Similar idents

[Sabre6]

I am under the impression that in Europe airline idents are composed of numbers and letters, such as BA24R or Kestrel 39WX, in order to solve the similar sounding ident issue. That identifier is often not the flight number used in the airline schedule but just externally to ATC to alleviate confusing similar call signs (usually 4 digit similar numbers).

Would someone please clarify this and if it is the case, then which agency assigns that call sign?

[Eurotraveller]

Hi Sabre,

Sometimes the schedule flight number is used, increasingly though a separate alpha-numeric callsign is used for ATC purposes. This is usually totally separate from the flight number and is designed to avoid callsign confusion. Most airlines typically use a mix of flight numbers and alpha-numerics - this is because some countries, such as Egypt and Turkey (except overflights), will not accept alpha-numeric callsigns at all and insist on the ticketed flight numbers being filed.

The callsigns are allocated by the airline itself and are normally fixed to a specific flight number - ie the same alpha-numeric will be used for the same flight number week after week. Typically an airline will work hard to deconflict its own callsigns to guard against confusion amongst their own flights, however there is no system at present to identify potential confusion between the alpha-numeric callsigns of different airlines - this only tends to be identified when confusion actually occurs on frequency and is becoming more and more of a problem.

Hope this helps.

Regards,
Eurotraveller

[Spitoon]

You might be interested in some work done by NATS in the UK and published by the CAA (http://www.caa.co.uk/docs/33/CAP704.pdf)some 10 years ago. Not directly relevant but maybe of some interest.

[Roffa]

If I'm not having a senior moment I recall that NATS have developed a computer programme that the airlines can access themselves and that aims to compare call signs and flag up similar ones. Thus hopefully reducing the occurrences of call sign confusion.

[Eurotraveller]

Hi Roffa,

Indeed they have, it's called the CCIA (I forget what that stands for!) The program will look at your schedule and your proposed callsigns, and identify potential confusion incidents based on callsign similarity. Where it identifies a potential for confusion, the software will suggest a 'safe' alternative callsign.

It's not a bad bit of software, and it's nice to see NATS being proactive, but unfortunately it will only consider your own airline's schedule, and it will only look at deconflicting flights within UK airspace. Of course, the program can only consider the scheduled departure/arrival time, and although there's a buffer of a few hours included there may be unidentified confusion incidents when things get seriously off schedule.

For these reasons in reality its usefulness is pretty limited and it does nothing to solve the problem of inter-airline callsign confusion, or confusion outside of the UK.

Eurotraveller