Mode S. The CAA decision

Richard Boyton · Post by **Richard Boyton** » Wed Jul 01, 2009 2:16 pm

The CAA Final Decision

http://tinyurl.com/llhkr4

Nigel Ramsay · Post by **Nigel Ramsay** » Wed Jul 01, 2009 4:55 pm

I guess this is the relevant part for most of us, unless you want to go abroad......

"The decision means that there is no current requirement for all aircraft to carry Mode S transponders in all UK
airspace.
The decision is not designed to facilitate an increase in the amount of commercial air traffic or UAVs operating in Class G
airspace and the measures are not linked to airspace charging or radio carriage. Also, nothing in the announcement will
lead to GA aircraft that cannot equip with Mode S transponders being grounded. However, aircraft that are not
equipped with transponders may encounter difficulty in obtaining clearance to access certain airspace."

David Broom · Post by **David Broom** » Wed Jul 01, 2009 5:05 pm

Interesting reading. I found the following paragraph interesting:

"Computer modelling carried out by the CAA indicates that
Mode S transponders on light aircraft will not saturate ATC
systems or TCAS."

I wonder if they used the same computer model that Schipol used !!

merlin · Post by **merlin** » Wed Jul 01, 2009 5:38 pm

Such models can be skewed by the preconceptions of those that build them. Rubbish in equals rubbish out.

Steve Brown · Post by **Steve Brown** » Thu Jul 02, 2009 3:04 pm

From http://www.caa.co.uk/default.aspx?catid=810&pagetype=90

'The issue at Schipol is a display issue rather than an SSR one and relates to the specific airspace design and controller tools. It is not the swamping of the radar system causing problems but the overlapping of large numbers of labels on the radar screen when GA are very active. This issue will not affect the UK, as NATS’ systems will be able to filter out responses from aircraft not in the controller’s area of interest. However, this filtering will not affect the ability of automated systems and safety nets to identify potential conflicts.'