Airworthiness Directives; Boeing Model 737-600, -700, and -800 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 737-600, -700, and -800 series airplanes. This proposal would require inspections of the fasteners in the elevator balance panel assemblies to detect various discrepancies; and corrective actions, if necessary. This proposal is prompted by a report that an elevator balance panel was found disconnected from the horizontal stabilizer due to the improper installation of fasteners during production. The actions specified by the proposed AD are intended to prevent jamming, restricting, or binding of the elevator control surfaces due to loose or missing fasteners, which could make the movement of the elevator difficult and decrease aerodynamic control of the airplane.

DATES:

Comments must be received by October 18, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-312-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:

Scott Fung, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1221; 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 filed in 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-312-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-312-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report indicating that an elevator balance panel was found disconnected from the horizontal stabilizer on a Boeing Model 737-600 series airplane. Investigation revealed that the fasteners of the elevator balance panel were improperly installed during production. Investigation also revealed that the fasteners connecting the balance panel to the elevator did not have an adequate grip length. The installation of fasteners with inadequate grip lengths occurred during production. These conditions, if not corrected, could result in jamming, restricting, or binding of the elevator control surfaces, which could make the movement of the elevator difficult and decrease aerodynamic control of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 737-55A1064, dated October 15, 1998. Paragraph 3.A. of the Accomplishment Instructions of the service bulletin describes procedures for a detailed visual inspection of the fasteners in the elevator balance panel to detect inadequate grip length, gaps between the bolt head, washer, and structure, and missing fasteners; and follow-on actions. The follow-on actions include repetitive inspections (i.e., 250 flight hours) for certain conditions; repetitive daily inspections for certain other conditions and installation of new fasteners, if necessary, and accomplishment of the procedures specified in Paragraph 3.B. of the Accomplishment Instructions of the service bulletin (described below); as applicable.

Paragraph 3.B. of the Accomplishment Instructions of the service bulletin describes procedures for a detailed visual inspection of the fasteners that attach the balance panels to the elevator and that attach the idler hinge to the stabilizer support beam for the correct length; inspection of related nut plates for correct locking torque; replacement of all fasteners and nut plates that are not satisfactory; and repair or replacement of any damaged structures. Accomplishment of these actions would eliminate the need for the repetitive inspections described above.

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. The proposed AD also would require that operators report results of inspection findings to the FAA.

Differences Between Proposed Rule and Service Bulletin

Operators should note that, unlike the procedures described in Boeing Service Bulletin 737-55A1064, dated October 15, 1998, this proposed AD would not permit further flight if any of the following conditions are detected:

• Inadequate grip length or gaps between the bolt head, washer, and structure in the balance panel;
• Loose (i.e., minimum locking torque of nut plate not achieved) or missing fasteners;
• Any fastener with an inadequate grip length in the elevator balance panel assemblies.

The FAA has determined that, because of the safety implications and consequences associated with such discrepant fasteners, any subject discrepant fastener that are found must be replaced with new fasteners, prior to further flight.

Operators also should note that the service bulletin does not specify procedures 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 approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

The service bulletin recommends accomplishing the detailed visual inspection of the fasteners in the elevator balance panel within 250 flight hours (after the release of the service bulletin). However, because of the low utilization rate of the affected airplanes and the degree of urgency associated with addressing the subject unsafe condition, the FAA has determined that accomplishing that inspection within 250 flight hours or 30 days after the effective date of this AD, whichever occurs first, represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Cost Impact

There are approximately 123 airplanes of the affected design in the worldwide fleet. The FAA estimates that 52 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 11 work hours per airplane (including access and close up hours) to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $34,320, or $660 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 AD were not adopted.

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.