[Federal Register Volume 73, Number 16 (Thursday, January 24, 2008)]
[Proposed Rules]
[Pages 4129-4131]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-1135]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0046; Directorate Identifier 2007-NM-270-AD]
RIN 2120-AA64


Airworthiness Directives; Airbus Model A318, A319, A320, and A321 
Series Airplanes Equipped With Certain Northrop Grumman (Formerly 
Litton) Air Data Inertial Reference Units

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede an existing airworthiness 
directive (AD) that applies to certain Airbus Model A319, A320, and 
A321 series airplanes equipped with certain Litton air data inertial 
reference units (ADIRUs). The existing AD currently requires modifying 
the shelf (floor panel) above ADIRU 3, modifying the polycarbonate 
guard that covers the ADIRUs for certain airplanes, and modifying the 
ladder located in the avionics compartment for certain airplanes. This 
proposed AD would require those modifications on additional airplanes. 
This proposed AD would also require replacing all three ADIRUs with 
improved ADIRUs. This proposed AD also adds Model A318 series airplanes 
to the applicability. This proposed AD results from reports that ``NAV 
IR FAULT'' messages have occurred during takeoff due to failure of an 
ADIRU and subsequent analysis showing that the shelf modification has 
not sufficiently addressed failure of an ADIRU. We are proposing this 
AD to prevent failure of an ADIRU during flight, which could result in 
loss of one source of critical attitude and airspeed data and reduce 
the ability of the flightcrew to control the airplane.

DATES: We must receive comments on this proposed AD by February 25, 
2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Airbus, 1 
Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (telephone 800-647-5527) is in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

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: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-0046; 
Directorate Identifier 2007-NM-270-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    On December 12, 2003, we issued AD 2003-26-03, amendment 39-13399 
(68 FR 74172, December 23, 2003), for certain Airbus Model A319, A320, 
and A321 series airplanes equipped with certain Litton air data 
inertial reference units (ADIRUs). That AD requires modifying the shelf 
(floor panel) above ADIRU 3, and, for certain airplanes, modifying the 
polycarbonate guard that covers the ADIRUs, and the ladder located in 
the avionics compartment, as applicable. That AD resulted from reports 
that ``NAV IR FAULT'' messages have occurred during takeoff due to 
failure of ADIRU 3 on several Model A319, A320, and A321 series 
airplanes. We issued that AD to prevent failure of ADIRU 3 during 
flight, which could result in loss of one source of critical attitude 
and airspeed data and reduce the ability of the flightcrew to control 
the airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 2003-26-03, the European Aviation Safety Agency 
(EASA), which is the Technical Agent for the Member States of the 
European Union, notified us that further analysis has shown that 
modifying the ADIRU shelf has not sufficiently addressed the unsafe 
condition. The clearance between the shelf and ADIRUs is still too 
small. Consequently, vibration during takeoff could cause the shelf to 
hit the top of an ADIRU, leading to loss of parameters (attitude, 
vertical speed, ground speed, etc.). The EASA has determined that, in 
addition to

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modifying the ADIRU shelf, all three ADIRUs must be replaced with 
improved ADIRUs that introduce a more robust shock resistance to 
adequately address the unsafe condition. The EASA has also determined 
that the unsafe condition exists on certain Model A318 series 
airplanes.

Relevant Service Information

    Airbus has issued Service Bulletin A320-34-1350, dated March 20, 
2006. The service bulletin describes procedures for replacing all three 
ADIRUs with improved ADIRUs having part number 465020-0303-0316, which 
introduce a more robust shock resistance and new magnetic variation 
tables.
    Airbus has also issued Service Bulletin A320-25-1248, Revision 01, 
dated April 16, 2003. The procedures in Revision 01 of the service 
bulletin are essentially the same as those in the original issue of the 
service bulletin, dated February 16, 2001. Revision 1 of the service 
bulletin adds airplanes to the effectivity of the service bulletin.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition. The EASA mandated 
the service information and issued airworthiness directive 2007-0217, 
dated August 9, 2007, to ensure the continued airworthiness of these 
airplanes in the European Union.

FAA's Determination and Requirements of the Proposed AD

    These airplanes are manufactured in France and are type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. As described in FAA 
Order 8100.14A, ``Interim Procedures for Working with the European 
Community on Airworthiness Certification and Continued Airworthiness,'' 
dated August 12, 2005, the EASA has kept the FAA informed of the 
situation described above. We have examined the EASA's findings, 
evaluated all pertinent information, and determined that AD action is 
necessary for airplanes of this type design that are certificated for 
operation in the United States.
    This proposed AD would supersede AD 2003-26-03 and retain the 
requirements of the existing AD. This proposed AD would also require 
accomplishing the actions specified in the service information 
described previously.

Change to Existing AD

    This proposed AD would retain all requirements of AD 2003-26-03. 
Since AD 2003-26-03 was issued, the AD format has been revised, and 
certain paragraphs have been rearranged. As a result, the requirement 
in paragraph (a) of AD 2003-26-03 corresponds to paragraph (f) of this 
proposed AD.

