Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F Airplanes Modified by Supplemental Type Certificate SA1731SW, SA1669SW, or SA1670SW, 69059-69061 [05-22215]
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<![CDATA[
Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations
Issued in Renton, Washington, on October
31, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 05–22216 Filed 11–10–05; 8:45 am]
Certification Office, ASW–190, FAA,
Rotorcraft Directorate, 2601 Meacham
Boulevard, Fort Worth, Texas 76137–
4298; telephone (817) 222–5138; fax
(817) 222–5785.
SUPPLEMENTARY INFORMATION:
BILLING CODE 4910–13–P
Examining the Docket
You may examine the AD docket on
the Internet at https://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.
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA–2005–20947; Directorate
Identifier 2004–NM–245–AD; Amendment
39–14364; AD 2005–23–06]
RIN 2120–AA64
Airworthiness Directives; Learjet
Model 23, 24, 24A, 24B, 24B–A, 24D,
24D–A, 24E, 24F, 25, 25A, 25B, 25C,
25D, and 25F Airplanes Modified by
Supplemental Type Certificate
SA1731SW, SA1669SW, or SA1670SW
Federal Aviation
Administration (FAA), Department of
Transportation (DOT).
ACTION: Final rule.
AGENCY:
SUMMARY: The FAA is adopting a new
airworthiness directive (AD) for certain
Learjet Model 23, 24, 24A, 24B, 24B–A,
24D, 24D–A, 24E, 24F, 25, 25A, 25B,
25C, 25D, and 25F airplanes. This AD
requires removing the thrust reverser
accumulator, and making the thrust
reverser hydraulic system and the thrust
reversers inoperable. This AD results
from reports of the failure of two thrust
reverser accumulators. We are issuing
this AD to prevent failure of the thrust
reverser accumulators, due to fatigue
cracking on the female threads, which
could result in the loss of hydraulic
power and damage to the surrounding
airplane structure.
DATES: This AD becomes effective
December 19, 2005.
The Director of the Federal Register
approved the incorporation by reference
of a certain publication listed in the AD
as of December 19, 2005.
ADDRESSES: You may examine the AD
docket on the Internet at https://
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 The Nordam Group, Nacelle/
Thrust Reverser Systems Division, 6911
North Whirlpool Drive, Tulsa,
Oklahoma 74117, for service
information identified in this AD.
FOR FURTHER INFORMATION CONTACT: Jim
Rankin, Aerospace Engineer, Special
VerDate Aug<31>2005
15:39 Nov 10, 2005
Jkt 208001
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, 24D, 24D–A, 24E,
24F, 25, 25A, 25B, 25C, 25D, and 25F
airplanes. That NPRM was published in
the Federal Register on April 14, 2005
(70 FR 19718). That NPRM proposed to
require removing the thrust reverser
accumulator, and making the thrust
reverser hydraulic system and the thrust
reversers inoperable.
Comments
We provided the public the
opportunity to participate in the
development of this AD. We have
considered the comments received.
Request To Withdraw NPRM
One commenter does not support the
NPRM. The commenter asserts that
deactivating the thrust reversers will
cause more accidents, especially under
wet or winter runway conditions. The
commenter also asserts that one in-flight
failure of a thrust reverser does not
justify the NPRM given the countless
safe operations without thrust reverser
failures. The commenter states that
‘‘[the FAA] also [has] not looked or
measured the increase of accidents that
will be caused by this [NPRM].’’ As
further justification for not supporting
the NPRM, the commenter states that
the NPRM does not account for the cost
of brake and tire wear that would be
incurred if the thrust reversers are
deactivated. We infer that the
commenter would like us to withdraw
the NPRM.
We do not agree, since we have
determined that an unsafe condition
exists, and that the interim actions of
this AD are necessary to ensure the
continued safety of the affected fleet.
The one thrust reverser failure on a
Learjet Model 25B airplane that
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69059
occurred in flight led to an emergency
landing. A second failure occurred
during proof testing and resulted in
injury to a person. We acknowledge the
commenter’s concern with deactivating
the thrust reversers; however, the
affected Model 23, 24, 24A, 24B, 24B–
A, 24D, 24D–A, 24E, 24F, 25, 25A, 25B,
25C, 25D, and 25F airplanes were not
originally type certificated with thrust
reversers installed. Furthermore, we
estimate that half of these Learjet model
airplanes in service today are operating
without thrust reversers. Therefore, an
increase in accidents due to
deactivation of the affected thrust
reversers is unlikely.
Regarding the cost impact of this AD,
we point out that the economic analysis
of the AD is limited only to the cost of
actions actually required by the AD; it
does not include incidental costs. In any
case, we have determined that direct
and incidental costs are outweighed by
the safety benefits of this AD. Therefore,
no change to this AD is necessary in this
regard.
Request To Revise Requirements of
NPRM
Two commenters request that we
revise the NPRM to require repetitive
nondestructive testing or x-ray
inspections of the thrust reverser
accumulator, instead of proposing to
deactivate the thrust reversers. One of
the commenters states that inspection of
the suspected point of failure (the
female threads of the accumulator)
would be sufficient to prevent failure of
the thrust reverser accumulator. The
commenter suggests that deactivation of
the thrust reversers could be required if
damage is found during an inspection.
We do not agree, since the
commenters provide no technical
justification for revising the
requirements of this AD. The history of
crack growth on the affected thrust
reversers is unknown. In addition, there
have been no studies done to determine
an appropriate inspection interval for
providing an acceptable level of safety.
As stated in the NPRM, the parts
manufacturer currently is developing a
modification that will address the
unsafe condition of this AD. Once this
modification is developed, approved,
and available, we may consider
additional rulemaking. Therefore no
change to this AD is necessary in this
regard.
Request To Expand Applicability
One commenter, the parts
manufacturer, requests that we delete
reference to Supplemental Type
Certificates (STCs) SA1731SW,
SA1669SW, and SA1670SW from the
E:\FR\FM\14NOR1.SGM
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69060
Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations
applicability of the NPRM. The
commenter states this change will
ensure that the NPRM is also applicable
to other Learjet Model 23, 24, 24A, 24B,
24B–A, 24D, 24D–A, 24E, 24F, 25, 25A,
25B, 25C, 25D, and 25F airplanes
equipped with the affected thrust
reverser accumulators. As an example,
the commenter mentions that Model 24,
24B, 24D, 24F, 25, 25B, 25C, and 25D
airplanes modified by STC SA944NW
are also equipped with the affected
thrust reverser accumulators, but are not
included in the applicability of the
NPRM.
We do not agree. We have determined
that Model 24, 24B, 24D, 24F, 25, 25B,
25C, and 25D airplanes modified by
STC SA944NW do not need to be added
to the applicability of this AD. The
thrust reverser accumulator is an
optional installation for STC SA944NW.
The current STC holder did not
purchase the thrust reverser data, and
the thrust reverser accumulators cannot
be installed without using the STCs
identified in this AD. Furthermore,
deleting reference to STCs SA1731SW,
SA1669SW, and SA1670SW would
expand the applicability of this AD,
creating further delay in addressing the
unsafe condition. If we become aware of
affected thrust reverser accumulators
equipped on other Learjet Model 23, 24,
24A, 24B, 24B–A, 24D, 24D–A, 24E,
24F, 25, 25A, 25B, 25C, 25D, and 25F
airplanes, we will consider further
rulemaking.
Operators should note that on August
12, 2005 we issued an NPRM, Docket
No. FAA–2005–22169 (70 FR 49210,
August 23, 2005), related to the unsafe
condition of this AD. The related NPRM
proposes to require replacement of the
spherical accumulator for the main
hydraulic system with a new cylindrical
accumulator. The related NPRM is
applicable 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. The spherical
accumulator used for the main airplane
hydraulic system on those Learjet model
airplanes is similar to the spherical
accumulator used for the thrust reverser
hydraulic system addressed in this AD.
