Airworthiness Directives; Learjet Model 60 Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-191-AD; Amendment 39-8748; AD 93-23-12]

Airworthiness Directives; Learjet Model 60 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; correction.

-----------------------------------------------------------------------

SUMMARY: This document corrects information in an existing

airworthiness directive (AD), applicable to certain Learjet Model 60

airplanes, that currently requires deactivation of the auxiliary cabin

and cockpit heating systems and installation of placards. This action

corrects the applicability of the rule. This action is necessary to

ensure that only airplanes subject to the addressed unsafe condition

are subject to the requirements of the rule.

DATES: Effective December 15, 1993.

The incorporation by reference of certain publications listed in

the regulations was previously approved by the Director of the Federal

Register as of December 15, 1993 (58 FR 63060, November 30, 1993).

ADDRESSES: The service information referenced in this AD may be

obtained from Learjet, Inc., P.O. Box 7707, Wichita, Kansas 67277-7707.

This information may be examined at the Federal Aviation Administration

(FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue

SW., Renton, Washington; or at the FAA, 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.

FOR FURTHER INFORMATION CONTACT: C. Dale Bleakney, Aerospace Engineer,

Systems and Equipment Branch, ACE-130W, FAA, Small Airplane

Directorate, Wichita Aircraft Certification Office, 1801 Airport Road,

Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316)

946-4135; fax (316) 946-4407.

SUPPLEMENTARY INFORMATION: On November 22, 1993, the FAA issued AD 93-

23-12, amendment 39-8748 (58 FR 63060, November 30, 1993), to require

deactivation of the auxiliary cabin and cockpit heating systems on all

Learjet Model 60 airplanes, and the installation of a placard stating,

``Cabin and Cockpit Heat Inop.'' That action was prompted by a report

of a fire in the aft fuselage of one airplane, which had resulted from

miswiring that was installed in an auxiliary cabin heater during

manufacture. The actions required by that AD are intended to prevent

overheating of the auxiliary cabin and cockpit heaters, which

potentially could result in a fire.

Recently, the FAA has become aware of the fact that the

applicability of the AD is unnecessarily broad. In developing the AD,

the FAA intended that its applicability be coextensive with the

effectivity listing of Learjet Alert Service Bulletin SB A60-21-1,

dated November 1, 1993. (That service bulletin was referenced in the

rule as the appropriate source of service information.) That service

bulletin indicates that only airplanes having serial numbers 60-002

through 60-021, inclusive, are subject to the addressed unsafe

condition; all other airplanes of this model were modified during

production in such a way so as to preclude the unsafe condition.

However, the applicability of the AD, as published, inadvertently

indicated that all airplanes of this model were applicable to the

requirements of the AD, rather than just those having serial numbers

60-002 through 60-021. That inadvertent action incorrectly made the

requirements of the AD redundant for airplanes other than those with

the specified serial numbers.

The FAA has determined that it is appropriate to take action to

correct the applicability of AD 93-23-12 to specify only airplanes that

are subject to the addressed unsafe condition. Therefore, action must

be taken to correctly limit the AD's applicability to only Learjet

Model 60 airplanes having serial numbers 60-002 through 60-021,

inclusive.

Action is taken herein to correct the error and to correctly add

the AD as an amendment to section 39.13 of the Federal Aviation

Regulations (14 CFR 39.13). The effective date of the rule remains

December 15, 1993.

The final rule is being reprinted in its entirety for the

convenience of affected operators.

Since this action only corrects an inadvertent error in the

applicability of the rule, so as to eliminate airplanes not subject to

the identified unsafe condition, it has no adverse economic impact and

imposes no additional burden on any person. Therefore, notice and

public procedures hereon are unnecessary.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Correction

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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by correctly adding the following

airworthiness directive (AD):

93-23-12 Learjet, Inc.: Amendment 39-8748. Docket 93-NM-191-AD.

Applicability: Model 60 airplanes having serial numbers 60-002

through 60-021, inclusive, certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent overheating of the auxiliary cabin and cockpit

heaters, which could potentially result in a fire, accomplish the

following:

(a) Within 10 flight hours after the effective date of this AD,

deactivate the auxiliary cabin and cockpit heating systems; and

install a placard stating, ``Cabin and Cockpit Heat Inop'' adjacent

to the AUX HT Switch (S44) on the co-pilot's switch panel; in

accordance with Learjet Alert Service Bulletin SB A60-21-1, dated

November 1, 1993.

(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: 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

section 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 deactivation and placard installation shall be done in

accordance with Learjet Alert Service Bulletin SB A60-21-1, dated

November 1, 1993. 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, as of December 15, 1993 (58 FR 63060,

November 30, 1993). Copies may be obtained from Learjet, Inc., P.O.

Box 7707, Wichita, Kansas 67277-7707. Copies may be inspected at the

FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,

Washington; or at the FAA, Wichita ACO, 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 December 15, 1993.

Issued in Renton, Washington, on September 20, 1994.

S.R. Miller,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-23718 Filed 9-26-94; 8:45 am]

BILLING CODE 4910-13-U