69056 Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2005–22110; Directorate 

Identifier 2004–NM–205–AD; Amendment 

39–14366; AD 2005–23–08] 

RIN 2120–AA64 

Airworthiness Directives; Airbus Model 

A300 B4–600 and A300 B4–600R Series 

Airplanes; and A300 F4–605R and 

A300 C4–605R Variant F Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Final rule. 

SUMMARY: The FAA is superseding an 

existing airworthiness directive (AD), 

which applies to all Airbus Model A300 

B4–600 and A300 B4–600R series 

airplanes, and all Model A300 F4–605R 

airplanes. That AD currently requires 

repetitive inspections to detect cracks of 

certain attachment holes, installation of 

new fasteners, follow-on inspections or 

repair if necessary, and modification of 

the angle fittings of fuselage frame FR47. 

This new AD revises certain inspection 

thresholds and intervals. This new AD 

also adds inspections to detect cracks of 

additional attachment holes. This AD 

results from reports of cracks found 

before the inspection thresholds in the 

existing AD and cracks found in nearby 

areas not inspected by the existing AD. 

We are issuing this AD to prevent 

fatigue cracking of the forward fitting of 

fuselage frame FR47, which could result 

in reduced structural integrity of the 

frame. 

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. 

On July 8, 2002 (67 FR 38193, June 3, 

2002), the Director of the Federal 

Register approved the incorporation by 

reference of Airbus Service Bulletin 

A300–57–6086, dated June 6, 2000. 

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 Airbus, 1 Rond Point Maurice 

Bellonte, 31707 Blagnac Cedex, France, 

for service information identified in this 

AD. 

FOR FURTHER INFORMATION CONTACT: Dan 

Rodina, Aerospace Engineer, 

International Branch, ANM–116, FAA, 

Transport Airplane Directorate, 1601 

Lind Avenue, SW., Renton, Washington 

98055–4056; telephone (425) 227–2125; 

fax (425) 227–1149. 

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 

supersedes AD 2002–11–04, amendment 

39–12765 (67 FR 38193, June 3, 2002). 

The existing AD applies to all Airbus 

Model A300 B4–600 and A300 B4–600R 

series airplanes, and all Model A300 

F4–605R airplanes. That NPRM was 

published in the Federal Register on 

August 16, 2005 (70 FR 48085). That 

NPRM proposed to continue to require 

repetitive inspections to detect cracks of 

certain attachment holes, installation of 

new fasteners, follow-on inspections or 

repair if necessary, and modification of 

the angle fittings of fuselage frame FR47. 

That NPRM also proposed to revise 

certain inspection thresholds and 

intervals and add inspections to detect 

cracks of additional attachment holes. 

Comments 

We provided the public the 

opportunity to participate in the 

development of this AD. We have 

considered the comment that has been 

received on the NPRM. 

Request To Clarify Inspection in 

Paragraph (k) 

One commenter, the manufacturer, 

requests that we clarify the inspection 

specified in paragraph (k) of the NPRM. 

The commenter states that the 

inspection of hole T is not required if 

‘‘any cracking is found’’ but is required 

only if cracking is found at hole G. 

We agree with the commenter that the 

inspection of hole T is required only if 

cracking is found at hole G. As specified 

in the Accomplishment Instructions of 

Airbus Service Bulletin A300–57–6086, 

Revision 01, dated April 2, 2002 (which 

is referenced as the appropriate source 

of service information for accomplishing 

the required actions for certain 

airplanes), the inspection of hole T is 

applicable only if cracking is found at 

hole G. For clarity, we have revised 

paragraph (k) of the final rule. 

Clarification of Service Bulletin 

References 

We have revised certain references to 

the service bulletins for clarity. We have 

clarified that the actions specified in 

paragraphs (j) and (k) of the final rule 

are done in accordance with the 

Accomplishment Instructions of Airbus 

Service Bulletin A300–57–6086, 

Revision 01, dated April 2, 2002. We 

have also clarified that the 

modifications specified in paragraph (l) 

of the final rule are done in accordance 

with the Accomplishment Instructions 

of Airbus Service Bulletin A300–57–

6050, Revision 03, dated May 31, 2001. 

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 comment 

that has been received, and determined 

that air safety and the public interest 

require adopting the AD with the 

changes described previously. We have 

determined that these changes will 

neither increase the economic burden 

on any operator nor increase the scope 

of the AD. 

Costs of Compliance 

The following table provides the 

estimated costs for U.S. operators to 

comply with this AD. This AD will 

affect about 74 airplanes of U.S. registry. 

Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations 69057 

ESTIMATED COSTS

Action Work hours 

Average 

labor rate 

per hour 

Parts Cost per airplane Fleet cost 

Inspection per Airbus Service 

Bulletin A300–57–6049.

13 $65 $0 $845 ........................................ $62,530, per inspection cycle. 

Inspection per Airbus Service 

Bulletin A300–57–6086.

30 65 6,637–19,091 $8,587–$21,041, per inspection cycle.$635,438–$1,557,034, per inspection cycle. 

