# 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 DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, Model MD-88 airplanes, and Model MD-90-30 series airplanes. This proposal would require installation of a pipe support and clamps on the hydraulic lines in the aft fuselage; replacement of the hydraulic pipe assembly in the aft fuselage with a new pipe assembly; and installation of drain tube assemblies and diverter assemblies in the area of the auxiliary power unit (APU) inlet; as applicable. This proposal is prompted by reports of smoke and odor in the passenger cabin and cockpit due to hydraulic fluid leaking into the APU inlet, and subsequently, into the air conditioning system. The actions specified by the proposed AD are intended to prevent such hydraulic fluid leakage due to fatigue vibration and cracking in the flared radius of a hydraulic pipe in the aft fuselage, which could result in smoke and odors in the passenger cabin or cockpit.

# DATES:

 Comments must be received by March 3, 2000.

# ADDRESSES:

 Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-227-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 Aircraft Group, Long Beach Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Dept. C1-L51 (2-60). This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California.

# FOR FURTHER INFORMATION CONTACT:

 Albert Lam, Aerospace Engineer, Systems and Equipment Branch, ANM-130L, FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5346; fax (562) 627-5210.

# 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-227-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-227-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

## Discussion

The FAA has received several reports of smoke and odor in the passenger cabin on McDonnell Douglas Model DC-9-82 (MD-82) series airplanes due to failure of a hydraulic pipe in the aft fuselage accessory compartment. Investigation revealed that hydraulic fluids leaked into the bilge area of the tailcone and out of the existing drains and were ingested into the air intake area of the auxiliary power unit (APU), and subsequently, into the air conditioning system. Further investigation revealed that the leaking fluid was due to fatigue vibration and cracking in the flared radius of a hydraulic pipe in the aft fuselage. This condition, if not corrected, could result in smoke and odors in the passenger cabin or cockpit.

The subject hydraulic pipe assembly on McDonnell Douglas Model DC-9-81 (MD-81), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, Model MD-88 airplanes, and Model DC-90-30 series airplanes is similar to those on the affected Model DC-9-82 (MD-82) airplanes. Therefore, all of these airplanes may be subject to the same unsafe condition. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved McDonnell Douglas Service Bulletin MD80-29-056, dated June 18, 1996 [for Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes], which describes procedures for installation of a pipe support and clamps on the hydraulic lines in the aft fuselage.

                    The FAA also has reviewed and approved McDonnell Douglas Service                     Start Printed Page 2556                    Bulletin MD80-29-062, Revision 01, dated August 3, 1999 [for Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC9-87 (MD-87) series airplanes, and Model MD-88 airplanes], which describes procedures for replacement of the hydraulic pipe assembly in the aft fuselage with a new pipe assembly having a greater wall thickness.                

In addition, the FAA has reviewed and approved McDonnell Douglas Service Bulletins MD80-53-286, dated September 3, 1999 [for Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, and Model MD-88 airplanes], and MD90-53-018, dated September 3, 1999 (for Model MD-90-30 series airplanes), which describe procedures for installation of drain tube assemblies and diverter assemblies in the area of the APU inlet.

Accomplishment of the actions specified in the service bulletins listed above 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.

## Differences Between Proposed Rule and Service Bulletins

Operators should note that, although McDonnell Douglas Service Bulletins MD80-29-056, dated June 18, 1996; MD80-53-286, dated September 3, 1999; and MD90-53-018, dated September 3, 1999; recommend accomplishing the modifications at the earliest practical maintenance period (after the release of the service bulletin), the FAA has determined that such an interval would not address the identified unsafe condition in a timely manner. 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 modifications. In light of all of these factors, the FAA finds that an 18-month compliance time for initiating the proposed actions 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 1,126 airplanes of the affected design in the worldwide fleet. The FAA estimates that 634 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 2 work hours per airplane [for 512 Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes] to accomplish the proposed installation of the pipe support and clamps, at an average labor rate of $60 per work hour. Required parts would cost approximately $226 per airplane. Based on these figures, the cost impact of this installation proposed by AD on U.S. operators is estimated to be $177,152, or $346 per airplane.

It would take approximately 2 work hours per airplane [for 634 Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, and Model MD-88 airplanes] to accomplish the proposed replacement, at an average labor rate of $60 per work hour. Required parts would cost approximately $520 per airplane. Based on these figures, the cost impact of this replacement proposed by this AD on U.S. operators is estimated to be $405,760, or $640 per airplane.

It would take approximately 14 work hours per airplane (for 22 Model MD-90-30 series airplanes) to accomplish the proposed installation of drain tube assemblies and diverter assemblies, at an average labor rate of $60 per work hour. Required parts would cost approximately $4,503 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $117,546, or $5,343 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 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. 

§ 39.13

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

**McDonnell Douglas:**                         Docket 99-NM-227-AD.                     

*Applicability:*                         Models and series of airplanes as listed in the applicable McDonnell Douglas service bulletin(s) specified in Table 1 of this AD, certificated in any category.                    
Start Printed Page 2557

# 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 (e) 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 prevent hydraulic fluid leakage into the auxiliary power unit (APU) inlet due to fatigue vibration and cracking in the flared radius of a hydraulic pipe in the aft fuselage, which could result in smoke and odors in the passenger cabin or cockpit; accomplish the following:

## Installation a Pipe Support and Clamps 

(a) For Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, as listed in McDonnell Douglas Service Bulletin 

MD80-29-056, dated June 18, 1996: Within 18 months after the effective date of this AD, install a pipe support and clamps on the hydraulic lines in the aft fuselage in accordance with the service bulletin. 

## Replacement of the Hydraulic Pipe Assembly 

(b) For Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, and Model MD-88 airplanes, as listed McDonnell Douglas Service Bulletin MD80-29-062, Revision 01, dated August 3, 1999: Within 18 months after the effective date of this AD, replace the hydraulic pipe assembly in the aft fuselage with a new pipe assembly having a greater wall thickness, in accordance with the service bulletin. Except for Model MD-88 airplanes that have been modified in accordance with McDonnell Douglas MD-80 Service Bulletin 29-54, dated February 2, 1993, or Revision 2, dated December 17, 1993, the requirements of this paragraph must be accomplished concurrently with the requirements of paragraph (a) of this AD 

## Installation of Drain Tube Assemblies and Diverter Assemblies 

(c) For Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, as listed in McDonnell Douglas Service Bulletin MD80-53-286, dated September 3, 1999; and Model MD-9-30 series airplanes, as listed in McDonnell Douglas Service Bulletin MD90-53-018, dated September 3, 1999: Within 18 months after the effective date of this AD, install drain tube assemblies and diverter assemblies in the area of the APU inlet, in accordance with the applicable service bulletin. 

## Spares 

(d) As of the effective date of this AD, no person shall install a hydraulic pipe assembly, part number 7936907-603, on any airplane. 

## Alternative Methods of Compliance 

(e) 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 Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. 

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 

(f) Special flight permits may be issued in accordance with sections 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 January 11, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-1118 Filed 1-14-00; 8:45 am] 

BILLING CODE 4910-13-U