[Federal Register Volume 64, Number 218 (Friday, November 12, 1999)]
[Rules and Regulations]
[Pages 61480-61482]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29054]


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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.

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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

[[Page 61481]]

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:

[[Page 61482]]

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. 99-29054 Filed 11-10-99; 8:45 am]
BILLING CODE 4910-13-P