[Federal Register Volume 65, Number 8 (Wednesday, January 12, 2000)]
[Notices]
[Pages 1941-1943]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-689]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration
[Policy Statement Number ACE-00-23.683-01]


Proposed Issuance of Policy Memorandum, Discussion of Compliance 
Methods in Advisory Circular (AC) 23.683-1

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of policy statement; request for comments.

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SUMMARY: This document announces an FAA proposed general statement of 
policy applicable to the type certification of normal, utility, 
acrobatic, and commuter category airplanes. This document advises the 
public, in particular manufacturers of normal, utility, acrobatic, and 
commuter category airplanes, of additional information related to the 
compliance methods in current advisory circular AC 23.683-1. This 
notice is necessary to advise the public of FAA policy and give all 
interested persons an opportunity to present their views on the policy 
statement.

DATE: Comments submitted must be received no later than February 11, 
2000.

ADDRESSES: Send all comments on this policy statement to the individual 
identified under FOR FURTHER INFORMATION CONTACT.

FOR FURTHER INFORMATION CONTACT: Lester Cheng, Federal Aviation 
Administration, Small Airplane Directorate, ACE-111, Room 301, 901 
Locust, Kansas City, Missouri 64106; telephone (816) 329-4120; fax 816-
329-3047; e-mail: Lester.C[email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to comment on this proposed policy 
statement, ACE-00-23.683-01, by submitting such written data, views, or 
arguments as they desire. Comment should be marked, ``Comments to 
policy statement ACE-00-23.683-01,'' and be submitted in duplicate to 
the above address. The Manager, Small Airplane Directorate, will 
consider all communications received on or before the closing date for 
comments.

Background

    After reviewing the compliance methods in advisory circular 23.683-
1, the directorate determined that there was additional information 
related to the compliance methods in current AC 23.683-1 that might be 
beneficial. This notice announces the availability of the following 
proposed policy memorandum, ACE-00-23.683-01, for review and comment. 
The purpose of this memorandum is to address certification projects 
initiated after the final date of the memo. Certification projects 
already in work do not necessarily need to comply. However, normal 
compliance and safety considerations, including the effects of 
deformation per Sec. 23.305(a), would apply to existing and future 
projects.

Effect of General Statement of Policy

    The FAA is presenting this information as a set of guidelines 
appropriate for use. However, this document is not intended to 
establish a binding norm; it does not constitute a new regulation and 
the FAA would not apply or rely upon it as a regulation. The FAA 
Aircraft Certification Offices (ACO's) that certify normal, utility, 
acrobatic, and commuter category airplanes should generally attempt to 
follow this policy when appropriate. Applicants should expect that the 
certificating officials would consider this information when making 
findings of compliance relevant to new certificate actions. Applicants 
also may consider the material contained in this proposed policy 
statement as a supplement to that currently contained in AC 23.683-1 
when developing a means of compliance with the relevant certification 
standards.
    Also, as with all advisory material, this statement of policy 
identifies one means, but not the only means, of compliance.
    Because this proposed general statement of policy only announces 
what the FAA seeks to establish as policy, the FAA considers it to be 
an issue for which public comment is appropriate. Therefore, the FAA 
requests comment on the following proposed general statement of policy 
relevant to compliance with Sec. 23.305(a) and other related 
regulations.

General Statement of Policy

    The method of showing compliance with 23.683 presented in AC 
23.683-1 dwells only on the control system. It does not explicitly 
specify the consideration of loading on adjacent structures and 
elements. This is consistent with the wording in Sec. 23.683 of the 
regulations. Testing, not analysis must be used to show compliance with 
Sec. 23.683. There are other regulations, related to 23.683, which must 
also be met. These include the following:
    Section 23.305(a), [Subpart C--Structure, General] Strength and

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Deformation, requires that ``At any load up to limit loads, the 
deformation may not interfere with safe operation.''
    Section 23.307, [Subpart C--Structure, General] Proof of Structure, 
states that ``Compliance with the strength and deformation requirements 
of Sec. 23.305 must be shown for each critical load condition. 
Structural analysis may be used only if the structure conforms to those 
for which experience has shown this method to be reliable. In other 
cases, substantiating load tests must be made.''
    Section 23.655(a), [Subpart D--Design and Construction, Control 
Surfaces] Installation, requires that ``Moveable surfaces must be 
installed so that there is no interference between any surfaces, their 
bracing, or adjacent fixed structure, when one surface is held in its 
most critical clearance positions and the others are operated through 
their full movement.''
    Section 23.681(a), [Subpart D--Design and Construction, Control 
Surfaces] Limit Load Static Tests, requires that ``Compliance with the 
limit load requirements of this part must be shown by tests in which--
    (1) The direction of the test loads produces the most severe 
loading in the control system; and
    (2) Each fitting, pulley, and bracket used in attaching the system 
to the main structure is included.''
    The current method in AC 23.683-1 is modified below to account for 
the deformation effects of adjacent structure or elements. In addition 
to Sec. 23.683, this modified method demonstrates compliance with 
Sec. 23.305(a) as it relates to Sec. 23.683. It also demonstrates 
compliance with Sec. 23.681(a). This testing may be conducted as 
follows:
    Except where otherwise specified, the tests described below in 
sections (1), (2), and (3) should be conducted within the following 
parameters.
    a. Conduct the control system operation tests by operating the 
controls from the pilot's compartment.
    b. All the control surfaces must be installed in accordance with 
the type design to their adjacent fixed surface on the airframe.
    c. The entire control system and adjacent fixed structure should be 
loaded simultaneously.
    d. The adjacent fixed surfaces (wings, horizontal stabilizers, 
vertical stabilizers, etc.) should be loaded to provide deflections 
equivalent to critical limit load flight conditions.
    e. The structural deflections should correspond to the limit flight 
conditions which represent the worst case conditions for increased 
cable tension, decreased cable tension, and control/fixed surface 
proximity for each control system as appropriate.
    f. The entire control system must be loaded to the limit airloads 
or the limit pilot forces whichever are less (Sec. 23.683 (b)(1)).
    g. Minimum clearances around control surfaces and minimum tensions 
in cable systems should be defined to be incorporated in the airplane's 
instructions for continued airworthiness. The test article should 
incorporate these minimum clearances and tensions, unless they are to 
be otherwise accounted for.
    h. If reductions in the minimum clearances described in paragraph g 
above are possible due to environmental conditions expected in service, 
then this must be accounted for. This can be accomplished through 
analysis or during testing by adjusting the test article clearances to 
encompass these effects.
    (1) The tests described in this section support the demonstration 
that the control system is free from jamming, excessive friction, and 
excessive deflection as required by Sec. 23.683(a)(1), (2), and (3). 
They also support the demonstration that structural deformations not 
interfere with safe operation as required by Sec. 23.305(a). Accomplish 
the following:
    (i) Load the adjacent fixed aerodynamic surface (wing, horizontal 
tail, or vertical tail) in accordance with one of the conditions of 
paragraphs d and e above.
    (ii) Support the control surface being tested while it is located 
at the neutral position.
    (iii) Load the control surfaces to the critical limit loads, as 
described in paragraph f above, and evaluate their proximity to the 
fixed adjacent structure for interference (contact).
    (iv) Load the pilot's control until the control surface is just off 
the support.
    (v) Determine the available control surface travel which is the 
amount of movement of the surface from neutral when the cockpit control 
is moved through the limits of its travel.
    (vi) The control surface under loads described in paragraph f 
above, should travel a minimum of 10 percent of the total unloaded 
travel, as measured from the neutral position. This should be 
demonstrated for both directions of travel.
    (vii) To address the possibility of a critical intermediate control 
surface loading, gradually remove load from the control surface (while 
maintaining the load on the adjacent fixed surface) until maximum 
control surface travel is achieved.
    (viii) The above procedure should be repeated in the opposite 
direction.
    (ix) With limit load applied to the adjacent fixed surface and 
limit or intermediate load applied to the control surface, no signs of 
jamming, or of any permanent set of any connection, bracket, 
attachment, etc., may be present.
    (x) The control system should operate freely without excessive 
friction.
    (xi) Cable systems should be checked with the loads applied to 
ensure that excessive slack does not develop in the system.
    (xii) Repeat this process for each of the critical loading 
conditions as defined by paragraphs d and f above.
    (2) The tests described in this section support the demonstration 
that structural deformations not interfere with safe operation as 
required by Sec. 23.305(a). Accomplish the following:
    (i) Load the adjacent fixed aerodynamic surface (wing, horizontal 
tail, or vertical tail) in accordance with one of the conditions of 
paragraph d and e above.
    (ii) Operate the unloaded control system from stop to stop.
    (iii) No signs of interference (contact) may be present.
    (iv) The control system should operate freely without excessive 
friction.
    (v) Repeat this process for each of the critical adjacent fixed 
surface loading conditions as defined by paragraphs d and e above.

    Note: An alternate procedure may be used to accommodate the 
testing described in sections (1) and (2) above during structural 
tests of a partial airplane. This method requires that all control 
system components that are attached to or enclosed by the loaded 
test structure be installed per type design. A sufficiently 
representative mockup of remaining control system components must be 
used to ensure that the full length of any cables which extend from 
the loaded test structure are included. This is necessary to make a 
reasonable assessment that slack that could develop in control 
cables is not excessive enough to cause an entanglement or jam. The 
control surface activation may be input at any convenient location 
between the mockup terminus and the cockpit.

    (3) The tests described in this section will demonstrate that the 
control system is free from excessive deflection as required by 
Sec. 23.683(a)(3). These tests complete the demonstration that the 
control system is free from jamming and excessive friction as required 
by Sec. 23.683(a)(1) and (2) as well as the demonstration that 
structural deformations not interfere with safe operation as required 
by Sec. 23.305(a). Also, these tests meet the limit load

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static test requirements of Sec. 23.681(a). Accomplish the following:
    (i) With the adjacent fixed surface (wing, horizontal tail, or 
vertical tail) unloaded, support the control surface being tested while 
it is located at the neutral position.
    (ii) Load the control surfaces to the critical limit loads, as 
described in paragraph f above, and evaluate their proximity to the 
fixed adjacent structure for jamming or contact.
    (iii) Load the pilot's control until the control surface is just 
off the support.
    (iv) Operate the cockpit control in the direction opposite the load 
to the extent of its travel.
    (v) The above procedure should be repeated in the opposite 
direction.
    (vi) The minimum loaded control surface travel from the neutral 
position in each direction is 10 percent of the total unloaded control 
surface travel.
    (vii) Under limit load, no signs of jamming, or of any permanent 
set of any connection, bracket, attachment, etc., may be present.
    (viii) The control system should operate freely without excessive 
friction.

    Note: The tests described in section (3) above are normally 
accomplished using a complete airplane. As a minimum, they must be 
completed using an airframe/control system that completely 
represents the final product from the cockpit controls to the 
control surface.

    Regardless of the amount of travel of a control surface when tested 
as described above, the airplane must have adequate flight 
characteristics as specified in Sec. 23.141. Any airplane which is a 
close derivative of a previous type certificated airplane needs not 
exceed the control surface travel of the original airplane; however, 
the flight characteristics should be tested to ensure compliance.

    Issued in Kansas City, Missouri, on December 21, 1999.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-689 Filed 1-11-00; 8:45 am]
BILLING CODE 4910-13-U