The actions proposed in the related
NPRM are intended 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
VerDate Aug<31>2005
15:39 Nov 10, 2005
Jkt 208001
potential source of ignition and result in
a consequent fire.
Request To Include Final Action
One commenter recommends adding
information about the final action being
developed under FAA project
ST8103SC–T. The commenter states that
referencing the proposed STC number
would provide information to operators
about the final action.
We do not agree. As stated in an
earlier comment, we may consider
additional rulemaking once a
modification is developed, approved,
and available. Therefore no change to
this AD is necessary in this regard.
Request To Eliminate Repetitive
Inspections of the Thrust Reverser
One commenter requests that we
eliminate repetitive inspections of the
thrust reverser (at intervals of 300 and
600 flight hours). The commenter
suggests these inspections are
unnecessary if a thrust reverser is
deactivated.
We do not agree because this AD and
the referenced service bulletin do not
require repetitive inspections of the
thrust reverser. We infer that the
commenter is referring to the repetitive
inspections of the thrust reversers
specified in The Nordam Group TR3000
Service Manual DHP–G–25–1. These
repetitive inspections are part of the
maintenance program for STCs
SA1731SW, SA1669SW, and
SA1670SW. After making the thrust
reverser accumulator inoperable,
operators should do repetitive general
visual inspections of the thrust reverser
system for cracking, corrosion, loose or
missing fasteners, etc., to ensure the
structural integrity of the thrust
reverser. (The Nordam Group has issued
Temporary Revision 78–04, dated July
8, 2005, to the TR3000 Service Manual
to add these new repetitive inspections.)
Operational checks should no longer be
done after the thrust reverser
accumulator is inoperable. Operators
may contact the Manager, Special
Certification Office, ASW–190,
Rotorcraft Directorate, for the revised
maintenance inspection program. No
change to this AD is necessary in this
regard.
Change to This AD
In paragraph (c) of the NPRM, we
inadvertently omitted the word
‘‘accumulators’’ where the applicability
identifies the part numbers of the
affected thrust reverser accumulators.
We have added ‘‘accumulators’’ before
the affected part numbers in paragraph
(c) of this AD to clarify the applicability.
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Sfmt 4700
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, including the comments
received, and determined that air safety
and the public interest require adopting
the AD with the changes described
previously. We have determined that
this change will neither increase the
economic burden on any operator nor
increase the scope of the AD.
Interim Action
This is considered to be interim
action. The manufacturer has advised
that it currently is developing a
modification that will address the
unsafe condition addressed by this
proposed AD. Once this modification is
developed, approved, and available, we
may consider additional rulemaking.
Costs of Compliance
There are about 321 airplanes of the
affected design in the worldwide fleet.
This AD affects about 255 airplanes of
U.S. registry. The actions in this AD
take about 2 work hours per airplane, at
an average labor rate of $65 per work
hour. Based on these figures, the
estimated cost of the AD for U.S.
operators is $33,150, or $130 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
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Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations
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
Accordingly, under the authority
delegated to me by the Administrator,
the FAA amends 14 CFR part 39 as
follows:
I
PART 39—AIRWORTHINESS
DIRECTIVES
1. The authority citation for part 39
continues to read as follows:
I
Authority: 49 U.S.C. 106(g), 40113, 44701.
§ 39.13
[Amended]
2. The Federal Aviation
Administration (FAA) amends § 39.13
by adding the following new
airworthiness directive (AD):
I
2005–23–06 Learjet: Amendment 39–14364.
Docket No. FAA–2005–20947;
Directorate Identifier 2004–NM–245–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, 24D, 24D–A, 24E, 24F, 25,
25A, 25B, 25C, 25D, and 25F airplanes;
certificated in any category; modified by
Supplemental Type Certificate SA1731SW,
SA1669SW, or SA1670SW; equipped with
Nordam (formerly Dee Howard Company)
thrust reverser accumulators having part
number (P/N) 25–0570–127–1, –3, –7, –13, or
–17.
