AD 98-06-28

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Learjet Model 31 and 35A airplanes, that currently requires replacement of two segments of 16 American Wire Gauge (AWG) wire with 8 AWG wire at the connector that is connected to the auxiliary cabin heater relay box. That AD was prompted by a report indicating that two segments of the 16 AWG wire in the auxiliary cabin heater, which were spliced during production, do not provide adequate current-carrying capacity. This amendment requires the installation of a new replacement wire assembly. The actions specified by this AD are intended to prevent electrical arcing and consequent fire hazard that could result from wiring with inadequate current-carrying capacity.

Final rule

98-06-28 LEARJET, INC.: Amendment 39-10406. Docket 96-NM-202-AD. Supersedes AD 96-11-07, Amendment 39-9632.

Applicability: Model 31 airplanes having serial numbers 31-002 through 31-029 inclusive, and Model 35A airplanes having serial numbers 35-647 through 35-670 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 requestshould include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent electrical arcing and consequent fire hazard, accomplish the following:

(a) Within 6 months after the effective date of this AD, replace two segments of 16 American Wire Gauge (AWG) wire with 8 AWG wire at the P190 connector that is connected to the E33 auxiliary cabin heater relay box, in accordance with Learjet Service Bulletin SB 31-21-10, Revision 1, dated May 17, 1996 (for Model 31 airplanes), or Learjet Service Bulletin SB 35-21-24, Revision 1, dated May 17, 1996 (for Model 35A airplanes), as applicable.

NOTE 2: Accomplishment of the replacement in accordance with the procedures specified in Learjet Service Bulletin SB 31-21-10 or SB 35-21-24 (original issue), both dated August 11, 1995, but using equipment that is identical or equivalent to that of the applicable kit specified in Revision 1 of those service bulletins, is considered to be acceptable for compliance with the requirements of paragraph (a) of this AD.

(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 3: 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 actions shall be done in accordance with Learjet Service Bulletin SB 31-21- 10, dated August 11, 1995, or Revision 1, dated May 17, 1996, or Learjet Service Bulletin SB 35-21-24, dated August 11, 1995, or Revision 1, dated May 17, 1996; as applicable.

(1) The incorporation by reference of Learjet Service Bulletin SB 31-21-10, Revision 1, dated May 17, 1996, and Learjet Service Bulletin SB 35-21-24, Revision 1, dated May 17, 1996, is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

(2) The incorporation by reference of Learjet Service Bulletins SB 31-21-10 dated August 11, 1995 and Learjet SB 35-21-24 dated August 11, 1995, was approved previously by the Director of the Federal Register as of June 28, 1996 (61 FR 26090, May 24, 1996).

(3) 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, Small Airplane Directorate, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, 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 April 24, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 96-11-07, amendment 39-9632 (61 FR 26090, May 24, 1996), which is applicable to certain Learjet Model 31 and 35A airplanes, was published in the Federal Register on October 28, 1996 (61 FR 55584). The action proposed to require the installation of a new replacement wire assembly.

Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were submitted in response to the proposal or the FAA's determination of the cost to the public.

Conclusion
The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

Cost Impact
There are approximately 52 Learjet Model 31 and 35A airplanes of the affected design in the worldwide fleet. The FAA estimates that 44 airplanes of U.S. registry will be affected by this AD.

The actions that are currently required by AD 96-11-07, and retained in this AD, take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be supplied by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the required actions on U.S. operators is estimated to be $10,560, or $240 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The FAA has been advised, however, that some operators already have installed equipment that is the equivalent to that which would be required by this AD. Therefore, the future economic cost impact of this proposed rule on U.S. operators is expected to be less than the cost impact figure indicated above.

Regulatory Impact
The regulations adopted hereinwill 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 removing amendment 39-9632 (61 FR 26090, May 24, 1996), and by adding a new airworthiness directive (AD), amendment 39-10406, to read as follows: