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gloom
Topic Author
Posts: 550
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Mode S transponder ID

Tue Apr 16, 2019 8:15 pm

Hello,

I was wondering, how is the transponder marked with its unique ID (hex-code, or fully: Icao 24-bit identifier). Is that factory built-in, or programmed later? Is that set forever (for example by some physical alterations, similar to OTP - one time programmable - chips), or could it be reprogrammed later, if for example plane get a new owner?

Also, are there any differences between units being part of a larger avionics set found on airliner, and units on trainers or gliders?

Any input welcome.

Cheers,
Adam
 
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zeke
Posts: 16158
Joined: Thu Dec 14, 2006 1:42 pm

Re: Mode S transponder ID

Tue Apr 16, 2019 8:56 pm

It’s assigned by the country that the aircraft is registered in. It is programmed into the unit.

The unique address is assigned to the aircraft, if a transponder is replaced it needs to be programmed with the correct id.

Essentially not a lot of difference between a light aircraft transponder and a large aircraft one. The large aircraft one has the addition of TCAS in it and a lot more inside to communicate with the other avionics.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
CeddP
Posts: 49
Joined: Sat Feb 23, 2013 12:04 am

Re: Mode S transponder ID

Wed Apr 17, 2019 3:26 pm

I use this thread to ask the million $ question : why are we still asked to use specific 4 digits squawk codes for each flight (sometimes several when crossing FIRs!) while pretty much everybody is mode S equipped now (at least in upper airspace) ?
 
ELBOB
Posts: 374
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Re: Mode S transponder ID

Thu Apr 18, 2019 9:00 am

CeddP wrote:
I use this thread to ask the million $ question : why are we still asked to use specific 4 digits squawk codes for each flight (sometimes several when crossing FIRs!) while pretty much everybody is mode S equipped now (at least in upper airspace) ?


Squawks relate to flight plan ( or absence thereof ), not aircraft. The various squawk ranges have distinct regionalised meanings to ATC, for example 4352 might indicate a flight routing from Shannon FIR to terminate in Scottish FIR; the within Scottish it might be reassigned 2582 to indicate that it's going to the EGPF TMA. With squawks set appropriately ATC manage the traffic better.

The Mode-S code just indicates the individual aircraft, not its intentions.
 
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fr8mech
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Re: Mode S transponder ID

Thu Apr 18, 2019 9:22 am

zeke wrote:
It’s assigned by the country that the aircraft is registered in. It is programmed into the unit.

The unique address is assigned to the aircraft, if a transponder is replaced it needs to be programmed with the correct id.

Essentially not a lot of difference between a light aircraft transponder and a large aircraft one. The large aircraft one has the addition of TCAS in it and a lot more inside to communicate with the other avionics.


I've changed more transponders than I can count, and I've never had to program one. Any coding is done by pin programming at the aircraft rack (on air transport aircraft), can't comment on GA.
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Woodreau
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Re: Mode S transponder ID

Thu Apr 18, 2019 10:35 am

Well it’s impossible to have a 2582 squawk. The transponder is incapable of generating that squawk number.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
CeddP
Posts: 49
Joined: Sat Feb 23, 2013 12:04 am

Re: Mode S transponder ID

Thu Apr 18, 2019 4:27 pm

ELBOB wrote:
CeddP wrote:
I use this thread to ask the million $ question : why are we still asked to use specific 4 digits squawk codes for each flight (sometimes several when crossing FIRs!) while pretty much everybody is mode S equipped now (at least in upper airspace) ?


Squawks relate to flight plan ( or absence thereof ), not aircraft. The various squawk ranges have distinct regionalised meanings to ATC, for example 4352 might indicate a flight routing from Shannon FIR to terminate in Scottish FIR; the within Scottish it might be reassigned 2582 to indicate that it's going to the EGPF TMA. With squawks set appropriately ATC manage the traffic better.

The Mode-S code just indicates the individual aircraft, not its intentions.


Thanks a lot for the answer!
 
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akoma
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Re: Mode S transponder ID

Thu Apr 18, 2019 4:36 pm

fr8mech wrote:
zeke wrote:
It’s assigned by the country that the aircraft is registered in. It is programmed into the unit.

The unique address is assigned to the aircraft, if a transponder is replaced it needs to be programmed with the correct id.

Essentially not a lot of difference between a light aircraft transponder and a large aircraft one. The large aircraft one has the addition of TCAS in it and a lot more inside to communicate with the other avionics.


I've changed more transponders than I can count, and I've never had to program one. Any coding is done by pin programming at the aircraft rack (on air transport aircraft), can't comment on GA.


Yes, the transponder code is pin programmed on the aircraft's avionics rack. I have had to re-do the pin programming often though, when we sell our used aircraft (Airbuses & Boeings) to other operators.

The TCAS box is usually a separate black box and it is not incorporated into the ATC transponder unit, although it (TCAS) needs the transponder to work.
 
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zeke
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Re: Mode S transponder ID

Thu Apr 18, 2019 7:42 pm

fr8mech wrote:
I've changed more transponders than I can count, and I've never had to program one. Any coding is done by pin programming at the aircraft rack (on air transport aircraft), can't comment on GA.


Light aircraft and the newer boxes are programmed, something like the older TDR-94D typically would be strapped with pins, depending on how it connected to the aircraft.

akoma wrote:
The TCAS box is usually a separate black box and it is not incorporated into the ATC transponder unit, although it (TCAS) needs the transponder to work.


Strapping the address as well as a separate transponder is older tech, current tech like the Collins Traffic Surveillance System (TSS-4100) has TCAS, transponder, and ADS all in one box. The cutting edge is like the Collins ISS-2100 which has TCAS, transponder, ADS, weather radar, and TAWS in one box.

The reason these are programmed now is the one integrated LRU contains multiple functions, the transponder, TCAS, and ADS-B have too many variables. This is from the TSS-4100 installation manual

2.6.2. ECU Bottom Half, First Partition.

Refer to Table 2-2 for a list of the parameters that need to be set and their possible values. The first partition of the bottom half has the characteristics that follow:.

• Programmed by the installer
• Contains installation strapping, including number of GPSs, ARINC 429 bus speeds, airplane height and length, etc.
• Must be data loaded.

2.6.3. ECU Bottom Half, Second Partition.

The second partition of the bottom half is used to store the Mode S address, and has the characteristics that follow:
• Programmed by the installer
• Contains the Mode S address
• Either data loaded, or programmed using the TSS-4100 ECU Mode S Address Programming Tool.“
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
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akoma
Posts: 29
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Re: Mode S transponder ID

Fri Apr 19, 2019 3:05 am

zeke wrote:
akoma wrote:
The TCAS box is usually a separate black box and it is not incorporated into the ATC transponder unit, although it (TCAS) needs the transponder to work.


Strapping the address as well as a separate transponder is older tech, current tech like the Collins Traffic Surveillance System (TSS-4100) has TCAS, transponder, and ADS all in one box. The cutting edge is like the Collins ISS-2100 which has TCAS, transponder, ADS, weather radar, and TAWS in one box.

The reason these are programmed now is the one integrated LRU contains multiple functions, the transponder, TCAS, and ADS-B have too many variables. This is from the TSS-4100 installation manual

2.6.2. ECU Bottom Half, First Partition.

Refer to Table 2-2 for a list of the parameters that need to be set and their possible values. The first partition of the bottom half has the characteristics that follow:.

• Programmed by the installer
• Contains installation strapping, including number of GPSs, ARINC 429 bus speeds, airplane height and length, etc.
• Must be data loaded.

2.6.3. ECU Bottom Half, Second Partition.

The second partition of the bottom half is used to store the Mode S address, and has the characteristics that follow:
• Programmed by the installer
• Contains the Mode S address
• Either data loaded, or programmed using the TSS-4100 ECU Mode S Address Programming Tool.“


Thanks, you are right and I stand corrected. I should have mentioned that what I was talking about was for the older generation a/c (not an excuse, but I should not have written the previous reply at 3:00am), up to around the B777.

Around the time of the A380, the functions of the XPDR, TCAS, TAWS and WXR/PWS started being integrated into one system. The A350 & B787 use an integrated black box for these functions. Some interfaces are using optical fibres and the black boxes are highly software driven.
 
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zeke
Posts: 16158
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Re: Mode S transponder ID

Fri Apr 19, 2019 5:08 am

akoma wrote:
Around the time of the A380, the functions of the XPDR, TCAS, TAWS and WXR/PWS started being integrated into one system. The A350 & B787 use an integrated black box for these functions. Some interfaces are using optical fibres and the black boxes are highly software driven.


Airbus is providing a pathway to retrofit the same technology on the older A320/A330/A340 aircraft as well. It is cheaper, and lighter to replace a number of legacy boxes with one new box that meets all the current standards with additional functionality.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949

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