Ad/RAD/43 Amdt 6 - ATC Transponder Systems with Active Mode C (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/RAD/43 Amdt 5 and issues the following AD under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Radio Communication and Navigation Equipment

AD/RAD/43 Amdt 6 ATC Transponder Systems with Active Mode C 11/2005

Applicability:	Air Traffic Control (ATC) transponder systems used in aircraft that operate under Instrument Flight Rules in controlled airspace, having an active automatic altitude reporting facility (Mode C).
Requirement:	1.    Ensure that the altimeter, which is used for primary control of aircraft altitude and which will be used for the Mode C data correspondence check, is calibrated in accordance with the requirements of United States Federal Aviation Regulations Part 43, Appendix E, Paragraph (b).
2.    Perform an integrated system test in accordance with the requirements contained in United States Federal Aviation Regulations Part 43, Appendix E, Paragraph (c).  Code 2100 should be used when carrying out transponder tests.
Compliance:	For Requirements 1 and 2:
(a)   At intervals not exceeding 24 calendar months, or
(b)   At the intervals approved in accordance with a System of Maintenance for the aircraft pursuant to Civil Aviation Regulation (CAR) 42M.
For Requirement 2:
For aircraft that utilise a separate direct reading altimeter for the primary control of aircraft altitude and have a separate blind encoder, air data computer or equivalent reporting directly to ATC via the aircraft transponder, checks are to be made on each occasion of:
(a)   any change of or modification to system component/s, and/or
(b)   any change or modification to system interwiring.
Note 1.  Correct operation needs to be confirmed after any maintenance on a system/component that has the potential to cause a difference in reported altitudes.

Note 2.  Aircraft that utilise a single altitude data source do not require a check after component change or maintenance unless there have been interwiring changes or system modifications.
Note 3.  For aircraft fitted with redundant single altitude data sources, cross checking between remote displays, each displaying altitude data from a different source, is sufficient to confirm absence or presence of correspondence error.
This Amendment becomes effective on 27 October 2005.
Background:	Amendment 2 clarified the Compliance requirement and brings it directly into line with the requirements of the United States Federal Aviation Administration (FAA).  Amendment 3 was issued to clarify the Compliance.  Amendment 4 was issued to correct the reference to CARs and to advise the correct code to be used when testing ATC transponder systems.  Amendment 5 was issued to clarify the intent of Requirement 2.
This amendment is issued following requests from industry to further align with the FAA by limiting the applicability to transponders used in aircraft that operate under Instrument Flight Rules in controlled airspace.
Amendment 5 became effective on 25 April 1996.
Amendment 4 became effective on 13 October 1994.
Amendment 3 became effective on 11 July 1991.
Amendment 2 became effective on 9 August 1990.
Amendment 1 became effective on 21 April 1988.
The original issue of this Directive became effective on 30 September 1984.

James Coyne
Delegate of the Civil Aviation Safety Authority

16 September 2005