Federal Register / Vol. 75, No. 94 / Monday, May 17, 2010 / Rules and Regulations 27411 

(i) Remove the studs by following the 

Accomplishment Instructions, paragraphs 

3.B.(1) through 3.B.(4) of the ASB. Visually 

inspect the tapped holes for any damage to 

the threads. Serrations on the entire counter 

bore (360 degrees) are acceptable. Serrations 

in the housing must be intact, and mating 

serrations on the lock ring must line up with 

serrations on the housing. Visually inspect 

the housing to determine that the housing 

threads are free from damage and corrosion. 

Visually inspect housing lockring 

counterbore to determine if the housing is 

airworthy. 

(ii) If you find damage or corrosion to the 

housing threads, the housing, or the lockring 

counterbore, stop work and contact Kirk 

Gustafson, Aviation Safety Engineer, Boston 

Aircraft Certification Office, Engine and 

Propeller Directorate, FAA, 12 New England 

Executive Park, Burlington, MA 01803, 

telephone (781) 238–7190, fax (781) 238– 

7170. 

(iii) If you do not find damage to the 

housing threads, the housing, or the lockring 

counterbore that requires repair, replace the 

mounting studs by following the 

Accomplishment Instructions, paragraphs 

3.B.(7) through 3.B.(15) of the ASB. 

(5) Install an airworthy, two-piece MGB 

filter bowl assembly modification kit, P/N 

92070–35005–011, as depicted in Figures 8 

and 9 of the ASB and by following the 

Accomplishment Instructions, paragraphs 

3.C.(1) through 3.C.(20), of the ASB. 

(b) To request a different method of 

compliance or a different compliance time 

for this AD, follow the procedures in 14 CFR 

39.19. Contact the Manager, Boston Aircraft 

Certification Office, Attn: Kirk Gustafson, 

Aviation Safety Engineer, Boston Aircraft 

Certification Office, Engine and Propeller 

Directorate, FAA, 12 New England Executive 

Park, Burlington, MA 01803, telephone (781) 

238–7190, fax (781) 238–7170, for 

information about previously approved 

alternative methods of compliance. 

(c) The Joint Aircraft System/Component 

(JASC) Code is 6320: Main Rotor Gearbox. 

(d) Inspecting and replacing the MGB filter 

bowl assembly shall be done by following the 

specified portions of Sikorsky Alert Service 

Bulletin No. 92–63–022A, dated December 

18, 2009. The Director of the Federal Register 

approved this incorporation by reference in 

accordance with 5 U.S.C. 552(a) and 1 CFR 

part 51. Copies may be obtained from 

Sikorsky Aircraft Corporation, Attn: Manager, 

Commercial Technical Support, mailstop 

s581a, 6900 Main Street, Stratford, CT, 

telephone (203) 383–4866, e-mail address 

tsslibrary@sikorsky.com, or at http:// 

www.sikorsky.com. Copies may be inspected 

at the FAA, Office of the Regional Counsel, 

Southwest Region, 2601 Meacham Blvd., 

Room 663, Fort Worth, Texas, or at the 

National Archives and Records 

Administration (NARA). For information on 

the availability of this material at NARA, call 

202–741–6030, or go to: http:// 

www.archives.gov/federal_register/ 

code_of_federal_regulations/ 

ibr_locations.html. 

(e) This amendment becomes effective on 

June 21, 2010. 

Issued in Fort Worth, Texas, on April 27, 

2010. 

Mark R. Schilling, 

Acting Manager, Rotorcraft Directorate, 

Aircraft Certification Service. 

[FR Doc. 2010–11069 Filed 5–14–10; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2005–21242; Directorate 

Identifier 2005–NE–09–AD; Amendment 39– 

16288; AD 2010–10–09] 

RIN 2120–AA64 

Airworthiness Directives; Turbomeca 

Arriel 1B, 1D, 1D1, and 1S1 Turboshaft 

Engines 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Final rule. 

