Airworthiness directives: Airbus,

[Federal Register: November 12, 1999 (Volume 64, Number 218)]

[Rules and Regulations]

[Page 61480-61482]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr12no99-5]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-106-AD; Amendment 39-11405; AD 99-23-09]

RIN 2120-AA64

Airworthiness Directives; Airbus Model A319, A320, and A321 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A319, A320, and A321 series airplanes, that requires modification of the electro-distributor for the nose wheel steering servo-control. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent uncommanded nose landing gear wheel rotation, due to defective seals in the wheel steering selector valve of the hydraulic control unit for the nose landing gear, which could result in reduced controllability of the airplane.

DATES: Effective December 17, 1999.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of December 17, 1999.

ADDRESSES: 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.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2110; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION: 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 A319, A320, and A321 series airplanes was published in the Federal Register on June 28, 1999 (64 FR 34579). That action proposed to require modification of the electro-distributor for the nose wheel steering servo-control.

Comments

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

Support for the Proposal

One commenter supports the proposed AD.

One commenter states that it is not affected by the proposed AD and therefore has no comments or objections.

One commenter states that it had previously decided to modify its airplanes in accordance with the proposed AD and is in the process of doing so now.

Request To Delete Spare Parts Restriction

One commenter supports the intent of the proposed AD, but has a concern with paragraph (b), which would require that spare parts be immediately subject to the proposed actions. In order to ensure compliance with the immediate deadline of paragraph (b) of the proposed AD, the commenter states it would have two major challenges. The first would be to issue special instructions to all of its maintenance personnel that the A320 nose landing gear (NLG) steering servo-control is a component that cannot be ``robbed'' from one aircraft to another during the course of the retrofit. The commenter states that its practice is to minimize the ``one-off'' special instructions to maintenance for human factors reasons. While it considers the likelihood of a robbed NLG steering servo-control from a pre-mod to a post-mod airplane to be remote, the commenter considers the inclusion of paragraph (b) of the

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proposed AD would require special actions to prevent this. Secondly, the commenter considers the inclusion of paragraph (b) of the proposed AD to mandate immediately making all existing spare servo-controls unserviceable until they could be modified at a certified vendor repair station. The commenter believes that this could adversely affect the line spares situation and could adversely impact dispatch reliability. The commenter requests that paragraph (b) of the proposed AD be deleted.

The FAA does not concur. Removing an unsafe condition that already exists on an airplane necessarily involves performing maintenance on this airplane, and the FAA has provided a compliance time of 12 months for the required modification in order to minimize disruption of operations. On the other hand, prohibiting installation of spares that have been determined to create an unsafe condition does not require any additional maintenance activity; it simply requires use of one part rather than another. In general, once an unsafe condition has been determined to exist, it is the FAA's normal policy not to allow that condition to be introduced into the fleet. The availability of parts that the AD will require to be installed is an important consideration in the development of the technical information on which every AD is based is. When it is determined that safe parts are available to operators, it is the FAA's policy to prohibit installation of the unsafe parts after the effective date of the AD. The FAA is not aware of any specific problems with availability of parts or anticipated difficulties in accomplishing the modification required by this AD.

Further, the FAA considers that the period of time between publication of the final rule in the Federal Register and the effective date of the final rule (usually 30 days) is sufficient to provide operators with an opportunity to determine their immediate need for modified spares and to obtain them. Of course, in individual cases where this is not possible, every AD contains a provision that allows an operator to obtain an extension of compliance time based upon a specific showing of need. The FAA considers that this policy does increase safety and does not impose undue burdens on operators.

Request To Expand the Applicability of the Proposed AD

One commenter states that a similar steering control unit was installed on the first 80 Model A330 and A340 series airplanes and that these airplanes could also be susceptible to failure of the selector valve's external seals. Although there are currently no U.S.-registered airplanes, the commenter requests that the FAA require a similar modification on Model A330 and A340 series airplanes in case these airplanes are placed on the U.S. Register in the future.

