Following the recent release by the CAA of an additional policy statement on TMZs and RMZs it seems appropriate to highlight this analysis of UK transponder carriage.
With the increasing use in the UK of transponder mandatory zones or TMZ’s an understanding of the effects these restrictions have on airspace users can only be truly achieved by also understanding the level of transponder carriage by aircraft.
The link below presents an analysis of UK aircraft transponder carriage based on 2014 data supplied by the CAA. The analysis was performed in 2014 by John Brady of the LAA. The data display was revised by Tom Hardie of the BHPA in 2015.
The full analysis is available here:
Of the 19,857 on the UK register at that time, 7,562 (or 38.1%) were equipped with a transponder of some form. When the 8,000 unregistered aircraft, none of which were equipped with transponders, were added in then the total becomes 27,857 aircraft and the 7,562 transponder equipped aircraft represent 27.1% of all aircraft in the UK.
So, (based on 2014 data) 72.9% of aircraft in the UK are ordinarily excluded from transponder mandatory zones unless they have a radio and can request and be granted access by ATC.