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Jan Naslund

Transponder difference Sweden Finland

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Hi,

I am a bit curious to know why when i fly to/from Arlanda or any other Swedish airport, it is expected that i squawk standby on ground but when i fly to/from Vantaa i am expected to squawk mode C on ground.

Personally i don't mind but i am wondering why there even is a difference. Everything else except maybe that Finnish controllers acknowledge readbacks but Swedish don't is almost the same.

Is this the case in the real world as well or is this only done on Vatsim?

Does anyone know why there is  this difference?

Best Regards / Janne (SAS335)

 

 

 

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Hello Janne!

What I know, you are expected to squawk mode C also in Sweden, when initiating your pushback and further movements. At least in airports with ground radar (ESSA and ESGG).

What I have heard in real life, there is the differens between Finnish and Swedish ATC, that Finnish ATC acknowledges readback rather often!

Magnus

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On Helsinki Airport with squawk mode C while moving on the ground is to simulator the ground radars that cannot be simulated right now on VATSIM with the correct mode. So to have at least something illuminated we ask pilots to squawk mode C so simulate the usage of ground radar. As far as I know you can also use squawk mode C on Sweden as well but controllers doesn't really specially tell you to if you don't. In Finland we have had this habit to tell the pilot on their taxi clearance if they don't alredy have squawk mode C so pilots would maybe remember it next time and use it. :)

So short answer. As far as I know there there is no harm done if you use squawk mode C on ground in Finland or in Sweden.

/ Jouka

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On VATSIM the transponder only has two modes: standby and Mode C. Depending on how the radar is set up we can decide what functions to simulate with each mode. The basic idea is that with the transponder in standby the controller cannot see any information about callsign, squawk code or altitude, but it's possible to circumvent this, so in our simulation of ground movement radar we can see all aircraft regardless of transponder setting.

In real life most aircraft have several more modes. For example on the 737s I fly you can select:

- STBY: The transponder is powered up but not transmitting or receiving
- ALT OFF: The transponder transmits the Mode A code (the 4 digit transponder code) and the Mode S callsign (as entered in the FMC).
- ALT ON: In addition to mode A/S the transponder transmits altitude information (mode C).
- TA ONLY: In addition to mode A/S and C TCAS is activated but limited to give TAs only (no RAs)
- TA/RA: Mode A/S and C, and TCAS fully active to give both TAs and RAs.

The way we use it is that whenever we are moving on the airport, from requesting startup until parking on stand, we use ALT OFF. This is because most airports don't want aircraft on the ground to have Mode C activated, i.e. altitude information should not be transmitted. However, mode A/S is by ground movement radar to identify the aircraft.

When entering the runway we select TA/RA so the transponder and TCAS are fully operational. The other modes would only be used in non-normal situations, for example TA ONLY would be used if we lose an engine or have to do an emergency descent and are unable to follow a climb RA.

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On 11/23/2017 at 1:50 AM, Jouka Ahponen said:

In Finland we have had this habit to tell the pilot on their taxi clearance if they don't alredy have squawk mode C

I'm being told this when starting pushback.

Anyone has a screenshot what it looks like with and without mode C?

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