AD Amdt-39-9491

[Federal Register Volume 61, Number 19 (Monday, January 29, 1996)]
[Rules and Regulations]
[Pages 2697-2699]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 96-591]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-03-AD; Amendment 39-9491; AD 96-01-52]


Airworthiness Directives; Airbus Model A310 and A300-600 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This document publishes in the Federal Register an amendment 
adopting Airworthiness Directive (AD) T96-01-52 that was sent 
previously to all known U.S. owners and operators of Airbus Model A310 
and A300-600 series airplanes by individual telegrams. Among other 
things, this AD requires repetitive inspections to ensure correct 
synchronization of the hydraulic control valves of the trimmable 
horizontal stabilizer (THS) actuator; replacement of the horizontal 
stabilizer actuator motors with new or serviceable motors and 
resynchronization of the valves, or adjustment of the synchronization, 
if necessary; and a functional test of the THS. This amendment is 
prompted by a report of desynchronization of the hydraulic control 
valves that direct fluid to the horizontal stabilizer actuator motors, 
which resulted in uncommanded movement of the THS. The actions 
specified by this AD are intended to prevent such desynchronization, 
which could lead to runaway of the horizontal stabilizer to its full up 
or down position, subsequent reduced maneuvering capability, and 
potential pitch upset.

DATES: Effective February 5, 1996, to all persons except those persons 
to whom it was made immediately effective by telegraphic AD T96-01-52, 
issued January 9, 1996, which contained the requirements of this 
amendment.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 5, 1996.
    Comments for inclusion in the Rules Docket must be received on or 
before March 29, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No.96-NM-03-AD, 1601 Lind Avenue SW., Renton, 
Washington 98055-4056.
    The applicable service information may be obtained from Airbus 
Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. 
This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: Tom Groves, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206) 
227-1503; fax (206) 227-1149.

SUPPLEMENTARY INFORMATION: The Direction Generale de l'Aviation Civile 
(DGAC), which is the airworthiness authority for France, recently 
notified the FAA that an unsafe condition may exist on certain Airbus 
Model A310 and A300-600 series airplanes. The DGAC advises that it 
recently received a report indicating that uncommanded movement of the 
trimmable horizontal stabilizer (THS) occurred on a Model A310 series 
airplane after the engine was started while the airplane was on the 
ground. Both pitch trim levers and the autopilot (AP) 1 tripped; 
additionally, the servo control push button (P/B) of one of the 
hydraulic systems illuminated. The servo control P/B was reset 
successfully following engagement of the pitch trim and AP1.
    The crew attempted to command the pitch trim by using one of the 
rocking switches; however, the pitch trim and AP1 tripped again. Then, 
without further action on the part of the crew, the pitch trim control 
wheel moved to a position of 14 degrees up (end of travel).
    During subsequent bench testing of the motor on one of the 
hydraulic systems of the airplane, the positioning pin on the cam plate 
was found to be broken. This pin is not designed to carry loads. The 
shape of the pin hole indicated that the pin was bent and ruptured.
    Further investigation revealed that the pin rupture was caused by 
desynchronization of the hydraulic control valves that direct fluid to 
the horizontal stabilizer actuator (HSA) motors. Desynchronization of 
the hydraulic control valves can result in one hydraulic motor being 
pressurized before the other. In this case, the nonpressurized motor 
opposes the torque of the motor that is pressurized first, which causes 
load to be applied to the positioning pin of the nonpressurized motor. 
Consequently, the pin can rupture due to fatigue. Such rupturing of the 
positioning pin of one motor can result in jamming of the THS actuator 
and can contribute to subsequent failure of the hydraulic system of the 
other motor.
    These conditions, if not corrected, could result in runaway of the 
horizontal stabilizer to its full up or down position, and subsequent 
reduced maneuvering capability and a potential pitch upset.
    The horizontal stabilizer actuator installed on Model A310 series 
airplanes is similar in design to the one installed on Model A300-600 
series airplanes. Therefore, the FAA finds that Model A300-600 series 
airplanes are subject to the same unsafe condition identified in the 
Model A310.
    Airbus has issued All Operators Telex (AOT) 27-21, Revision 1, 
dated January 5, 1996, which describes procedures for repetitive 
inspections to ensure correct synchronization of the hydraulic control 
valves of the THS actuators; replacement of the hydraulic motors with 
new or serviceable motors and resynchronization of the valves, or 
adjustment of the synchronization, if necessary; and a functional test 
of the THS.
    For airplanes on which the hydraulic motor or hydraulic valve block 
of the HSA has been subject to previous maintenance action, the AOT 
also describes procedures for replacement of both hydraulic motors of 
the HSA with new or serviceable motors.
    In lieu of replacing the motors, the AOT also describes procedures 
for removal of the hydraulic motors of the HSA, accomplishment of 
various follow-on actions, and repair of any discrepancy found. (The 
follow-on actions include checking the motors and the cam seats, 
assembling the motors, and metal stamping the modification plate of the 
motors.)
    Additionally, the AOT describes procedures for eventual removal of 
certain motors for inspection to detect any wear or damage caused by 
desynchronization; and, if necessary, either replacement of the motors 
with 

[[Page 2698]]
new or serviceable motors, or removal of the motors, accomplishment of 
various follow-on actions, and repair of any discrepancy found.
    The DGAC classified this AOT as mandatory in order to assure the 
continued airworthiness of these airplanes in France.
    This airplane model is manufactured in France and is type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the DGAC has kept the FAA informed 
of the situation described above. The FAA has examined the findings of 
the DGAC, reviewed all available information, and determined that AD 
action is necessary for products of this type design that are 
certificated for operation in the United States.
    Since the unsafe condition described is likely to exist or develop 
on other airplanes of the same type design registered in the United 
States, the FAA issued Telegraphic AD T96-01-52 to prevent runaway of 
the horizontal stabilizer to its full up or down position, subsequent 
reduced maneuvering capability, and a potential pitch upset. The AD 
requires repetitive inspections to ensure correct synchronization of 
the hydraulic control valves of the THS actuator; replacement of the 
motors with new or serviceable motors, and resynchronization of the 
valves or adjustment of the synchronization, if necessary; and a 
functional test of the THS.
    In addition, for airplanes on which the hydraulic motor or 
hydraulic valve block of the HSA has been subject to previous 
maintenance action, this AD requires replacement of both hydraulic 
motors of the HSA with new or serviceable motors. If an operator 
considers that such maintenance action would not have affected the 
synchronization of the valves, the operator may seek approval of an 
alternative method of compliance with the AD, in accordance with 
paragraph (c) of this AD.
    In lieu of replacing the hydraulic motors, this AD provides for 
removal of the motors, accomplishment of various follow-on actions, and 
repair of any discrepancy found.
    The actions are required to be accomplished in accordance with the 
AOT described previously.
    Operators should note that the Airbus AOT recommends that, within 
one year, certain hydraulic motors be removed and inspected for wear or 
damage caused by desynchronization. However, this AD does not require 
such action. The FAA may consider additional rulemaking to require the 
removal and inspection of the motors, but has determined that the 
repetitive inspections to ensure correct synchronization of the 
hydraulic control valves will maintain an adequate level of safety in 
the fleet in the meantime.
    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual telegrams 
issued on January 9, 1996, to all known U.S. owners and operators of 
Airbus Model A310 and A300-600 series airplanes. These conditions still 
exist, and the AD is hereby published in the Federal Register as an 
amendment to Sec. 39.13 of the Federal Aviation Regulations (14 CFR 
39.13) to make it effective as to all persons.
    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this rule by 
submitting such written data, views, or arguments as they may desire. 
Communications shall identify the Rules Docket number and be submitted 
in triplicate to the address specified under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the rule. All comments submitted will be 
available, both before and after the closing date for comments, in the 
Rules Docket for examination by interested persons. A report that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-03-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

96-01-52 Airbus: Amendment 39-9491. Docket 96-NM-03-AD.