VerDate Aug<31>2005
15:39 Nov 10, 2005
Jkt 208001
Unsafe Condition
(d) This AD was prompted by reports of the
failure of two thrust reverser accumulators.
We are issuing this AD to prevent failure of
the thrust reverser accumulators, due to
fatigue cracking on the female threads, which
could result in the loss of hydraulic power
and damage to the surrounding airplane
structure.
69061
Issued in Renton, Washington on October
28, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 05–22215 Filed 11–10–05; 8:45 am]
BILLING CODE 4910–13–P
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.
DEPARTMENT OF TRANSPORTATION
Remove Thrust Reverser Accumulator
(f) Within 60 days after the effective date
of this AD, remove the thrust reverser
accumulator, and make the thrust reverser
hydraulic system and the thrust reversers
inoperable, by doing all of the actions
specified in the Accomplishment
Instructions of The Nordam Group Alert
Service Bulletin A3000 78–21, dated
November 25, 2002. Where there are
differences between the Master Minimum
Equipment List and the AD, the AD prevails.
Although the service bulletin referenced in
this AD specifies to submit certain
information to the manufacturer, this AD
does not include that requirement.
[Docket No. FAA–2005–22255; Directorate
Identifier 2005–NM–106–AD; Amendment
39–14362; AD 2005–23–04]
Parts Installation
(g) As of the effective date of this AD, no
person may install a thrust reverser
accumulator having P/N 25–0570–127–1, –3,
–7, –13, or –17 on any airplane.
Alternative Methods of Compliance
(AMOCs)
(h)(1) The Manager, Special Certification
Office, Rotorcraft Directorate, 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 14 CFR 39.19 on any
airplane to which the AMOC applies, notify
the appropriate principal inspector in the
FAA Flight Standards Certificate Holding
District Office.
Material Incorporated by Reference
(i) You must use The Nordam Group Alert
Service Bulletin A3000 78–21, dated
November 25, 2002, to perform the actions
that are required by this AD, unless the AD
specifies otherwise. 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 The Nordam Group, Nacelle/Thrust
Reverser Systems Division, 6911 North
Whirlpool Drive, Tulsa, Oklahoma 74117, 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 https://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 https://
www.archives.gov/federal-register/cfr/ibrlocations.html.
PO 00000
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Federal Aviation Administration
14 CFR Part 39
RIN 2120–AA64
Airworthiness Directives; Saab Model
SAAB 2000 Airplanes
Federal Aviation
Administration (FAA), Department of
Transportation (DOT).
ACTION: Final rule.
AGENCY:
SUMMARY: The FAA is adopting a new
airworthiness directive (AD) for certain
Saab Model SAAB 2000 airplanes. This
AD requires modifying the manual
feather-and-unfeather system for the
propellers to make the design of the
system more robust. This AD results
from reports of in-flight engine
shutdown caused by uncommanded
operation of the feather pump of the
propeller. We are issuing this AD to
prevent uncommanded feathering of the
propeller, which could result in the
shutdown of an engine during flight and
consequent reduced controllability of
the airplane.
DATES: This AD becomes effective
December 19, 2005.
The Director of the Federal Register
approved the incorporation by reference
of a certain publication listed in the AD
as of December 19, 2005.
ADDRESSES: You may examine the AD
docket on the Internet at https://
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 Saab Aircraft AB, SAAB
Aircraft Product Support, S–581.88,
¨
Linkoping, Sweden, for service
information identified in this AD.
FOR FURTHER INFORMATION CONTACT:
Mike Borfitz, Aerospace Engineer,
International Branch, ANM–116,
Transport Airplane Directorate, FAA,
1601 Lind Avenue, SW., Renton,
Washington 98055–4056; telephone
(425) 227–2677; fax (425) 227–1149.