Costs of Compliance

    This proposed AD would affect about 658 airplanes of U.S. registry.
    The actions that are required by AD 2003-26-03 and retained in this 
proposed AD take about 4 work hours per airplane, at an average labor 
rate of $80 per work hour. Required parts cost about $300 per airplane. 
Based on these figures, the estimated cost of the currently required 
actions for U.S. operators is $407,960, or $620 per airplane.
    The new proposed actions would take about 3 work hours per 
airplane, at an average labor rate of $80 per work hour. The 
manufacturer states that it will supply the required parts to operators 
at no cost. Based on these figures, the estimated cost of the new 
actions specified in this proposed AD for U.S. operators is $157,920, 
or $240 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 proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would 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 the proposed 
regulation:
    1. Is not a ``significant regulatory action'' under Executive Order 
12866;
    2. Is not a ``significant rule'' under the 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 proposed 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, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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.


Sec.  39.13  [Amended]

    2. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
removing amendment 39-13399 (68 FR 74172, December 23, 2003) and adding 
the following new airworthiness directive (AD):

Airbus: Docket No. FAA-2008-0046; Directorate Identifier 2007-NM-
270-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by February 
25, 2008.

Affected ADs

    (b) This AD supersedes AD 2003-26-03.

Applicability

    (c) This AD applies to Airbus Model A318, A319, A320, and A321 
series airplanes, certificated in any category; equipped with at 
least one Northrop Grumman (formerly Litton) air data inertial 
reference unit (ADIRU), part number (P/N) 465020-0303-0307, -0308, -
0309, -0312, -0314, -0315, or -0316; except airplanes equipped with 
three ADIRUs having P/N 465020-0303-0316 and on which Airbus 
Modification 30650 or 30872 has been incorporated in production.

Unsafe Condition

    (d) This AD results from reports that ``NAV IR FAULT'' messages 
have occurred during takeoff due to failure of an ADIRU and

[[Page 4131]]

subsequent analysis showing that the shelf modification has not 
sufficiently addressed failure of an ADIRU. We are issuing this AD 
to prevent failure of an ADIRU during flight, which could result in 
loss of one source of critical attitude and airspeed data and reduce 
the ability of the flightcrew to control the airplane.

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.

Restatement of Requirements of AD 2003-26-03

Modification

    (f) For Model A319, A320, and A321 series airplanes, equipped 
with any Litton ADIRU installed in accordance with Airbus 
Modification 24852, 25108, 25336, 26002, or 28218: Within 2 years 
after January 27, 2004 (the effective date of AD 2003-26-03), do the 
modifications specified in paragraphs (f)(1), (f)(2), and (f)(3) of 
this AD, as applicable, in accordance with paragraphs A. through D. 
of the Accomplishment Instructions of Airbus Service Bulletin A320-
25-1248, dated February 16, 2001; or Airbus Service Bulletin A320-
25-1248, Revision 01, dated April 16, 2003; as applicable.
    (1) For all airplanes: Modify the shelf (floor panel) above 
ADIRU 3 by installing shims between the shelf and the webs of the 
shelf support structure.
    (2) For airplanes with Airbus Modification 25900P3941 or Airbus 
Service Bulletin A320-25-1200 accomplished as of January 27, 2004: 
Modify the polycarbonate guard (umbrella) protecting the ADIRUs by 
installing shims between the guard and the shelf support structure.
    (3) For airplanes with Airbus Modification 23027P2852 or Airbus 
Service Bulletin A320-52-1038 accomplished as of January 27, 2004: 
Modify the ladder located in the avionics compartment by machining 
the slot at the foot of the ladder to increase the depth by 0.236 
inch.

New Requirements of This AD

Modification for Certain Airplanes

    (g) For all airplanes equipped with any ADIRU installed in 
accordance with Airbus Modification 31070, 31742, or 35517, except 
airplanes on which Airbus Modification 30650 or 30872 has been 
accomplished in production: Within 46 months after the effective 
date of this AD, modify the ADIRU shelf supports by accomplishing 
all of the applicable actions specified in the Accomplishment 
Instructions of Airbus Service Bulletin A320-25-1248, Revision 01, 
dated April 16, 2003.

Replacement of ADIRUs

    (h) For all airplanes except those on which Airbus Modification 
35517 has been incorporated in production: Within 46 months after 
the effective date of this AD, replace all three ADIRUs with 
improved ADIRUs having P/N 465020-0303-0316 in accordance with the 
Accomplishment Instructions of Airbus Service Bulletin A320-34-1350, 
dated March 20, 2006.

Alternative Methods of Compliance (AMOCs)

    (i)(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) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

Related Information

    (j) European Aviation Safety Agency airworthiness directive 
2007-0217, dated August 9, 2007, also addresses the subject of this 
AD.

    Issued in Renton, Washington, on January 14, 2008.
Stephen P. Boyd,
Assistant Manager, Transport Airplane Directorate, Aircraft 
Certification Service.
 [FR Doc. E8-1135 Filed 1-23-08; 8:45 am]
BILLING CODE 4910-13-P