[Federal Register Volume 61, Number 46 (Thursday, March 7, 1996)]
[Proposed Rules]
[Pages 9119-9121]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-5368]



      
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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-197-AD]


Airworthiness Directives; Learjet Model 31 and 35A Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Learjet Model 31 and 35A 
airplanes. This proposal would require 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. This proposal is 
prompted by a report that two segments of the 16 AWG wire in the 
auxiliary cabin heater that were spliced during production do not 
provide adequate current-carrying capacity. The actions specified by 
the proposed AD are intended to prevent electrical arcing and a 
subsequent fire hazard that could result from wiring with inadequate 
current-carrying capacity.

DATE: Comments must be received by April 17, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-197-AD, 1601 Lind Avenue, SW.,

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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 Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-
2942. This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: Dale Bleakney, Aerospace Engineer, 
Flight Test Branch, ACE-117W, FAA, Small Airplane Directorate, Wichita 
Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-
Continent Airport, Wichita, Kansas; telephone (316) 946-4135; fax (316) 
946-4407.

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 95-NM-197-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-103, Attention: Rules 
Docket No. 95-NM-197-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report indicating that, during regularly 
scheduled maintenance on a Learjet Model 35 series airplane, two 
segments of the 16 American Wire Gauge (AWG) wire in the auxiliary 
cabin heat circuit were found to provide inadequate current-carrying 
capacity. Investigation revealed that, during production, the 16 AWG 
wire had been spliced into a 10 AWG circuit at the P190 connector that 
is connected to the E33 auxiliary cabin heater relay box. The use of 
this manufacturing splicing technique (16 AWG wire into a 10 AWG 
circuit) can allow the rated current-carrying capability of the wire to 
be exceeded. This condition, if not corrected, could result in 
electrical arcing and may lead to a potential fire hazard.
    The FAA has reviewed and approved Learjet Service Bulletin SB 31-
21-10, dated August 11, 1995 (for Model 31 airplanes), and Learjet 
Service Bulletin SB 35-21-24, dated August 11, 1995 (for Model 35A 
airplanes), which describes procedures for replacement of two segments 
of 16 AWG wire with 8 AWG wire at the P190 connector that is connected 
to the E33 auxiliary cabin heater relay box. The replacement will 
ensure that the wire size is adequate for the electrical current 
requirements of that circuit.
    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 replacement of two segments of 16 AWG wire 
with 8 AWG wire at the P190 connector that is connected to the E33 
auxiliary cabin heater relay box. The actions would be required to be 
accomplished in accordance with the applicable service bulletin 
described previously.
    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 would be affected by this proposed AD, that 
it would take approximately 4 work hours per airplane to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Required parts would be supplied by the manufacturer at no cost to the 
operators. Based on these figures, the cost impact of the proposed AD 
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 proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted.
    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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

Learjet, Inc.: Docket 95-NM-197-AD.

    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

[[Page 9121]]

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 electrical arcing and subsequent 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, dated August 11, 1995 (for Model 31 airplanes), or Learjet 
Service Bulletin SB 35-21-24, dated August 11, 1995 (for Model 35A 
airplanes), as applicable.
    (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 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 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.

    Issued in Renton, Washington, on March 1, 1996.

Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-5368 Filed 3-6-96; 8:45 am]
BILLING CODE 4910-13-U