AD 97-05-04

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A320-111, -211, and -231 series airplanes, that currently requires replacing the existing standby generator control unit (GCU) with a new improved standby GCU. That action was prompted by reports of improper functioning of the standby GCU. This amendment requires replacement of the GCU on additional affected airplanes. For some airplanes, it also will require that a wiring modification be accomplished prior to replacement of the GCU. The actions specified by this AD are intended to prevent such improper functioning of the GCU, which could result in the loss of the standby emergency generation system.

Final rule.

97-05-04 AIRBUS INDUSTRIE: Amendment 39-9948. Docket 96-NM-11-AD. Supersedes AD 91-01-01, Amendment 39-6845.

Applicability: Model A320 series airplanes; on which a generator control unit (GCU) having part number (P/N) 520915 has not been installed, or on which Airbus Modification 21052 (reference Airbus Service Bulletin A320-24-1022) and Airbus Modification 21736 (reference Airbus Service Bulletin A320-24-1035) have not been accomplished; certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been 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 ofthe 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 loss of the standby emergency generation system, which provides necessary back-up capability when both main generators fail, accomplish the following:

NOTE 2: Airbus Service Bulletin A320-24-1035 and Airbus Service Bulletin A320-24- 1022 refer to Vickers Service Bulletin No. 520754-24-01 as an additional source of specific procedural information.

(a) For Model A320-111, -211, and -231 series airplanes; having serial numbers 003 through 058, inclusive, 060 through 067, inclusive, 069 through 072, inclusive, 074 through 083, inclusive, and 085: Within 150 days after January 28, 1991 (the effective date of AD 91-01-01, amendment 39-6845), remove one generator control unit (GCU) identified as 1XE part number (P/N) 520754, and install a modified GCU identified as 1XE, P/N 520915, in accordance with Airbus Service Bulletin A320-24-1035, Revision 1, dated February 27, 1990, or Revision 2, dated June 24, 1994. Following installation, perform an operational test of the emergency generation system, emergency GCU from the centralized fault display system, and the static inverter, in accordance with the service bulletin.

(b) For airplanes not subject to paragraph (a) of this AD: Within 150 days after the effective date of this AD, accomplish either paragraph (b)(1) or (b)(2) of this AD, as applicable.

NOTE 3: Replacement of the GCU accomplished prior to the effective date of this AD in accordance with Airbus Service Bulletin A320-24-1035, Revision 1, dated February 27, 1990, is considered acceptable for compliance with the actions specified in this paragraph.

(1) For airplanes equipped with GCU 1XE having P/N 520754: Replace the GCU 1XE, having P/N 520754, in zone 125 of the avionics compartment, with a modified GCU 1XE, having P/N 520915, in accordance with Airbus Service Bulletin A320-24-1035, Revision 2, dated June 24, 1994. Prior to further flight following accomplishment of the replacement, perform an operational test of the affected components in accordance with that service bulletin.

(2) For airplanes equipped with GCU 1XE having P/N 520738: Accomplish the requirements of paragraphs (b)(2)(i) and (b)(2)(ii) of this AD:

(i) Modify the wiring in relay box 103VU, the wiring in power center AC/DC emergency 106VU, and the wiring between 103VU and 106VU, in accordance with Airbus Service Bulletin A320-24-1022, Revision 1, dated February 27, 1990.

NOTE 4: Modification accomplished prior to the effective date of this AD in accordance with Airbus Service Bulletin A320-24-1022, dated June 16, 1989, is considered acceptable for compliance with this paragraph.

(ii) After modifying the wiring, replace the GCU 1XE, having P/N 520738, located in the nose gear well in zone 125, with a modified GCU 1XE, having P/N 520915, in accordance with Airbus Service Bulletin A320-24-1035, Revision 2, dated June 24, 1994. Prior to further flight following accomplishment of the replacement, perform an operational test of the affected components in accordance with that service bulletin.

(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, FAA, Transport Airplane Directorate. 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 5: 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 actions shall be done in accordance with the following Airbus Service Bulletins, which contain the specified lists effective pages:

Service Bulletin
Number and Date

Page Number
Revision Level
Shown on Page
Date
Shown on Page
A320-24-1035,
Revision 1,
February 27, 1990
1, 2
3,4
1
Original
February 27, 1990
October 20, 1989
A320-24-1035,
Revision 2,
June 24, 1994
1-4
2
June 24, 1994
A320-24-1022,
Revision 1,
February 27, 1990
1, 5, 6, 13, 14, 19-21
2-4, 7-12, 15-18, 22
1
Original
February 27, 1990
June 16, 1989

The incorporation by reference of the service documents listed above is 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 fromAirbus 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 3, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 91-01-01, amendment 39-6845 (55 FR 51895, December 18, 1990), which is applicable to certain Airbus Model A320-111, -211, and -231 series airplanes, was published in the Federal Register on October 23, 1996 (61 FR 54963). The action proposed to supersede AD 91-01-01 to continue to require replacement of the existing standby GCU with an improved standby GCU. The action also proposed to require the identical replacement to be accomplished on additional airplanes. In addition, for some airplanes, the action proposed that a wiring modification be accomplished prior to replacement of the GCU.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the two comments received.

Support for the Proposal
Both commenters support the proposed AD.

Conclusion
After careful reviewof the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

Cost Impact
There are approximately 106 Airbus Model A320 series airplanes of U.S. registry that will be affected by this AD. Of this number, 18 were previously subject to the requirements of AD 91-01-01, and the remaining 88 are the airplanes that have been added to the AD applicability by this action.

The replacement of the GCU that is required by this AD takes approximately 1.5 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $450 per airplane. Based on these figures, the cost impact of this required action on U.S. operators is estimated to be $57,240 for the entire affected fleet (or $540 per airplane). However, based on the effective date and the compliance time established by AD 91-01-01, the FAA assumes that the 18 airplanes that were previously subject to that AD already have completed the required replacement of the GCU. Therefore, the future cost impact of the replacement action is only $47,520 (for the 88 airplanes that have been added to the applicability of the AD).

For airplanes on which the modification of the wiring assembly is required, it will take approximately 8.5 work hours to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this action on U.S. operators of those airplanes is estimated to be $510 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the new requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

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 thedistribution 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, Incorporationby 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 removing amendment 39-6845 (55 FR 51895, December 18, 1990), and by adding a new airworthiness directive (AD), amendment 39-9948, to read as follows: