History

7 Dec 2007

Project CS 07/15 - Proposed Airworthiness Directive - Microair T2000SFL Air Traffic Control Transponder

This project has been approved and information is now available.

Project CS 07/15
Proposed Airworthiness Directive - Microair T2000SFL Air Traffic Control Transponder

Background

Microair T2000SFL transponders without the Revision 7 upgrade may, when operated in a Mode S Secondary Surveillance Radar (SSR) environment, ‘lock-up’ when interrogated, display a ‘NO COMM’ message and/or generate intermittent replies. This phenomenon may also occur when the transponder receives Mode S or extended squitter messages, this includes messages transmitted by aircraft equipped with Airborne Collision Avoidance Systems (ACAS). The transponder when displaying the ‘NO COMM’ message will not reply to interrogations from either Mode A, C or S ground SSR interrogators or Mode A/C ‘All Call’ interrogations from ACAS equipped aircraft, rendering the aircraft invisible to interrogators and increasing the possibility of a mid-air collision.

The anomaly with the T2000SFL transponder was first detected in early 2006 following the trial installation of a Mode S SSR interrogator at Auckland airport by Airways Corporation of New Zealand. The initial fix was a software modification which upgraded the transponder to Revision 6, this fix did not prove adequate and Microair Avionics introduced the upgrade to Revision 7 by Service Bulletin T2000SFL-SB-06. The technical content of the Service Bulletin was approved by the Civil Aviation Safety Authority on 1 August 2006. Currently most Revision 7 upgrades have been for transponders operating in overseas Mode S radar environments.

The number of transponders affected will increase with the planned introduction of Mode S SSR interrogators at eight Australian airports by Airservices Australia during 2008-09. Transponders may also be affected by the introduction of Wide Area Multilateration surveillance in Tasmania during early 2008.

Purpose/Objectives

To develop a Notice of Proposed Rule Making for an Airworthiness Directive to ensure the safety issues relating to the Microair T2000SFL Air Traffic Control Transponder 'NO COMM' 'lock-up' fault are corrected.

Status

The project was approved by Acting General Manager, Airworthiness Engineering Branch, and registered on 6 December 2007.

Notice of Proposed Rule Making being prepared.

Project management

Project Sponsor: Jim Coyne
Project Leader: Graeme Ward

Contact details

Email: Graeme Ward