SUMMARY: The FAA is superseding an 

existing airworthiness directive (AD) for 

certain Turbomeca Arriel 1B, 1D, 1D1, 

and 1S1 turboshaft engines. That AD 

requires initial and repetitive relative 

position checks of the gas generator 2nd 

stage turbine blades on Turbomeca 

Arriel 1B (that incorporate Turbomeca 

Modification (mod) TU 148), Arriel 1D, 

1D1, and 1S1 turboshaft engines that do 

not incorporate mod TU 347. That AD 

also requires initial and repetitive 

replacements of 2nd stage turbines on 

Arriel 1B, 1D, and 1D1 engines. This AD 

requires lowering the initial and 

repetitive thresholds for replacement of 

2nd stage turbines on Arriel 1B, 1D, and 

1D1 engines. This AD results from 

reports of new cases of failures of 2nd 

stage turbine blades since we issued AD 

2008–07–01. We are issuing this AD to 

prevent the failure of 2nd stage turbine 

blades, which could result in an 

uncommanded in-flight engine 

shutdown, and a subsequent forced 

autorotation landing or accident. 

DATES: This AD becomes effective June 

21, 2010. The Director of the Federal 

Register approved the incorporation by 

reference of certain publications listed 

in the regulations as of June 21, 2010. 

ADDRESSES: You can get the service 

information identified in this AD from 

Turbomeca, 40220 Tarnos, France; 

telephone (33) 05 59 74 40 00, fax (33) 

05 59 74 45 15. 

The Docket Operations office is 

located at Docket Management Facility, 

U.S. Department of Transportation, 1200 

New Jersey Avenue, SE., West Building 

Ground Floor, Room W12–140, 

Washington, DC 20590–0001. 

FOR FURTHER INFORMATION CONTACT: 

Kevin Dickert, Aerospace Engineer, 

Engine Certification Office, FAA, Engine 

and Propeller Directorate, 12 New 

England Executive Park, Burlington, MA 

01803; e-mail: kevin.dickert@faa.gov; 

phone: (781) 238–7117, fax: (781) 238– 

7199. 

SUPPLEMENTARY INFORMATION: The FAA 

proposed to amend 14 CFR part 39 by 

superseding AD 2008–07–01, 

Amendment 39–15442 (73 FR 15866, 

March 26, 2008), with a proposed AD. 

The proposed AD applies to Turbomeca 

Arriel 1B (that incorporate mod TU 

148), 1D, 1D1, and 1S1 turboshaft 

engines that do not incorporate mod TU 

347. We published the proposed AD in 

the Federal Register on March 10, 2010 

(75 FR 11072). That action proposed to 

require lowering the repetitive threshold 

for relative position checks on Arriel 1B 

engines. That action also proposed to 

require lowering the initial and 

repetitive thresholds for replacement of 

2nd stage turbines on Arriel 1B, 1D, and 

1D1 engines. 

Examining the AD Docket 

You may examine the AD docket on 

the Internet at http:// 

www.regulations.gov; or in person at the 

Docket Operations office between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. The AD docket 

contains this AD, the regulatory 

evaluation, any comments received, and 

other information. The street address for 

the Docket Operations office (phone 

(800) 647–5527) is provided in the 

ADDRESSES section. Comments will be 

available in the AD docket shortly after 

receipt. 

Comments 

We provided the public the 

opportunity to participate in the 

development of this AD. We received no 

comments on the proposal or on the 

determination of the cost to the public. 

Conclusion 

We have carefully reviewed the 

available data and determined that air 

safety and the public interest require 

adopting the AD as proposed. 

Costs of Compliance 

Based on the service information, we 

estimate that this AD will affect about 

587 Turbomeca Arriel 1B, 1D, 1D1, and 

1S1 turboshaft engines installed on 

products of U.S. registry. We also 

estimate that it will take about 2 workhours per engine to perform one 

inspection, and about 40 work-hours per 

engine to replace the gas turbine discs 


srobinson on DSKHWCL6B1PROD with RULES
27412 Federal Register / Vol. 75, No. 94 / Monday, May 17, 2010 / Rules and Regulations 

and blades. The average labor rate is $85 

per work-hour. Required parts will cost 

about $54,000 per engine. Based on 

these figures, we estimate the cost of the 

AD on U.S. operators to be $33,793,590. 

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 summary of the costs 

to comply with this AD and placed it in 

the AD Docket. You may get a copy of 

this summary at the address listed 

under ADDRESSES. 

