Build your own PowerFLARM!
Darryl Ramm
device has been discussed in other threads. And as pointed out there I
think the renderings on the PowerFLARM web site makes the unit look a
bit larger that it really is.
Anyhow being a visual kind of person (and somebody who "thinks" in
Photoshop and Illustrator). I've made a very simple paper cutout model
that anybody interested in the actual size of a PowerFLARM can print,
cut out, fold and stick together. You can use this to see how the
PowerFLARM will look in your cockpit.
The PDF files are on my blog at http://www.darryl-ramm.com/2010/08/build-your-own-powerflarm-paper-model/
Maybe this would also be handy for leaving lying around the house and
using it to casually bring up with your better half why its a good
idea to spend some more money on the soaring addiction. :-)
Cheers
Darryl
sisu1a
> cut out, fold and stick together. You can use this
Darryl,
I downloaded the pdf and very carefully followed the assembly
instructions, then installed it in my ship, it looks great! It was
real quiet for a long flight I used it on, but that's to be expected
since there are no other units on other ships yet. Afterward I wanted
to download my flightlog to OLC but am having trouble extracting the
IGC file. Also got any tips on how to get it to work with an HP310
running SYM?
TIA,
-Paul
Darryl Ramm
Sorry you are having trouble Paul. Since these units are assembled by
the customer they do not include a factory warranty and it is hard to
guess what might be the problem. If you return the unit to me I will
get my service team to look at it straight away. Please enclose $200
with your return unit for inspection costs. Quote RMA #3AT-M3.
BTW I am also working on a UAT transceiver model for glider cockpits.
It consists of several hundred little paper cutouts of people and some
paper model meeting tables. And you can arrange and rearrange all the
little paper people around the meeting tables to show how UAT device
development works. (Oh I'm in trouble for that).
Darryl
Frank Whiteley
> OK this is kind of silly but the the actual size of the PowerFLARM
> device has been discussed in other threads. And as pointed out there I
> think the renderings on the PowerFLARM web site makes the unit look a
> bit larger that it really is.
>
> Anyhow being a visual kind of person (and somebody who "thinks" in
> Photoshop and Illustrator). I've made a very simple paper cutout model
> that anybody interested in the actual size of a PowerFLARM can print,
> cut out, fold and stick together. You can use this to see how the
> PowerFLARM will look in your cockpit.
>
>
> Maybe this would also be handy for leaving lying around the house and
> using it to casually bring up with your better half why its a good
> idea to spend some more money on the soaring addiction. :-)
>
> Cheers
>
> Darryl
I found the paper edition a bit delicate, so I ruggedized mine with
card stock.
Frank Whiteley
John Godfrey (QT)
Unfortunately there is a serious design flaw in the UAT transceiver
model. Without the augmentation of the model with additional little
tables containing coffee and donuts the development moves forward.
Retrofit kits can be obtained locally.
Mike Schumann
Why the insulting attitude towards UAT???? There are many people within
the FAA, MITRE, AOPA, and the avionics industry who have spent a decade
working on this technology. The technology is great. The deployment
strategy has been the problem, partly due to a lack of vision and focus
at the FAA and other foreign regulators, and a lot to do with the
logistical nightmare of converting from a 1940s technology to the 20th
century in a cost effective manner (just look at Digital TV for another
example of this kind of painful effort).
It doesn't help soaring the have glider pilots pissing on people like
this. There are people within the SSA (Bernald Smith for one), who have
been heavily involved in these issue for years and are trying to
represent soaring's interests within the broader aviation community.
When people in the FAA, AOPA, etc... read these kind of comments, what
do you think happens to our sport's credibility?
--
Mike Schumann
Darryl Ramm
wrote:
Gee Mike it was mostly put there because I miss hearing from you.
Our sport will have a lot more credibility if glider pilots were not
involved in so many-mid air collisions and don't get run into by fast
jets or scare airline pilots. I understand the *wish* to have a nice
single piece of technology that solves many problems. But people,
including you, who have strongly advocated UAT capabilities/technology
in the past would have more credibility of this was done with a calmer
and more holistic view of collision avoidance technology and UATs were
not presented as a silver technology bullet able to solve all
problems.
AOPA, EAA and FAA staff know well my concerns about ADS-D technology
and deployment, including for use in gliders, and don't need to read
r.a.s to find that out.
As I've stated before it would be great to give a low-cost UAT device
suitable for use in glider cockpits - including given how things are
look they are going a UAT transmitter to use with devices like the
PowerFLARM. However I get especially concerted when I see things like
UAT technology misrepresented by people as an obvious replacement for
transponders, people wanting to ignore serious issues like usability
and compatibility with existing glider cockpits, fanciful cost
projections and generally hyping UAT products. These are especially
concerning when they have a side effect of people delaying/skipping
adopting transponders where they should be used or technology like
Flarm in glider contests etc. So for reason alone I will keep
correcting UAT hype and exaggeration, and will do as well for other
collision avoidance technology. I'll praise UAT technology/products
when they deserve it. As I have said before UAT work to look at issues
of power consumption, RF specifications, GPS requirements etc. are all
interesting things, but they are long-term research and regulatory
projects, interesting maybe to many potential low-end users. There is
a huge difference between that kind of research and really developing
and convincing somebody to build a product that actually meets the
needs of our community.
The bureaucracy involved in all this is precisely one of the problems,
so I'm not going to apologize for making fun of that.
Darryl
sisu1a
> do you think happens to our sport's credibility?
Running the risk of being accused of having a sense of humor *can* be
pretty damaging, please censor yourself accordingly.
Kinda reminds me of a story I heard a few years back (forgot by who,
but it was out east...). A few syndicate owners of a glider found
themselves with an empty hole in the panel to fill so for kicks, one
of them took an instrument carcass and made a new Fun-meter
(Funometer?), with a nicely made scale and pointer to measure how much
fun was being had at any given moment, with "Fun" written on the scale
to indicate such. After rigging the ship one day, another club member
came up and was quietly studying the panel in the ship for a awhile,
puzzling over this new gadget. Eventually he pipes up and asks one of
the guys: "What does F.U.N.stand for"?
-Paul
Mark Berger
What does UAT stand for?
Mark
Dave Nadler
Was the stock reinforced with steel or Spectra ?
Darryl Ramm
Short answer...UAT stands for Universal Access Transceiver.
Long answer...
UAT is one of the two physical link layers used for ADS-B in the USA.
The other is 1090ES.
UAT stands for Universal Access Transceiver. Even though "transceiver"
is part of the name not all "UAT" boxes are transceivers, some are
receivers only and some might be transmitters (but by the time a
manufacturer goes to all the effort of building and certifying a
transmitter I expect them to include a receiver).
Ultimately UAT is specified by RTCA standard DO282B and 1090ES is
specified by RTCA standard DO260B and these specs are what roll up
into the FAA 2020 carriage mandates (for powered aircraft not gliders)
and TSO approval specs for the devices.
For powered aircraft 1090ES is required in the 2020 mandate for flight
above FL180.
1090ES layers on top of the data transmission and reception capability
in Mode S transponders. 1090ES operate on 1090MHz, the current
transponder reply frequency, hence their name. The "ES" part is for
"extended squitter", "extended" = larger data packet, squitter =
automatic broadcast without begin interrogated.
UATs operate on 978 MHz.
UAT are mostly a USA thing, Europe in particular has standardized on
Mode S transponders as a step towards 1090ES based ADS-B. That has
some implications on the glider community for products coming from of
Europe. Specifically this likely the reason the PowerFLARM contains a
1090ES receiver and not a UAT receiver. It is also the reason we have
interesting Mode S/1090ES capable products usable in gliders like the
Trig TT21.
Part of the original desire for UAT in the USA was to avoid congestion
on 1090MHz but I am far from convinced on that. The Europeans don't
necessarily agree with the USA analysis. TCAS, TCAD etc. hammering on
Mode C transponders especially consumes a lot of bandwidth. And one of
the ways to free up a lot of that bandwidth is to require Mode C
transponders to be replaced with Mode S. Sounds scary but much less if
we had started early to allow this to be done over 5-10 years. Now
ironically it looks at least to me that many GA aircraft are going to
equip with 1090ES data out it does not matter since they will be
transmitting on 1090MHz only - but at least that upgrade gets rid of
that aircraft's bandwidth wasteful Mode C transponder.
And Raytheon actually bid on the FAA ADS-B deployment contract as
1090ES only - kind of calling bullshit on many dual-link assumptions.
Ironically had their bid been accepted we might actually ended up with
a more usable ADS-B system.
A benefit of UATs over 1090ES is they will receive FIS-B data (e.g.
weather, TFR, NOTAM etc.) once the USA ADS-B ground infrastructure is
in place. This requires you have a display able to display the data
and line of sight to a GBT ground station (ie. you may not be able
receive on the ground at some locations, e.g. before flight).
The main benefit of 1090ES is it is layered on top of Mode S and that
capability is already in or can be added to current Mode S
transponders. Since carriage mandates in the USA for power aircraft
for transponders and ADS-B data-out equipment overlap I expect many GA
aircraft to equip with Mode S/1090ES data-out. UATs that meet the
carriage requirements once avaible at low cost might be compelling for
many lower end GA and sports airceaft with Mode C transpodners who do
not want to upgrade to a Mode S 1090ES capable transponder. For
gliders the interest there is a single box like a Trig TT21 can
provide transponder capability with airline and fast-jet TCAS *and*
provide ADS-B data out via 1090ES.
One of the desires of UAT is that maybe lower cost devices that
transponders could be produced. I am somewhat pessimistic of that
happening, especially not down to the sub $1,000 price point for a
transceiver which I suspect is completely unrealistic. Even if current
UAT specs are simplified the relatively small USA market for UAT
devices (large parts of the GA market I expect to go 1090ES anyhow)
will keep UAT pricing high.