The FAA acknowledges the commenter's concerns, and may consider additional rulemaking to address those concerns in the future on certain airplanes. However, until such final action is identified, the FAA considers it appropriate to proceed with issuance of this final rule. No change to the final rule is required.

Request To Require Examination of the Braking and Steering Control Unit

The same commenter also states that its investigation has revealed another feature of the steering system on Model A320 series airplanes that can contribute to uncommanded nosewheel rotation. The Braking and Steering Control Unit (BSCU), which positions the steering servo valve in response to steering orders on the ground, performs an automatic test of the nosewheel steering in flight after the landing gear is extended. If a sufficient disagreement between the commanded and actual steering position occurs during the test, the BSCU will attempt to deactivate the steering system by deenergizing the selector valve. However, failure of the selector valve can defeat this protection and cause uncommanded rotation of the nosewheels. Although the action proposed by the notice of proposed rulemaking (NPRM) will address failures of the selector valve's seals of Model A320 series airplanes, the commenter is concerned about the ability of the BSCU to deactivate steering control. Airbus has indicated to the commenter that it is considering a modification to the BSCU that will maintain the nose gear in the neutral position in flight.

The FAA infers that the commenter requests that a requirement to modify the BSCU be added to this final rule. The FAA does not concur. Because the suggested changes would alter the actions currently required by this AD, additional rulemaking would be required. Further, the BSCU modification described by the commenter is not currently available. The FAA finds that to delay this action until the modification is available would be inappropriate in light of the identified unsafe condition. No change to this final rule is necessary.

Conclusion

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 as proposed.

Cost Impact

The FAA estimates that 208 airplanes of U.S. registry will be affected by this AD, that it will take approximately 7 work hours per airplane to accomplish the modification, and that the average labor rate is $60 per work hour. Required parts will cost approximately $335 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $157,040, or $755 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.

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:

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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. Section 39.13 is amended by adding the following new airworthiness directive:

   99-23-09 Airbus Industrie: Amendment 39-11405. Docket 99-NM-106-AD.

   Applicability: Model A319, A320, and A321 series airplanes; except those airplanes on which Airbus Modification 23740 was accomplished during production, and those airplanes on which Airbus Service Bulletin A320-32-1197, dated October 9, 1998, or Revision 01, dated February 11, 1999, has 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 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 uncommanded nose landing gear wheel rotation, due to defective seals in the wheel steering selector valve of the hydraulic control unit for the nose landing gear, which could result in reduced controllability of the airplane, accomplish the following:

   Modification

   (a) Within 12 months after the effective date of this AD, modify the electro-distributor for the nose wheel steering servo-control in accordance with Airbus Industrie Service Bulletin A320-32-1197, Revision 01, dated February 11, 1999.

   Note 2: Airbus Service Bulletin A320-32-1197 references Messier- Bugatti Service Bulletin C24736-32-3166, dated December 4, 1998, as an additional source of service information for accomplishment of the modification.

   Note 3: Replacement of the by-pass valve in accordance with Messier-Bugatti Service Bulletin C24736-32-3126, dated February 15, 1995, as revised by Change Notice Number 1, dated March 16, 1999, is considered acceptable for compliance with the action specified in paragraph (a) of this AD.

   Spares

   (b) As of the effective date of this AD, no person shall install a hydraulic control unit, part number C24736000 or C24736001, on any airplane, unless it has been modified in accordance with the actions required by paragraph (a) of this AD.

   Alternative Methods of Compliance

   (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, International Branch, ANM-116, 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, International Branch, ANM-116.

   Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

   Special Flight Permits

   (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.

   Incorporation by Reference

   (e) The modification shall be done in accordance with Airbus Industrie Service Bulletin A320-32-1197, Revision 01, dated February 11, 1999. 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.

   Note 5: The subject of this AD is addressed in French airworthiness directive 1999-124-129(B), dated March 24, 1999.

   (f) This amendment becomes effective on December 17, 1999.

   Issued in Renton, Washington, on November 1, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

   [FR Doc. 99-29054Filed11-10-99; 8:45 am]

   BILLING CODE 4910-13-P