Confused re transponders and ADS-B

[Andrew Gideon]

I understand that mode S transponders have unique identifiers, thus
eliminating the need for beacon "codes" as we use them today. Is that
right? Do people flying with mode S today still need to use beacon codes
for compatibility reasons?

TIS travels via the mode S data link. TIS-B uses ADS-B's data link. So
no mode S transponder is required.

So, in an ADS-B world, what's the story on transponders. Is mode C still
required? Does the ADS-B UAT replace a transponder? Something else?

Thanks...

Andrew

[Newps]

Andrew Gideon wrote:
> I understand that mode S transponders have unique identifiers, thus
> eliminating the need for beacon "codes" as we use them today. Is that
> right?


No.


Do people flying with mode S today still need to use beacon codes
> for compatibility reasons?

Not for compatibility reasons. Take your average Boeing 757 used by an
airline. The mode S transponder is registered to the N number. The
airline will never use that N number in flight and that aircraft will
fly under a different identification every day.


>
> TIS travels via the mode S data link. TIS-B uses ADS-B's data link. So
> no mode S transponder is required.

Right but the transponder will allow others to see you.

[Andrew Gideon]

On Sun, 25 Jun 2006 16:47:18 -0600, Newps wrote:


> Not for compatibility reasons. Take your average Boeing 757 used by an
> airline. The mode S transponder is registered to the N number. The
> airline will never use that N number in flight and that aircraft will fly
> under a different identification every day.

It doesn't need to be this way. The controller could "assign" a "code" to
the mode S id. The aircraft would never need to be involved.

Still, from what you describe it apparently doesn't work that way. Oh
well; I guess we're stuck with those base 8 codes.

I suppose that this does provide the benefit of assuring that the object
on the screen is in fact the aircraft the controller thinks it is.

I'm a little surprised, though. I vaguely recall something about these
being too limited for future applications. Perhaps I misunderstood (or am
misremembering).

>> TIS travels via the mode S data link. TIS-B uses ADS-B's data link. So
>> no mode S transponder is required.
>
> Right but the transponder will allow others to see you.

Which "others"?

Does that mean that, as soon as those "others" "upgrade", the transponder
will be a thing of the past? No more beacon codes?

- Andrew

[Bob Noel]

In article >,
Andrew Gideon > wrote:

> I understand that mode S transponders have unique identifiers, thus
> eliminating the need for beacon "codes" as we use them today.

It *could* eliminate the need for beacon codes, but only if everyone
switched to Mode S transponders and all secondary radars were Mode S.


> TIS travels via the mode S data link. TIS-B uses ADS-B's data link. So
> no mode S transponder is required.

no mode S required for ADS-B (still required for other reasons - for example
a TCAS II system still requires Mode S)

>
> So, in an ADS-B world, what's the story on transponders. Is mode C still
> required? Does the ADS-B UAT replace a transponder? Something else?

The ADS-B UAT provides an alternate datalink in lieu of the Mode $ tran$ponder's
datalink.

The transponder is still required at this time. In theory, we could dump
transponders but that would require a change in how aircraft are located and
identified. Numerous issues have to be addressed (no pun), including
problems with spoofing.

--
Bob Noel
Looking for a sig the
lawyers will hate

[Ron Natalie]

Andrew Gideon wrote:
> I understand that mode S transponders have unique identifiers,

True, they not only have unique identifiers but can also transmit
a settable identification number (such as a flight number).

> thus
> eliminating the need for beacon "codes" as we use them today.

It might, but ATC still operates in a discrete code based world.
I've got mode S but it hasn't changed squat with respect to ACTC

>
> So, in an ADS-B world, what's the story on transponders. Is mode C still
> required? Does the ADS-B UAT replace a transponder? Something else?
>
Transponders are still required because ATC is ignorant about ADS-B
and so is TCAS.

[Andrew Gideon]

On Sun, 25 Jun 2006 20:22:33 -0400, Ron Natalie wrote:

> Transponders are still required because ATC is ignorant about ADS-B and so
> is TCAS.

But only mode C? That is, in an ADS-B world there's no need to upgrade to
mode S?

- Andrew

[Ron Natalie]

Andrew Gideon wrote:
> On Sun, 25 Jun 2006 20:22:33 -0400, Ron Natalie wrote:
>
>> Transponders are still required because ATC is ignorant about ADS-B and so
>> is TCAS.
>
> But only mode C? That is, in an ADS-B world there's no need to upgrade to
> mode S?
>
> - Andrew

My crystal ball is cloudy as to whether the FAA is going to continue
to take the political pressure and graft that led to the disaster of
Mode S and TCAS to begin with.