Resurrecting this thread as, in my dotage, I appear to have become mistaken for a subject matter expert on various aviation matters ;-). A lot of ATPL theory books, and question banks, are under the impression that aircraft with Mode A transponders are detected by TCAS II but can only provide TA's due to the lack of altitude information. Sounds reasonable until you glance at the Eurocontrol ACAS guide which states:
'Aircraft equipped with only Mode A transponders are not tracked nor detected by TCAS II because TCAS II does not use Mode A interrogations.' It then goes on to describe how Mode A/C transponders are detected,when Mode C is disabled, using mode c only 'all call'.
This appears to backed up by Mr Honeywell too. Interestingly a document provided by Airbus contradicts this so we're into the 'who plagiarised who' scenario and from what source.
My understanding is that TCAS II detects aircraft with Mode A/C transponders and if there's no altitude infomation provided by Mode C it will track them but only provide a TA (below FL155). Aircraft equipped with only a Mode A transponder aren't detected?
Last edited by Specaircrew; 11th January 2025 at 09:15.