ACARS

You obviously see the aircraft's tail number and flight number. That information is of course in the headers of the ACARS packet, which once you have that information, you can figure out the airline, route, and who owns the aircraft. ACARSD tries to lookup that information but sometimes that information isn't there. This is an downlink message, i.e. from the air to the ground. This is also whats called a free text message, where one of the crew members on this flight typed it out.

ACARS has lots of automatic messages. Here's one example:

ACARS mode: 2  Aircraft reg: N374UA  [Boeing B737-322]  Message label: H1 [Message to/from terminal]  Block id: 8  Msg no: D02A  Flight id: UA1164  [Vancouver, Canada-San Diego, CA, USA via San Fransisco, SA, USA]  [United Airlines]  Message content:-  #DFB/PIREPUA./WX YVRSFO5 3740C1164/10YVRSFO N46053W1232290241P37028M5700100190000 N45359W1232210245P37016M5580060210000 N45065W1232150249P37020M5580100200000 N44371W1232090253P37016M5583590180000   North: 46.05 West: 123.23

 
The PIREP means its its a Pilot Report. UA obviously implies its a United Airlines specific one. In this case, it shows its last 4 current positions. The first one is the most current and ACARSD decodes it for you in plain english. After the PIREPUA and the slash is a outgoing command to the ground. In this case, WX means weather and would like it for the route of YVR-SFO.  The line consisting of 3740C1164/10YVRSFO is going to get a bit cryptic here. I'm not sure what exactly the 3740 means, but C11 is United's code of an Internationl PIREP beause this flight is coming from Vancouver, BC, Canada. Its mainly explaning its a PIREP report for the route of YVR-SFO. More information on these airline specific codes can be found at http://www.acarsonline.co.uk/about/message-labels/ and http://www.cosmic.com.au/acarsanalyser/v3/DataRes/MsgLabels.htm

Uplink messages require you to be close to a ground station. In my case, I am near the ground station at Portland International Airport or PDX. There's usually a ground station at every major airport, sometimes more. These sometimes are handy to read if your trying to follow an actual conversation. I'll use a example for a request response:

ACARS Mode: 2  Aircraft reg: N11187 Aircraft type: Emb.145XR Message Label: RA Block ID: U  Message Number:  Flight Number:  Operator: Continental Express Message Content:- QUDPCRUCO.1GATE TO 1365/10 ////////////////////// CURRENT GATE UNASSIGNED FLIGHT 1365/10SEP FROM SJC  TO  PDX /////////////////////

ACARSD will usually in tan note its an upink message, but if you need to you can figure out from hte Message Label. In this case, its RA which means Command Response. The pilot earlier sent a request  to find out what gate he will be assisged at PDX. Unfortunalty, he has not received an gate assisgment. Some of these messages are designed to be printed on the printer that is in the flight deck such as this one.

---

Frequencies used by ACARS

ACARS has several major frequencies assigned for its use in all over the world. ARNIC handles North America, while SITA handles Europe.

There's only 4 I really monitor; most of the time I sit on the worldwide channel as thats the most used here by PDX.