Modification per Airbus Service Bulletin A300–57–6050.65–365 65 3,370 $7,595–$27,095 ...................... $562,030–$2,005,030. 

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 

■ 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 removing amendment 39–12765 (67 

FR 38193, June 3, 2002) and by adding 

the following new airworthiness 

directive (AD): 

2005–23–08 Airbus: Amendment 39–14366. 

Docket No. FAA–2005–22110; 

Directorate Identifier 2004–NM–205–AD. 

Effective Date 

(a) This AD becomes effective December 

19, 2005. 

Affected ADs 

(b) This AD supersedes AD 2002–11–04. 

Applicability 

(c) This AD applies to Airbus Model A300 

B4–601, B4–603, B4–620, and B4–622 

airplanes; Model A300 B4–605R and B4–

622R airplanes; Model A300 F4–605R 

airplanes; and Model A300 C4–605R Variant 

F airplanes; certificated in any category; 

except airplanes on which Airbus 

Modification 12171 or 12249 has been 

accomplished or on which Airbus Service 

Bulletin A300–57–6069 has been 

accomplished. 

Unsafe Condition 

(d) This AD was prompted by reports of 

cracks found before the inspection thresholds 

in the existing AD and cracks found in 

nearby areas not inspected by the existing 

AD. We are issuing this AD to prevent fatigue 

cracking of the forward fitting of fuselage 

frame FR47, which could result in reduced 

structural integrity of the frame. 

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. 

Inspections for Attachment Holes on the 

Internal Angles of the Wing Center Box, and 

Corrective Action 

(f) Perform a rotating probe inspection to 

detect cracking of the applicable attachment 

holes on the left and right internal angles of 

the wing center box in accordance with the 

Accomplishment Instructions of Airbus 

Service Bulletin A300–57–6049, Revision 06, 

dated July 15, 2004. Do the inspection at the 

applicable time specified by paragraph 

1.E.(2), Accomplishment Timescale, of 

Revision 06 of the service bulletin, except as 

required by paragraph (m) of this AD. Repeat 

the rotating probe inspection specified in this 

paragraph thereafter at intervals not to 

exceed the applicable interval specified in 

Revision 06 of the service bulletin, except 

that all touch-and-go landings must be 

counted in determining the total number of 

flight cycles between consecutive 

inspections. 

(g) If no cracking is found during any 

inspection required by paragraph (f) of this 

AD: Prior to further flight, install new 

fasteners in accordance with the 

Accomplishment Instructions of Airbus 

Service Bulletin A300–57–6049, Revision 06, 

dated July 15, 2004. 

(h) If any cracking is found during any 

inspection required by paragraph (f) of this 

AD: Prior to further flight, perform applicable 

corrective actions (including reaming, 

drilling, drill-stopping holes, chamfering, 

performing follow-on inspections, and 

installing new or oversize fasteners) in 

accordance with the Accomplishment 

Instructions of Airbus Service Bulletin A300–

57–6049, Revision 06, dated July 15, 2004, 

except as required by paragraph (n) of this 

AD. 

Inspections for Attachment Holes in the 

Horizontal Flange of the Internal Corner 

Angle Fitting of Fuselage Frame FR47, and 

Corrective Action 

(i) Perform a rotating probe inspection to 

detect cracking of the applicable attachment 

holes in the horizontal flange of the internal 

corner angle fitting of fuselage frame FR47, 

in accordance with the Accomplishment 

Instructions of Airbus Service Bulletin A300–

57–6086, Revision 01, dated April 2, 2002. 

Do the inspection at the applicable time 

specified in paragraph 1.E., Compliance, of 

Airbus Service Bulletin A300–57–6086, 

69058 Federal Register / Vol. 70, No. 218 / Monday, November 14, 2005 / Rules and Regulations 

Revision 01, dated April 2, 2002, except as 

provided by paragraph (m) of this AD; or 

within 1,500 flight cycles after July 8, 2002 

(the effective date of AD 2002–11–04, 

amendment 39–12765); whichever occurs 

later. Repeat the rotating probe inspection 

specified in this paragraph thereafter at 

intervals not to exceed the applicable interval 

specified in Airbus Service Bulletin A300–

57–6086, dated June 6, 2000, except that all 

touch-and-go landings must be counted in 

determining the total number of flight cycles 

between consecutive inspections. 

(j) If no cracking is found during any 

inspection required by paragraph (i) of this 

AD: Prior to further flight, install new 

fasteners in accordance with the 

Accomplishment Instructions of Airbus 

Service Bulletin A300–57–6086, Revision 01, 

dated April 2, 2002. 

(k) If any cracking is found during any 

inspection required by paragraph (i) of this 

AD: Prior to further flight, perform applicable 

corrective actions (including inspecting hole 

T if any cracking is found at hole G, reaming 

the holes, and installing oversize fasteners) in 

accordance with the Accomplishment 

Instructions of Airbus Service Bulletin A300–

57–6086, Revision 01, dated April 2, 2002, 

except as required by paragraph (n) of this 

AD. 

