How should I interpret this raw SID data from the FAA?

Question

I am trying to make sense of the SID structures from the FAA's 28 day NASR subscription files (SSD and/or STARDP, raw data in txt files), and I have two questions.

First, I notice that there are SIDs without any path: no transition FIX/NAVAIDs and no main bodies. What's the point of referencing a SID that does not contain anything else except the airport(s)? Take this SID for example (no other records exist for BELLEVUE SID):

D0075     NA N4729353W12212567RNT     BELVU3.BELVU BELLEVUE THREE 
D0075     AA N4729353W12212567RNT

Second, another thing that prevents me from interpreting these SIDs is the difference between "NA" airports and "AA" airports. From the layout file which explains how to read and interpret the records, I read that "If there are airports served by the DP that are not served by any body, there will be one or more records describing these airports, with the FIX/facility type code field containing an 'NA'".

The problem is that in each SID where an 'NA' record exists, another one 'AA' record exists for the SAME airport described by the 'NA' record, so I cannot really understand if they are served by the SID's main body (if any). I am not sure how to interpret this, or the fact that SIDs like the one already mentioned (BELLEVUE) contain neither a main body nor any transition paths.

Another example is this SID; every "NA" airport seems to be also an "AA" airport:

D0161     NA N3832426W08950067BLV     CARDS1.CSX   CARDS ONE 
D0161     NA N3844553W09022121STL 
D0161     NA N3834133W09009183CPS 
D0161     NA N3853237W09002456ALN 
D0161     NA N3839436W09039074SUS 
D0161     AA N3832426W08950067BLV 
D0161     AA N3844553W09022121STL 
D0161     AA N3834133W09009183CPS 
D0161     AA N3853237W09002456ALN 
D0161     AA N3839436W09039074SUS 
D0161     ND N3845099W09021395CSX     CARDS1.BDF BRADFORD TRANSITION 
D0161     R  N3921383W09013256SKYPE K5 
D0161     R  N4004061W09003391SKUTR K5 
D0161     NW N4109350W08935163BDF 
D0161     ND N3845099W09021395CSX     CARDS1.LEBOY LEBOY TRANSITION 
D0161     R  N3922076W09033098DEECE K5 
D0161     R  N3926003W09034230LEBOY K5 
D0161     ND N3845099W09021395CSX     CARDS1.NEENS NEENS TRANSITION 
D0161     R  N3923033W09025555MYKEY K5 
D0161     R  N4014535W09031538NEENS K5 
D0161     ND N3845099W09021395CSX     CARDS1.SPI   SPINNER TRANSITION 
D0161     R  N3919223W09000200TEWHY K5 
D0161     NW N3950230W08940398SPI

Am I missing something here? I apologize for the lengthy post but I would really appreciate if someone could point me to the right direction.

Answer 1

To your first question, some SIDs exist to provide a basic set of information that will almost always be given as part of a clearance, rather than a path to fly. This allows a controller to not have to state that part of the clearance verbally, saving time and confusion.

On the Bellevue Three Departure from KRNT, the departure is as follows:

Climb heading 350°, maintain 3000, expect RADAR vectors, expect filed altitude within 5 minutes after departure.

There's no location to code in the procedure (other than that from the Lost Communications section) so while the SID exists, there's not much to code for an automated system to interpret.

Answer 2

I think another good procedure to help understand this is the BLUES6. It is used at some of the same airports and also requires vectors to CSX, but it's defined by the following lines:

D0106     ND N3845099W09021395CSX     BLUES6.ENL   BLUES SIX
D0106     NW N3825120W08909324ENL  

So why is this one defined by the ND and NW lines? It's because all of the airports share the "body" of CSX to ENL before starting a transition. For the CARDS1, there is no body that is shared; all transitions start at CSX.

Even for procedures using the 'NA' code to define the procedure, the 'AA' code is still needed to list the airports that use the procedure. It does get repetitive, but that's the way they chose to code it.

---

Definitions from the layout file for what the NA and AA codes are used for:

AA     ADAPTED AIRPORT
NA     NAVAID - AIRPORT
...
FOLLOWING THE DESCRIPTION OF THE BASIC STAR ARE ONE OR MORE RECORDS DESCRIBING ALL AIRPORTS USING THIS STAR. THE FIX/FACILITY TYPE CODE FIELD WILL CONTAIN AN 'AA'.
...
IF THERE ARE AIRPORTS SERVED BY THE DP THAT ARE NOT SERVED BY ANY BODY, THERE WILL BE ONE ONE OR MORE RECORDS DESCRIBING THESE AIRPORTS, WITH THE FIX/FACILITY TYPE CODE FIELD CONTAINING AN 'NA'. THE FIRST OF THESE RECORDS WILL CONTAIN THE COMPUTER CODE AND NAME OF THE BASIC DP. THESE RECORDS WILL BE THE FIRST RECORDS FOR THE DP IF THERE ARE NO BODIES FOR THE DP, AND WILL FOLLOW THE LAST BODY DESCRIPTION IF THERE ARE ANY BODIES.