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 modification of the canted pressure deck drain system in the wheel well of the main landing gear (MLG). This proposal is prompted by reports of ice accumulation on the aileron control cables and on the MLG door and door seal, during flight, due to fluid entering the canted pressure deck area, leaking into the MLG wheel well, and freezing. The actions specified by the proposed AD are intended to prevent such ice accumulation, which could render one of the aileron control systems and/or the MLG doors inoperative, resulting in reduced controllability of the airplane.

DATES:

Comments must be received by March 20, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-374-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:

James G. Rehrl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2783; 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-374-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-374-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received several reports indicating ice accumulation on the aileron control cables in the wheel well of the main landing gear (MLG) during flight on certain Model 767 series airplanes. The ice build-up was attributed to fluid from the sloping pressure deck leaking into the wheel well and freezing. One operator reported a large volume of fluid had leaked into the canted pressure deck area and ice had accumulated on the MLG door and door seal inside and outside the MLG wheel well. The ice caused the MLG door to jam and prevented extension of the MLG. Investigation revealed that fluid entered the canted pressure deck area through the sloping pressure deck seals and subsequently leaked into the wheel well and solidified. Such ice accumulation could render one of the aileron control systems and/or the MLG doors inoperative, resulting in reduced controllability of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 767-51A0020, Revision 1, dated July 22, 1999, which describes procedures for modification of the canted pressure deck drain system in the wheel well of the MLG. The modification includes, among other things, installation of canisters on the outboard pressure activated drain lines, re-routing of the existing drain lines, and installation of larger diameter drain lines to drain the water out through the underwing fairing thermal panel into the hot air stream from the ram outlets.

Accomplishment of the actions specified in the service bulletin described previously 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 modification of the canted pressure deck drain system in the wheel well of the MLG. 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 This Proposed AD

Operators should note that, although the service bulletin recommends accomplishment of the modification at the first available maintenance period as soon as parts, manpower, and facilities are available, the FAA has determined that a 24-month compliance time would address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the modification. In light of all of these factors, the FAA finds a 24-month compliance time for completion of the proposed modification to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Cost Impact

There are approximately 716 Model 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 278 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 15 work hours per airplane to accomplish the proposed modification, and that the average labor rate is $60 per work hour. Required parts would cost approximately $6,623 per airplane. Based on these figures, the cost impact of the modification proposed by this AD on U.S. operators is estimated to be $2,091,394, or $7,523 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.