Squawk Ident on departure?

[timelapse]

Why is it that departing aircraft are often asked to squawk ident after they are airborne and transfer to area control? Presumably if they say their callsign, SID and altitude it should be fairly evident where they're going to be on the radar screen?

Please forgive my ignorance :O

[Defruiter]

From MATS 1:

Radar services comprise:
a) Separation of arriving, departing and en route traffic;
b) Radar vectoring;
c) Position information to assist in the navigation of aircraft;
d) Monitoring traffic to provide information to the non radar controller;
e) Assistance to aircraft crossing controlled airspace.

Before a controller provides any of the above radar services he shall either:
a) identify the aircraft, using either secondary or primary methods; or
b) have had the identity of the aircraft transferred from another controller.

On departure, the aircraft has to be identified, and the mode C verified - to make sure everything is correct. It is obvious that the aircraft calling is the aircraft on the screen, but still, the procedures dictate that the mode A must be validated, and then the mode C verified.

I'm sure people with a greater knowledge than me will also chip in :)

DF

[timelapse]

Yeah I thought the tower controller verified the squawk (but presumably not the mode C) as they departed..

[coracle]

Aircraft are indeed asked to squawk indent on depature to identify them. Also by squawking ident, it triggers the computer into producing "live strips" and reasonable time estimates for sectors further down the line.

It also helps if aircraft DON'T squawk ident unless specifically asked to, but I fear that may need a whole new thread!

[AlanM]

Squawks are VALIDATED - levels are VERIFIED!

To answer the second part of your question, most towers check the correct squawk from the ATM - as there is one digit wrong. Otherwise by the time they check in on radar, (and some self ident but like Coracle says ignore that for now!!) it could DM the wrong callsign.

[timelapse]

Validated - of course, how silly of me.

Makes a lot of sense now, thanks for the replies :)

[radian]

OK, but usually you don't need ident to identify the aircraft. I think most of identification is made by "1NM after departure" technique.
Is there some other reason to request ident from the crew?

[Defruiter]

The Departure method of ident can only be done if you have an airborne time from the TWR.

The Tower will call you on the phone "XXYYZZ airborne 24"

If you see the target within 1nm of the runway you can identify it, if not, then another method of ident has to be used - squawk ident for example.

I think some of the regional airports in the UK use this method, but I am not sure if the busier London airports will call up with airborne times, which is why the "squawk ident" method is used

DF

[Scuzi]

In the London TMA we have television screens showing when departing aircraft for the major airfields have been given take off clearance as well as an airborne time.

[Defruiter]

I presume the ident method is only used then if they miss it within 1nm from the end of the runway?

[radian]

OK. Well, here at Krakow every departure has to be co-ordinated with radar (we have no standard departures). So, TWR has to phone APP before every departure and this method is used instead of giving exact airborne time.

[tuan74]

Is 'squawk ident' a must procedure after airborne of every airport?

Just curious..coz some atc will always asked to squawk while some never at all...:confused:

[Say Again, Over!]

Many towers and terminal units in Canada use EXCDS, a computerized system which is used (among other things) to pass exact departure time and take-off sequence from the tower to the departure controller.

I understand that 3 (or is it 4 now) towers in the UK now use this system.

This link has a picture of it (http://www.navcanada.ca/NavCanada.asp?Language=FR&Content=ContentDefinitionFiles/Newsroom/NR-Related/2005/0113/photo2.xml)

Cheers,

SAO

[Singe]

Tuan74 - I would only use the ident if the tower had given me a late call with the departure time of the aircraft and it had gone beyond 1 mile/2 miles (depending on the runway, MATS 2...)
Otherwise it is validated with the departure time passed.

[tired-flyboy]

Further to Scuzi's post.

In the London TMA, some towers will validate the A others don't. We always verify the C on climbout.

Eg LL tower don't validate OR verify.

GW tower validate but don't verify.

All very confusing.

