragraph.

Inspections

(1) Within 50 flight cycles after accomplishment of the inspection required by paragraph (a) of this AD: Perform a close visual inspection of each side of the track, at the lower chord, for cracks emanating from the forward four fail-safe bar bolt holes, and repeat the inspection thereafter at intervals not to exceed 50 flight cycles.

(2) Within 250 flight cycles after accomplishment of the inspection required by paragraph (a) of this AD: Perform an eddy current inspection for cracks of the bolt holes, and repeat the inspection thereafter at intervals not to exceed 250 flight cycles.

(3) Prior to each flight on which a fifth engine is to be carried, perform a close visual inspection of each side of the track, at the lower chord, for cracks emanating from the forward four fail-safe bar bolt holes. Start Printed Page 44119

New Requirements of This AD

Cadmium Plating Applied During Production

(c) For airplanes on which cadmium plating of the forward four bolt holes was applied during production: No further action is required by this AD. If operator records indicate that during the inspection required by paragraph (a) of this AD cadmium plating was applied during production (not during rework or replating), no further action is required by this AD. (Indications of rework include oversized fasteners and/or fasteners with repair sleeves, and/or flap track dash numbers that have been changed per the service bulletin.)

Compliance Time for Borescope Inspection

(d) For airplanes on which cadmium plating of the forward four bolt holes was NOT applied during production: Do the action required by paragraph (e) of this AD at the later of the times given in paragraphs (d)(1) and (d)(2) of this AD.

(1) Within 2 years or 2,000 flight cycles after the effective date of this AD, whichever is first; or

(2) Within 6 years after doing the initial bolt hole rework per AD 91-03-17.

Borescope Inspection

(e) Do a borescope inspection of the forward four bolt holes on each side of the fail-safe bar of the flap tracks of the trailing edge flaps for discrepancies (corrosion, cracks, damaged cadmium plating), per Part 2 of the Work Instructions of Boeing Service Bulletin 747-57-2256, Revision 3, dated June 21, 2001. Then, do the actions specified in paragraph (e)(1), (e)(2), or (e)(3) of this AD, as applicable, and repeat the borescope inspection every 8 years or 8,000 flight cycles, whichever is first. Accomplishment of the actions specified in this paragraph terminates the requirements of paragraph (a) of this AD.

Corrective Actions

(1) If the cadmium plating is damaged, but no corrosion or cracking is found: Before further flight, do the eddy current inspection specified in and per Part 2.F. of the Work Instructions of the service bulletin. If no cracking is found, before further flight, cadmium plate the affected bolt holes per Part 2.F. of the Work Instructions of the service bulletin.

(2) If any corrosion is found, before further flight, rework the affected bolt holes as specified in and per Part 2.G. of the Work Instructions of the service bulletin.

(3) If any cracking is found, before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), or per 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.

Alternative Methods of Compliance

(f)(1) 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.

(2) Alternative methods of compliance, approved previously in accordance with AD 91-03-17, amendment 39-6884, are approved as alternative methods of compliance with paragraphs (a) and (b) of this AD.

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

(g) 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.

Start Signature

Issued in Renton, Washington, on June 24, 2002.

Kalene C. Yanamura,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 02-16406 Filed 6-28-02; 8:45 am]

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