Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

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 767 series airplanes. This proposal would require an inspection of the tripod strut assembly of the inboard support of the leading edge slat of the wing for a preload condition, and follow-on actions. For certain airplanes, this proposal also would require inspection and replacement of the existing tripod struts with new, adjustable struts, if necessary. This action is necessary to prevent damage to the tripod strut assembly due to a preload condition, which could result in loss of control of the inboard leading edge slat or separation of the slat from the airplane, and consequent reduced controllability of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by February 19, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-209-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. 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. 2001-NM-209-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 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:

John Craycraft, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2782; 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 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 2001-NM-209-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. 2001-NM-209-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The airplane manufacturer has informed the FAA that damaged bushings were found in the tripod strut assembly of the inboard support of the leading edge slat of the wings of a Model 767 series airplane in production. The damage was due to preload in the tripod assembly during installation. The tripod assembly is used to support the inboard leading edge slat and is the primary inboard-outboard load path of the slat. Loss of primary inboard-outboard load path for the slat can result in an unstable slat-to-wing connection, and separation of the slat from the airplane. Such conditions, if not corrected, could result in reduced controllability of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 767-57A0058, Revision 1, dated May 27, 1999, which describes procedures for a check (inspection) of the tripod strut assembly of the inboard support of the leading edge slat of the wing for a preload condition, and follow-on actions. The follow-on actions include:

• If no preload condition is found, a visual inspection of the components in the fitting assembly to determine if bushing holes are round.
• Replacement of the fitting assembly if the bushing holes are not round.
• If a preload condition is found, a high frequency eddy current inspection of the lug bore and base of the fitting assembly for cracking.
• Rework of the fitting assembly if no cracking is found, or if cracking is found in the lug bore only.
• Replacement of the fitting assembly if cracking is found in the lug base or the lug bore and base.
• Adjustment of the tripod struts, if necessary, to eliminate preload condition, and a check of the rigging of the inboard leading edge slat, and re-rigging if necessary.
• For certain airplanes, inspection for improperly cut and spliced struts, and strut replacement, if necessary.

The FAA also has reviewed and approved Boeing Service Bulletin 767-57-0037, dated January 14, 1993. For Group 2 airplanes (as defined in the service bulletin) the service bulletin describes procedures for doing a visual inspection of the tripod struts of the inboard leading edge of the wings to determine if they have been cut and spliced, and replacement with new, adjustable struts if the existing struts are cut and spliced with fewer than six hi-loks.

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 require accomplishment of certain actions specified in the service bulletins described previously, except as discussed below.

Differences Between This Proposed AD and the Service Bulletins

The service bulletins do not specify what type of visual inspection of the tripod assembly and tripod struts should be used. The FAA has determined that the procedures in the service bulletins describe a general visual inspection. Note 2 of this proposed AD defines that type of inspection.

Other differences include the following:

• Boeing Service Bulletin 767-57A0058, Revision 1, specifies doing a “check” for preload, however, this proposed AD uses the term “general visual inspection.”
• The compliance time for doing the actions specified in the Boeing Service Bulletin 767-57A0058, Revision 1, is within 5,000 flight cycles or 24 months after the receipt of the service bulletin, whichever comes first. The airplane manufacturer has informed us that “whichever comes first” is an error in the compliance time and would put certain airplanes immediately out of compliance. The correct compliance time is “whichever comes later,” and this proposed AD requires that compliance time.
• The effectivity in Boeing Service Bulletin 767-57-0037 specifies line numbers 1 through 469 inclusive. The airplane manufacturer has informed us that line numbers 1 through 159 inclusive had a fixed strut which was not cut and spliced or preloaded. Line numbers 160 through 469 inclusive may have had a fixed strut which was cut and spliced, and if it was not cut and spliced it was still subject to being preloaded. Therefore, the affected line numbers are 160 through 469 inclusive, and those line numbers are included in this proposed AD.

Cost Impact

There are approximately 379 airplanes of the affected design in the worldwide fleet. The FAA estimates that 136 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 1 work hour per airplane to accomplish the proposed inspections of the tripod strut assembly and bushing holes, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspections proposed by this AD on U.S. operators is estimated to be $8,160, or $60 per airplane.

The cost impact figure discussed above is 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 proposed 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 rework of the fitting assembly, it would take approximately 4 work hours per airplane to accomplish the proposed rework, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed rework would be $240 per airplane.

Should an operator be required to accomplish the high frequency eddy current inspection, it would take approximately 5 work hours 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 proposed inspection would be $300 per airplane.

Should an operator be required to accomplish the replacement of the main strut support fitting, it would take approximately 14 work hours per airplane to accomplish the proposed replacement (on both the left and right wings of the airplane, excluding the time for gaining access and closing up), at an average labor rate of $60 per work hour.

Required parts would cost approximately $12,380 per airplane. Based on these figures, the cost impact of the proposed replacement would be $13,220 per airplane.

Should an operator be required to accomplish the inspection for improperly cut and spliced struts, 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 struts proposed by this AD would be $60 per airplane.

Should an operator be required to accomplish the replacement of a cut and spliced strut with a new, adjustable tripod strut, it would take approximately 4 work hours per airplane to accomplish the proposed replacement, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the replacement proposed by this AD would be $240 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.

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.