[This is a crisis]

Sometimes the IDENT feature is used as an alternative for matching code callsign conversion pairing.
e.g. An Aerodrome launches an aircraft and identifies the primary return within one mile of the end of the runway. The Mode A is then associated with this return and so becomes validated.
The next unit along the line can then use this validated return (subject to local agreements) but if code callsign conversion is in use, they have to confirm the pairing before the return can be considered identified to them. This quite often involves messing around with toggling codes and callsigns. It is therefore usually much quicker just to get the aircraft to squawk IDENT.
Mats Part 1:
Identification:
b) Recognising a validated four digit code previously assigned to an aircraft callsign.
When code/callsign conversion procedures are in use, and the code/callsign pairing
can be confirmed, the callsign displayed in the data block may be used to establish
and maintain identity;
c) Observing an IDENT feature when it has been requested. Caution must be
exercised when employing this method because simultaneous requests for SPI
transmissions within the same area may result in misidentification. Aircraft
displaying the conspicuity code are not to be identified by this method.

[10W]

In the Scottish ACC, there are very few airfields where we can see traffic 1NM from the end of the runway since we use remote radar sites and only tend to use the airfield SSR (Glasgow and Belfast only) as a back up source if the en route radar fails.

For the Scottish TMA, we never know if the approach radar has worked the aircraft and identified it, or if it has come straight from the tower. Hence we identify it.

For Aberdeen and Belfast TMA departures, I don't see any reason why we can't accept that the SSR approach unit having already worked the traffic has done the necessary.

I suspect the fact we need to identify aircraft at Scottish might be a cover your ass procedure since the code callsign conversion databases are not linked between our unit and the airfields which could lead to Swiss cheese error with the airfield thinking all is well but with the wrong code or callsign showing on our display.

[tuan74]

Thanx all..appreciate it.:ok:

[Point Seven]

Eg LL tower don't validate OR verify.

AFAIK LL Tower DO validate the A code. The code appears as a callsign on their A-SMGCS and if it does not convert then they are meant to ask the aircraft to recycle Mode A. Since the end of the CCTV cell then this method ensures that TC know about the outbounds coming their way.

P7

[Dr Winston O'Boogie]

I was told that many moons ago a mis-ident occurred with 2 aircraft departing ISZ that had taken each other's squawk. ScATCC "squawk IDENT" all departures to prevent this highly unlikely scenario repeating itself. Belt, braces, bit of string just in case?

[misterblue]

So having been asked to "squawk ident" do you expect to hear a reply "squawk ident Bigair 123", or just silence?
Cap 413 says you should read back transponder settings, yet the example given in the new glossy book sent to me implies that no reply is necessary.
Which is correct?
Thanks,
MisterB

[Dr Winston O'Boogie]

I would expect an acknowledgement of the instruction to squawk Ident, as you say, it is a transponder setting.

The glossy book, if it's the same one I received, contains errors, omissions and contradictions!

Normally at Aberdeen we identify prenotified departures within 1nm, as 10W mentioned. However, a few months ago we had to use a remote radar head for a while, and we then had to use the Ident on all departures. The use of the Alanshill radar also led to an increased radar separation requirement from 3 nm to 5 nm, with a commensurate increase in the need for holding and/or extended routing on arrivals. Thankfully, the usual Perwinnes radar is back and "normal" service has been resumed.

[throw a dyce]

The blue book on page 12 says read backs required for any SSR operating instructions.

[ImnotanERIC]

i always expect a reply and 9 out of 10 times i get one. the odd time i don't i find myself pausing, not wanting to transmit my next instruction to another a/c incase this a/c's reply is just a couple of seconds late and I don't want to end up crossing with other stations and generally stamping on each others transmissions. Which as we all know is THE most annoying thing when you are really busy and have 5 things to do at once!! ha ha

[anotherthing]

Misterblue -

Please reply - it annoys the hell out of me if pilots don't....

a) it's rude
b) it's an instruction
c) if "C/S squawk ident" is the only thing I say in my first transmission to a departing A/C and they do not reply, how do I know they heard me? I cannot use the fact that they display the ident feature as confirmation that they heard me, as that may be coincidence... hell, the crew might be doing it because they did not hear my reply and they want to somehow attract my attention!!!