Airworthiness Directives; McDonnell Douglas Model MD-90-30 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 McDonnell Douglas Model MD-90-30 airplanes. This proposal would require measuring the length of the wear indicator on the brake stack of the main landing gear (MLG) brake assembly to determine the degree of wear, and follow-on actions. This proposal also would require eventual replacement of the existing MLG brake assembly with a new, improved or modified assembly, which would constitute terminating action for any repetitive actions being performed per this proposed AD. This action is necessary to prevent failure of the MLG brakes and consequent loss of braking capability, which could result in the airplane overrunning the runway during take-off or landing. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by October 21, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-212-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. 2001-NM-212-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 Aircraft Group, Long Beach Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Data and Service Management, Dept. C1-L5A (D800-0024). This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT:

Technical Information: Ken Sujishi, Aerospace Engineer, Systems & Equipment Branch, ANM-130L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5353; fax (562) 627-5210.

Other Information: Judy Golder, Airworthiness Directive Technical Editor/Writer; telephone (425) 687-4241, fax (425) 227-1232. Questions or comments may also be sent via the Internet using the following address: judy.golder@faa.gov. Questions or comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

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-212-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-212-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports of discrepancies of the carbon brake assembly installed on the main landing gear (MLG) of certain McDonnell Douglas Model MD-90-30 airplanes. On the discrepant MLG brake assemblies, which had wear of 50 percent or more, piston insulators had pushed below the surface of the pressure plate. In a few cases where the brake assembly was near “full worn” condition, the piston insulators had broken through the pressure plate and pushed into the rotating carbon disk of the brake assembly. This condition, if not corrected, could result in failure of the MLG brakes and consequent loss of braking capability, which could result in the airplane overrunning the runway during take-off or landing.

Explanation of Relevant Service Information

We have reviewed and approved Boeing Alert Service Bulletin MD90-32A042, Revision 01, dated August 17, 2000, which recommends accomplishment of Aircraft Braking Systems Corporation (ABS) Service Bulletin MD90-32-13.

ABS Service Bulletin MD90-32-13, Revision 2, dated April 28, 2000, describes procedures for measuring the wear indicator on the MLG brake stack. When the wear indicator on the brake stack measures 1.30 inches or less, the ABS service bulletin specifies inspecting the contact area between the piston insulators and the pressure plate to find discrepancies of the pressure plate (i.e., the surface of the piston insulator is flush with or has pushed beyond the surface of the counterbore). The follow-on actions are as follows:

• If no discrepancy of the pressure plate is found—repetitive inspections for discrepancies of the pressure plate.
• If any discrepancy is found and the length of the wear indicator on the MLG brake is within certain limits—overhaul of the MLG brake, including replacement of the carbon brake stack.
• If any discrepancy is found and the length of the wear indicator on the MLG brake is outside certain limits—repair of the brake assembly, which involves replacing the swage tube subassembly of the brake with a new subassembly, replacing the pressure plate with a new, improved pressure plate, shortening the wear indicator tube, inspecting to determine the radius of the piston insulators, and replacing the piston insulators with reworked insulators if necessary.

Overhaul or repair of the brake assembly eliminates the need for the repetitive inspections.

The FAA also has reviewed and approved Boeing Service Bulletin MD90-32-045, Revision 01, dated December 15, 2000. That service bulletin describes procedures for replacement of the MLG brake assembly with a brake assembly that has been modified according to ABS Service Bulletin MD90-32-14, dated May 9, 2000.

ABS Service Bulletin MD90-32-14 describes procedures for modifying brake assemblies in certain configurations to a new configuration. The modification involves replacing certain wear indicator tubes with new tubes, measuring the radius of the piston insulators, reworking the piston insulators if necessary, installing new or refurbished components, and reidentifying the brake assembly.

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

Differences Between Service Bulletins and Proposed AD

ABS Service Bulletin MD90-32-13, Revision 2, specifies that, if the wear indicator on the brake stack measures more than 1.30 inches, no further action is necessary to comply with the service bulletin. However, we find that, as the brake continues in service and the wear indicator on the brake stack decreases to 1.30 inches or less, the actions in that service bulletin will apply. Therefore, this proposed AD would require repetitive measurements of the wear indicator on the brake stack every 260 landings, until the wear indicator on the brake stack measures 1.30 inches or less, at which time the proposed follow-on actions would apply.

As part of the follow-on actions that would be required by the proposed AD, Boeing Alert Service Bulletin MD90-32A042, Revision 01; and ABS Service Bulletin MD90-32-13, Revision 2; specify performing an inspection of the MLG brake assembly. However, neither service bulletin specifies what type of inspection is necessary. We have determined that a general visual inspection is necessary; therefore, paragraph (b) of this proposed AD would require a general visual inspection of the MLG brake assembly for discrepancies of the pressure plate (i.e., the surface of the piston insulator is flush with or has pushed beyond the surface of the counterbore). Note 2 of this proposed AD defines such an inspection.

Also, ABS Service Bulletin MD90-32-13, Revision 2, specifies to use the repair procedure in that service bulletin only when the wear indicator on the MLG brake is not longer than 2.10 inches. For a wear indicator on the MLG brake that is longer than 2.10 inches, the pressure plate modification cannot be accomplished per the service bulletin, and is not necessary until the MLG brake is worn further. Thus, we have clarified in this proposed AD that an MLG brake with a wear indicator longer than 2.10 inches may remain installed without repair or replacement until the MLG brake assembly is replaced with a new, improved or modified MLG brake assembly.

These issues have been discussed with the airplane manufacturer, and the manufacturer concurs with our decision to issue this proposed AD with these differences.

Cost Impact

There are approximately 115 airplanes of the affected design in the worldwide fleet. The FAA estimates that 21 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 measurement of the brake stack wear indicator, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this proposed action on U.S. operators is estimated to be $1,260, or $60 per airplane, per measurement cycle.

It would also take approximately 1 work hour per airplane to accomplish the proposed inspection for discrepancies of the pressure plate of the MLG brake, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this proposed action on U.S. operators is estimated to be $1,260, or $60 per airplane, per inspection cycle.

It would take approximately 6 work hours per airplane to accomplish the proposed replacement of the MLG brake assembly, at an average labor rate of $60 per work hour. Required parts would cost approximately $55,000. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $1,162,560, or $55,360 per airplane.

The cost impact figures discussed above are 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.