It's explained adequately in the bottom panel (as highlit). However, see the simplified version just below.

So it is now an interesting surmise to wonder what effect an original trim knob (or a knob #2) mistakenly fitted to a wiring-modified panel (2nd AD with knob#3 and its longer shaft) may have done (in the flight-control havoc regime). It's maybe a question that should be asked. It seems pertinent to AA587.

Airbus Industrie A300 & A310 Series Aeroplanes

 

AD/AB3/107

Rudder Trim Control Switch

9/97

 

Applicability:	All models A300-600.
Requirement:	Replace control switches P/N 097-023-00 with new switches P/N 097-023-01 in accordance with Airbus Industrie Service Bulletin A300-27-6037.
	Note 1. AD/AB3/90 is cancelled.
	Note 2. DGAC AD 97-111-219(B) refers.
Compliance:	Unless previously accomplished prior to 14 January 1998.
	This airworthiness directive becomes effective on 14 August 1997.
Background:	The actions required by this AD are to prevent any interference between the 408VU panel and the rudder trim control knob, which could prevent the self recentering of the switch to the neutral position when released, thus causing a rudder movement up to the maximum deflection, and which could lead to critical flight situations. AD/AB3/90 required an ongoing compliance whenever the switch was replaced. This AD supersedes AD/AB3/90 and constitutes terminating action for that AD.

from this link

[Federal Register: October 5, 1999 (Volume 64, Number 192)]
[Proposed Rules]               
[Page 53951-53953]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr05oc99-34]                         

========================================================================
Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

========================================================================



[[Page 53951]]


=======================================================================
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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-194-AD]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

-----------------------------------------------------------------------

SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to certain Airbus Model A310 and A300-600 
series airplanes, that would have required replacement of the rudder 
trim switch in the flight compartment with a new switch having a longer 
shaft; modification of wiring in panel 408VU; and replacement of the 
rudder trim control knob with a new knob, as necessary. This new action 
revises the proposed rule by requiring replacement of the control knob 
with an improved new knob. This proposal is prompted by issuance of 
mandatory continuing airworthiness information by a foreign civil 
airworthiness authority. The actions specified by this new proposed AD 
are intended to prevent inadvertent and uncommanded rudder trim 
activation, which could result in yaw and roll excursions and 
consequent reduced controllability of the airplane.

DATES: Comments must be received by November 1, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 96-NM-194-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule 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.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-194-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 96-NM-194-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain Airbus Model A310 and A300-600 series airplanes, was published 
as a supplemental notice of proposed rulemaking (NPRM) in the Federal 
Register on February 12, 1998 (63 FR 7076). That supplemental NPRM 
would have required replacement of the rudder trim switch in the flight 
compartment with a new switch having a longer shaft; modification of 
wiring in panel 408VU; and replacement of the control knob with a new 
knob, as necessary. That supplemental NPRM was prompted by reports of 
in-flight uncommanded rudder trim activation due to inadvertent 
activation of the rudder trim switch, failure of the switch, or 
incorrect installation of the switch. That condition, if not corrected, 
could result in uncommanded yaw/roll excursions and consequent reduced 
controllability of the airplane.

Comments

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

Request To Include Inspection Requirement

    One commenter, the manufacturer, suggests that the proposed AD be 
revised to include an inspection to ensure appropriate clearance 
between the rudder trim knob and panel 408VU, following installation of 
a new rudder trim switch in accordance with Airbus Service Bulletins 
A310-27-2084 and A300-27-6037, both dated February 12, 1997 (Reference 
Airbus Modification 11662). The commenter states that in-service 
retrofits have shown that this modification may not be sufficient to 
provide the required clearance if all parts involved are at their 
tolerance limits. This condition may exist even following replacement 
of the rudder trim knob with a modified knob as described in Airbus 
Service Bulletins A310-27-2058 and A300-27-6022, and for this reason, 
an additional inspection for adequate clearance was included in those 
service bulletins.
    The commenter notes that a decision has been made to replace the 
rudder

[[Page 53952]]

trim knob with an improved new knob as described in new Airbus Service 
Bulletins A310-27-2087 and A300-27-6042 (Reference Airbus Modification 
11874) described below. Following accomplishment of this replacement, 
adequate clearance is expected to be provided for all parts tolerances. 
The knob replacement is anticipated to be mandated by issuance of a new 
French airworthiness directive following issuance of the service 
bulletins. The commenter suggests the supplemental NPRM be revised to 
include the additional inspection for adequate clearance until all 
airplanes have been retrofitted with this final solution, which is 
expected to require up to 15 months.
    The FAA does not concur. In light of the information from the 
manufacturer regarding inadequate clearance in certain cases following 
installation of the rudder trim switch, the FAA has determined that 
replacement of the rudder trim control knob with a new knob, even with 
a subsequent inspection for clearance, would not fully correct the 
identified unsafe condition. However, as noted by the commenter, 
replacement of the rudder trim control knob with an improved new knob 
is expected to provide adequate clearance in all cases between panel 
408VU and the rudder trim control knob. Therefore, the FAA considers 
that the appropriate course of action is to require such replacement in 
this AD. In order to allow sufficient time for operators to comply with 
the new requirement, the replacement of the knob with an improved new 
knob would be required within 10 months after the effective date of 
this AD.

Explanation of Relevant Service Information

    Airbus has issued Service Bulletins A300-27-6037 (for Model A300-
600 series airplanes) and A310-27-2084 (for Model A310 series 
airplanes), both Revision 01, both dated September 29, 1998. The 
original service bulletins, dated February 12, 1997, are cited in 
paragraph (a)(1) of the previous supplemental NPRM as the appropriate 
sources of service information for accomplishment of replacement of the 
rudder trim switch in the flight compartment with a new switch having a 
longer shaft and modification of wiring in panel 408VU. Revision 01 of 
these service bulletins is essentially identical to the original 
service bulletins, except that certain procedures are clarified and 
maintenance manual references are revised.
    Airbus also has issued new Service Bulletins A310-27-2087, dated 
October 2, 1998, and Revision 01, dated February 17, 1999 (for Model 
A310 series airplanes); and A300-27-6042, dated October 2, 1998, and 
Revision 01, dated February 17, 1999 (for Model A300-600 series 
airplanes). These service bulletins describe procedures for replacement 
of the rudder trim control knob with an improved new knob.
    Accomplishment of the actions specified in the service bulletins is 
intended to adequately address the identified unsafe condition. The 
Direction Generale de l'Aviation Civile (DGAC), which is the 
airworthiness authority for France, classified these service bulletins 
as mandatory and issued French airworthiness directive 1999-012-275(B), 
dated January 13, 1999, in order to assure the continued airworthiness 
of these airplanes in France.

Conclusion

    The FAA concludes that the previous supplemental NPRM must be 
revised to require replacement of the rudder trim knob with an improved 
new knob, in accordance with the new service bulletins described 
previously. Since these changes expand the scope of the originally 
proposed rule, the FAA has determined that it is necessary to reopen 
the comment period to provide additional opportunity for public 
comment. The FAA also has revised the applicability of this 
supplemental NPRM to exclude airplanes on which Airbus Modification 
11874 has been accomplished.

Cost Impact

    The FAA estimates that 90 airplanes of U.S. registry would be 
affected by this proposed AD.
    Replacement of the rudder trim switch and modification of the 
wiring would take approximately 7 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Required 
parts would be provided by the manufacturer at no cost to the 
operators. Based on these figures, the cost impact of this action on 
U.S. operators is estimated to be $37,800, or $420 per airplane.
    Replacement of the rudder trim control knob would take 
approximately 1 work hour per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts would be provided by 
the manufacturer at no cost to the operators. Based on these figures, 
the cost impact of this action on U.S. operators is estimated to be 
$5,400, or $60 per airplane.
    The cost impact figures discussed above are 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

Airbus Industrie: Docket 96-NM-194-AD.

    Applicability: Model A310 and A300-600 series airplanes, 
certificated in any category; except those on which Airbus 
Modification 11874 [reference Airbus Service Bulletin A310-27-2087 
(for Model A300 series airplanes) or A300-27-6042 (for Model A300-
600 series airplanes), both dated October 2, 1998] has been 
accomplished.

[[Page 53953]]

    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 (d) 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 inadvertent and uncommanded rudder trim activation, 
which could result in yaw and roll excursions and consequent reduced 
controllability of the airplane, accomplish the following:

Corrective Actions

    (a) Within 90 days after the effective date of this AD, replace 
the rudder trim switch, part number (P/N) 097-023-00, in the flight 
compartment, with a new switch, P/N 097-023-01; and modify the 
wiring in panel 408VU; in accordance with Airbus Service Bulletin 
A310-27-2084, Revision 01 (for Model A310 series airplanes), or 
A300-27-6037, Revision 01 (for Model A300-600 series airplanes); 
both dated September 29, 1998; as applicable.

    Note 2: Accomplishment of the actions required by paragraph (a) 
of this AD in accordance with Airbus Service Bulletin A310-27-2084 
(for Model A310 series airplanes), or A300-27-6037 (for Model A300-
600 series airplanes), both dated February 12, 1997; as applicable; 
is acceptable for compliance with that paragraph.

    (b) Within 10 months after the effective date of this AD, 
replace the rudder trim control knob on the rudder trim switch with 
an improved new knob in accordance with Airbus Service Bulletin 
A310-27-2087, Revision 01 (for Model A310 series airplanes); or 
A300-27-6042, Revision 01 (for Model A300-600 series airplanes); 
both dated February 17, 1999; as applicable.

    Note 3: Accomplishment of the actions required by paragraph (b) 
of this AD in accordance with Airbus Service Bulletin A310-27-2087 
(for Model A310 series airplanes), or A300-27-6042 (for Model A300-
600 series airplanes); both dated October 2, 1998; as applicable; is 
acceptable for compliance with that paragraph.

Spares

    (c) As of the effective date of this AD, no person shall install 
in the flight compartment of any airplane a rudder trim switch 
having P/N 097-023-00.

Alternative Methods of Compliance

    (d) 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.

    (e) 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.

    Note 5: The subject of this AD is addressed in French 
airworthiness directives 97-111-219(B), dated May 7, 1997, and 1999-
012-275(B), dated January 13, 1999.

    Issued in Renton, Washington, on September 28, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-25770 Filed 10-4-99; 8:45 am]
BILLING CODE 4910-13-P

from this link

AIRWORTHINESS DIRECTIVE REGULATORY SUPPORT DIVISION P.O. BOX 26460 OKLAHOMA CITY, OKLAHOMA 73125-0460

U.S. Department of Transportation Federal Aviation Administration

The following Airworthiness Directive issued by the Federal Aviation Administration in accordance with the provisions of Title 14 of the Code of Federal Regulations (14 CFR) part 39, applies to an aircraft model of which our records indicate you may be the registered owner. Airworthiness Directives affect aviation safety and are regulations which require immediate attention. You are cautioned that no person may operate an aircraft to which an Airworthiness Directive applies, except in accordance with the requirements of the Airworthiness Directive (reference 14 CFR part 39, subpart 39.3).

99-26-08 AIRBUS INDUSTRIE: Amendment 39-11467. Docket 96-NM-194-AD. Issued December 9, 1999.

from this link