    Applicability: Model A310 and A300-600 series airplanes; 
equipped with a trimmable horizontal stabilizer (THS) actuator 
having 

[[Page 2699]]
part number (P/N) 47142-201 or P/N 47142-203; 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 use the authority 
provided in paragraph (c) of this AD to request approval from the 
FAA. This approval may address either no action, if the current 
configuration eliminates the unsafe condition; or different actions 
necessary to address the unsafe condition described in this AD. Such 
a request should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent runaway of the horizontal stabilizer to its full up 
or down position, subsequent reduced maneuvering capability, and a 
potential pitch upset, accomplish the following:
    (a) Within 12 days after the effective date of this AD, perform 
an inspection to ensure correct synchronization of the hydraulic 
control valves of the trimmable horizontal stabilizer (THS) 
actuator, in accordance with paragraph 4.2.2.1 of Airbus All 
Operators Telex (AOT) 27-21, Revision 1, dated January 5, 1996.
    (1) If the actuator is synchronized correctly, prior to further 
flight, perform a functional test of the THS in accordance with 
paragraph 4.2.2.1 of the AOT. Thereafter, repeat the inspection 
required by paragraph (a) of this AD at intervals not to exceed 500 
hours time-in-service.
    (2) If the actuator is desynchronized slightly, as specified in 
the AOT, prior to further flight, adjust the synchronization, and 
perform a functional test of the THS, in accordance with paragraph 
4.2.2.2 of the AOT. Thereafter, repeat the inspection required by 
paragraph (a) of this AD at intervals not to exceed 500 hours time-
in-service.
    (3) If the actuator is desynchronized significantly, as 
specified in the AOT, prior to further flight, accomplish either 
paragraph (a)(3)(i) or (a)(3)(ii) of this AD. Prior to further 
flight following the accomplishment of either of those paragraphs, 
adjust the synchronization, and perform a functional test of the 
THS, in accordance with paragraph 4.2.2.3 of the AOT. Thereafter, 
repeat the inspection required by paragraph (a) of this AD at 
intervals not to exceed 500 hours time-in-service.
    (i) Remove and replace the hydraulic motors of the horizontal 
stabilizer actuator (HSA) with new or serviceable motors in 
accordance with procedures specified in the Airplane Maintenance 
Manual. Or
    (ii) Remove the hydraulic motors of the HSA and perform the 
various follow-on actions specified in paragraph 4.2.2.4 of the AOT, 
in accordance with that paragraph. (The follow-on actions include 
checking the motors and the cam seats, assembling the motors, and 
metal stamping the modification plate of the motors.) If any 
discrepancy is found during the check, prior to further flight, 
repair in accordance with paragraph 4.2.2.4 of the AOT.
    (b) For airplanes on which any maintenance action relating to a 
hydraulic motor or a hydraulic valve block of the HSA has occurred 
since the airplane was new: Within 12 days after the effective date 
of this AD, accomplish either paragraph (b)(1) or (b)(2) of this AD.
    (1) Replace both hydraulic motors of the HSA with new or 
serviceable motors in accordance with the procedures specified in 
the Airplane Maintenance Manual. Adjust the synchronization, and 
perform a functional test of the THS in accordance with paragraph 
4.2.2.3 of Airbus AOT 27-21, Revision 1, dated January 5, 1996. 
Thereafter, perform the repetitive inspections required by paragraph 
(a) of this AD at intervals not to exceed 500 hours time-in-service. 
Or
    (2) Remove the hydraulic motors of the HSA and perform the 
various follow-on actions specified in paragraph 4.2.2.4 of the AOT, 
in accordance with that paragraph of the AOT. Adjust the 
synchronization, and perform a functional test of the THS in 
accordance with paragraph 4.2.2.3 of the AOT. (The follow-on actions 
include checking the motors and the cam seats, assembling the 
motors, and metal stamping the modification plate of the motors.) If 
any discrepancy is found during the check, prior to further flight, 
repair in accordance with paragraph 4.2.2.4 of the AOT. Thereafter, 
perform the repetitive inspections required by paragraph (a) of this 
AD at intervals not to exceed 500 hours time-in-service.
    (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 2: 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 Airbus All 
Operators Telex (AOT) 27-21, Revision 1, dated January 5, 1996. 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.
    (f) This amendment becomes effective on February 5, 1996, to all 
persons except those persons to whom it was made immediately 
effective by telegraphic AD T96-01-52, issued January 9, 1996, which 
contained the requirements of this amendment.

    Issued in Renton, Washington, on January 12, 1996.
Darrell M. Pederson,
 Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-591 Filed 1-26-96; 8:45 am]
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