SUPPLEMENTARY INFORMATION:
E:\FR\FM\14NOR1.SGM
14NOR1
]]>Agencies
[Federal Register Volume 70, Number 218 (Monday, November 14, 2005)]
[Rules and Regulations]
[Pages 69059-69061]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-22215]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2005-20947; Directorate Identifier 2004-NM-245-AD;
Amendment 39-14364; AD 2005-23-06]
RIN 2120-AA64
Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A,
24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F Airplanes
Modified by Supplemental Type Certificate SA1731SW, SA1669SW, or
SA1670SW
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, 24D, 24D-A, 24E, 24F,
25, 25A, 25B, 25C, 25D, and 25F airplanes. This AD requires removing
the thrust reverser accumulator, and making the thrust reverser
hydraulic system and the thrust reversers inoperable. This AD results
from reports of the failure of two thrust reverser accumulators. We are
issuing this AD to prevent failure of the thrust reverser accumulators,
due to fatigue cracking on the female threads, which could result in
the loss of hydraulic power and damage to the surrounding airplane
structure.
DATES: This AD becomes effective December 19, 2005.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in the AD as of December 19,
2005.
ADDRESSES: You may examine the AD docket on the Internet at https://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 The Nordam Group, Nacelle/Thrust Reverser Systems Division,
6911 North Whirlpool Drive, Tulsa, Oklahoma 74117, for service
information identified in this AD.
FOR FURTHER INFORMATION CONTACT: Jim Rankin, Aerospace Engineer,
Special Certification Office, ASW-190, FAA, Rotorcraft Directorate,
2601 Meacham Boulevard, Fort Worth, Texas 76137-4298; telephone (817)
222-5138; fax (817) 222-5785.
SUPPLEMENTARY INFORMATION:
Examining the Docket
You may examine the AD docket on the Internet at https://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, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D,
and 25F airplanes. That NPRM was published in the Federal Register on
April 14, 2005 (70 FR 19718). That NPRM proposed to require removing
the thrust reverser accumulator, and making the thrust reverser
hydraulic system and the thrust reversers inoperable.
Comments
We provided the public the opportunity to participate in the
development of this AD. We have considered the comments received.
Request To Withdraw NPRM
One commenter does not support the NPRM. The commenter asserts that
deactivating the thrust reversers will cause more accidents, especially
under wet or winter runway conditions. The commenter also asserts that
one in-flight failure of a thrust reverser does not justify the NPRM
given the countless safe operations without thrust reverser failures.
The commenter states that ``[the FAA] also [has] not looked or measured
the increase of accidents that will be caused by this [NPRM].'' As
further justification for not supporting the NPRM, the commenter states
that the NPRM does not account for the cost of brake and tire wear that
would be incurred if the thrust reversers are deactivated. We infer
that the commenter would like us to withdraw the NPRM.
We do not agree, since we have determined that an unsafe condition
exists, and that the interim actions of this AD are necessary to ensure
the continued safety of the affected fleet. The one thrust reverser
failure on a Learjet Model 25B airplane that occurred in flight led to
an emergency landing. A second failure occurred during proof testing
and resulted in injury to a person. We acknowledge the commenter's
concern with deactivating the thrust reversers; however, the affected
Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C,
25D, and 25F airplanes were not originally type certificated with
thrust reversers installed. Furthermore, we estimate that half of these
Learjet model airplanes in service today are operating without thrust
reversers. Therefore, an increase in accidents due to deactivation of
the affected thrust reversers is unlikely.
Regarding the cost impact of this AD, we point out that the
economic analysis of the AD is limited only to the cost of actions
actually required by the AD; it does not include incidental costs. In
any case, we have determined that direct and incidental costs are
outweighed by the safety benefits of this AD. Therefore, no change to
this AD is necessary in this regard.