Modification of Angle Fittings of the Wing 

Center Box 

(l) Modify the left and right internal angle 

fittings of the wing center box. The 

modification includes performing a rotating 

probe inspection to detect cracking, repairing 

cracks, cold expanding holes, and installing 

medium interference fitting bolts. Perform 

the modification in accordance with the 

Accomplishment Instructions of Airbus 

Service Bulletin A300–57–6050, Revision 03, 

dated May 31, 2001; and at the applicable 

time specified by paragraph 1.B.(4), 

Accomplishment Timescale, of Airbus 

Service Bulletin A300–57–6050, Revision 03, 

dated May 31, 2001; except as required by 

paragraphs (m) and (n) of this AD. 

Exceptions to Specifications in Service 

Bulletins 

(m) Where the service bulletins specified 

in paragraphs (f), (i), and (l) of this AD 

specify a grace period relative to receipt of 

the service bulletin, this AD requires 

compliance within the applicable grace 

period following the effective date of this AD, 

if the threshold has been exceeded. 

(n) If any crack is detected during any 

inspection required by this AD, and the 

applicable service bulletin specifies to 

contact the manufacturer for disposition of 

certain corrective actions: Prior to further 

flight, repair in accordance with a method 

approved by either the Manager, 

International Branch, ANM–116, Transport 

Airplane Directorate, FAA; or the Direction 

Ge ́ne ́rale de l’Aviation Civile (DGAC) (or its 

delegated agent). 

Actions Accomplished According to 

Previous Issue of Service Bulletins 

(o) Actions accomplished prior to the 

effective date of this AD in accordance with 

Airbus Service Bulletin A300–57–6086, 

dated June 6, 2000, are acceptable for 

compliance with the requirements of 

paragraph (i) of this AD. 

(p) Modifications accomplished prior to 

the effective date of this AD in accordance 

with Airbus Service Bulletin A300–57–6050, 

Revision 02, dated February 10, 2000; are 

acceptable for compliance with the 

requirements of paragraph (l) of this AD. 

No Reporting Requirement 

(q) Although Airbus Service Bulletin 

A300–57–6049, Revision 06, dated July 15, 

2004; and Airbus Service Bulletin A300–57–

6086, Revision 01, dated April 2, 2002; 

specify to submit certain information to the 

manufacturer, this AD does not include that 

requirement. 

Alternative Methods of Compliance 

(AMOCs) 

(r)(1) The Manager, International Branch, 

ANM–116, Transport Airplane 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. 

(3) AMOCs approved previously according 

to AD 2002–11–04, are not approved as 

AMOCs with this AD. 

Related Information 

(s) French airworthiness directive F–2004–

159, dated September 29, 2004, also 

addresses the subject of this AD. 

Material Incorporated by Reference 

(t) You must use the service bulletins listed 

in Table 1 of this AD to perform the actions 

that are required by this AD, unless the AD 

specifies otherwise. 

(1) The Director of the Federal Register 

approved the incorporation by reference of 

the service bulletins listed in Table 2 of this 

AD in accordance with 5 U.S.C. 552(a) and 

1 CFR part 51. 

(2) On July 8, 2002 (67 FR 38193, June 3, 

2002), the Director of the Federal Register 

approved the incorporation by reference of 

Airbus Service Bulletin A300–57–6086, 

dated June 6, 2000. 

(3) Contact Airbus, 1 Rond Point Maurice 

Bellonte, 31707 Blagnac Cedex, France, 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. 

TABLE 1.—ALL MATERIAL

INCORPORATED BY REFERENCE

Airbus service 

bulletin 

Revision 

level Date 

A300–57–6049, 

excluding Appendix 01.

06 ............ July 15, 2004. 

A300–57–6050 03 ............ May 31, 2001. 

A300–57–6086 Original .... June 6, 2000. 

A300–57–6086 01 ............ April 2, 2002. 

TABLE 2.—NEW MATERIAL

INCORPORATED BY REFERENCE

Airbus service 

bulletin 

Revision 

level Date 

A300–57–6049, 

excluding Appendix 01.

06 ............ July 15, 2004. 

A300–57–6050 03 ............ May 31, 2001. 

A300–57–6086 01 ............ April 2, 2002. 

Airbus Service Bulletin A300–57–6050, 

Revision 03, dated May 31, 2001, contains 

the following effective pages: 

Page number 

Revision 

level 

shown on 

page 

Date shown on 

page 

1, 4, 10A–11, 75–76 .............................................................................................................................................. 03 ............ May 31, 2001. 

2, 8–9, 17–32, 41–42, 57–58, 61–63, 77 ............................................................................................................. 02 ............ February 10, 2000. 

3, 5–7, 10, 12, 33–34, 37–38, 47, 59–60 ............................................................................................................. 01 ............ May 31, 1999. 

13–16, 35–36, 39–40, 43–46, 48–56, 64–74 ........................................................................................................ Original .... September 9, 1994. 

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