[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
