transponder codes

[Guy Elden Jr.]

Just got back from a _great_ trip down to Atlanta and back to Caldwell, NJ
over the Thanksgiving holiday. Departed 8:25am Tuesday morning with my wife
in a 172SP, got in around 3:50pm to Gwinett Field (LZU) after a 20 minute
fuel stop at Roanoke Regional (ROA). Trip back up was about an hour faster
with great tailwinds for part of the journey. Folks at ROA were absolutely a
joy to do business with... very quick service, even with several jets on the
ramp on the way back Sunday, and more on the way in. Highly recommended for
you East Appalachian flyers. :)

On the way back up, as we were departing Roanoke, the tower controller and
then departure controller gave me some weird transponder codes. I was
wondering if anybody here could enlighten me as to what may have been
happening. First, I was told to squawk 7000 (this was an IFR trip, btw).
After liftoff, tower hadn't handed me off to departure like I expected, so I
asked if I should change frequencies. He responded that he was waiting for
another transponder code for me to try before handing me off... new one was
1234. At this point I began to suspect I was about to be a victim of some
cruel ATC joke, and I knew I was when he handed me off to departure, who
assigned me yet another new code... 0123.

I kept putting the new codes in and recycling the transponder for them,
because it seemed they couldn't get me on their scopes. This seemed pretty
bizarre because I had just flown a 2.75 hour IFR trip up from Atlanta with
zero transponder problems. After a couple more minutes the departure
controller asked me to squawk 2012 (or something that sounded like a "real"
code to me), and then I idented for him just to be sure. Finally he was able
to get a radar contact, and the rest of the flight was uneventful.

I'm just wondering if there's any significance to the codes 7000, 1234, or
0123, besides their numerological significance. I imagine they just wanted
to find me on their scope first, or maybe the computer that generates the
codes was having a bad day?

--
Guy Elden Jr.

[Steven P. McNicoll]

"Guy Elden Jr." > wrote in message
...
>
> On the way back up, as we were departing Roanoke, the tower controller and
> then departure controller gave me some weird transponder codes. I was
> wondering if anybody here could enlighten me as to what may have been
> happening. First, I was told to squawk 7000 (this was an IFR trip, btw).
>

The 7000 code block is used by Washington ARTCC for departures that will be
exiting their airspace. But only discrete codes would be assigned from that
block; 7001, 7002, etc. If you're departing a non-ARTS facility, which I
assume ROA is not, the computer assigned code will time-out after one hour
and revert to the non-discrete base code, i.e., a 7032 code would become
7000. If the aircraft does depart within the next hour a new discrete code
will be generated when the departure is entered in the computer.


>
> After liftoff, tower hadn't handed me off to departure like I expected, so
I
> asked if I should change frequencies. He responded that he was waiting for
> another transponder code for me to try before handing me off... new one
> was 1234.
>

Codes 1201-1272, unless otherwise allocated, are used for DVFR aircraft.


>
> At this point I began to suspect I was about to be a victim of some
> cruel ATC joke, and I knew I was when he handed me off to departure, who
> assigned me yet another new code... 0123.
>

Codes 0100-0477 are assigned for terminal operations, radar services to VFR
aircraft and local IFR operations not entered in the flight data processing
computer.