Airworthiness Directives; Boeing Model 737-100, -200, and -200C 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 737-100, -200, and -200C series airplanes. This proposal would require a one-time inspection for damage (i.e., chafing) of the power feeder wire bundle for the auxiliary power unit (APU) generator and the first officer's elevator down control cable and for proper separation between that wire bundle and control cable, and corrective action, if necessary. For certain airplanes, this proposal also would require attaching the power feeder wire bundle to adjacent wire bundles. This action is necessary to prevent a short circuit and resultant arcing between the wire bundle and control cable, which could sever the control cable. Failure of the first officer's elevator down control cable, if combined with a subsequent failure of the captain's elevator down control cable, could result in loss of elevator control of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by September 6, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-221-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-221-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:

Stephen Oshiro, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2793; 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-221-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-221-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Background

In July 1996, a Boeing Model 747 series airplane was involved in an accident. As part of re-examining all aspects of the service experience of the airplane involved in the accident, the FAA participated in design review and testing to determine possible sources of ignition in center fuel tanks. As part of the review, we examined fuel system wiring with regard to the possible effects that wire degradation may have on arc propagation.

In 1997 in a parallel preceding, at the recommendation of the White House Commission on Aviation Safety and Security, the FAA expanded its Aging Transport Program to include non-structural systems and assembled a team for evaluating these systems. This team performed visual inspections of certain transport category airplanes for which 20 years or more had passed since date of manufacture. In addition, the team gathered information from interviews with FAA Principal Maintenance Inspectors and meetings with representatives of airplane manufacturers. This evaluation revealed that the length of time in service is not the only cause of wire degradation; inadequate maintenance, contamination, improper repair, and mechanical damage are all contributing factors. From the compilation of this comprehensive information, we developed the Aging Transport Non-Structural Systems Plan to increase airplane safety by increasing knowledge of how non-structural systems degrade and how causes of degradation can be reduced.

In 1998, an accident occurred off the coast of Nova Scotia involving a McDonnell Douglas Model MD-11 series airplane. Investigation indicates that a fire broke out in the cockpit and first class overhead area. Although the ignition source of the fire has not been determined, the FAA, in conjunction with Boeing and operators of Model MD-11, DC-8, DC-9, DC-10, and DC-9-80 series airplanes, is reviewing all aspects of the service history of those airplanes to identify potential unsafe conditions associated with wire degradation due to various contributing factors (e.g., inadequate maintenance, contamination, improper repair, and mechanical damage) and to take appropriate corrective actions. We have issued a series of airworthiness directives (AD) that address unsafe conditions identified during that process. This process is continuing and we may consider additional rulemaking actions as further results of the review become available. The cause of the Nova Scotia MD-11 accident has not yet been determined.

In 1999, the FAA Administrator established a formal advisory committee to facilitate the implementation of the Aging Transport Non-Structural Systems Plan. This committee, the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC), is made up of representatives of airplane manufacturers, operators, user groups, aerospace and industry associations, and government agencies. As part of its mandate, ATSRAC will recommend rulemaking to increase transport category airplane safety in cases where solutions to safety problems connected to aging systems have been found and must be applied. Detailed analyses of certain transport category airplanes that have been removed from service, studies of service bulletins pertaining to certain wiring systems, and reviews of previously issued ADs requiring repetitive inspections of certain wiring systems, have resulted in valuable information on the cause and prevention of wire degradation due to various contributing factors (e.g., inadequate maintenance, contamination, improper repair, and mechanical damage).

In summary, as a result of the investigations described above, the FAA has determined that corrective action may be necessary to minimize the potential hazards associated with wire degradation and related causal factors (e.g., inadequate maintenance, contamination, improper repair, and mechanical damage).

Identification of Unsafe Condition

The FAA has received reports of chafing between the power feeder wire bundle for the auxiliary power unit (APU) generator and the first officer's elevator down control cable beneath the right side cockpit floor on certain Boeing Model 737-100, -200, and -200C series airplanes. Investigation has revealed that this problem originates when the power feeder wire bundle for the APU generator is not properly repositioned during replacement of the circuit breaker for the APU generator. If certain clamps on the APU generator's power feeder wire bundle are not loosened, the wire bundle may be pulled up or pushed down and may start to form a loop. If this loop chafes against the first officer's elevator down control cable, a short circuit and resultant arcing between the wire bundle and control cable could occur, which could sever the control cable. The resultant failure of the control cable may not be evident because both the captain's and first officer's positions have elevator control cables and both positions can control the elevator using either cable. However, failure of the first officer's elevator down control cable, if combined with a subsequent failure of the captain's elevator down control cable for another (unrelated) reason, could result in loss of elevator control of the airplane.

Other Related Rulemaking

This proposed AD is one of a series of actions identified as part of the ATSRAC program initiative to maintain continued operational safety of aging non-structural systems in transport category airplanes. The program is continuing and the FAA may consider additional rulemaking actions as further results of the review become available.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Special Attention Service Bulletin 737-24-1144, Revision 1, dated June 21, 2001, which describes procedures for a one-time inspection for damage (i.e., chafing) of the power feeder wire bundle for the APU generator (wire bundle W146) and the first officer's elevator down control cable and for proper separation between that wire bundle and control cable. If necessary, corrective actions include the following:

• Replacing the first officer's elevator down control cable with a new cable if any damage is found.
• Repairing wire bundle W146 if any damage is found.
• Rerouting the wire bundle by turning wire bundle clamps to a position that provides minimum separation between the wire bundle and control cable, if the wire bundle and control cable are not separated by the minimum distance specified in the service bulletin.

For certain airplanes, the service bulletin also describes procedures to attach wire bundle W146 to adjacent wire bundles.

Accomplishment of the actions specified in the service bulletin is intended to 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 AD and Service Bulletin

This proposed AD differs from the service bulletin in the following ways:

• The service bulletin recommends that the actions be accomplished “at the next normally scheduled maintenance period when manpower, materials, and facilities are available.” The FAA finds that such a compliance time would not ensure that the identified unsafe condition is addressed in a timely manner. In developing an appropriate compliance time for this proposed AD, we considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition. In light of all relevant factors, we find a compliance time of 18 months after the effective date of the AD for completing the proposed actions is warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.
• The service bulletin does not specify what method to use for the inspection described in the Accomplishment Instructions. We find that the procedures in the service bulletin describe a detailed visual inspection. A note has been included in this proposed AD to define such an inspection.

Cost Impact

There are approximately 136 airplanes of the affected design in the worldwide fleet. The FAA estimates that 47 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, 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 $2,820, 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.

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.