Request To Revise Requirements of NPRM
Two commenters request that we revise the NPRM to require
repetitive nondestructive testing or x-ray inspections of the thrust
reverser accumulator, instead of proposing to deactivate the thrust
reversers. One of the commenters states that inspection of the
suspected point of failure (the female threads of the accumulator)
would be sufficient to prevent failure of the thrust reverser
accumulator. The commenter suggests that deactivation of the thrust
reversers could be required if damage is found during an inspection.
We do not agree, since the commenters provide no technical
justification for revising the requirements of this AD. The history of
crack growth on the affected thrust reversers is unknown. In addition,
there have been no studies done to determine an appropriate inspection
interval for providing an acceptable level of safety. As stated in the
NPRM, the parts manufacturer currently is developing a modification
that will address the unsafe condition of this AD. Once this
modification is developed, approved, and available, we may consider
additional rulemaking. Therefore no change to this AD is necessary in
this regard.
Request To Expand Applicability
One commenter, the parts manufacturer, requests that we delete
reference to Supplemental Type Certificates (STCs) SA1731SW, SA1669SW,
and SA1670SW from the
[[Page 69060]]
applicability of the NPRM. The commenter states this change will ensure
that the NPRM is also applicable to other Learjet Model 23, 24, 24A,
24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F
airplanes equipped with the affected thrust reverser accumulators. As
an example, the commenter mentions that Model 24, 24B, 24D, 24F, 25,
25B, 25C, and 25D airplanes modified by STC SA944NW are also equipped
with the affected thrust reverser accumulators, but are not included in
the applicability of the NPRM.
We do not agree. We have determined that Model 24, 24B, 24D, 24F,
25, 25B, 25C, and 25D airplanes modified by STC SA944NW do not need to
be added to the applicability of this AD. The thrust reverser
accumulator is an optional installation for STC SA944NW. The current
STC holder did not purchase the thrust reverser data, and the thrust
reverser accumulators cannot be installed without using the STCs
identified in this AD. Furthermore, deleting reference to STCs
SA1731SW, SA1669SW, and SA1670SW would expand the applicability of this
AD, creating further delay in addressing the unsafe condition. If we
become aware of affected thrust reverser accumulators equipped on other
Learjet Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A,
25B, 25C, 25D, and 25F airplanes, we will consider further rulemaking.
Operators should note that on August 12, 2005 we issued an NPRM,
Docket No. FAA-2005-22169 (70 FR 49210, August 23, 2005), related to
the unsafe condition of this AD. The related NPRM proposes to require
replacement of the spherical accumulator for the main hydraulic system
with a new cylindrical accumulator. The related NPRM is applicable 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. The spherical
accumulator used for the main airplane hydraulic system on those
Learjet model airplanes is similar to the spherical accumulator used
for the thrust reverser hydraulic system addressed in this AD. The
actions proposed in the related NPRM are intended 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.
Request To Include Final Action
One commenter recommends adding information about the final action
being developed under FAA project ST8103SC-T. The commenter states that
referencing the proposed STC number would provide information to
operators about the final action.
We do not agree. As stated in an earlier comment, we may consider
additional rulemaking once a modification is developed, approved, and
available. Therefore no change to this AD is necessary in this regard.
Request To Eliminate Repetitive Inspections of the Thrust Reverser
One commenter requests that we eliminate repetitive inspections of
the thrust reverser (at intervals of 300 and 600 flight hours). The
commenter suggests these inspections are unnecessary if a thrust
reverser is deactivated.
