I am looking for some help regarding decoding ARINC 429 data. I have a CSV document that contains sequentially stored ARINC 429 labels.

My overall goal is to be able to scan for 4 specific labels and only decode those frames (data field, label field, and ssm field) and append them to the document.

Does ARINC 429 randomly come in different data formats (i.e. BCD, BNR, Discrete Bits, etc)?

Since I am looking for specific labels, is it okay to only have it set to decode BNR format or do I need to be able to identify and decode all the data formats?

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    $\begingroup$ This is a bit off topic for this exchange but you may want to check out this project. $\endgroup$
    – Dave
    Jun 14, 2017 at 17:00
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    $\begingroup$ Your question seems a bit off topic since it's more related to programming. If you don't find what you are looking for, try asking it on a programming exchange instead. $\endgroup$
    – Jimy
    Jun 14, 2017 at 17:18
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    $\begingroup$ I think it's on topic as the actual question is about Aviation data, not the programming, that's just background info. $\endgroup$ Jun 14, 2017 at 17:55
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    $\begingroup$ Do you have a specific list of labels you are trying to decode? $\endgroup$ Jun 14, 2017 at 18:02
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    $\begingroup$ Arinc 429 is not about aviation? Isn't it a data bus found in......aircraft? $\endgroup$
    – Koyovis
    Jun 15, 2017 at 16:07

2 Answers 2


ARINC 429 is a defined standard that not only describes the packet structure (32 bits) but also the data formats for different labels depending on the equipment ID. To know how to properly decode an ARINC 429 label you need to know the Equipment ID, which can then be used to look up the meaning of a specific label.

The manufacturer of the device that the data came from may also provide the definition of any non-standard/custom labels

If you know which labels you are looking for you don't have to decode the entire label, you just need to inspect the bits 8-1 to determine the label.

In general though, the ARINC 429 specification provides a guideline for labels:

Binary coded decimal (BCD) sub-group 001 to 067, 125, 165, 170, 200, 201,230 to 237.

Binary (BNR) subgroup 070 to 124, 126 to 144, 150 to 154, 162 to 164, 166, 167, 171 to 177, 202 to 227, 240 to 257, 262 to 265, 267, 310 to 347, 360 to 376.

Mixed BCD and BNR subgroup 260, 261

Discretes subgroup 145 to 147, 270 to 276

Maintenance and discrete data subgroup 155, 156

Maintenance data subgroup 157 to 161, 350 to 354

Test word subgroup 266, 277

Application dependent subgroups 300 to 307

Acknowledgement subgroup 355

Maintenance ISO #5 subgroup 356

ISO #5 message subgroup 357

  • $\begingroup$ Ohh, I see now! I currently have 2 of the 4 labels I need (204 & 210), but still looking for the other 2 (Outside Air Temperature & Barometric Pressure). So assuming I get the other two between 202 and 227, I wouldn't need to identify what format it is, I could go straight to translating two's compliment (BNR) to decimal? $\endgroup$
    – woudie
    Jun 14, 2017 at 18:47
  • $\begingroup$ Also, sorry if this is a silly question, but if I end up getting a label of 376, how would that be transmitted if the bnr representation is 9 bits long? (something like 0010000111) $\endgroup$
    – woudie
    Jun 14, 2017 at 18:54
  • $\begingroup$ do you know what equipment ID the device you are receiving data from is using? $\endgroup$ Jun 14, 2017 at 19:49
  • $\begingroup$ Yes, the devices for the individual (i think), I managed to find a document with a bunch of labels w/ eqpt ids. The eqpt id I have for 210 is 006 and 204 is 060. another (possibly silly) question, are equipment ids unique to the air data computer? edit: nevermind, I think I answered my own question based on what I just read. So yes, the eqpt id is unique to the avionics device. My next step should be to acquire the eqpt id of the air data computer I will be receiving from, correct? how can I go about that? I should note that the air data computer is not exactly accessible to me at this time $\endgroup$
    – woudie
    Jun 14, 2017 at 20:11
  • $\begingroup$ The Equipment ID describes what type of transmitting computer. ID 006 is Air Data System and ID 060 is GNSS Navigation Unit. For ID 006 - label 210 is True Airspeed in Knots, 204 is Baro Corrected Altitude in feet. $\endgroup$ Jun 14, 2017 at 20:17

Out of the 32 bits ARINC 429 word, the label is coded by bits 1 to 8 as follows: bits 1 to 3 for the least weighted octal digit, bits 4 to 6 for the next higher, and bits 7 & 8 for the most weighted octal digits. So the label is decoded in base 8 and not base 10, here an example. For instance given the following binary label: 11100110 The 3 bits 110 are decoded 0+2+4=6 The 3 bits 100 are decoded 0+0+4=4 The two digits 11 are decoded 1+2=3 The label is therefore 346 Note: If all bits are set to 1, the greatest label is therefore 377. Of course you may transmit more than 377 parameters, because similar parameters from different sources or sensors for instance AOA left, AOA right, do have the same label. To distinguish similar parameters having different sources, two additional bits (SDI - Source Destination Identifier) are transmitted to define the source.


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