Build your own PowerFLARM!

On Aug 16, 9:37 pm, Mike Schumann
wrote:
On 8/16/2010 10:50 PM, kirk.stant wrote:
[snip]
A. "Right Now Benefits of PowerFlarm" - This product does not currently
exist. Has it been submitted to the FCC for approval yet? What is the
expect ship date?

Late 2010/December according to their USA dealers.

[snip]

C. PCAS - How does PCAS tell you anything about what kind of target is
aiming for you? In fact, it doesn't give you any information on where
the target is, whether it's getting closer or moving away. All you know
is altitude and range (NO bearing). It's not going to tell you if it's
a jet, another glider, or your tow plane. And you are only going to get
that much info if the transponder equipped plane is being interrogated.
That's not a given if you are flying low in remote areas without radar
coverage.

What is your point? If the PCAS in PowerFLARM works anwhere nears as
well as PCAS units like the Zaon MRX then it is a very useful tool
today especially against GA threats. Yes there are restrictions on
this, and they've been discussed to death already.

Including PCAS capabilities in a 1090ES receiver is easy since all the
hardware you need is already there for free. It is just plain and
simple a really great idea to add that feature in this product. I
expect other 1090ES receiver manufacturers in the portable/low-end
market to do exactly the same. Of course without additional 1090MHz
receiver hardware a UAT receiver cannot do this.

But to caution other folks here, PCAS relies on the inverse square of
distance fall of in RF power and assumptions about transponder power
output to guesstimate distance, while it works OK it has limits. It is
part of the reason why PCAS systems have a relatively short warning
range for threats. With fast closure rates like with airliners and
jets (esp. at altitude/outside airspace speed restrictions) PCAS
systems are quite likely to give unusably short warning times. I see
PCAS as making more sense with GA threats and when flying with a
reasonably small number of gliders -- what many of us have done with
it given the lack of Flarm availability in the USA.

What's my agenda? Making sure that people know what they are buying and
the limitations thereof.

--
Mike Schumann


Darryl

On Aug 16, 10:40*pm, Darryl Ramm wrote:
Again that was not what Andy was claiming.

I'd actually prefer it if I made the statements as to what I was
claiming.

I have actually claimed nothing about what PowerFLARM will do as
regard alert suppression.

I have, however, expresseed the hope that PowerFLARM will have
intelligent alert suppression of transponder based (PCAS) targets.
And by that I did mean suppression of certain PCAS targets but not
others.

Certainly it is possible for Power FLARM to determine the squawk code
of a received transponder. In areas where gliders are assigned a
specific discrete code then PowerFLARM could be programmed to handle
targets with this code in a different way from target not squawking
that code.

It would also be possible to track a target based on range and
altitude information. When on tow the tug's transponder signal will
indicate a constant range and a constant altitude difference. Any
other transponder target that could be a threat will appear at the max
detection range and then come progressively closer. It seems quite
reasonable to assume that a well designed system would allow
suppression of the tug alert but still alert for the approaching
threat. It would also be possible to remove the tug transponder from
the suppressed target list when tow release is detected by a
significant change in altitude difference or range.

Similary if I am in a gaggle with several gliders that have
transponders it would be possible to suppress alerting on all those
targets while they remain within a certain range but still provide
alerting to the King Air that approaches from max detection range and
is closing rapidly. Again the suppressed transponders could be removed
for the suppression list if they show an increase in range
corresponding to leaving the thermal.

So my hope is that, if a transponder equipped glider joined my thermal
I will be alerted. When I visually acquire the glider and decide it
is the one causing the alert I select mute. I will then no longer be
alerted to that transponder but will be alerted to any other
transponder target that approaches me. I will then chose to to mute
that alert if I wish, and still be alerted to the next on that
approaches.

All this assumes that the unit is smart enough to keep track of
individual targets based on range (signal strength), altitude, and
perhaps also squawk code. I see no reasons why this is not
technically possible but again make no claim that such a feature is
include in PowerFLARM

Andy

On Aug 17, 9:42*am, Andy wrote:
On Aug 16, 10:40*pm, Darryl Ramm wrote:

Again that was not what Andy was claiming.

I'd actually prefer it if I made the statements as to what I was
claiming.

I have actually claimed nothing about what PowerFLARM will do as
regard alert suppression.

I have, however, expresseed the hope that PowerFLARM will have
intelligent alert suppression of transponder based (PCAS) targets.
And by that I did mean suppression of certain PCAS targets but not
others.

Certainly it is possible for Power FLARM to determine the squawk code
of a received transponder. *In areas where gliders are assigned a
specific discrete code then PowerFLARM could be programmed to handle
targets with this code in a different way from target not squawking
that code.

It would also be possible to track a target based on range and
altitude information. *When on tow the tug's transponder signal will
indicate a constant range and a constant altitude difference. *Any
other transponder target that could be a threat will appear at the max
detection range and then come progressively closer. *It seems quite
reasonable to assume that a well designed system would allow
suppression of the tug alert but still alert for the approaching
threat. *It would also be possible to remove the tug transponder from
the suppressed target list when tow release is detected by a
significant change in altitude difference or range.

Similary if I am in a gaggle with several gliders that have
transponders it would be possible to suppress alerting on all those
targets while they remain within a certain range but still provide
alerting to the King Air that approaches from max detection range and
is closing rapidly. Again the suppressed transponders could be removed
for the suppression list if they show an increase in range
corresponding to leaving the thermal.

So my hope is that, if a transponder equipped glider joined my thermal
I will be alerted. *When I visually acquire the glider and decide it
is the one causing the alert I select mute. *I will then no longer be
alerted to that transponder but will be alerted to any other
transponder target that approaches me. *I will then chose to to mute
that alert if I wish, and still be alerted to the next on that
approaches.

All this assumes that the unit is smart enough to keep track of
individual targets based on range (signal strength), altitude, and
perhaps also squawk code. *I see no reasons why this is not
technically possible but again make no claim that such a feature is
include in PowerFLARM

Andy

will all this muting and un-muting cause a large increase in pilot
work load?

Thanks,
Brad

On Aug 17, 9:47*am, Brad wrote:

will all this muting and un-muting cause a large increase in pilot
work load?

In my proposal there is no workload associated with "unmuting" it's
automatic.

In the flow - hear alert, scan for target, associate target with
alert, mute alert - the action of muting the alert is an
insignificant part of the workload if it requires a single press of
the control knob.

Certainly a single action mute of all alerts would be a lower workload
but if that was the objective you could just turn it off, or not buy
one in the first place.


Andy

Darryl,

Thanks for taking the time to answer my question; It pretty much
confirms what I suspected. The fact that the PowerFlarm will detect
and show 1090ES traffic is a huge feature for me, as it will give me
an even better heads up on fast movers at altitude.

To me FLARM is a no-brainer for glider pilots - even those who don't
race.

Now if I could just figure out how to mount an APG-82 AESA radar in
the nose of my LS6...

Kirk

A. *"Right Now Benefits of PowerFlarm" - This product does not currently
exist. *Has it been submitted to the FCC for approval yet? *What is the
expect ship date?

Later this year, which is fine for me. And FLARM itself is well
proven - even if that was all the PowerFlarm did it would be worth
it. UAT ADS-B isn't.

B. *1090ES ADS-B - You aren't going to see anything on PowerFLARM unless
you are also equipped with, and transmitting a properly configured ADS-B
Out Signal. *That part is NOT provided by PowerFLARM.

Wrong. I'll see the 1090ES mode S directly. Which is exactly what I
want to see.

C. *PCAS - How does PCAS tell you anything about what kind of target is
aiming for you? *In fact, it doesn't give you any information on where
the target is, whether it's getting closer or moving away. *All you know
is altitude and range (NO bearing). *It's not going to tell you if it's
a jet, another glider, or your tow plane. *And you are only going to get
that much info if the transponder equipped plane is being interrogated.
* That's not a given if you are flying low in remote areas without radar
coverage.

If I look out the window and see a dot, all I know at first is that it
is something out there. I'll watch it until I determine if it's a
threat and react accordingly. PCAS helps me find that dot by warning
me to look level or slightly high/low, and if I already have an idea
where the traffic is coming from (arrival departure routes, VOR/
Airports nearby, VFR/IFR altitudes) I can focus my search there. What
else do you need, the pilot's daughter's phone number? The biggest
reason pilots don't see other traffic is not that it isn't visible,
but that they aren't looking for it - and PCAS/FLARM/ADS-B are all
designed to make the pilot get his head out of his PDA and look for
traffic.

What's my agenda? *Making sure that people know what they are buying and
the limitations thereof.

Fair enough.

Cheers,

Kirk

On Aug 17, 9:42*am, Andy wrote:
On Aug 16, 10:40*pm, Darryl Ramm wrote:

Again that was not what Andy was claiming.

I'd actually prefer it if I made the statements as to what I was
claiming.

I have actually claimed nothing about what PowerFLARM will do as
regard alert suppression.

I have, however, expresseed the hope that PowerFLARM will have
intelligent alert suppression of transponder based (PCAS) targets.
And by that I did mean suppression of certain PCAS targets but not
others.

Certainly it is possible for Power FLARM to determine the squawk code
of a received transponder. *In areas where gliders are assigned a
specific discrete code then PowerFLARM could be programmed to handle
targets with this code in a different way from target not squawking
that code.

It would also be possible to track a target based on range and
altitude information. *When on tow the tug's transponder signal will
indicate a constant range and a constant altitude difference. *Any
other transponder target that could be a threat will appear at the max
detection range and then come progressively closer. *It seems quite
reasonable to assume that a well designed system would allow
suppression of the tug alert but still alert for the approaching
threat. *It would also be possible to remove the tug transponder from
the suppressed target list when tow release is detected by a
significant change in altitude difference or range.

Similary if I am in a gaggle with several gliders that have
transponders it would be possible to suppress alerting on all those
targets while they remain within a certain range but still provide
alerting to the King Air that approaches from max detection range and
is closing rapidly. Again the suppressed transponders could be removed
for the suppression list if they show an increase in range
corresponding to leaving the thermal.

So my hope is that, if a transponder equipped glider joined my thermal
I will be alerted. *When I visually acquire the glider and decide it
is the one causing the alert I select mute. *I will then no longer be
alerted to that transponder but will be alerted to any other
transponder target that approaches me. *I will then chose to to mute
that alert if I wish, and still be alerted to the next on that
approaches.

All this assumes that the unit is smart enough to keep track of
individual targets based on range (signal strength), altitude, and
perhaps also squawk code. *I see no reasons why this is not
technically possible but again make no claim that such a feature is
include in PowerFLARM

Andy

On Aug 17, 9:42 am, Andy wrote:
On Aug 16, 10:40 pm, Darryl Ramm wrote:

Again that was not what Andy was claiming.

I'd actually prefer it if I made the statements as to what I was
claiming.

I have actually claimed nothing about what PowerFLARM will do as
regard alert suppression.

I have, however, expresseed the hope that PowerFLARM will have
intelligent alert suppression of transponder based (PCAS) targets.
And by that I did mean suppression of certain PCAS targets but not
others.

Certainly it is possible for Power FLARM to determine the squawk code
of a received transponder. In areas where gliders are assigned a
specific discrete code then PowerFLARM could be programmed to handle
targets with this code in a different way from target not squawking
that code.

It would also be possible to track a target based on range and
altitude information. When on tow the tug's transponder signal will
indicate a constant range and a constant altitude difference. Any
other transponder target that could be a threat will appear at the max
detection range and then come progressively closer. It seems quite
reasonable to assume that a well designed system would allow
suppression of the tug alert but still alert for the approaching
threat. It would also be possible to remove the tug transponder from
the suppressed target list when tow release is detected by a
significant change in altitude difference or range.

Similary if I am in a gaggle with several gliders that have
transponders it would be possible to suppress alerting on all those
targets while they remain within a certain range but still provide
alerting to the King Air that approaches from max detection range and
is closing rapidly. Again the suppressed transponders could be removed
for the suppression list if they show an increase in range
corresponding to leaving the thermal.

So my hope is that, if a transponder equipped glider joined my thermal
I will be alerted. When I visually acquire the glider and decide it
is the one causing the alert I select mute. I will then no longer be
alerted to that transponder but will be alerted to any other
transponder target that approaches me. I will then chose to to mute
that alert if I wish, and still be alerted to the next on that
approaches.

All this assumes that the unit is smart enough to keep track of
individual targets based on range (signal strength), altitude, and
perhaps also squawk code. I see no reasons why this is not
technically possible but again make no claim that such a feature is
include in PowerFLARM

Andy

Andy

Sorry, I misunderstood and though you were talking about. Now that I'm
not confusing what you meant I appreciate the thought process you are
going though but I want to try to emphasize that PCAS just cannot be
pushed very far to do really advanced things, certainly not with Mode
C transponders in larger gaggles. And Mode C likely starts having
problems with less than what many would consider a "large gaggle".
Things are a lot better if we have a Mode S environment but many
gliders in the USA are going to have Mode C transponders. So I'll run
though the main issues below, kind of in a jumbled up way, hope it
makes sense....

In a gaggle type environment when an interrogation hits the gaggle all
Mode C transponders (an actual Mode C transponder or a Mode S being
interrogated as a Mode A/C) reply at the same time and their
transmissions overlap. This is called synchronous garbling and it only
takes a few overlapping replies for this to make the signal
unreadable. Forget what might be possible, the PCAS is quite likely to
just not be able to read the altitudes of any of the replies. SSR
radar and TCAS systems have fancy hardware decorrelators that help
them try to pull out signals from each other but they can only handle
a few close overlaps. SSR radar obviously also sweeps the
interrogation beam and TCAS II uses a wider quadrant interrogation
(and other tricks) to interrogate as few transponders as possible at a
time. But any of these systems will just fail with reasonable large
number of Mode C equipped gliders in a gaggle. Synchronous garbling
is the reason why there are procedures for formation flights with Mode
C transponders to have everybody but the leader squawk standby. There
has been research done on Mode C synchronous garbling of SSR radar in
glider gaggles by European researchers and the results were bad as
expected. Synchronous garbling is a really fundamental problems that
will severely limit PCAS usability against Mode C threats if you are
flying close to or in a gaggle type environment.

Gliders in a gaggle will all be squawking 1200 or 1201 not unique
squawk codes. Nobody flying those gliders is going to be on a flight
plan or under flight following and the FAA with limited Mode A
allocation blocks is unlikely ever to give away squawk codes for this
even if it would make any difference. And here is another reason you
don't want to do this (see below later).

It could be that most interrogations of a glider gaggle come from TCAS
systems. TCAS does not interrogate Mode A (although there is a slight
qualification on that I don't want to get into). It has no idea what
the squawk codes of aircraft are, all TCAS wants to know is a threat's
relative altitude and direction (which it gets from phased array
antennas (those two blade next to each other you see on aircraft)). So
there are may be none or few Mode A replies to correlate Mode C reply
altitude replies with.

PCAS does do not actually listen on 1030MHz so never see the
transponder interrogations (just the replies on 1090MHz), it makes no
sense to bother to do this because the moment the replying transponder
is any distance away the PCAS would not know if the interrogation it
sees is what the transponder is actually replying to. So a PCAS unit
has no idea whether a Mode C transponder (an actual Mode C transponder
or a Mode S being interrogated as a Mode A/C) is replying to a Mode C
or Mode A interrogation. All it sees is a series of encoded pulses.
PCAS units know from the ranges of valid patterns that some reply
patterns must be Mode C replies and some must be Mode A. However there
is an significant overlap range where the PCAS cannot know for sure
what the reply actually is. PCAS units clearly try to do some tricks
to reduce this "aliasing" problem but vendors do not disclose how they
do this, an obvious filter is if the code does not change over a
reasonable time then it is more likely to be Mode A than Mode C. But
an auto-pilot with very accurate altitude hold may break that
assumption. I'm pointing this out for completeness but it is actually
a non-issue for us since 1200 and 1201 (and 0440 for folks flying near
Reno, and all the emergency squawk codes etc.) do not alias to valid
altitude codes. It is a possible issue however with discrete allocated
squawk codes and I think I've seen it in practice with my Zaon MRX.
BTW this is the reason you would *not* want to try to have Mode C
equipped gliders in a gaggle with discrete squawk codes.

With Mode S transponders replying to Mode S interrogations things
quickly get more complex, but the good news is easy to correlate a
squawk code, and what is an altitude for a Mode S transponder replying
to a Mode S interrogation. But even better you don't need to worry,
you can mostly forget about the squawk code and instead use the
transponder's ICAO ID itself is the unique marker that differentiates
replies from different transponders.

Mode S transponders are a lot more advanced than Mode C transponders,
it's impressive that Trig can make the TT21 and get it to market at
what we used to pay for Mode C transponders (let alone that it also
does 1090ES data-out). There is no end-of life for Mode C in the USA
and Mode C transponders continue to give good visibility of gliders to
ATC and TCAS systems so I'd not hold my breath for lots of glider
owners to replace Mode C with Mode S transponders. Over time they may
do so to gain 1090ES data-out capability. But this stuff all starts
adding up in cost fairly quickly.

With a Mode C transponders (either an actual Mode C transponder or a
Mode S transponder being interrogated as a Mode A or CC) the is no way
in high density environments to really correlate an aircraft's
transponder Mode A interrogation reply (containing the squawk code)
and the same transponders separate Mode C interrogation reply
(containing altitude). The only thing that (unidirectionl) PCAS has to
go on is the strength of the RF signals and trying to guess that the
strength of a Mode A reply matches a Mode C reply. If the PCAS unit
like the XRX has directional ability that can help as well, it might
be able to help but it is likely to get very confused when the threats
are moving around relative to the antenna. This problem crops up in
general in transponder in multiple other situations and is sometimes
called "code swapping".

There were was at least one early PCAS systems that did display threat
aircraft squawk codes and that was kind of handy (gave a clue if a
threat was on flight following/plan for example). They seemed to do
that that pretty well in typical GA environments, but that would fail
in dense gaggles for the reasons described above.

If interrogators are coming from a single approach radar then
interrogations will occur every 5 seconds. If from an area radar every
12 seconds. These radars will interleave multiple Mode A/C/S
interrogations across the gaggle in each rotation. But the PCAS even
if it can decode the replies (ie. is not killed by synchronous
garbling) will start having problems trying to "track" Mode C targets
by comparing RF power strengths at these relatively large time
intervals given how sensitive the RF power received will be to
obscuration and relative antenna orientation. If it can decode the
replies it will have accurate altitude (+/- 100' for Mode C) for them.
And luckily in many places you'll get more frequent interrogation from
airborne interrogators or have overlapping SSR radar interrogations
(but most of those then won't be Mode A interrogations).

With Mode S transponders being interrogated by a Mode S system (most
radars and all TCAS systems, but there are still Mode C interrogators
out there) a PCAS system could use the Mode S ICAO ID to "keep track"
of separate aircraft. I have no idea if the PowerFLARM or other PCAS
do this. Once the Mode S transponders have done their initial
handshake with the interrogator they will be selectively interrogated
and so their replies will not suffer the same rapid synchronous
garbling problem that Mode C transponders do. Right now most
transponders in gliders are Mode C so synchronous garbling is likely a
very large issue. Also in very large gaggles like big contests you
will likely run into congestion problems with selective interrogation.
I'm not able to model that in my head and/or guess what the limit
really is. It depends on the mix of interrogations.

In a gaggle or dense glider type environment the received RF power of
another transponder depends on slant distance and also relative
orientation of both aircraft (especially with blanking effects) and
antennas. This is very different from PCAS working in a much more
stable type state environment with a few nearby powered aircraft
cruising along. I expect the distance guesstimates and filtering the
PCAS systems used to have lots of problems getting range accurately,
but then PCAS systems alarm mostly on altitude conflicts for this
reason.

(Getting off topic but..) For the glider on tow situation with two
Mode C transponders in a glider and tow plane you may get synchronous
garbling and see occasional strange jumps in the signals seen. Where
for for example at one point in time the PCAS might think it sees one
threat, (two Mode C transponders squawking the same altitude bit
pattern and mistaken for one transponder) then the as you climb a bit
later it sees a garbled reply (two transponders synchronous garbling
with slightly different bit patterns as one of the encoders rolls over
the next 100' mark). I suspect this is a cause of some of the
interestign things we see with Zaon MRX at times when on tow. And it
just varies a lot as to the relative strength of the towplane
transponder signal and the leakage of the local transponder seen by
the PCAS. Again with Mode S in both aircraft it would be relatively
trivial to disambiguate aircraft and deduplicate/suppress threats.

In a PowerFLARM environment with lots of gliders also with
transponders what you want to do is correlate the Flarm ID of a glider
with it's transponder signal (and also extend that to ADS-B as well)
and suppress the PCAS warning for that glider. This in principle is be
easy to do for Mode S. You just have have the Flarm transmitter also
transmit the aircraft's Mode S ICAO ID). With Mode C you are pretty
much out of luck. The Flarm box is only going to be able to guess at
best. And there is the trade off between suppression a duplicate alert
and suppressing a real alert. It is so insurmountable that personally
I'd not bother trying if I was developing the box. And to be clear, I
have no idea what Flarm does inside their PCAS system in PowerFLARM.

Hope that helps explain some of the issues.

Darryl

On 8/17/2010 11:42 AM, Andy wrote:
On Aug 16, 10:40 pm, Darryl wrote:
Again that was not what Andy was claiming.

I'd actually prefer it if I made the statements as to what I was
claiming.

I have actually claimed nothing about what PowerFLARM will do as
regard alert suppression.

I have, however, expresseed the hope that PowerFLARM will have
intelligent alert suppression of transponder based (PCAS) targets.
And by that I did mean suppression of certain PCAS targets but not
others.

Certainly it is possible for Power FLARM to determine the squawk code
of a received transponder. In areas where gliders are assigned a
specific discrete code then PowerFLARM could be programmed to handle
targets with this code in a different way from target not squawking
that code.

It would also be possible to track a target based on range and
altitude information. When on tow the tug's transponder signal will
indicate a constant range and a constant altitude difference. Any
other transponder target that could be a threat will appear at the max
detection range and then come progressively closer. It seems quite
reasonable to assume that a well designed system would allow
suppression of the tug alert but still alert for the approaching
threat. It would also be possible to remove the tug transponder from
the suppressed target list when tow release is detected by a
significant change in altitude difference or range.

Similary if I am in a gaggle with several gliders that have
transponders it would be possible to suppress alerting on all those
targets while they remain within a certain range but still provide
alerting to the King Air that approaches from max detection range and
is closing rapidly. Again the suppressed transponders could be removed
for the suppression list if they show an increase in range
corresponding to leaving the thermal.

So my hope is that, if a transponder equipped glider joined my thermal
I will be alerted. When I visually acquire the glider and decide it
is the one causing the alert I select mute. I will then no longer be
alerted to that transponder but will be alerted to any other
transponder target that approaches me. I will then chose to to mute
that alert if I wish, and still be alerted to the next on that
approaches.

All this assumes that the unit is smart enough to keep track of
individual targets based on range (signal strength), altitude, and
perhaps also squawk code. I see no reasons why this is not
technically possible but again make no claim that such a feature is
include in PowerFLARM

Andy
My gut feeling is that an algorithm like what you describe would be much
harder to implement than you envision.

In busy areas, where transponders are constantly being interrogated, you
might be able to track an isolated aircraft using just altitude and
range. Once you have multiple targets at similar altitude and ranges in
the same time periods, it would be very difficult to keep track of which
target is which without also knowing the bearing.

In remote ares the problem is much worse, as transponder interrogations
might not be happening with any regular frequency. As a result you may
see targets suddenly pop up and then disappear.

The only real solution is ADS-B or FLARM, which transmit the actual
position every second. The problem we face is getting everyone
(including power aircraft) to standardize on a single format, so
everyone can see everyone else. The FAA has told us that should be
ADS-B in the US (unfortunately they gave us the option for two flavors).
Hopefully we will see the price of this equipment drop in the next
couple of years to the point where everyone starts jumping on board.

--
Mike Schumann

On 8/17/2010 1:55 PM, kirk.stant wrote:

A. "Right Now Benefits of PowerFlarm" - This product does not currently
exist. Has it been submitted to the FCC for approval yet? What is the
expect ship date?

Later this year, which is fine for me. And FLARM itself is well
proven - even if that was all the PowerFlarm did it would be worth
it. UAT ADS-B isn't.

B. 1090ES ADS-B - You aren't going to see anything on PowerFLARM unless
you are also equipped with, and transmitting a properly configured ADS-B
Out Signal. That part is NOT provided by PowerFLARM.

Wrong. I'll see the 1090ES mode S directly. Which is exactly what I
want to see.

C. PCAS - How does PCAS tell you anything about what kind of target is
aiming for you? In fact, it doesn't give you any information on where
the target is, whether it's getting closer or moving away. All you know
is altitude and range (NO bearing). It's not going to tell you if it's
a jet, another glider, or your tow plane. And you are only going to get
that much info if the transponder equipped plane is being interrogated.
That's not a given if you are flying low in remote areas without radar
coverage.

If I look out the window and see a dot, all I know at first is that it
is something out there. I'll watch it until I determine if it's a
threat and react accordingly. PCAS helps me find that dot by warning
me to look level or slightly high/low, and if I already have an idea
where the traffic is coming from (arrival departure routes, VOR/
Airports nearby, VFR/IFR altitudes) I can focus my search there. What
else do you need, the pilot's daughter's phone number? The biggest
reason pilots don't see other traffic is not that it isn't visible,
but that they aren't looking for it - and PCAS/FLARM/ADS-B are all
designed to make the pilot get his head out of his PDA and look for
traffic.

What's my agenda? Making sure that people know what they are buying and
the limitations thereof.

Fair enough.

Cheers,

Kirk

When you get a PCAS alarm, the aircraft could easily be coming from
behind you or another blind spot. Or you could have two aircraft at the
same range coming from opposite directions. All PCAS (and PowerFLARM)
gives you is an alert to start looking. It doesn't come close to giving
you all the information you need to avoid disaster in certain situations.

A classic example of this was a couple of years ago when I was flying a
K-8 south of Mpls. Earlier in the day, we saw a couple of C-130s
heading south. About an hour later, I heard them coming up behind me
(low tech audio PCAS+). What do I do? If they saw me and were avoiding
me, a sudden turn could put me in their path.

With ADS-B, I could have seen exactly where they were and reacted
accordingly. With PCAS, I wouldn't be any better off than with my basic
hearing.

--
Mike Schumann

On Aug 17, 3:56 pm, Darryl Ramm wrote:

Hope that helps explain some of the issues.

Yes it does, thanks. You present a number of cases where the target
specific muting I would like to see could not be made to work.
However I still don't see that in some less severe scenarios it would
not be useful.

Right now I mute my MRX if I'm in a gaggle with one other glider that
remains inside my alert volume. I also mute my MRX if I'm in cruise
with one other glider that remains inside my alert volume. In many
cases I may forget to turn alerting back on after I separate from the
other glider. In either of those scenarios a target specific muting
with automatic removal from mute when leaving the alert volume would
be a huge improvement. The system would only need to track one target
and to recognize a new one for that to be effective.

The ZAON MRX manual indicates that multiple targets are tracked and
prioritized. Within all the other constraints you have detailed it
would not seem to be difficult to have mute defeated when a new target
of greater threat is detected.

"MRX tracks the most significant threat to your course of travel (the
primary aircraft). Should MRX determine that a new aircraft has become
a greater threat than the one currently being displayed, the unit will
beep once and “–NEW–” will be displayed for two seconds, followed by
the new aircraft information."

If NEW then MUTE OFF (obviously simplified).

It appears that the MRX would not alert for the case where a gaggle of
gliders gave synchoronously garbled replies. ("MRX boasts the unique
ability to filter out any erroneous signals and only display verified
transponder-equipped aircraft. Incoming signals must be completely
decoded, the Mode A/C must correctly correspond to a valid altitude
code, and MRX must be able to do this twice with the same aircraft.
This process, among others, virtually guarantees
that, if an aircraft information is being displayed, it can only be
from a valid transponder-equipped aircraft.")

Why wouldn't it be possible to alert to a new target that was not
synchronously garbled? (The King Air about drive through the gaggle.)

And there is the trade off between suppression a duplicate alert
and suppressing a real alert. It is so insurmountable that personally
I'd not bother trying if I was developing the box.

Isn't the trade off between suppressing all (PCAS) alerts with a
blanket mute function, or having the opportunity to alert to some, but
perhaps not all, higher threat (PCAS) targets.

Andy

p.s. The MRX manual is an interesting read for anyone that has no
experience with this unit. Click on the newsflash item at
http://www.zaon.aero/component/optio...man/Itemid,33/