AD 97-07-01 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A330 and A340 series airplanes. This action requires the deactivation of the avionics ground refrigeration unit (GRU) of the air conditioning system until a modification of avionics ventilation circuit and the GRU is accomplished. This amendment is prompted by reports of water accumulation found in the Air Data/Inertial Reference Unit (ADIRU) trays of the avionics rack; the accumulation is the result of operation of the GRU in high ambient humidity. The actions specified in this AD are intended to prevent water accumulating in this area, which could result in the failure of the ADIRU and consequent loss of air data and navigational information to the flightcrew.

Final rule; request for comments.

97-07-01 AIRBUS INDUSTRIE: Amendment 39-9974. Docket 97-NM-22-AD.

Applicability: Model A330-301 series airplanes having manufacturer's serial number (MSN) 1 through 106, inclusive; and Model A340-211, -212, -311, and -312 series airplanes having MSN 1 through 113, inclusive; on which Airbus Modification No. 40063S10052 (ground cooling system) has been installed; certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent water from accumulating in the Air Data/Inertial Reference Unit (ADIRU) trays of the avionics racks, which could result in the damage to or failure of the ADIRU(s) and consequent loss of air data and navigational information to the flightcrew, accomplish the following:

(a) Within 500 hours time-in-service after the effective date of this AD, deactivate the avionics ground refrigeration unit (GRU) in accordance with Airbus All Operators Telex 21-01, dated March 28, 1995.

(b) Modification of the avionics equipment ventilation system in accordance with Airbus Service Bulletin A330-21-3028, Revision 2, dated May 5, 1995 (for Model A330 series airplanes); or Airbus Service Bulletin A340-21-4046, Revision 2, dated May 5, 1995 (for Model A340 seriesairplanes); as applicable; constitutes terminating action for the requirements of paragraph (a) of this AD. Once the modification is completed, the avionics GRU may be reactivated.

(c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Standardization Branch, ANM-113. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(d) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(e) The modification, if accomplished, shall be done in accordance with the following Airbus service bulletins, which contain the specified list of effective pages:

Service Bulletin
Number and Date

Page Number
Revision Level
Shown on Page
Date
Shown on Page
A330-21-3028,
Revision 2,
May 5, 1995
1, 3-6

2, 11, 23, 24,
29-30

7-10, 12-22,
25-28
2

1

Original
May 5, 1995

March 3, 1995

January 19, 1995
A340-21-4046,
Revision 2,
May 5, 1995

1-4

5-12, 14-24,
27-30

13, 25, 26, 31, 32
2

Original

1
May 5, 1995

January 19, 1995

March 3, 1995

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on April 15, 1997.

The Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified the FAA that an unsafe condition may exist on certain Airbus Model A330 and A340 series airplanes. The DGAC advises that there have been reports of water accumulation found in the Air Data/Inertial Reference Unit (ADIRU) trays of the avionics racks on in-service airplanes. All of the airplanes on which this phenomenon occurred were equipped with a ground cooling system, identified as Airbus Modification No. 40063S10052. (This is an optional modification available to Model A330 and A340 series airplanes.)

Investigation revealed that water droplets can accumulate on the evaporator cores of the ground refrigeration unit (GRU) as a result of high ambient humidity. The water droplets are then carried within the airflow and accumulate in the low points of the avionics ventilation ducting.

In at least two cases, this accumulation of water resulted in the failure of one or two ADIRU s during flight. In one of these incidents, both inertial reference systems on one airplane were lost, and the flight crew was compelled to execute an in-flight turn-back. Upon the subsequent approach, all instrument landing system data disappeared from the airplane's primary flight displays.

Failure of the ADIRU(s) during flight, which can occur as a result of the consequences associated with water accumulation in the relevant avionics rack, could result in loss of air data and navigational information to the flightcrew. This could compromise the ability of the flight crew to maintain the safe flight and landing of the airplane.

Explanation of Relevant Service Information
Airbus has issued All Operators Telex (AOT) 21-01, dated March 28, 1995, which describes procedures for deactivating the avionics GRU, if one is installed on the airplane. The DGAC classified this AOT as mandatory and issued French airworthiness directives (CN) 95-089-010(B) (for Model A330 series airplanes) and 95-093-020(B) (for Model A340 series airplanes), both dated May 24, 1995, in order to assure the continued airworthiness of these airplanes in France.

Airbus also has issued Service Bulletin A330-21-3028, Revision 2, dated May 5, 1995 (for Model A330 series airplanes), and Service Bulletin A340-21-4046, Revision 2, dated May 5, 1995 (for Model A340 series airplanes). These service bulletins describe procedures for modifying the avionics equipment ventilation system and the GRU on airplanes equipped with one. The modification procedures include:

1. air tappings for relocation of ADIRU ventilation from the lower to the upper side of the ventilation ducting;

2. installing water drains at the lower side of the ventilation ducting;

3. drilling a hole in each ADIRU tray; and

4. on airplanes equipped with a GRU, increasing the inner diameter of the existing GRU drain line.

Accomplishment of this modification will prevent water from accumulating in the ventilation ducting low points and subsequently damaging the ADIRU s. [This modification was installed during production on Model A330 series airplanes beginning at manufacturer's serial number (MSN) 107, and on Model A340 series airplanes beginning at MSN 114.]

The DGAC has classified Revision 2 of Airbus Service Bulletins A330-21-3028 and A340-21-4046 as "recommended."

FAA's Conclusions
This airplane model is manufactured in France and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.19) 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 the 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, this AD is being issued to prevent water from accumulating in the ADIRU trays of the avionics racks, which could result in the damage to or failure of the ADIRU(s) and consequent loss of air data and navigational information to the flightcrew. This AD requires the deactivation of the GRU on those airplanes equipped with a GRU. The deactivation must be accomplished in accordance with the Airbus AOT described previously.

Should an operator want to reactivate the GRU, it must first modify the avionics equipment ventilation system in accordance with the procedures contained in the Airbus service bulletin, described previously.

Cost Impact
None of the Model A330 and A340 series airplanes affected by this action are on the U.S. Register. All airplanes included in the applicability of this rule currently are operated by non-U.S. operators under foreign registry; therefore, they are not directly affected by this AD action. However, the FAA considers that this rule is necessary to ensure that the unsafe condition is addressed in the event that any of these subject airplanes are imported and placed on the U.S. Register in the future.

Should an affected airplane be imported and placed on the U.S. Register in the future, it would require approximately 1 work hour to accomplish the deactivation of the GRU at an average labor charge of $60 per work hour. Based on these figures, the cost impact of this required action would be $60 per airplane.

If an operator elected to the modify avionics equipment ventilation system so that the GRU could be reactivated, it would take 4 work hours to accomplish the modification, at an average labor charge of $60 per work hour. Required parts would be provided to operators free of charge by the manufacturer. Based on these figures, the cost impact of this optional action would be $240 per airplane.

Determination of Rule's Effective Date
Since this AD action does not affect any airplane that is currently on the U.S. register, it has no adverse economic impact and imposes no additional burden on any person. Therefore, prior notice and public procedures hereon are unnecessary and the amendment may be made effective in less than 30 days after publication in the Federal Register.

Comments Invited
Although this action is in the form of a final rule and was not preceded by notice and opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-22-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 97-NM-22-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD 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; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Charles Huber, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2589; fax (206) 227-1149.