Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations 69059 

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] 

BILLING CODE 4910–13–P 

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 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 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 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, 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 

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 

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 

Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations 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 

■ Accordingly, under the authority 

delegated to me by the Administrator, 

the FAA amends 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. 

§ 39.13 [Amended] 

■ 2. The Federal Aviation 

Administration (FAA) amends § 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 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/cfr/ibrlocations.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 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2005–22255; Directorate 

Identifier 2005–NM–106–AD; Amendment 

39–14362; AD 2005–23–04] 

RIN 2120–AA64 

Airworthiness Directives; Saab Model 

SAAB 2000 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 

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 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 Saab Aircraft AB, SAAB 

Aircraft Product Support, S–581.88, 

Linko ̈ping, 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: