AD 94-23-06 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A320-111, -211, and -231 airplanes, that requires modification of the currently installed one-stage shock absorbers on the main landing gear to two-stage shock absorbers. This amendment is prompted by the results of an evaluation of the air-to-ground sensing logic relative to the operation of other airplane systems during landing in adverse weather conditions. The actions specified by this AD are intended to prevent a delay in sensing by the air-to-ground logic system that the airplane is on the ground, which could prevent the airplane from achieving the landing distances specified in the FAA-approved Airplane Flight Manual (AFM).

Final rule.

94-23-06 AIRBUS INDUSTRIE: Amendment 39-9068. Docket 93-NM-210-AD.

Applicability: Model A320-111, -211, and -231 airplanes, as listed in Airbus Industrie Service Bulletin A320-32-1058, Revision 2, dated June 16, 1993, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent a delay in sensing by the air-to-ground logic system that the airplane is on the ground, which could prevent the airplane from achieving the landing distances specified in the FAA-approved Airplane Flight Manual (AFM), accomplish the following:

(a) Within 18 months after the effective date of this AD, modify the currently installed one-stage shock absorbers to two-stage shock absorbers, in accordance with Airbus Industrie Service Bulletin A320-32-1058, Revision 2, dated June 16, 1993.

(b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by theManager, 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: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(c) 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.

(d) The modification shall be done in accordance with Airbus Industrie Service Bulletin A320-32-1058, Revision 2, dated June 16, 1993. 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.

(e) This amendment becomes effective on December 21, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Airbus Model A320-111, -211, and -231 airplanes was published in the Federal Register on December 29, 1993 (58 FR 68786). That action proposed to require modification of the currently installed one-stage shock absorbers on the main landing gear (MLG) to two-stage shock absorbers.

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

One commenter supports the proposed rule.

One commenter opposes the proposed requirement to modify the currently installed one-stage shock absorber on the MLG to two-stage shock absorbers. This commenter states that the requirement is unnecessary due to the fact that the one-stage absorbers currently installed on Model A320 series airplanes, when operated within the certification standards of the airplane, do not adversely affect the airworthiness of these airplanes. This commenter contends that the purpose of the two-stage shock absorber is solely to improve passenger comfort. The FAA does not concur that this rulemaking action is unnecessary. The FAA has determined that the installation of the two-stage shock absorber will improve the airplane's ability to achieve the landing distances specified in the FAA-approved Airplane Flight Manual (AFM). Earlier activation of supplemental braking devices, which would be available by installing two-stage shock absorbers, will enhance deceleration of the airplane when necessary to meet the required landing distances. The FAA has re-evaluated the air-to-ground sensing logic, has reviewed all other available data, and has determined that an unsafe condition exists with regard to the airplane failing to achieve the landing distances specified in the FAA-approved AFM. Further, the FAA has determined that this AD action is necessary for airplanes of this type design that are certificated for operation in the United States.

One commenter asserts that the FAA is taking action contrary to the normal course of action by proposing to issue the AD, when the French Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, has not issued a parallel AD. From this comment, the FAA infers that the commenter is requesting that the rule be withdrawn or delayed until the DGAC issues a similar mandatory action. The FAA does not concur. While the United States and France observe the provisions of the bilateral airworthiness agreement, it remains the responsibility of the FAA to monitor and maintain the continuing airworthiness of U.S-type certificated and registered airplanes. The bilateral airworthiness agreements do not restrict the FAA from issuing AD's based upon its own finding of an unsafe condition, regardless of the decision made by another airworthiness authority relative to the same subject. In that the FAA has determined that an unsafe condition exists, and that action is necessary to correct that condition in the fleet, the issuance of this AD is not only appropriate, but warranted.

One commenter suggests that the issuance of this rule be delayed until such time that a lower cost alternative can be developed by the manufacturer. In the interim, this commenter suggests that the proposal be revised to require a periodic inspection to be performed at 15-month intervals. The FAA does not concur. To delay this action would be inappropriate, since the FAA has determined that an unsafe condition exists, a corrective modification is currently available, and the modification must be accomplished to ensure continued safety. However, paragraph (b) of the final rule does provide affected operators the opportunity to obtain approval from the FAA for alternative methods of compliance by presenting justification for thosealternatives.

Two commenters request that the proposed compliance time of 12 months be extended to accomplish the proposed modification of the shock absorbers. One of these commenters requests that the compliance time be extended to 24 months. The other commenter requests that the compliance time be extended to 60 months, in light of the low probability of duplicating the combination of factors that may result in an accident. This commenter notes that, due to the unavailability of manpower and tooling, the proposed modification would result in a minimum of three days of downtime per airplane. Both commenters state that the manufacturer may be unable to provide an adequate number of MLG pistons to accomplish the modification within the proposed 12-month compliance time.

The FAA concurs that the compliance time may be extended somewhat. The FAA acknowledges the low probability of duplicating all of the factors that may result in an accident. However, in the unlikely eventthat all of the factors should be duplicated, airplanes equipped with dual stage shock absorbers would be able to activate, at an earlier stage of the landing roll, all available braking devices, including the deployment of ground spoilers, application of wheel brakes, and deployment of thrust reversers. Proper activation of braking devices would permit the airplane to land within the distances specified in the FAA-approved AFM. In light of the potential for these airplanes to overrun the end of the runway due to delayed onset of braking, the FAA cannot concur with the one commenter's request to extend the compliance time to 60 months; the FAA considers that such an extension (five times the amount of time proposed) would adversely affect safety. However, it was not the FAA's intent to impose an undue economic burden on operators by requiring them to take airplanes out of service for an extended period of time due to the problem posed by a lack of available parts to accomplish the modification required by this AD. Although the airframe manufacturer has indicated that ample modification parts are currently available, the supplier of those parts has indicated that shipping to operators may take an extended period of time. In light of this, the FAA has determined that an extension of the compliance time to 18 months is appropriate; it will allow sufficient time for operators to obtain the parts necessary to accomplish the modification, while minimizing the economic burden on operators. The FAA finds that this extension of the compliance time will not adversely affect the safety of the fleet. Accordingly, paragraph (a) of the final rule has been revised to extend the compliance time to accomplish the modification of the shock absorber to 18 months.

After careful review of 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 with the change previously described.The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

The FAA estimates that 35 airplanes of U.S. registry will be affected by this AD, that it will take approximately 58 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will cost approximately $16,000 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $671,650, or $19,190 per airplane.

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

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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.
39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:

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 Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Stephen Slotte, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2797; fax (206) 227-1320.