ACARS - An Overview and Discussion

[Anmer]

Since Kinetic released its ACARS decoder beta, I've spent quite a bit of time trawling for more information and existing software.

I've come to a number of conclusions:

1. The SBS-3 offers a much tidier ACARS interface than a separate receiver and soundcard connection.  The decoded data is passed directly to the Basestation software.

2. Deciphered ACARS messages can add value for the spotter.

3. Unencrypted ACARS may have a short shelf-life.

4. Not all airlines use ACARS or if they do, some use encryption.

5. Depending on where one is located, even with a good antenna position, received messages may be in short supply.

6. The Basestation beta could be further developed but Kinetic may not see any value in doing so.

To try and provide a better understanding of ACARS and explore how it could add value to the aircraft spotting hobby, I've prepared a short  Overview hoping to encourage wider debate.  To date the posts on "other" forums are mostly between a handful of ACARS aficionados with little discussion about future developments.  Then again, maybe there's no real interest in the topic?

Please feel free to criticise my document and put forward alternative views.  That's my main reason for publishing it.

Download the Overview here.

[nzradar]

Hi Mike,

An interesting document.

In your example message you have a question mark against ACARS Mode in the header.  Here's my take on it:

In downlink messages ACARS Mode, is a single UPPERCASE character and is the ground station that the aircraft is addressing.  Your example  using the letter "M" would infer that the aircraft is downlinking to the Manchester ground station. 

It goes without saying that these allocated codes are regionalised, but I have found here in Australasia that they are reasonably intuitive to guess, C = Christchurch if in New Zealand or Canberra if in Australia. 

If one lives close to a ground station then the uplink message ACARS Mode is in lowercase "m".

Further, I have found through my 16 years of monitoring ACARS that the Message Type is very airline orientated.  The codes British Airways use to define their message types may not be the same as Air New Zealand.  When each message is received by the ground station it is routed to the airline by a combination of aircraft registration and flight id, so that only messages for BA are received by the BA ACARS message system.  This method allows airlines to define their own message types depending on their own requirements.  That is to say they are not globally defined.

From a more broader perspective, I seldom delve into the contents of messages but use ACARS to identify which aircraft are in my area.  This is particularly useful as a gap filler where aircraft are not ADS-B or Mode-S equipped but do use ACARS, in particular some biz-jets fall into this category quite nicely.

[Anmer]

Thank you very much Mike.  Your feedback and experience confirms some of the impressions I gained during my recent research.

Deciphering message content, especially airline specific formats, has to be a compromise and the majority of ACARS messages will yield little more than the aircraft registration and flight number, the latter possibly using an IATA rather than a Mode-S ATC designation.  But this in itself can be of value, especially where the aircraft can't be identified from a Mode-S hex code.

I was also trying to explore how Basestation could deliver messages in a more usable layout and with enhanced functionality.  Whether Kinetic has the appetite is another matter.

Once again, thanks for your input.

[maximus_mike]

Hi Mike,

You will by now have seen my posting re my SBS3-ACARS-Display program which combines the output from the SBS3 ACARS stream with databases of Aircraft/Airlines/Flight Nos to provide a more detailed display of aircraft data which can be used alongside Basestation data and links from the aircraft's rego.

Some users find this useful, others don't.  Just depends upon what they are used to.

Certainly here in the Sydney area, I copy about as many ACARS messages as I do Mode-S as most of the regular airlines here now use ACARS.  HF-ACARS is also expanding rapidly, certainly in the Pacific Basin.

One point I would like to make though is that the SBS-3 although great at receiving ACARS messages on multiple freqs. is very deaf compared with my Winradio G305e - On the same antenna, using the Winradio G305e, I receive about 25 pct more ACARS messages on 131.55 MHz than I do using the SBS3 on 3 freqs combined...

Mike Simpson

[Anmer]

Thanks Mike.

Your application is very good, as too is Stuart's BS Acars Aircraft List.  Both add value to the Kinetic beta and we are all very grateful for your efforts on behalf of the community.

Personally, going forward I'd like to see Kinetic integrate such products within Basestation itself but time will tell.

Maybe I'd prefer your application a bit more if it wasn't supporting a particular forum?