03-25494. Airworthiness Directives; Airbus Model A319, A320, and A321 Series Airplanes Equipped with Certain Litton Air Data Inertial Reference Units

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Airbus Model A319, A320, and A321 series airplanes equipped with certain Litton air data inertial reference units (ADIRU). This proposal would require modifying the shelf (floor panel) above ADIRU 3, and for certain airplanes modifying the polycarbonate guard which covers the ADIRUs, and the ladder located in the avionics compartment, as applicable. This action is necessary 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. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by November 7, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-92-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-92-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Tim Dulin, Aerospace Engineer, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-92-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-92-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The Direction Generale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, notified the FAA that an unsafe condition may exist on certain Airbus Model A319, A320, and A321 series airplanes equipped with certain Litton air data inertial reference units (ADIRU). The DGAC advises that operators have reported that “NAV IR FAULT” messages have occurred during takeoff on several of these airplanes due to failure of ADIRU 3. Investigation revealed that vibrations during takeoff may cause contact between ADIRU 3 and the shelf (floor panel) above it, due to minimal clearance between the shelf and the ADIRU. Such contact may cause excessive vertical acceleration, which could result in failure of ADIRU 3. Due to its location on the shelf, ADIRU 3 is more sensitive to vibration than the other two ADIRUs. Failure of ADIRU 3 during flight could result in loss of one source of critical attitude and airspeed data and reduce the ability of the flightcrew to control the airplane.

Explanation of Relevant Service Information

Airbus has issued Service Bulletin A320-25-1248, dated February 16, 2001, which describes procedures for modifying the shelf (floor panel) above the Litton ADIRUs by installing shims on the webs of the shelf support structure in the avionics rack. In addition, for certain airplanes, the service bulletin includes procedures for modifying the polycarbonate guard which covers the ADIRUs, and machining the ladder located in the avionics compartment to increase the depth of the slot at the foot of the ladder, as applicable. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. The DGAC classified this service bulletin as mandatory and issued French airworthiness directive 2002-125(B), dated March 6, 2002, to ensure the continued airworthiness of these airplanes in France.

FAA's Conclusions

These airplane models 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. Pursuant to this bilateral airworthiness agreement, the DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between the Proposed Rule and the French Airworthiness Directive

Operators should note that, although the French airworthiness directive contains operational dispatch restrictions for airplanes with one ADIRU inoperative, this proposed AD does not include these restrictions because the FAA-approved Master Minimum Equipment List already restricts operations accordingly.

Cost Impact

The FAA estimates that 200 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 4 work hours per airplane to accomplish the proposed modification of the shelf, and that the average labor rate is $65 per work hour. Required parts would cost approximately $300 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $112,000, or $560 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive:

Airbus: Docket 2002-NM-92-AD.

Applicability: Model A319, A320, and A321 series airplanes; certificated in any category; equipped with Litton air data inertial reference units (ADIRU) installed per Airbus Modification 24852, 25108, 25336, 26002, or 28218; except those airplanes on which Airbus Modification 30650 or 30872 has been accomplished.

Compliance: Required as indicated, unless accomplished previously.

To prevent loss 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, accomplish the following:

Modification

(a) Within 2 years after the effective date of this AD: Do the modifications specified in paragraphs (a)(1), (a)(2), and (a)(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; 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 the effective date of this AD: 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 the effective date of this AD: 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.

Alternative Methods of Compliance

(b) In accordance with 14 CFR 39.19, the Manager, International Branch, FAA, Transport Airplane Directorate, is authorized to approve alternative methods of compliance for this AD.

Note 1:

The subject of this AD is addressed in French airworthiness directive 2002-125(B), dated March 6, 2002.

Issued in Renton, Washington, on October 2, 2003.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.