Airworthiness Directives; McDonnell Douglas Model MD-90-30 Series Airplanes

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-210-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-210-AD, 1601 Lind Avenue, SW., Renton, Washington 98055- 4056.

Discussion

The FAA has received reports of main landing gear (MLG) piston failures during towing of McDonnell Douglas Model DC-9-80 (MD-80) series airplanes. Investigation revealed that the fracture surface extended around the barrel section at the piston/axle transition. The fractures originated at a fatigue crack located where the inner/upper edge of a torque link lug blended into this transition. This condition, if not corrected, could result in failure of the pistons, and consequent damage to the airplane structure and injury to flight crew, passengers, or ground personnel. The subject MLG torque link lugs on Model MD-90-30 series airplanes are similar to those on the affected McDonnell Douglas Model DC-9-80 series airplanes. Therefore, all of these airplanes may be subject to the same unsafe condition.

Other Relevant Rulemaking

On September 5, 1996, the FAA issued AD 96-19-09, amendment 39-9756 (61 FR 48617, September 16, 1996), applicable to certain McDonnell Douglas DC-9 and MD-88 series airplanes, to require a one-time inspection to detect cracking of the MLG pistons, and repair or replacement of the pistons with new or serviceable parts, if necessary. However, this proposed AD would not affect the current requirements of that previously issued AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved McDonnell Douglas Service Bulletin MD90-32-012, dated May 19, 1997, and Revision 01, dated June 2, 1998, which describes procedures for repetitive fluorescent penetrant and magnetic particle inspections of the MLG torque link lugs to detect fatigue cracking, and repair, if necessary. 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.

Differences Between Proposed Rule and Service Bulletin

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA. Operators also should note that, although the service bulletin recommends accomplishing the fluorescent inspections only for MLG's that have accumulated more than a specified number of landings, the FAA has determined that all of the subject parts are subject to the same fatigue cracking. Therefore, the compliance times for the proposed inspections address all MLG's of the affected design. In developing an appropriate compliance time for this proposed 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 inspection (two hours). In light of all of these factors, the FAA finds that intervals of 4,000 landings for inspection of MLG piston, part number (P/N) 5935347-509, and 5,000 landings for MLG piston, P/N's 5935347-511 and -513, address the identified unsafe condition in a timely manner. Therefore, the FAA has determined these compliance times for initiating the required actions to be warranted, in that they represent an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Interim Action

This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the

FAA may consider additional rulemaking.

Cost Impact

There are approximately 19 airplanes of the affected design in the worldwide fleet. The FAA estimates that 15 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 2 work hours per airplane to accomplish the proposed inspections, 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 $1,800, or $120 per airplane, per inspection cycle. 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 substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

McDonnell Douglas: Docket 99-NM-210-AD.

Applicability: Model MD-90-30 airplanes, as listed in McDonnell Douglas Service Bulletin MD90-32-012, Revision 01, dated June 2, 1998; certificated in any category.

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously. To detect and correct fatigue cracking of main landing gear (MLG) pistons, which could result in failure of the pistons, and consequent damage to the airplane structure and injury to flight crew, passengers, or ground personnel, accomplish the following:

Inspection of MLG Piston Part Number 5935347-509

(a) For MLG pistons, part number (P/N) 5935347-509: Perform fluorescent penetrant and magnetic particle inspections to detect fatigue cracking of the MLG pistons, in accordance with McDonnell Douglas Service Bulletin MD90-32-012, dated May 19, 1997; or Revision 01, dated June 2, 1998, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD. Repeat the inspections thereafter at intervals not to exceed 2,500 landings. (1) Prior to the accumulation of 4,000 landings; or (2) Within 2,500 landings or 12 months after the effective date of this AD whichever occurs first.

Inspection of MLG Piston Part Numbers 5935347-511 and -513

(b) For MLG pistons P/N's 5935347-511 and -513: Within 5,000 landings after the effective date of this AD, perform fluorescent penetrant and magnetic particle inspections to detect fatigue cracking of the MLG pistons, in accordance with McDonnell Douglas Service Bulletin MD90-32-012, dated May 19, 1997; or Revision 01, dated June 2, 1998. Repeat the inspections thereafter at intervals not to exceed 5,000 landings.

Repair

(c) If any crack is found during any inspection required by this AD: Repair in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

Alternative Methods of Compliance

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles ACO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO.

Special Flight Permits

(e) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Issued in Renton, Washington, on October 21, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-28078 Filed 10-26-99; 8:45 am] BILLING CODE 4910-13-U