UAT receivers may also be popular with all GA aircraft (and gliders?)
for receiving FIS-B (unlike with traffic you do not need any ASD-B
transmitter capability for FIS-B to work). The competition there is
for-fee XM Weather which may already has significant penetration
amongst people who want in-flight weather services. We'll have to see
how all this shakes out, including if widespread reception on the
ground is an issue, a free products vs. XM weather, etc. UAT FIS-B is
also expected to add commercial charge-for service data products in
future - I expect that to be hard to pull off against XM Weather.
The dual-link ADS-B scheme in the USA has some pretty unfortuante
implications on use of ADS-B in gliders, including like not being
usable with mixed UAT and 1090ES equipment when running ridges etc.
outside of GBT (ground station) coverage. I see no way around that at
the ADS-B level except the availability of dual-link receivers that
receive on both 1090ES and UAT links.
Traffic display and warning requirements, Flarm with ADS-B and Flarm
vs. ADS-B technologies has been talked about in other threads
recently.
Hope that helps. :-)
Darryl
sisu1a
Specra of course, steel can no longer be insured in the US. Jeez Dave,
I thought at least you were paying attention...
-p
Mark Berger
It helps a lot. Clearest introduction and explanation of all these
systems I've read. Thanks.
Mark
Darryl Ramm
And I should have added one thing that some folks like about UAT is
that it supports an anonymous mode. With 1090ES (or Mode S in general)
you are always transmitting the ICAO ID so the feds can always find
out who you are if they see you on radar or their ADS-B ground
systems.
Broadcasting who you are is not nice if you want to bust airspace and
hope to get away with it, but it is nice if the feds are trying to
find you in a SAR situation.
--
[Less useful digression... Anonymous mode also has me a bit concerned
about possible local UAT transmitter ghosting issues. Where a receiver
in the aircraft may mistake its local transmitter as belonging to
another aircraft or another aircraft's transmitter as belonging to it.
That's easy to untangle when you have an integrated system or single
box UAT transceiver but might start being a problem with other
portable avionics used in combination with a UAT transmitter or
transceiver. If UAT anonymous mode is used it removes an the obvious
filter of aircraft ID that a receiver manufacturer would use to keep
track of which transmitter signal is belongs to its aircraft. Maybe
this won't be a practical issue. There are several possible related
issues with ADS-B "ghosting" and target duplication for 1090ES and UAT
devices that we'll have to wait and see how well the devices and ADS-B
ground infrastructure does on this in practice. Especially given there
is a lot of flexibility in how vendors implement things of the
portable (non-certified) receiver products. I think all ADS-B is going
to take a while to shake out a lot of these issues in general].
Darryl
Rex
There are people in the SSA that where presented with the idea of the
Soaring Safety Foundation purchasing 100 FLARM units to rent to all
National Soaring Championship contestants.
This concept worked at the WCG in Australia a few years back for GPS
FRs. Look how that turned out.
The idea was to plant the seed at contersts and have the contestants
experience and learn what Flarm could do. Those pilots would take the
experience back to their regions and Flarm would certainly have been
discussed and I believe implemented.
But the "Supreme Leaders" of the SSA clearly have choosen to wait
for ADS-B.
I know the arguement about how Flarm would not work in the USA because
it would not protect Gliders from the airplane traffic in general.
I maintain that the greatest, threat of midair for gliders are other
gliders. Yes we have had airplane Vs Glider mid-airs. In my 28 year
soaring career, I can mostly recall the mid-air incidents happening
in contest gaggles. I suppose I can be proven wrong by a statistical
analysis of all glider mid-air incidents. I do not think I am alone
in my recollection of events driving my impression of risks.
Now here we are. For some reason the folks at Flarm have decided to
not market the proven design of Flarm, but instead, develope the
Power Flarm for the US market. I think it is going to be great. But
is shameful that the Soaring Society did not do anything to appeal to
the producers of Flarm, or the SSA membership to demand this
technology be available 4-5 years ago.
I (not so) patiently wait for word that PowerFlarm has shipped. I
will shamelessly market them as a dealer as I shake my head at what we
could have done sooner.
We should not stand in the way of the development fof ADS-B, UAT,
ES1090..... but the soaring market is not going to drive that
technology. I am surprised that the SSA spends a dime to be at the
table.
The SSA needs to finally endorse and promote for technologly that is
already developed.
I suspect the next response wil be that the technology is not
available in the US so my views are pointless. My answer to this is
B.S. as a group the SSA COULD have made Flarm happen but ADS-B was
simply choosen no matter that is was and is decades away from being a
useful reality.
Flame on......
Rex
Mike Schumann
The reason FLARM didn't take off in the US has relatively little to do
with the SSA. A big reason is that the FLARM folks not only
discouraged, but prohibited its use in the US when they initially
introduced the product. If they had agressively gone after the US
market then it's entirely possible that they would have had the same
success in the US as in Europe.
Now, 10 years later, ADS-B is finally getting some traction, and the
FLARM guys decide the US market is lucrative after all.
As far as mid-airs go, the statistics may be weighted towards
glider-glider accidents due to the much higher risks associated with
contests. Probably less than 10% of US glider pilots participate in
contests. For those of us that don't, getting hit by a GA aircraft (or
a jet), is just as big a concern as getting nailed by another glider.
