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 FAApublic 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 selfaddressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 2000NM128AD.'' 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, ANM114, Attention: Rules Docket No. 2000NM128AD, 1601 Lind Avenue, SW., Renton, Washington 980554056.

Discussion

The FAA has received numerous reports of sheared brake valve adjustment bolts on certain Learjet Model 60 airplanes. Additionally, we have received a report indicating that loss of all hydraulic fluid during taxi occurred on one airplane, which was attributed to broken brake valve adjustment bolts. Loss of all hydraulic fluid, if not prevented, could result in loss of normal braking capability. Explanation of Relevant Service Information

The FAA has reviewed and approved Bomardier Service Bulletins 60 3210, Revision 1, dated June 22, 2000 (for Learjet Model 60 airplanes), and 553214, dated November 9, 1999 (for Learjet Model 55 series airplanes). Both service bulletins describe procedures for installing a new brake valve lever stop and replacing the brake valve adjustment screws with new improved screws. Accomplishment of the actions specified in the service bulletins 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.
[[Page 15363]]

Cost Impact

There are approximately 331 airplanes of the affected design in the worldwide fleet. The FAA estimates that 285 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 16 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required parts would cost approximately $2,368 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $948,480, or $3,328, 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 39AIRWORTHINESS 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:

Learjet: Docket 2000NM128AD.

Applicability: Model 55 series airplanes, serial numbers 55003 through 55147 inclusive, and Model 60 airplanes, serial numbers 60 002 through 60189 inclusive; 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 (b) 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 bottoming of the valve components before contact of the brake valve lever with the stop, which could result in loss of all hydraulic fluid and consequent loss of normal braking; accomplish the following:
Replacement of Brake Valve Lever Stop Switch
(a) Within 300 flight hours or one year after the effective date of this AD, whichever occurs first, accomplish the actions specified in paragraph (a)(1), (a)(2), or (a)(3), as applicable.
(1) For Learjet Model 60 airplanes having serial numbers 60002 through 60093 inclusive, and 60095 through 60188 inclusive: Replace the existing brake valve lever stop switch with a new brake valve lever stop switch, and replace the brake valve adjustment screws with new improved screws, per Bombardier Service Bulletin 60 3210, Revision 1, dated June 22, 2000.
(2) For Learjet Model 60 airplanes having serial number 60094 or 60189: Replace the brake valve adjustment screws with new improved screws, per Bombardier Service Bulletin 603210, Revision 1, dated June 22, 2000.
(3) For Learjet Model 55 series airplanes having serial numbers 55003 through 55147 inclusive: Replace the existing brake valve lever stop with a new brake valve lever stop, and replace the brake valve adjustment screws with new improved screws, per Bombardier Service Bulletin 553214, dated November 9, 1999.
Alternative Methods of Compliance
(b) 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, Wichita Aircraft Certification Office, FAA. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita ACO.
Special Flight Permits
(c) 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 March 12, 2001. Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 016646 Filed 31601; 8:45 am] BILLING CODE 491013U

FOR FURTHER INFORMATION CONTACT Shane Bertish, Aerospace Engineer, Systems and Propulsion Branch, ACE116W, FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, MidContinent Airport, Wichita, Kansas 67209; telephone (316) 9464156; fax (316) 9464407.