Reasons for Transponders
 

When giving GA traffic a transponder code, Liverpool ATC generally add that it is for "conspicuity". I would have thought that was a fairly obvious reason, so why the need to state it? Is there any other reason?

But not obvious to some people!
It is emphasised to stop some people thinking they are receiving a radar service and also to prevent the fairly common response of " you've given that code to me as well".
Its only one particular code of 0260 and is neither validated nor verified.

I'd be prepared to bet that the vast majority of VFR pilots (and probably a fair chunk of IFRs) don't know what "conspicuity code" (as opposed to any other purpose of a squawk) means, nor indeed would they know what "validated" or "verified" means, so telling them wouldn't achieve much other than maybe covering your back if there's an incident. Same goes for many other ATC practices.
NS

Thanks Friio.

There are many codes allocated to units across the UK, some of which are 'conspicuity codes' (they are not all 0260). As well as the explanation given by Friio4, the instruction to select a conspicuity code (which may be allocated to a non-SSR or radar equipped unit such as Cranfield Approach or Cambridge Approach) can allow neighbouring radar units to know who to call if they want to know about something that traffic is doing.

OK. Would you be so kind as to play "help the Yank" again? Why the 'conspicuity codes?' Is this not a discreet code environment? Granted, I've only been doing this for about 26 years, but I've only had to work four nondiscreet codes in my career: 1200 (VFR), 7500, 7600, and 7700. What's with assigning nondiscreet codes for conspicuity? Why not a discreet code?

Thanks in advance,

Dave

The conspicuity code only signals that the aircraft is under the control of a particular ATSU, for the benefit of other radar units. To use discrete codes would be pointless (such aircraft don't need to be distinguished from each other as they have not been identified by a radar unit) and we're short enough of Mode A codes already in the UK.

From just a pilot's perspective - The US system seems to allow any controller who might issue a code to 'push a button' and get a unique code from a large pool; where as, the European system seems to have many codes pre-allocated and hence a limited (possibly nil) pool of codes for general allocation. I suspect that, in the UK, codes that are issued to all flights not on an 'airways flight plan' come from a set that are preallocated to that controlling unit and therefore frequently not unique.


I would be interested in hearing more from the controllers both sides of the pond if my 'user perception' is broadly correct.

mm_flynn

absolutely correct from the UK perspective - I can't comment from the US one.

Over here, international flights are allocated an "ORCAM" squawk, one specific for the FIR you are departing to, and retained through the entire flight. All other flights don't have this luxury - every ATC unit has a set of squawks allocated to it, so every time you change unit you will have to change squawk.

The advantage of this is that we can see who you're working from your squawk. I believe for example that a 370x squawk means you're under Brize Zone control, while a 371x squawk means you're under a service from Brize radar - helpful as you know which button to press on the phone.

Maybe worth a note that the UK system is still driven by NAS. We can press a button and get a code. We do have an increasinf code shortage in Europe, how are rhese codes managed in the US, do you have shortages?
Also for our American colleagues; how many NAS systems operate in California?

Conspicuity codes mean the transponder is on = TCAS :) targets

Eurocontrol's Centralised Code Assignment and Management System (CCAMS) will be phased in at the end of 2008; see page 3 of 'Readability 5' April 2007 from GATCO for further info.

Chevron, NATS have been taking a very active role in CCAMS development. 2008 is for some former eastern block states, more like 2011 here.

Hmm, SO CCAMS will comein just as we getting close to implementing the use of Mode S Flight ID instead of Mode A to identify flights......yay for the strategy teams

What makes you think we are close?

Mode A code utilisation will be around for a while yet. Too many legacy systems are still in use which rely on Mode A, both in the air and on the ground.

It was my understanding that limited use of Mode S Flight ID was coming soon at Maastricht UAC, with associated Mode A conspicuity codes in use for Mode S flights.

The date for Mode S flight identity is "under discussion" - watch this space :suspect: :ugh:

Maastricht in 2008 is planned, PM me if you want the other dates.