Transponderz

On 11/2/2012 4:55 PM, Dave Nadler wrote:


For this reason:
- aircraft in formation only have ONE aircraft's
transponder turned on
- aircraft approaching Oshkosh are required to turn
their transponders OFF (except Mode S)
- the rest of the world has effectively outlawed
Mode A/C in favor of Mode S.

Hope that's clear,
Best Regards, Dave

What to do is not at all clear to me. I've never been in a thermal that
decided to turn off some transponders, and I don't hear of any contests
where a protocol was put in place to achieve this. For example, how does
this statement "aircraft in formation only have ONE aircraft's
transponder turned on" apply in these situations; i.e., what constitutes
a "formation"?

- two gliders thermalling at the same altitude? Three? Four? Five?

- How about 10 gliders spread over two thousand feet of altitude? Should
only one have it's transponder on, or should the gliders at the top and
bottom have them on? Or one transponder every 1000'?

- Or two gliders cruising together: are they a formation if they are
100' apart? 500'? 1000'? Or if it's three gliders? Four?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Saturday, November 3, 2012 12:22:00 PM UTC-4, Eric Greenwell wrote:
What to do is not at all clear to me. I've never been in a thermal that
decided to turn off some transponders, and I don't hear of any contests
where a protocol was put in place to achieve this. For example, how does
this statement "aircraft in formation only have ONE aircraft's
transponder turned on" apply in these situations; i.e., what constitutes
a "formation"?

- two gliders thermalling at the same altitude? Three? Four? Five?
- How about 10 gliders spread over two thousand feet of altitude? Should
only one have it's transponder on, or should the gliders at the top and
bottom have them on? Or one transponder every 1000'?
- Or two gliders cruising together: are they a formation if they are
100' apart? 500'? 1000'? Or if it's three gliders? Four?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Get a Mode S transponder so you don't have to worry about this !

Just had to change the atrocious spelling in the subject line...


"Dave Nadler" wrote in message
...
On Friday, November 2, 2012 8:45:43 PM UTC-4, Mike C wrote:
I am wondering if using Oshkosh as an example applicable to a few
sailplanes, in a thermal, is not a bit of a strawman argument.

Oshkosh was used as an example of where Mode A/C cannot work.

A separate point, it is my impression that traffic is so congested
there that the controllers are overwhelmed, not that the signals are
garbled and unreadable.

"Your impression" ? The controllers are not overwhelmed, they use
appropriate tools and manage the highest traffic density anywhere,
very professionally. As you would know if you've flown into
Oshkosh (or in the airshow ;-)

Mode C is valid, safe and not the worthless tired technology
that it seems to be portrayed as.

Sure, which is why Mode C was phased out in Germany years ago,
with the rest of the world following...

For new installations, get Mode S and we'll all be happier
with the results. And it won't have to be replaced if/when
FAA catches up with the rest of the world (not holding my
breath).

Mode C does work in many cases, but...

Dave Nadler wrote:
On Saturday, November 3, 2012 12:22:00 PM UTC-4, Eric Greenwell wrote:
What to do is not at all clear to me. I've never been in a thermal that
decided to turn off some transponders, and I don't hear of any contests
where a protocol was put in place to achieve this. For example, how does
this statement "aircraft in formation only have ONE aircraft's
transponder turned on" apply in these situations; i.e., what constitutes
a "formation"?

- two gliders thermalling at the same altitude? Three? Four? Five?
- How about 10 gliders spread over two thousand feet of altitude? Should
only one have it's transponder on, or should the gliders at the top and
bottom have them on? Or one transponder every 1000'?
- Or two gliders cruising together: are they a formation if they are
100' apart? 500'? 1000'? Or if it's three gliders? Four?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Get a Mode S transponder so you don't have to worry about this !

No! Just keep using your Mode C and don't worry about it. This whole
excessive worry about a what-if corner case is typical post-season
rasterbation, can we please at least get back to PW5 bashing?

Darryl

"Dan Marotta" wrote:
Just had to change the atrocious spelling in the subject line...

And that mostly just annoys a lot of people, forks the thread in many
newsreaders etc. Leave usenet subject lines alone please.

Darryl

I'm pleased to know a gaggle full of Mode C transponders doesn't become
invisible to ATC and probably not even TCAS, but is just more difficult
for the system.

If it really became invisible, then it would important/critical for a
gaggle to coordinate their transponder usage, a big hassle if it's more
than a few gliders. It would lead to a lot of radio discussion to decide
who shuts off their transponder, and who turns it back on when the
"designated transponder" leaves the gaggle, and likely leading to some
pilots forgetting to turn their transponder back on when they leave.

On 11/2/2012 9:17 PM, Darryl Ramm wrote:

Does ATC see anything out there, even if the TCAS system can not?


The danger here is this is not written for a technical audience and
is confusing on multiple levels.

Firstly you can have several Mode-C equipped gliders in a gaggle or
otherwise close by and the TCAS may well decode the transponders and
see them as individual targets with valid direction, range and
altitude data. As I mentioned with the decorrelators (or called
"degarblers") and other tricks TCAS can handle some degree of
garbling.

The mention of "TCAS collision avoidance" is likely meaning the RA
(resolution advisory) capability of TCAS II, and if you have any
threat that the Mode-C altitude replies really are not being clearly
read then the RA part of TCAS II can not/will not function at all.

The TCAS may display a threat direction/range even of the altitude
information is being garbled but there is no simple guarantee in
garbled environment of what exactly will happen, it may or may not
display all the aircraft with or without altitude data or (hopefully
rarely) with incorrect altitude. But what matters really is the TA
and RA and you really need the Mode C replies decoded properly for
that. I expect TCAS I to be very useful against Mode C equipped
gliders in usual buddy flying or small gaggles. Fly an airliner
straight into a large (vertically spaced) gaggle of gliders and I
have zero expectations that it will have a clue what to do with an
RA, and that RA may well fly the airliner into a collision. OTOH I
expect the gaggle to also be visible on the TCAS display -- not that
I ever want to rely on the pilots looking a that display. An airliner
going into a huge gaggle of Mode-S equipped gliders may also not fare
well and TCAS may compute an unsafe RA (since RAs are based on
altitude actions only and it can't/won't steer you around the
gaggle). I'd hope ATC has noticed any very large gaggles and the
gliders are in touch with ATC. So at some extent I find some of this
worrying about what happens with large gaggles with Mode-C kind of
unnecessary.

I hope ATC would be well aware there is say a large gaggle of gliders
in a location (one benefit of a dedicated glider transponder code),
be able to route traffic around that gaggle. And I'd hope that ATC
would be savvy enough to suspect they may have very poor target
acquisition, altitude reporting and garbling problems. And hopefully
a large gaggle will show up even on primary radar in many locations.
And I'd expect them to be upset if a large gargle is parked near
where they usually want to route traffic. But hope is not always a
good thing, go talk to your local ATC guys, radar techs are usually
pretty friendly if you want to have a detailed talk with them.

You can always just ask your local ATC guys what they prefer if
gliders are buddy flying etc. Most places I've asked (e.g. Reno
approach in pre NORCAL days -- I dont' know about now) never felt
they needed push for it but were happy to work with gliders buddy
flying etc. where one or more of them wanted to go squawk standby.

Again the message is get a transponder if you fly near airliners and
fast jets, lots of GA traffic etc. There is absolutely no need to
replace a Mode C transponder, they work fine but if buying a new
transponder it make no sense to get a Mode C when more modern Mode S
transponders are available.

Darryl



--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Saturday, November 3, 2012 3:19:53 PM UTC-4, Eric Greenwell wrote:
I'm pleased to know a gaggle full of Mode C transponders doesn't become
invisible to ATC and probably not even TCAS

Absolutely wrong.

It *may* work.
It is a probability problem, related to
number of aircraft, antenna installation,
aircraft position, orientation, and bank, etc.

On 11/3/2012 9:57 AM, Dave Nadler wrote:
On Saturday, November 3, 2012 12:22:00 PM UTC-4, Eric Greenwell wrote:
What to do is not at all clear to me. I've never been in a thermal that
decided to turn off some transponders, and I don't hear of any contests
where a protocol was put in place to achieve this. For example, how does
this statement "aircraft in formation only have ONE aircraft's
transponder turned on" apply in these situations; i.e., what constitutes
a "formation"?

- two gliders thermalling at the same altitude? Three? Four? Five?
- How about 10 gliders spread over two thousand feet of altitude? Should
only one have it's transponder on, or should the gliders at the top and
bottom have them on? Or one transponder every 1000'?
- Or two gliders cruising together: are they a formation if they are
100' apart? 500'? 1000'? Or if it's three gliders? Four?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Get a Mode S transponder so you don't have to worry about this !

Maybe I'm asking for details that nobody knows, and it appears that the
question hasn't even come up in contests where multiple Mode C gaggles
are likely routine.

Since at least 98% of my flying is not near other gliders, I'm not
motivated to upgrade to Mode S, and frankly, I don't expect significant
numbers of Mode C users to upgrade to Mode S, either, so I'm trying to
learn what is sensible to do during the 2% of the time I am near other
gliders.

Back to this: "Get a Mode S transponder so you don't have to worry about
this !"

So, a TCAS equipped aircraft will react properly to a Mode S transponder
in a big gaggle of Mode C equipped gliders - is that what you are
implying? I don't want to guess at this; I want to know what is actually
required for TCAS aircraft to be able to avoid a gaggle I'm in.

If so, the "formation protocol" in a gaggle could be to first find out
if at least one of the gliders is Mode S equipped, then all the Mode C
equipped gliders can leave their transponders on. Of course, that might
not protect the Mode C gliders circling 2000 feet above or below the
Mode S glider.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Nov 3, 8:59*am, Dave Nadler wrote:
On Friday, November 2, 2012 8:45:43 PM UTC-4, Mike C wrote:
I am wondering if using Oshkosh as an example applicable to a few
sailplanes, in a thermal, is not a bit of a strawman argument.

Oshkosh was used as an example of where Mode A/C cannot work.

A separate point, it is my impression that *traffic is so congested
there that the controllers are overwhelmed, not that the signals are
garbled and unreadable.

"Your impression" ? The controllers are not overwhelmed, they use
appropriate tools and manage the highest traffic density anywhere,
very professionally. As you would know if you've flown into
Oshkosh (or in the airshow ;-)

Mode C is valid, safe and not the worthless tired technology
that it seems to be portrayed as.

Sure, which is why Mode C was phased out in Germany years ago,
with the rest of the world following...

For new installations, get Mode S and we'll all be happier
with the results. And it won't have to be replaced if/when
FAA catches up with the rest of the world (not holding my
breath).

Mode C does work in many cases, but...

On Nov 3, 8:59*am, Dave Nadler wrote:
On Friday, November 2, 2012 8:45:43 PM UTC-4, Mike C wrote:
I am wondering if using Oshkosh as an example applicable to a few
sailplanes, in a thermal, is not a bit of a strawman argument.

Oshkosh was used as an example of where Mode A/C cannot work.

A separate point, it is my impression that *traffic is so congested
there that the controllers are overwhelmed, not that the signals are
garbled and unreadable.

"Your impression" ? The controllers are not overwhelmed, they use
appropriate tools and manage the highest traffic density anywhere,
very professionally. As you would know if you've flown into
Oshkosh (or in the airshow ;-)

Mode C is valid, safe and not the worthless tired technology
that it seems to be portrayed as.

Sure, which is why Mode C was phased out in Germany years ago,
with the rest of the world following...

For new installations, get Mode S and we'll all be happier
with the results. And it won't have to be replaced if/when
FAA catches up with the rest of the world (not holding my
breath).

Mode C does work in many cases, but...

Dave,

Are you sure that the reason that formation pilots only have one
transponder on, is not because of collision alerts with aircraft in
close proximity of each other? That is what I was told. Also told the
reason transponders are turned off is because of alerts in heavy
traffic

Mike.