We do not agree because this AD and the referenced service bulletin
do not require repetitive inspections of the thrust reverser. We infer
that the commenter is referring to the repetitive inspections of the
thrust reversers specified in The Nordam Group TR3000 Service Manual
DHP-G-25-1. These repetitive inspections are part of the maintenance
program for STCs SA1731SW, SA1669SW, and SA1670SW. After making the
thrust reverser accumulator inoperable, operators should do repetitive
general visual inspections of the thrust reverser system for cracking,
corrosion, loose or missing fasteners, etc., to ensure the structural
integrity of the thrust reverser. (The Nordam Group has issued
Temporary Revision 78-04, dated July 8, 2005, to the TR3000 Service
Manual to add these new repetitive inspections.) Operational checks
should no longer be done after the thrust reverser accumulator is
inoperable. Operators may contact the Manager, Special Certification
Office, ASW-190, Rotorcraft Directorate, for the revised maintenance
inspection program. No change to this AD is necessary in this regard.
Change to This AD
In paragraph (c) of the NPRM, we inadvertently omitted the word
``accumulators'' where the applicability identifies the part numbers of
the affected thrust reverser accumulators. We have added
``accumulators'' before the affected part numbers in paragraph (c) of
this AD to clarify the applicability.
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, including the
comments received, and determined that air safety and the public
interest require adopting the AD with the changes described previously.
We have determined that this change will neither increase the economic
burden on any operator nor increase the scope of the AD.
Interim Action
This is considered to be interim action. The manufacturer has
advised that it currently is developing a modification that will
address the unsafe condition addressed by this proposed AD. Once this
modification is developed, approved, and available, we may consider
additional rulemaking.
Costs of Compliance
There are about 321 airplanes of the affected design in the
worldwide fleet. This AD affects about 255 airplanes of U.S. registry.
The actions in this AD take about 2 work hours per airplane, at an
average labor rate of $65 per work hour. Based on these figures, the
estimated cost of the AD for U.S. operators is $33,150, or $130 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
[[Page 69061]]
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):
2005-23-06 Learjet: Amendment 39-14364. Docket No. FAA-2005-20947;
Directorate Identifier 2004-NM-245-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,
24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F airplanes;
certificated in any category; modified by Supplemental Type
Certificate SA1731SW, SA1669SW, or SA1670SW; equipped with Nordam
(formerly Dee Howard Company) thrust reverser accumulators having
part number (P/N) 25-0570-127-1, -3, -7, -13, or -17.
Unsafe Condition
(d) This AD was prompted by reports of the failure of two thrust
reverser accumulators. We are issuing this AD to prevent failure of
the thrust reverser accumulators, due to fatigue cracking on the
female threads, which could result in the loss of hydraulic power
and damage to the surrounding airplane structure.
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.
Remove Thrust Reverser Accumulator
(f) Within 60 days after the effective date of this AD, remove
the thrust reverser accumulator, and make the thrust reverser
hydraulic system and the thrust reversers inoperable, by doing all
of the actions specified in the Accomplishment Instructions of The
Nordam Group Alert Service Bulletin A3000 78-21, dated November 25,
2002. Where there are differences between the Master Minimum
Equipment List and the AD, the AD prevails. Although the service
bulletin referenced in this AD specifies to submit certain
information to the manufacturer, this AD does not include that
requirement.
Parts Installation
(g) As of the effective date of this AD, no person may install a
thrust reverser accumulator having P/N 25-0570-127-1, -3, -7, -13,
or -17 on any airplane.
Alternative Methods of Compliance (AMOCs)
(h)(1) The Manager, Special Certification Office, Rotorcraft
Directorate, 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 14 CFR
39.19 on any airplane to which the AMOC applies, notify the
appropriate principal inspector in the FAA Flight Standards
Certificate Holding District Office.
Material Incorporated by Reference
(i) You must use The Nordam Group Alert Service Bulletin A3000
78-21, dated November 25, 2002, to perform the actions that are
required by this AD, unless the AD specifies otherwise. 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 The Nordam Group, Nacelle/Thrust Reverser Systems Division,
6911 North Whirlpool Drive, Tulsa, Oklahoma 74117, 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 https://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 https://www.archives.gov/federal-register/cfr/ibr-locations.html.
Issued in Renton, Washington on October 28, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 05-22215 Filed 11-10-05; 8:45 am]
BILLING CODE 4910-13-P
