Squark Ident

[Easy226]

Just out of interest, what does squark ident actually do. I hear controllers saying this to pilots on departure and i have always wondered what it does??
Many thanks

[Carnage Matey!]

It brings up a flashy thingy round your blip on their radar screens. Saves them having to strain their eyes looking for you!

[Crotalus]

Carnage Matey is essentially correct .When I ask an aircraft to "Squawk Ident" a flashing circle does appear around the blip.From this I can determine where the aircraft is and that the aircraft IS in fact the one I SUSPECTED it to be (if you were out in the wilds and lost/unsure of position THAT WOULD BE HELPFUL) ..and with a little more help from CM determine that his transponder(the box of tricks inside the aircraft that transmits the data)is coding correctly.It can display to the controller Callsign of aircraft/ Destination/whether climbing or descending/and lastly an accurate ground speed, useful for maintaining separation .Oh and one final thing it also allows me to check that Carnage has set the correct four figure code in the transponder:D :D .

[twistedenginestarter]

Really they should only ask you to ident if two of you are using the same squawk. But if you're asked you say 'yessir'. You hope they'll then be gentle with you.

[bookworm]

As a pilot, I always thought that an ident was required when first identifying an aircraft, unless it was observed changing code or it was observed on departure. But both PANS-RAC and MATS Pt 1 seem to suggest that it's sufficient to recognise the callsign on a labelled display.

Nevertheless, climbing out of Cambridge on an IFR departure into the TMA, I always get asked to ident by Essex Radar. Seems sensible -- of course I've never mis-set a transponder code, but I have a friend that has once or twice :). Is an ident actually required, or is the controller just using a belt-and-braces approach?

[Spitoon]

As usual, there's no simple answer to a straightforward question as the answers we've already have show.

A lot depends on the radar display that the controiler has. In days gone by it was common for the tatget to have to IDENT in order for the machinery to show the callsign instead of the raw squawk. More modern dispays will do this automatically but there is a catch (and this is probably for the way that older display systems worked) - the first controller to work an aircraft taking off into an SSR environment (or who allocates a discrete code to an aircraft) is responsible for making sure that the aircraft is wearing the right code. There are a number of ways to do this but seeing the IDENT on the display on the right aircraft does it nicely. Apart from letting the controller who's looking after the aircraft know that he's looking at the right target, subject to a few conditions, any other controller who sees the target on his display can make certain assumptions about it.

Although it's slightly off the main topic, in the same way, once it is established that the mode C is correct, other controllers can assume that the level information is correct.

Twisted is therefore not strictly correct and, really, there shouldn't be two aircraft wearing the same squawk in the same area unless it's a special purpose code or conspicuity. If a controller wants to identify such an aircraft, he will normally allocate a discrete code.

Bookworm, I mentioned earlier that IDENT was one way to identify an aircraft using SSR. Another is for the controller to see the code he's allocated to you come up next to a target immediately following his instruction to select the code but if you set the code on take-off but didn't work Essex for some time the easiest way is to get you to IDENT on first contact with Essex. I don't know if Cambridge has got SSR - if it has, Essex ought to be able to assume the code to have been validated but, given the sort of traffic that Essex deals with it's probably as easy for them to IDENT everything on first contact.

Hope that helps. Hope it's all 100% correct 'cos I did it from memory and its years since I had to quote it perfectly for an exam.

And sorry for being sexist - lady controllers will do the same :) :)

[bookworm]

Spitoon

I think you're spot on. Cambridge has no SSR so Essex is the first check that I've got the correct squawk.

Thanks for that.

[Easy226]

Thanks a lot for the information, very interesting reading!!

[Lucifer]

Often, the request is "squark ident, and flight level passing", for which one would reply, "squarking ident, passing 3,700 on 989" (or FL046 etc as required) since this validates your altitude encoding in addition to ensuring that you are who they think you are.

[HEATHROW DIRECTOR]

A quote from our "bible":

"Unless it is known that a departing aircraft has been identified by an SSR equipped radar unit, ALL departures from LTMA airfields including, Birmingham and Coventry, are to be requested to squawk IDENT. The observation of the SPI transmission in association with the expected code/callsign displayed constitutes identification."

There are a number of other occasions when we may ask you to squawk too.. it's not simply to differentiate between two a/c wearing the same codes.

[Captain Stable]

A question for HD and his colleagues:-

I assume that is you don't have a/c bound into/out of Northolt, Fairoaks, Farnborough etc. etc. filtered out on your screens and whoever is controlling them asks them to ident, you also see the ident?

[eyeinthesky]

Yes, you see all idents.