In this market, I don't see a lot of interest in a solution that doesn't
address the entire threat environment.
--
Mike Schumann
Craig
> OK this is kind of silly but the the actual size of the PowerFLARM
> device has been discussed in other threads. And as pointed out there I
> think the renderings on the PowerFLARM web site makes the unit look a
> bit larger that it really is.
>
> Anyhow being a visual kind of person (and somebody who "thinks" in
> Photoshop and Illustrator). I've made a very simple paper cutout model
> that anybody interested in the actual size of a PowerFLARM can print,
> cut out, fold and stick together. You can use this to see how the
> PowerFLARM will look in your cockpit.
>
>
> Maybe this would also be handy for leaving lying around the house and
> using it to casually bring up with your better half why its a good
> idea to spend some more money on the soaring addiction. :-)
>
> Cheers
>
> Darryl
Thanks Darryl,
It's up and running, but when I hold it on one particular
configuration it shows a loss of signal strength. Will you be
offering rubber bumpers to address this issue?
Craig
Westbender
Darryl Ramm
wrote:
No solution addresses the entire threat environment. But you keep
coming back to seeming to think UATs and ADS-B do. And people are
interested in a solution that actually is available and actually is
usable to actually solve their problem(s).
Pilots are dying in glider on glider (and tow plane) collisions and
that problems just absolutely has to be addressed asap and Flarm is
clearly head and shoulders above any other choice of possible
technology that could help. And as we've been over several times
before is just no ADS-B product that provides collision alerts that
will likely work in a busy gaggle as no vendor or developer (except
Flarm) has focused work on the software needed for that scenario.
At least one benefit of the PowerFLARM unti with PCAS and 1090ES data-
in is it does span much more of the collision problem space than many
other options, including traditional FLARM units. And it starts with
the only practically avaiable glider-glider collision avoidance. With
PCAS it adds stuff that works today to help with many GA traffic
scenarios and has an ADS-B receiver that provides compatibility with
an ADS-B future in the USA. It needs an ADS-B transmitter to work
fully but by building the receiver part into the Flarm box you get the
data-in integration we need in our cockpits done properly (e.g. Flarm
serial display protocol for ADS-B traffic data, Flarm style alerts on
ADS-B data) etc. Talking any other ADS-B box UAT or 1090ES whether a
receiver or transceiver without that stuff (like the current Mitre
prototype or the Trig 1090ES receiver) is just a non-starter in out
market as a practical product (but for researching other long-term
technical and regulatory stuff the Mitre project does not need that
integration). There will be an increasing range of choices for devices
suitable for use in gliders for people who want to do full ADS-B with
the PowerFLARM as a receiver. Starting with the Trig TT21 today, and
hopefully also including UAT transmitters in future.
Darryl
Darryl Ramm
Just avoid holding it that way.
Darryl
Craig
Product support at it's finest ;-)
Thanks,
Craig
uncl...@ix.netcom.com
Maybe I was snoozing when the Flarm for competition proposal described
above was introduced. When was this? As chair of the SSA rules
committee, I admit to not having been made aware of this proposal.
In any case, my PERSONAL view (not speaking for Rules committee) is
that the mid air collision risk that most threatens us all is not the
glider to glider collision risk, scary as that is, but the risk that
one of our gliders is going to knock a jet out of the sky(that is what
will be described in the news notwithstanding who hit who).
Given my perspective, the coming Power Flarm device offers, from what
I read, a significant group of potential benefits not currently
available to us, once it is commercial and we can put them in gliders.
Hopefully that will be sooner than later.
FWIW- another opinion.
vaughn
<uncl...@ix.netcom.com> wrote in message
news:35b70b35-e8b3-477d...@z25g2000vbn.googlegroups.com...
>...the risk that
>one of our gliders is going to knock a jet out of the sky(that is what
>will be described in the news notwithstanding who hit who).
>Given my perspective, the coming Power Flarm device offers, from what
I share your concern about the potential negative effects of an airliner/glider
crash, but what role does Power Flarm have in preventing that?
Vaughn
uncl...@ix.netcom.com
> <unclh...@ix.netcom.com> wrote in message
As I understand it, Power Flarm will incorporate ADS-B ( protocall not
completely clear to me) as well as transponder PCAS annunciation.
Daryl need not jump in and repeat all that has been previously posted.
I know some forlks are putting together good information on a page in
Gliderpilot.net which will have much more good information.
If I believe their projections, this will offer a device that could
help in the competition environment while also providing at least a
basic degree of conflict warning during other flying which I don't
have now.
FWIW
UH
noel.wade
> As I understand it, Power Flarm will incorporate ADS-B ( protocall not
> completely clear to me) as well as transponder PCAS annunciation.
Here's a short Not-Totally-Technically-Accurate-But-Close-Enough
Explanation:
There are two "flavors" of ADS-B: 1090ES and UAT. The 1090ES system
is more likely to be used by big/fast airplanes. UAT is more likely
to be equipped on small GA aircraft. PowerFLARM supports 1090ES. It
does not support UAT or ground-based relays of traffic information
(according to the specs released so far). So you'll see some ADS-B
aircraft with the PowerFLARM; but you won't necessarily detect _every_
ADS-B aircraft. I believe that "some" ADS-B detection is better than
"none", especially when you add in the ability to see Mode C/S
transponders (when replying to radar pings) and other FLARM-equipped
gliders.
--Noel
(who will have a PowerFLARM this fall)
mattm
That looks like a pretty good explanation, but I'll clarify based on
what
I've digested from Darryl's excellent in-depth explanations. 1090ES
actually rides along with mode-S transponder replies, so if you have
a suitably equipped transponder (like the Trig) with the right flags
set,
you'll get informed by the ground transmitter of aircraft with UAT.
Plus, you'll know about any aircraft with 1090ES ADS-B, FLARM, or
mode A/C/S transponders (you'll only know altitude and distance to
those).
Given all that I'll be a PowerFLARM user as well (except it will be a
bit
longer for me to afford one), plus eventually the Trig.
-- Matt
Mike Schumann
You keep talking about PowerFlarm as if it were "available". It is not
currently shipping. Has it been submitted to the FCC yet for approval?
What is the estimated ship date?
ADS-B UAT transceivers are currently available and shipping and FCC
approved from Navworx and Garmin (granted the Garmin box is totally
overpriced and essentially obsolete).
Granted, there may not be any collision avoidance systems available for
ADS-B UAT transceivers that rival the sophistication of what FLARM
provides for gliders in Europe. There is no technical reason that
someone can't come up with the equivalent, or potentially even superior
solution as an open source or proprietary solution.
So rather than poo-poo any ADS-B solution, why not encourage people like
See-You, Clear Nav, and others to support both platforms and let the
best solution win.
--
Mike Schumann
Mike Schumann
see. By itself it does absolutely nothing to protect us against
mid-airs against jets.
--
Mike Schumann
Brian
> PowerFlarm is ADS-B In only. It only transmits FLARM, which jets can't
> see. By itself it does absolutely nothing to protect us against
> mid-airs against jets.
>
> --
except that it will tell you the jet near you before you mid-air if I
understand correctly
"transponder PCAS annunciation. "
uncl...@ix.netcom.com
wrote:
>
I respectfully disagree. The assumption that you must be transmitting
a signal to not get hit is not correct. Yes- a transponder seen by
TCAS in the jet is a significant benefit- some may say huge.
BUT- getting information that I have a conflict I don't know about
hugely increases my chances of taking action that could avoid the
disaster. We are more likely to make the disaster avoiding move than
the guys in the jet on autopilot talking to unicom to make sure Mr
Smith's limo will be at the gate.
UH
Mike Schumann
someone is near you at your altitude. You get altitude and distance,
but not a clue of which direction they are coming from. The jet and his
TCAS doesn't see you at all.
--
Mike Schumann
Andy
wrote:
> all you get is a warning that
> someone is near you at your altitude. You get altitude and distance,
> but not a clue of which direction they are coming from.
Having flown with the ZAON MRX for 2 seasons I find that alerting to
be useful. Certainly much more useful than "absolutely nothing to
protect us ".
As mentioned previously PowerFLRAM has the opportunity to be a big
improvement over the MRX if they include target specific alert
suppression. (let me mute the gliders I am thermalling with and still
be alerted to the B737 or King Air that is about to mow us all down)
Andy
uncl...@ix.netcom.com
wrote:
If I have a warning, I have a chance.
I'm convinced he will not avoid me.
UH
noel.wade
wrote:
> So rather than poo-poo any ADS-B solution, why not encourage people like
> See-You, Clear Nav, and others to support both platforms and let the
> best solution win.
Mike - Believe it or not, we're not "poo-poo"ing your precious Navworx
box. I think what most people are convinced of is that an ADS-B Out
box is not a sufficient solution. They want something that covers a
broad spectrum of signals and is also tuned for glider usage. The
PowerFLARM system fits this well. You are correct - the PowerFLARM
unit has not shipped; but it is being produced by a company that
already has thousands of devices sold & in-use, which lends confidence
in their ability to pull it off. By comparison, what company has
produced and sold a similar number (15,000+) of ADS-B units?
Oh, and I believe SeeYou and many other PDA/Flight-Computers already
support the FLARM protocol. If they support ADS-B systems as well,
great!
--Noel
Mike Schumann
Does anyone have any detailed technical data on how PowerFLARM is able
to distinguish a Mode C transponder equipped glider from a Mode C
transponder equipped powered aircraft?
ATC radar can track an individual Mode C transponder equipped aircraft,
because it can not only see the range and altitude of the aircraft's
location, but also the bearing. The PowerFLARM unit can not track the
transponder bearing, so some healthy skepticism is in order on the claim
that they can intelligently suppress glider induced false alarms while
not inadvertently also suppressing some real collision threats.
--
Mike Schumann
kirk.stant
wrote:
Mike, what is your agenda? You seem determined to trash the potential
right-now benefits of PowerFlarm for the dubious future advantage (to
glider pilots) of ADS-B (specifically the REALLY stupid UAT part of
it). Worried about an airliner hitting you and not smart enough to
look out the window when PCAS tells you there is a big jet nearby? Get
a Mode S transponder. Or you can look at a chart and figure out the
arrival and departure routes of the local airlines and look in that
direction when you get a PCAS warning! Ditto lightplanes - they are
most likely cruising at VFR or IFR hemispheric altitudes, so if the
relative alitude is not changing, look in that direction! (Unless your
altimeter is set to QFE, of course....) What I want a FLARM device
for is to warn me of the not so random presence of other GLIDERS!
Here is a simple mental exercise: 2 power planes takeoff from the
same airfield. No coordination between the two. What is the
probability that they will have a midair? Now, two glider launch from
that same airfield, on a good soaring day. What is the probability
that they will have a midair? Let's see, the power planes have all
day to pick a time to go, and they can go in any direction, at pretty
much any altitude, to pretty much any destination. OTOH, the gliders
will likely launch at about the same time, and go the the best lift,
fly in the same altitude band, and return at roughly the same time.
THATS WHY ADS-B IS LESS IMPORTANT TO GLIDERS THAN FLARM!
And on the ridge on a good day? Yikes!!! 200knot closure, 50 feet
above the trees. Yeah, ADS-B is going to be lots of help there!
But here is a question: PowerFlarm claims it can detect ADS-B 1090ES
signals and provide bearing/rangealtitude info; it's just the legacy
Mode C transponders that will only give a range/relative altitude
warning (similar to PCAS). Are you saying that this is not possible
and that you also need a UAT in/out box to detect Mode -S equipped
1090ES ADS-B participants? I understand that with only a Powerflarm
you won't see UAT - only participants - but since they will probably
still need Mode C even that isn't true - you are just down to PCAS
level of detection. Please correct me if I'm wrong on this.
Finally, all this reminds me of my days sailing a Laser in the
Intercoastal waterway - sure I had right of way over the big barges
in the shipping channel, but no way was I going to push it! Ditto
airliners. If you are so clueless that you miss an airliner coming at
you on a VFR day, when you should know where he is coming from, and
have a 5 or more mile warning from your PCAS or PowerFlarm, you
shouldn't be flying there! Or just pony up for a Trig and be done
with it!
Finally, how about SSA working on the insurance companies to give
pilots who fly with anti-collision devices and transponders a break on
their insurance? I read somewhere Italy does that for FLARM. A 10%
reduction on my annual premium would go a long way!
Rant off/
Kirk
66
Saving my pennies for a PowerFlarm for next season (and a Trig in the
future) but not holding my breath for UAT or ADS-B
Mike Schumann
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?
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.
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's my agenda? Making sure that people know what they are buying and
the limitations thereof.
--
Mike Schumann
Darryl Ramm
wrote:
> On 8/16/2010 7:47 PM, Andy wrote:
>
>
>
> > On Aug 16, 5:14 pm, Mike Schumann<mike-nos...@traditions-nospam.com>
> > wrote:
> >> all you get is a warning that
> >> someone is near you at your altitude. You get altitude and distance,
> >> but not a clue of which direction they are coming from.
>
> > Having flown with the ZAON MRX for 2 seasons I find that alerting to
> > be useful. Certainly much more useful than "absolutely nothing to
> > protect us ".
>
> > As mentioned previously PowerFLRAM has the opportunity to be a big
> > improvement over the MRX if they include target specific alert
> > suppression. (let me mute the gliders I am thermalling with and still
> > be alerted to the B737 or King Air that is about to mow us all down)
>
> > Andy
>
> Does anyone have any detailed technical data on how PowerFLARM is able
> to distinguish a Mode C transponder equipped glider from a Mode C
> transponder equipped powered aircraft?
It cannot. You should know that Mode C includes no identification
about aircraft type or other information. But that is not what Andy
was saying.
Andy was pointing out PowerFARM has detection type suppression (e.g.
suppress PCAS and just tell me about Flarm threats.) Contest pilots
will absolutely need this in large gaggles if a reasonable number of
those gliders have transponders (esp. Mode C).
> ATC radar can track an individual Mode C transponder equipped aircraft,
> because it can not only see the range and altitude of the aircraft's
> location, but also the bearing.
>
> The PowerFLARM unit can not track the
> transponder bearing, so some healthy skepticism is in order on the claim
> that they can intelligently suppress glider induced false alarms while
> not inadvertently also suppressing some real collision threats.
Again that was not what Andy was claiming.
But issues with transponders in gaggles really has little to do with
tracking direction, there is no directional PCAS (i.e. Zaon XRX) or
TCAD or TCAS system that has a hope in hell of working in a really
crowded gaggle type environment. Especially not one with a good
fraction of those gliders having Mode C transponders. That is what
Flarm is for.
Please no hate mail from PCAS users, I have a Zaon MRX and love it as
well, but things will hit the wall in crowded environments.
The PowerFLARM PCAS capability as a very nice adjunct to it's Flarm-
Flarm capability, handy out on course against transponder equipped
gliders and against GA traffic etc.
> --
> Mike Schumann
Yes we know.
Sigh.
Darryl
Rex
a glider, light airplane, heavy jet or business jet, so that I can
look for and possibly avoid it.
I do not want to hope that it is equipped with TCAS and count on the
other pilot being alerted to my transponder presence and avoid me. My
glider is much less visible than any other aircraft so I will have
the better chance of seeing and avoiding the traffic. For this reason
I feel the Zaon Pcas is enough protection for glider to airplane
collision threat. However, Powerflarm (when available) is a better
solution for areas were there is a high concentration of gliders (more
than 1 actually). When thermalling or ridge soaring, I do not want to
be allerted every time a glider is with in 3 miles of me. I only want
to be alerted to the one that poses a high threat of collision. I do
want to be alerted to transient airplane traffic with in 3 miles. So
in my world, I would not install transponders in gliders unless the
glider was operated in airspace where transponders were required.
I sell, install and certify transponders in gliders and I think they
are reasonable tools to have but I will fly with and equip my fleet
gliders with PowerFlarm.
Rex
Williams Soaring Center
Darryl Ramm
> On Aug 16, 4:41 pm, Mike Schumann <mike-nos...@traditions-nospam.com>
> wrote:
>
> But here is a question: PowerFlarm claims it can detect ADS-B 1090ES
> signals and provide bearing/rangealtitude info; it's just the legacy
> Mode C transponders that will only give a range/relative altitude
> warning (similar to PCAS). Are you saying that this is not possible
> and that you also need a UAT in/out box to detect Mode -S equipped
> 1090ES ADS-B participants? I understand that with only a Powerflarm
> you won't see UAT - only participants - but since they will probably
> still need Mode C even that isn't true - you are just down to PCAS
> level of detection. Please correct me if I'm wrong on this.
Kirk let me try to give you a useful answer to your actual questions.
Let me know if I do not cover them all enough.
Also see my more technical post in the "Flarm in the USA" thread
(Google News users see if this link works... http://bit.ly/9jOA1p)
The PowerFLARM 1090ES receiver will "see" ADS-B 1090ES data-out
equipped aircraft aka "ADS-B Direct". Which means you will start
seeing some early adopter 1090ES equipped traffic now and by the end
of this decade you will see all airliners, all fast jets, all
turboprops, and many high performance singles and twins - they all get
caught in the above FL180 requirement for 1090ES data-out in the 2020
carriage mandate. I expect you will also directly see most mid-range
and above GA aircraft as I expect many of those will meet ADS-B data-
out requirements by upgrading their Mode S transponders with 1090ES.
We'll have to wait and see what actually happens in that lower-end
market.
The PowerFLARM will see Mode C and Mode S transponders via (non-
directional) PCAS if those transponders are being interrogated by an
external source (SSR radar, TCAS, TCAD etc.). Mode S transponders that
have 1090ES data-out would be seen via 1090ES and the PowerFLARM
should automatically suppress the PCAS alert for that threat (its
technically trivial and obvious to do that).
Kirk you are correct in that UAT data-out equipped aircraft will
likely have a transponder and therefore a PowerFLARM would see them
via PCAS (if the transponder is being interrogated). Aircraft flying
in airspace that requires them to have ADS-B also requires them to
have transponders. So I expect the common configs to be Mode S with
1090ES or UAT with Mode C. Although you could have both UAT and ModeS/
1090ES or Mode S (with no 1090ES)and UAT. Powered aircraft not
required to have transponders because they don't fly in/near
controlled airspace/above 10,000' etc might voluntarily equip with UAT
only (no transponder) over time to get benefits of ADS-B data-in. But
I expect this to be a small group (who wants to build up an expensive
panel but limit severely where the aircraft can fly).
Without an ADS-B transmitter you will not reliably receive ADS-R (ie.
you won't reliably see any other UAT data-out equipped traffic) or TIS-
B (ie. you won't see the ADS-B relay of SSR radar position data for
other aircraft. And TIS-B only works where there is current SSR ATC
radar coverage). By not reliably, I mean you *really* need an ADS-B
transmitter if you you want to receive TIS-B or ADS-R. You may see
some TIS-B and ADS-R aircraft near other ADS-B data-out equipped
aircraft just not near you - not a good thing. And the danger for
people who do not understand what is going on is they will see some
ADS-B traffic on their ADS-B receiver system. But not realize they
could be missing lots of ADS-R and TIS-B traffic if they don't have a
(correctly configured) ADS-B transmitter.
TIS-B will be interesting as it can give you pretty nice traffic
information if you fly where there is radar coverage (and high enough
to be in that coverage). You also need ADS-B ground station coverage
for this to work - which is rolling out over the next few years for
the entire USA.
As pointed out by people in other threads the PowerFLARM will add TIS-
B support some time after first availability, and so until TIS-B is
supported at all in PowerFLARM it is irrelevant whether you have a
transmitter or not. There are very few UAT data-out equipped aircraft
yet so ADS-R is likely not that interesting (existing UAT deployments
up to now have been mostly in Alaska in ADS-B trials).
And to be clear the challenge here will not be PowerFLARM receiving a
TIS-B data message its working out how to effectively warn about that
traffic with as few false alarms as possible with the inherently less
precise location information that a TIS-B threat has (because the
threat location comes from SSR radar). So somebody could jump up and
down now and claim their UAT or other box receives ADS-R and
PowerFLARM does not. That claim really requires looking at details of
how the internal or external traffic display and threat warning part
handles TIS-B threats.
---
OK now some more editorializing...
Personally if I had to chose only to have an ADS-B receiver I'd much
rather have a 1090ES receiver than a UAT receiver because starting now
and getting better over time it will show 1090ES equipped airliners
and fast jets directly and over a long range and all altitude
difference (the display software always needs to let you limit that -
I don't know what PowerFLARM does there, I trust them to get it right
or it to be what glider pilots need). As better/cheaper/smaller/etc.
UAT transmitters or transponders and the GPS systems to drive become
available I can add that device and do full ADS-B.
With a UAT receiver only and no transmitter you won't reliable receive
position data from airlines, fast jets or high-performance singles.
But then if you go the next step and install an ADS-B transmitter (UAT
or 1090ES) you will only be guaranteed of seeing TIS-B and ADS-R
threats that are wihtin the "service volume" around your aircraft,
typically +/- 3,500' and within 15 nautical miles of you (there may be
velocity/time to enter threat volume enhancements of this like there
is for Mode S TIS, but good luck finding out how that works). I'd just
much rather directly receive the 1090ES ADS-B data-out from the big
fast airliners and fast jets. I might feel differently if I was
worried about a lot of GA traffic with UAT data-out. But I'm not sure
that UAT data-out is going to get much penetration in GA at all, we'll
have to wait and see.
I am not advocating relying on traffic awareness tools in the glider
cockpits as the the primary technology adjunct near high density
airliner and fast jet traffic - for that the best idea is put a Mode C
or Mode S transponder in your glider and let the combination of ATC
and TCAS II look out for you. A TCAS II RA likely gets anybody's
attention off the rental car reservations and back on flying the jet,
or at least just doing what the RA tells them.
In the USA ADS-B is going to roll out big time this decade, but right
now it still is mostly futureware. Nice neat geek stuff for early
adopters to worry about now. On the other hand I'd be concerned to
see hundreds of glider pilots in the USA rushing out now to buy Flarm
classic (Flarm protocol only) units even if they were available in the
USA (which they are not). Those pilots will likely be pleasantly
surprised what PCAS can do now outside of crowded contest
environments, and how 1090ES direct can show them some traffic and
what more they can get if they want to add ADS-B data-out in future.
The USA is different from Europe and other places where gliding is
popular, we don't have any flarm adoption here yet, and yet we are the
most advanced ADS-B strategy and rollout happening from GA up to
airliners. I really like that PowerFLARM combines both. (And to be
very clear by "most advanced" here I mean in terms of having
regulations in place that require so many aircraft to equip with ADS-B
data-out on a hard time line (by 2020), not "most advanced" as in
actually being a more sensible or coherent ADS-B or airspace strategy
compared to other locations like Europe.).
Hope that all helped.
Darryl
Darryl Ramm
wrote:
> On 8/16/2010 10:50 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?
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
Andy
> 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
Brad
will all this muting and un-muting cause a large increase in pilot
work load?
Thanks,
Brad
Andy
> 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
kirk.stant
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
kirk.stant
> 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
Darryl Ramm
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
Mike Schumann
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
Mike Schumann
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
Andy
> 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/option,com_docman/Itemid,33/
kirk.stant
wrote:
>
> 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.
>
> --
>
I still have to disagree. Using your example, with PCAS you would
have been warned well prior to hearing the C-130s. If the warning
continued to show decreasing range, and possible altitude conflict,
and you could not see the threat aircraft in front, then a turn to
check 6 would put you in a position to see them (hard to miss two
Herks). As far as the concern that a turn will put you in their path,
think of the relative speeds and distances involved. Unless the other
plane is right on top of you, your turn is not going to move you in
space very much, but on the other hand may make you visible to the
other plane and allow normal rules of the road to apply.
Mike, I don't disagree that ADS-B, when fully implemented, will be a
wonderful thing - for GA. I've been using the military version
(JTIDS) for years and love it, but unless the hardware requirements
come down to something reasonable it will take a while to get into
gliders. Flarm, OTOH, is here now, and solves some nasty, glider
specific problems (which ADS-B will probably never do, given the
market). Unlike you, I am comfortable with the level of warning that
PCAS gives me for transponder - equipped threats (especially VFR
traffic that won't see your transponder or be talking to Center). I
also am comfortable staying away from airliners - but I'm not flying
near Minden/Reno. Around Phoenix, I know pretty well where the
heavies are and scan accordingly.
I also think the nature of glider flight makes the chance of a midair
with another glider much higher than that of getting hit by an
airliner or GA plane. My experience in 2500 hours of gliding, all
over the US, supports that view.
Kirk
Dave Nadler
> ... 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.
Sorry I missed this earlier, to amplify one of Darryl's points...
You can set the aircraft ICAO ID in the FLARM config file,
in which case this is used instead of the distinct FLARM unit ID.
Hope that helps,
Best Regards, Dave