[Federal Register Volume 70, Number 218 (Monday, November 14, 2005)]
[Rules and Regulations]
[Pages 69069-69071]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-22220]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2005-22169; Directorate Identifier 2005-NM-094-AD; 
Amendment 39-14361; AD 2005-23-03]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A, 
24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F 
Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Final rule.

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

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 
24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F airplanes. This AD requires 
replacement of the spherical accumulator for the main hydraulic system 
with a new cylindrical accumulator. For certain airplanes, this AD also 
requires modification of the accumulator pressure gauge. This AD 
results from reports of the failure of two thrust reverser accumulators 
(which are similar to the main hydraulic system's spherical 
accumulator) and fatigue cracks found on four thrust reverser 
accumulators. We are issuing this AD to prevent failure of the 
spherical accumulator for the main hydraulic system, due to fatigue 
cracking on the threads, which could result in the loss of hydraulic 
power, damage to the surrounding airplane structure, and loss of 
airplane control. The failure of the accumulator could also result in 
injury to any persons in the surrounding area. The loss of hydraulic 
fluid could also leak onto a potential source of ignition and result in 
a consequent fire.

DATES: This AD becomes effective December 19, 2005.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in the AD as of December 19, 
2005.

ADDRESSES: You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility, U.S. 
Department of Transportation, 400 Seventh Street SW., Nassif Building, 
room PL-401, Washington, DC.
    Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, 
for service information identified in this AD.

FOR FURTHER INFORMATION CONTACT: Robert Busto, Aerospace Engineer, 
Systems and Propulsion Branch, ACE-116W, FAA, Wichita Aircraft 
Certification Office, 1801 Airport Road, Room 100, Mid-Continent 
Airport, Wichita, Kansas 67209; telephone (316) 946-4157; fax (316) 
946-4107.

SUPPLEMENTARY INFORMATION:

Examining the Docket

    You may examine the airworthiness directive (AD) docket on the 
Internet at http://dms.dot.gov or in person at the Docket Management 
Facility office between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The Docket Management Facility office 
(telephone (800) 647-5227) is located on the plaza level of the Nassif 
Building at the street address stated in the ADDRESSES section.

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to include an AD that would apply to certain Learjet Model 
23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 
25B, 25C, 25D, and 25F airplanes. That NPRM was published in the 
Federal Register on August 23, 2005 (70 FR 49210). That NPRM proposed 
to require replacement of the spherical accumulator for the main 
hydraulic system with a new cylindrical accumulator. For certain

[[Page 69070]]

airplanes, that proposed AD would also require modification of the 
accumulator pressure gauge.

Comments

    We provided the public the opportunity to participate in the 
development of this AD. We received no comments on the NPRM or on the 
determination of the cost to the public.

Clarification of Alternative Method of Compliance (AMOC) Paragraph

    We have revised this action to clarify the appropriate procedure 
for notifying the principal inspector before using any approved AMOC on 
any airplane to which the AMOC applies.

Conclusion

    We have carefully reviewed the available data, and determined that 
air safety and the public interest require adopting the AD with the 
change described previously. We have determined that this change will 
neither increase the economic burden on any operator nor increase the 
scope of the AD.

Costs of Compliance

    There are about 434 airplanes of the affected design in the 
worldwide fleet. This AD will affect about 242 airplanes of U.S. 
registry. The actions will take about 9 to 13 work hours per airplane, 
at an average labor rate of $65 per work hour. Required parts will cost 
about $1,336 to $1,363 per airplane. Based on these figures, the 
estimated cost of the AD for U.S. operators is $464,882 to $534,336, or 
$1,921 to $2,208 per airplane.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
subtitle VII, part A, subpart III, section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will not have a 
substantial direct effect 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.
    For the reasons discussed above, I certify that this AD:
    (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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this AD and placed it in the AD docket. See the ADDRESSES 
section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

2005-23-03 Learjet: Amendment 39-14361. Docket No. FAA-2005-22169; 
Directorate Identifier 2005-NM-094-AD.

Effective Date

    (a) This AD becomes effective December 19, 2005.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Learjet Model 23, 24, 24A, 24B, 24B-A, 
24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F 
airplanes, certificated in any category; having serial numbers 23-
003 through 23-099 inclusive, 24-100 through 24-284 inclusive, and 
25-003 through 25-153 inclusive.

Unsafe Condition

    (d) This AD results from reports of the failure of two thrust 
reverser accumulators (which are similar to the main hydraulic 
system's accumulator) and fatigue cracks found on four thrust 
reverser accumulators. We are issuing this AD to prevent failure of 
the spherical accumulator for the main hydraulic system, due to 
fatigue cracking on the threads, which could result in the loss of 
hydraulic power, damage to the surrounding airplane structure, and 
loss of airplane control. The failure of the accumulator could also 
result in injury to any persons in the surrounding area. The loss of 
hydraulic fluid could also leak onto a potential source of ignition 
and result in a consequent fire.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Replacement

    (f) Within 60 days after the effective date of this AD, replace 
the spherical accumulator having part number (P/N) 2380025-() or P/N 
2380167-() with a new cylindrical accumulator having P/N 2497202-
801, in accordance with the Accomplishment Instructions of 
Bombardier Alert Service Bulletin A23/24/25-29-4, Revision 1, dated 
January 17, 2005.

Concurrent Action

    (g) For airplanes having serial numbers 23-003 through 23-014 
inclusive: Prior to or concurrently with the actions in Bombardier 
Alert Service Bulletin A23/24/25-29-4, Revision 1, dated January 17, 
2005, relocate the accumulator pressure gauge in accordance with 
Learjet Service Kit SK23-215, dated April 4, 1966.

Parts Installation

    (h) As of the effective date, no spherical accumulator having P/
N 2380025-() or P/N 2380167-() may be installed on any airplane.

Previous Actions

    (i) Replacements done before the effective date of this AD in 
accordance with Bombardier Alert Service Bulletin A23/24/25-29-4, 
dated August 20, 2004, are acceptable for compliance with the 
requirements of paragraph (f) of this AD.

No Reporting Required

    (j) Although the service bulletin referenced in this AD 
specifies to submit certain information to the manufacturer, this AD 
does not include that requirement.

Alternative Methods of Compliance (AMOCs)

    (k)(1) The Manager, Wichita Aircraft Certification Office, FAA, 
has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.

[[Page 69071]]

Material Incorporated by Reference

    (l) You must use Bombardier Alert Service Bulletin A23/24/25-29-
4, Revision 1, dated January 17, 2005; and Learjet Service Kit SK23-
215, dated April 4, 1966; as applicable, to perform the actions that 
are required by this AD, unless the AD specifies otherwise. (The 
issue date of Learjet Service Kit SK23-215 is located only on the 
first and last pages of the document.) The Director of the Federal 
Register approved the incorporation by reference of this document in 
accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Learjet, 
Inc., One Learjet Way, Wichita, Kansas 67209-2942, for a copy of 
this service information. You may review copies at the Docket 
Management Facility, U.S. Department of Transportation, 400 Seventh 
Street SW., room PL-401, Nassif Building, Washington, DC; on the 
Internet at http://dms.dot.gov; or at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

    Issued in Renton, Washington, on October 26, 2005.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-22220 Filed 11-10-05; 8:45 am]
BILLING CODE 4910-13-P