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 Federal Aviation Administration 

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 FAA amends § 39.13 by 

removing Amendment 39–15442 (73 FR 

15866, March 26, 2008), and by adding 

a new airworthiness directive, 

Amendment 39–16288, to read as 

follows: 

2010–10–09 Turbomeca: Amendment 39– 

16288. Docket No. FAA–2005–21242; 

Directorate Identifier 2005–NE–09–AD. 

Effective Date 

(a) This airworthiness directive (AD) 

becomes effective June 21, 2010. 

Affected ADs 

(b) This AD supersedes AD 2008–07–01, 

Amendment 39–15442. 

Applicability 

(c) This AD applies to Turbomeca Arriel 1B 

(that incorporate Turbomeca Modification 

(mod) TU 148), Arriel 1D, 1D1, and 1S1 

engines that do not incorporate mod TU 347. 

Arriel 1B engines are installed on, but not 

limited to, Eurocopter AS–350B and AS– 

350BA ‘‘Ecureuil’’ helicopters. Arriel 1D 

engines are installed on, but not limited to, 

Eurocopter France AS–350B1 ‘‘Ecureuil’’ 

helicopters. Arriel 1D1 engines are installed 

on, but not limited to, Eurocopter France AS– 

350B2 ‘‘Ecureuil’’ helicopters. Arriel 1S1 

engines are installed on, but not limited to, 

Sikorsky Aircraft Corporation S–76C 

helicopters. 

Unsafe Condition 

(d) This AD results from reports of new 

cases of failures of 2nd stage turbine blades 

since we issued AD 2008–07–01. We are 

issuing this AD to prevent the failure of 2nd 

stage turbine blades, which could result in an 

uncommanded in-flight engine shutdown, 

and a subsequent forced autorotation landing 

or accident. 

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. 

Initial Relative Position Check of 2nd Stage 

Turbine Blades 

(f) Do an initial relative position check of 

the 2nd stage turbine blades using the 

Turbomeca Mandatory Service Bulletins 

(MSBs) specified in the following Table 1. Do 

the check before reaching any of the intervals 

specified in Table 1 or within 50 hours timein-service after the effective date of this AD, 

whichever occurs later. 

TABLE 1—INITIAL AND REPETITIVE RELATIVE POSITION CHECK INTERVALS OF 2ND STAGE TURBINE BLADE

Turbomeca engine model Initial relative position check 

interval Repetitive interval Mandatory Service Bulletin 

Arriel 1B (that incorporate mod TU 

148), 1D1, and 1D.

Within 1,200 hours time-sincenew (TSN) or time-since-overhaul (TSO) or 3,500 cyclessince-new (CSN) or cyclessince-overhaul (CSO), whichever occurs earlier.Within 150 hours time-in-servicesince-last-relative-positioncheck (TSLRPC).A292 72 0807, Version E, dated 

October 29, 2009, paragraphs 

2B(1)(a) and (b), or 2B(2)(a). 

Arriel 1S1 ....................................... Within 1,200 hours TSN or TSO 

or 3,500 CSN or CSO, whichever occurs earlier.

Within 150 hours TSLRPC ........... A292 72 0810, Version C, dated 

July 24, 2009, paragraphs 

2B(1)(a) and (b), or 2B(2)(a), 

(b), and (c). 

Repetitive Relative Position Check of 2nd 

Stage Turbine Blades 

(g) Recheck the relative position of 2nd 

stage turbine blades at the TSLRPC intervals 

specified in Table 1 of this AD, using the 

Turbomeca MSBs indicated. 

Credit for Previous Relative Position Checks 

(h) Credit is allowed for previous relative 

position checks of 2nd stage turbine blades 

done using the following Turbomeca MSBs: 

(1) MSB No. A292 72 0263, Update Nos. 1 

through 5. 

(2) MSB No. A292 72 0807, Original, and 

Update No. 1 through Version D. 

(3) MSB No. A292 72 0809, Update No. 1. 

(4) MSB No. A292 72 0810, Original, and 

Version A through Version B. 


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Federal Register / Vol. 75, No. 94 / Monday, May 17, 2010 / Rules and Regulations 27413 

Initial Replacement of 2nd Stage Turbines 

on Arriel 1B Engines 

(i) Initially replace the Arriel 1B 2nd stage 

turbine disk and blades with an inspected 

2nd stage turbine that does not incorporate 

mod TU 347 and is fitted with new blades 

or with a 2nd stage turbine that incorporates 

mod TU 347, using Turbomeca MSB No. 

A292 72 0807, Version E, dated October 29, 

2009, paragraphs 2B(1)(c) or (d), or 2B(2)(b) 

or (c), at the following times: 

(1) Replace before further flight on engines 

with a 2nd stage turbine disk having 

accumulated more than 2,200 hours TIS 

since-new or since-last-inspection, 

whichever occurs later, or with 2nd stage 

turbine blades that have accumulated more 

than 3,000 hours TIS since-new. 

(2) For engines with 2nd stage turbine 

blades having accumulated on the effective 

date of this AD, more than 1,800 hours TIS 

since-new, but 3,000 or fewer hours TIS 

since-new, replace before reaching any of the 

following: 

(i) 400 hours TIS from the effective date of 

this AD, or 

(ii) 3,000 hours TIS since-new on the 2nd 

stage turbine blades, or 

(iii) 2,200 hours TIS since-new or sincelast-inspection, whichever occurs later, on 

the 2nd stage turbine disk. 

(3) For engines with 2nd stage turbine 

blades having accumulated on the effective 

date of this AD, more than 900 hours TIS 

since-new, but 1,800 or fewer hours TIS 

since-new, replace before reaching any of the 

following: 

(i) 800 hours TIS from the effective date of 

this AD, or 

(ii) 2,200 hours TIS since-new or since-lastinspection, whichever occurs later, on the 

2nd stage turbine disk. 

(4) For engines with 2nd stage turbine 

blades having accumulated on the effective 

date of this AD, 900 or fewer hours TIS sincenew, replace before the 2nd stage turbine 

blades have accumulated 1,200 hours TIS 

since-new. 

Repetitive Replacements of 2nd Stage 

Turbines on Arriel 1B Engines 

(j) Thereafter, for 2nd stage turbines that do 

not incorporate mod TU 347, replace the 2nd 

stage turbine disk and blades before the 

blades have accumulated 1,200 hours TIS 

since-new. 

Initial Replacement of 2nd Stage Turbines 

on Arriel 1D and 1D1 Engines 

(k) Initially replace the Arriel 1D and 1D1 

2nd stage turbine disk and blades with an 

inspected turbine that does not incorporate 

mod TU 347 and is fitted with new blades 

or with a turbine that incorporates mod TU 

347, using Turbomeca MSB No. A292 72 

0807, Version E, dated October 29, 2009, 

paragraphs 2B(1)(c) or (d), or 2B(2)(b) or (c), 

at the following times: 

(1) Replace before further flight on engines 

with a 2nd stage turbine disk having 

accumulated more than 1,500 hours TIS 

since-new or since-last-inspection, 

whichever occurs later, or with 2nd stage 

turbine blades having accumulated more 

than 1,500 hours TIS since-new. 

(2) For engines with 2nd stage turbine 

blades having accumulated on the effective 

date of this AD, more than 900 hours TIS 

since-new, but 1,500 or fewer hours TIS 

since-new, replace before the 2nd stage 

turbine blades have accumulated 1,500 hours 

TIS since-new, or before the 2nd stage 

turbine disk has accumulated 1,500 hours 

TIS since-new, whichever occurs first. 

(3) For engines with 2nd stage turbine 

blades having accumulated on the effective 

date of this AD, 900 or fewer hours TIS sincenew, replace before the 2nd stage turbine 

blades have accumulated 1,200 hours TIS 

since-new. 

Repetitive Replacements of 2nd Stage 

Turbines on Arriel 1D and 1D1 Engines 

(l) Thereafter, for 2nd stage turbines that do 

not incorporate mod TU 347, replace the 2nd 

stage turbine disk and blades before the 

blades have accumulated 1,200 hours TIS 

since-new. 

Relative Position Check Continuing 

Compliance Requirements 

(m) All 2nd stage turbines, including those 

that are new or overhauled, must continue to 

comply with the actions specified in 

paragraphs (f) and (g) of this AD, unless mod 

TU 347 has been incorporated. 

Optional Terminating Action 

(n) Installing a new turbine, P/N 0 292 25 

039 0, (incorporation of mod TU 347) 

terminates the requirements to perform the 

repetitive actions specified in paragraphs (g), 

(j), and (l) of this AD. 

Alternative Methods of Compliance 

(o) The Manager, Engine Certification 

Office, has the authority to approve 

alternative methods of compliance for this 

AD if requested using the procedures found 

in 14 CFR 39.19. 

Related Information 

(p) The EASA airworthiness directive 

2009–0236, dated October 29, 2009, also 

addresses the subject of this AD. 

(q) Contact Kevin Dickert, Aerospace 

Engineer, Engine Certification Office, FAA, 

Engine and Propeller Directorate, 12 New 

England Executive Park, Burlington, MA 

01803; e-mail: kevin.dickert@faa.gov; phone: 

(781) 238–7117, fax: (781) 238–7199, for 

more information about this AD. 

Material Incorporated by Reference 

(r) You must use the service information 

specified in the following Table 2 to perform 

the actions required by this AD. The Director 

of the Federal Register approved the 

incorporation by reference of the documents 

listed in the following Table 2 in accordance 

with 5 U.S.C. 552(a) and 1 CFR part 51. 

Contact Turbomeca, 40220 Tarnos, France; 

phone: (33) 05 59 74 40 00, fax: (33) 05 59 

74 45 15, for a copy of this service 

information. You may review copies at the 

FAA, New England Region, 12 New England 

Executive Park, Burlington, MA; or at the 

National Archives and Records 

Administration (NARA). For information on 

the availability of this material at NARA, call 

202–741–6030, or go to: http:// 

www.archives.gov/federal-register/cfr/ibrlocations.html. 

TABLE 2—INCORPORATION BY REFERENCE

Turbomeca mandatory Service Bulletin No. Page Version Date 

A 292 72 0807 ........................................................................................................................ ALL ............... E ................... October 29, 2009. 

Total Pages: 20 

A 292 72 0810 ........................................................................................................................ ALL ............... C .................. July 24, 2009. 

Total Pages: 15 


srobinson on DSKHWCL6B1PROD with RULES
27414 Federal Register / Vol. 75, No. 94 / Monday, May 17, 2010 / Rules and Regulations 

Issued in Burlington, Massachusetts, on 

April 28, 2010. 

Peter A. White, 

Assistant Manager, Engine and Propeller 

Directorate, Aircraft Certification Service. 

[FR Doc. 2010–10720 Filed 5–14–10; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2010–0129; Directorate 

Identifier 2009–NM–245–AD; Amendment 

39–16287; AD 2010–10–08] 

RIN 2120–AA64 

Airworthiness Directives; Airbus A318, 

A319, A320, A321 Series Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Final rule. 

SUMMARY: We are adopting a new 

airworthiness directive (AD) for the 

products listed above. This AD results 

from mandatory continuing 

airworthiness information (MCAI) 

originated by an aviation authority of 

another country to identify and correct 

an unsafe condition on an aviation 

product. The MCAI describes the unsafe 

condition as: 

Several occurrences of loss of the AC 

[alternating current] BUS 1 have been 

reported which led in some instances to the 

loss of the AC ESS [essential] BUS and DC 

[direct current] ESS BUS and connected 

systems. The affected systems include 

multiple flight deck Display Units (Primary 

Flight Display, Navigation Display and Upper 

Electronic Centralised Aircraft Monitoring 

display). 

* * * * * 

The loss of multiple display units, if not 

corrected expediently during a high 

workload period, potentially affects the 

capability of the flight crew and could 

contribute to a loss of situational awareness 

and consequent control of the aeroplane, 

which would constitute an unsafe condition. 

* * * * * 

We are issuing this AD to require 

actions to correct the unsafe condition 

on these products. 

DATES: This AD becomes effective June 

21, 2010. 

The Director of the Federal Register 

approved the incorporation by reference 

of a certain publication listed in this AD 

as of June 21, 2010. 

ADDRESSES: You may examine the AD 

docket on the Internet at http:// 

www.regulations.gov or in person at the 

U.S. Department of Transportation, 

Docket Operations, M–30, West 

Building Ground Floor, Room W12–140, 

1200 New Jersey Avenue, SE., 

Washington, DC. 

FOR FURTHER INFORMATION CONTACT: Tim 

Dulin, Aerospace Engineer, 

International Branch, ANM–116, 

Transport Airplane Directorate, FAA, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; telephone 

(425) 227–2141; fax (425) 227–1149. 

SUPPLEMENTARY INFORMATION: 

Discussion 

We issued a notice of proposed 

rulemaking (NPRM) to amend 14 CFR 

part 39 to include an AD that would 

apply to the specified products. That 

NPRM was published in the Federal 

Register on February 23, 2010 (75 FR 

8003). That NPRM proposed to correct 

an unsafe condition for the specified 

products. The MCAI states: 

Several occurrences of loss of the AC 

[alternating current] BUS 1 have been 

reported which led in some instances to the 

loss of the AC ESS [essential] BUS and DC 

[direct current] ESS BUS and connected 

systems. The affected systems include 

multiple flight deck Display Units (Primary 

Flight Display, Navigation Display and Upper 

Electronic Centralised Aircraft Monitoring 

display). 

The reasons for these events have been 

investigated but have not been fully 

established for all cases. 

Due to the range of system losses some 

crews reported difficulty in establishing the 

failure cause during the events and, 

consequently, the appropriate actions to be 

taken may not be completed in a timely 

manner. 

The loss of multiple display units, if not 

corrected expediently during a high 

workload period, potentially affects the 

capability of the flight crew and could 

contribute to a loss of situational awareness 

and consequent control of the aeroplane, 

which would constitute an unsafe condition. 

This AD therefore mandates the 

modification of the electrical network 

configuration management logic consisting in 

adding an automatic switching of the AC and 

DC ESS BUS power supply such that upon 

the loss of the AC BUS 1, the AC BUS 2 will 

automatically take over the power supply. On 

pre-MOD aeroplanes, this power supply 

switching can only be accomplished 

manually from the cockpit and is covered by 

an Electronic Centralized Aircraft Monitoring 

(ECAM) procedure. 

The modification of the electrical power 

distribution system includes, depending 

on the configuration, adding a new 

circuit breaker and new relay to the AC/ 

DC ESS BUS circuit, and adding a diode 

between a certain relay and terminal 

block. You may obtain further 

information by examining the MCAI in 

the AD docket. 

Comments 

We gave the public the opportunity to 

participate in developing this AD. We 

considered the comment received. 

Support and Request to Reduce 

Compliance Time 

The Airline Pilots Association, 

International (ALPA) supports this AD, 

and asks that the 48-month compliance 

time proposed in the NPRM be reduced 

to 24 months. ALPA states that, given 

the potentially serious consequences of 

the flightcrew experiencing a very high 

workload during a critical phase of 

flight, the compliance time should be 

reduced based on the number of events 

and the safety risk associated with BUS 

failures. 

We do not agree that the compliance 

time should be reduced. In developing 

the compliance time for this AD action, 

we considered not only the safety 

implications of the identified unsafe 

condition, but the average utilization 

rate of the affected fleet, the practical 

aspects of modifying the fleet during the 

compliance time, and the availability of 

required parts. In addition, we have 

coordinated with the European Aviation 

Safety Agency (EASA), which is the 

Technical Agent for the Member States 

of the European Community. We have 

determined that the 48-month 

compliance time to do the modification 

addresses the identified unsafe 

condition and ensures an adequate level 

of safety for the affected fleet. We have 

made no change to the AD in this 

regard. 

Conclusion 

We reviewed the available data, 

including the comment received, and 

determined that air safety and the 

public interest require adopting the AD 

as proposed. 

Differences Between This AD and the 

MCAI or Service Information 

We have reviewed the MCAI and 

related service information and, in 

general, agree with their substance. But 

we might have found it necessary to use 

different words from those in the MCAI 

to ensure the AD is clear for U.S. 

operators and is enforceable. In making 

these changes, we do not intend to differ 

substantively from the information 

provided in the MCAI and related 

service information. 

We might also have required different 

actions in this AD from those in the 

MCAI in order to follow our FAA 

policies. Any such differences are 

highlighted in a NOTE within the AD. 


srobinson on DSKHWCL6B1PROD with RULES