Airworthiness Directives; Learjet Model 60 Airplanes

[Federal Register Volume 63, Number 152 (Friday, August 7, 1998)]
[Rules and Regulations]
[Pages 42208-42210]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-20970]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-227-AD; Amendment 39-10694; AD 98-16-18]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 60 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Learjet Model 60 airplanes. This action 
requires repetitive measurements of the brake wear dimension between 
the housing subassembly and the pressure plate that is adjacent to the 
top pistons of the brake assembly; and follow-on corrective actions, if 
necessary. This amendment is prompted by reports of abnormal (uneven) 
brake wear. The actions specified in this AD are intended to detect and 
repair an abnormal brake wear condition, which could result in loss of 
brake effectiveness and cause the airplane to leave the runway surface.

DATES: Effective August 24, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 24, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before October 6, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-227-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
Aircraft Braking Systems Corporation, 1204 Massillon, Akron, Ohio 
44306. 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; or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Paul C. DeVore, Aerospace Engineer, 
Systems and Propulsion Branch, ACE-116W, FAA, Small Airplane 
Directorate, Wichita Aircraft Certification Office, 1801 Airport Road, 
Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316) 
946-4142; fax (316) 946-4407.

SUPPLEMENTARY INFORMATION: The FAA has received reports from Learjet of 
an abnormal brake wear condition on certain Learjet Model 60 airplanes. 
Subsequent investigation, conducted by Aircraft Braking Systems 
Corporation (ABS) (the manufacturer of the brakes), revealed an 
abnormal (uneven) brake

[[Page 42209]]

wear condition of the friction material (friction mix) on the rotating 
disks. The uneven wear has been attributed to thermal gradients within 
the brake stack of the ABS brake assembly. Such abnormal brake wear, if 
not corrected, could result in loss of brake effectiveness, which could 
cause the airplane to leave the runway surface.

Explanation of Relevant Service Information

    The FAA has reviewed Aircraft Braking Systems Service Bulletin 
LEAR60-32-03, dated March 5, 1998, which describes procedures for 
repetitive measurements of the brake wear dimension between the housing 
subassembly and the pressure plate that is adjacent to the top pistons 
of the brake assembly; and follow-on corrective actions, if necessary. 
These follow-on actions include performing a visual inspection to 
detect abnormal wear of the friction mix on the rotating disks, and 
replacing both rotating disks with new disks, if necessary; and 
replacing the disk stack with a new disk stack or overhauling it. 
Accomplishment of certain actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design, this AD is 
being issued to detect and repair an abnormal (uneven) brake wear 
condition, which could result in loss of brake effectiveness and cause 
the airplane to leave the runway surface. This AD requires 
accomplishment of certain actions specified in the service bulletin 
described previously.
    Operators should note that the service bulletin lists other actions 
in addition to those described previously. The FAA considers these 
additional actions to be routine maintenance and therefore has not 
specified their performance in this AD.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-227-AD.'' The postcard will be date stamped and 
returned to the commenter.

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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket.
    A copy of it, if filed, 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.


Sec. 39.13  [Amended]

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

98-16-18  Learjet: Amendment 39-10694. Docket 98-NM-227-AD.

    Applicability: Model 60 airplanes equipped with Aircraft Braking 
Systems (ABS) brake assemblies having part number 5003096-7, 
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 (c) 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 detect and repair an abnormal (uneven) brake wear condition, 
which could result in loss of brake effectiveness and cause the 
airplane to leave the runway surface, accomplish the following:
    (a) Within 10 flight hours after the effective date of this AD, 
measure the brake wear dimension between the housing subassembly and 
the pressure plate that is adjacent to the top pistons of the brake 
assembly, in accordance with ABS Service Bulletin LEAR60-32-03, 
dated March 5, 1998.
    (1) If the dimension is less than 0.359 inch (9.12 mm), 
thereafter repeat the measurement at intervals not to exceed 25 
flight cycles.

[[Page 42210]]

    (2) If the dimension is equal to or greater than 0.359 inch 
(9.12 mm) and less than 0.464 inch (11.79 mm), prior to further 
flight, perform a visual inspection to detect abnormal wear of the 
friction mix on the rotating disks, in accordance with the service 
bulletin.
    (i) If the friction mix is not worn to the disk cores on either 
disk, thereafter repeat the measurement at intervals not to exceed 
25 flight cycles.
    (ii) If the friction mix is worn to the disk core on either 
disk, replace both rotating disks with new disks in accordance with 
the service bulletin. Thereafter, repeat the measurement at 
intervals not to exceed 25 flight cycles.
    (3) If the dimension is greater than or equal to 0.464 inch 
(11.769 mm), replace the disk stack with a new disk stack or 
overhaul it, in accordance with the service bulletin. Thereafter, 
repeat the measurement at intervals not to exceed 25 flight cycles.
    (b) As of the effective date of this AD, no person shall install 
on any airplane a used ABS brake assembly, part number 5003096-7, 
unless it has been inspected and applicable corrective actions have 
been performed in accordance with the requirements of this AD.
    (c) 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.

    (d) 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.
    (e) The actions shall be done in accordance with Aircraft 
Braking Systems Corporation Service Bulletin LEAR60-32-03, dated 
March 5, 1998. 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, 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.
    (f) This amendment becomes effective on August 24, 1998.

    Issued in Renton, Washington, on July 30, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-20970 Filed 8-6-98; 8:45 am]
BILLING CODE 4910-13-P

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