AD 96-18-01

This amendment adopts a new airworthiness directive (AD), applicable to certain Learjet Model 60 airplanes, that requires modification of the aft core cowl nozzle of the engine nacelles. This amendment is prompted by a report that the sealant material in the aft core cowl nozzle of the engine nacelle was found to extend higher than the nozzle's forward flange, which can allow it to interfere with the proper operation of the emergency fuel shutoff actuating mechanism. The actions specified by this AD are intended to prevent physical interference of the emergency fuel shutoff actuating mechanism and resultant engine shutdown.

Final rule

96-18-01 LEARJET: Amendment 39-9725. Docket 95-NM-240-AD.

Applicability: Model 60 airplanes, as listed in Learjet Service Bulletin SB 60-71-2, dated May 12, 1995; certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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, unlessaccomplished previously.

To prevent the sealant material in the aft core cowl nozzle of the engine nacelles from interfering with the lever of the emergency fuel shutoff actuating mechanism, which could result in the failure of the emergency fuel shutoff actuating mechanism and resultant engine shutdown, accomplish the following:

(a) Within 90 days after the effective date of this AD, modify the aft core cowl nozzle of the engine nacelles in accordance with Learjet Service Bulletin SB 60-71-2, dated May 12, 1995.

(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 (ACO), FAA, Small 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, 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.

(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.

(d) The modification shall be done in accordance with Learjet Service Bulletin SB 60-71-2, dated May 12, 1995, which includes Nordam Service Bulletin PW300L71-1, dated April 26, 1995. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita Aircraft Certification Office, Small Airplane Directorate, 1801 Airport Road, Room 100, Mid-ContinentAirport, Wichita, Kansas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on October 2, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Learjet Model 60 airplanes was published in the Federal Register on May 30, 1996 (61 FR 27030). That action proposed to require modification of the aft core cowl nozzle of the engine nacelles.

Comments
No comments were submitted in response to the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

Cost Impact
There are approximately 39 Learjet Model 60 airplanes of the affected design in the worldwide fleet. The FAA estimates that 26 airplanes of U.S. registry will be affected by this AD, that it will take approximately 44 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will be supplied by themanufacturer at no cost to the operators. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $68,640, or $2,640 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the 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 adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: