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Addition Of Letter To Callsign

Tue Jul 20, 2004 1:18 am

I was listening to the scanner recently and on contacting approach the crew mentioned that the cabin was depressurized. After that the callsign included a letter at the end. It was Flagship 714 Alpha. What the reason for this? What are the procedures for a depressureization?

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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 1:35 am

It is quite common to use some letter after the flight number. It is just to make the callsign easier identifiable. Some airlines don't even use flight numbers in their callsign anymore... Like SN Brussels Airlines or Lufthansa, for example. LH 3012 might have a callsign like "Lufthansa, 4 Bravo".

What comes to depressurization, it depends what is their altitude when this happens. If you experience sudden (explosive) depressurization at high cruise altitudes then you have to make an emergency descent and notify ATC as well. Basically there is different ways how to do an emergency descent, but I'm not so sure about those so maybe some other could explain those.

In this case they were not so high anymore if they were talking with approach, so I believe it wasn't emergency descent. Very difficult to say what has happened, but maybe they noticed during normal descent at lower altitudes that pressurization didn't work properly. Or maybe they were climbing and leveled the aircraft due the pressurization problems? Just my best guesses...

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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 4:59 am

Maybe there were two flights with simular callsigns, so to differentiate, I guess they add a letter to the callsign.
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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 6:06 am

There are no clear rules on how callsign's are assigned. They may use their flight number, rout identifier, registration number or even some other totally made up number. As long as nobody else has the same ID they can use just about anything within reason.

There were several times that an aircraft being taxied by maintenance and a flight number had the same call sign. When being taxied by maint. the aircraft goes by the gate number in which they are taxiing too. Say if there was a flight 84 which goes by say flagship-84 and a maint. taxi going to gate 84 they would assign the maint. taxi the call sign of flagship-84A.

Or to complicate things even more... I've seen a very late flight arriving and another aircraft taking that flights spot leaving at the same time. So, there are two flights with the same number. So, it's also very possible there was another Flagship 714 of some kind in the area.

Why they would advise "depressurized" on approach I don't know.
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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 7:03 am

The letter 'Alpha' being assigned to an aircraft's callsign indicates there are two of the same flight number that will be airborne at or near the same time. For instance, if TRS421 from MDW to ATL is running 2 hours late, we may run the second half of the thru-flight with a different and aircraft and crew, to put it back on time. So, you'd have TRS421 from MDW to ATL and TRS421A from ATL to PNS.

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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 6:05 pm

You do want to make sure the cabin is depressurized before you attempt to open the cabin doors. So the scanner might not have been on an ATC freq, but probably on a company freq where the plane could talk to the ground crew?

Just my guess. re the depressurized comment.

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RE: Addition Of Letter To Callsign

Tue Jul 20, 2004 9:17 pm

AF adds letters to its callsigns to identify domestic flights as opposed to international flights.
Examples :

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Photo © William Ronciere

This flight was AF7645, however, as you can see from the paper on the panel, we were assigned AF645PQ as callasign by ATC.
Whereas this GVA flight keeps a number-only callsign :

View Large View Medium
Click here for bigger photo!

Photo © William Ronciere


[Edited 2004-07-20 14:28:31]
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RE: Addition Of Letter To Callsign

Wed Jul 21, 2004 10:58 am

I just flew flagship 3714 the other day  Smile It wasnt this flight that you were listening to though..we didnt have the amended callsign to 714A. Been a few weeks since ive had to use one of those.

We do the letter to the callsign to keep there from being confusion on the radio and 2 planes with the same callsign in the sky.

Flagship 3714 is the original flight callsign for this one (northwest airlink flight 3714).... if it comes within a certain amount of time of the continuation of the flight being in the air, we will have in our release "ATC CALLSIGN FLG 714A."

As far as the cabin being depressurized, the outflow valve is usually locked open by maintenance, and we dont cruise above 10,000 feet- 10,000 being the preference because you can accelerate above 250 KIAS at that altitude. ATC typically will try to climb us up higher, and we will refuse it...for obvious reasons. We do a greatly reduced power climb, only keeping about 400-500 fpm. In short- theres not much that we do that is different in an unpressurized flight.. I'll say something about it in my PA, apologizing for any uncomfort...and keep it gentle on the climbs and descents-refusing any expedites unless its an emergency...(first segment climb has to be normal profile though due to obastacle clearance).

Hopefully my ramblings made sense.  Smile

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RE: Addition Of Letter To Callsign

Wed Jul 21, 2004 11:23 am

Thanks very much XFSUgimpLB41X for that detailed explaination!

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RE: Addition Of Letter To Callsign

Wed Jul 21, 2004 3:16 pm

It's a rather frequent occurrence in Croatian ATC - as XFSUgimpLB41X said, you get two aircraft in the same sector that have similar IDs - like say LH469 and OU469. A less common practice, here at least, is to add letters, but usually controllers assign a different temporary ID, like LH469 and OU969 or something that would distinguish them from one another, that "expires" when the aircraft pass to another controller. Or if the planes are flying on such paths that they will meet in the other sector as well, the controller assigning the change coordinates with the controller of the other sector, so that both use the same distinction. Of course, the crew are asked about this and informed of the change if they agree.
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RE: Addition Of Letter To Callsign

Wed Jul 21, 2004 9:31 pm

In Thomas Cook its Topjet-123K outbound and Topjet-123L inbound on a flight. Quite nice because I don`t think anybody else uses K/L suffixes so its that little bit easier to pick up your callsign when listening to Greek/Spanish/Italian ATC!
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