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"Do It Yourself" airborne proximity warning device



 
 
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  #11  
Old December 10th 13, 10:41 PM posted to rec.aviation.soaring
Sarah[_2_]
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Default "Do It Yourself" airborne proximity warning device

Well, define "accurate", and "could put in a glider".

I've never seen one, but the rather boxy Zaon "XRX" was supposed to give azimuth information. I believe it was crude ( quadrant or octant ), and I have no information about how well it worked other than reviews. I have a Zaon "MRX", which is a small altitude-only reporting receiver, and find it useful. Too bad Zaon closed operations recently.

Review: http://www.flyingmag.com/avionics-ge...oidance-system

On Tuesday, December 10, 2013 2:34:45 PM UTC-6, wrote:
...


I am not aware of any system you could even adapt to put in a glider that would allow you to get accurate azimuth information off of transponder returns - even in theory.



9B

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  #12  
Old December 10th 13, 11:02 PM posted to rec.aviation.soaring
[email protected]
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Default "Do It Yourself" airborne proximity warning device

On Tuesday, December 10, 2013 1:41:26 PM UTC-8, Sarah wrote:

Well, define "accurate", and "could put in a glider".


Fair enough.

If you were able to put TCAS in a glider that would do it, but trying to get azimuth information off of passive monitoring of radar returns (like PCAS does) has to be a hit-or-miss proposition (pun intended) since you don't have the ability to actively interrogate other transponder-equipped aircraft to string together enough bits of information to get good direction. You are dependent on ground radar or TCAS-equipped aircraft to do the interrogating for you which is no always reliable. Some sort of directional antenna added to a PCAS might help in the way you describe (showing quadrants), but I have to believe it's not the sort of thing you could really count on and would totally suck for glider-glider scenarios.

I'd also add that the research shows that no matter how diligent the scan, see-and-avoid detects not more than half the targets that are collision threats. Non-threats are much easier to pick up because of the angular movement of non-collision targets. So, the fact that you see other aircraft when you are flying to some extent generates a false sense of security - your are much less likely to see the one that's going to actually hit you. There are scenarios in the research where successful detection in time to act is on the order of 10-20%. That gave me some pause.

9B



  #13  
Old December 11th 13, 02:20 AM posted to rec.aviation.soaring
kirk.stant
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Default "Do It Yourself" airborne proximity warning device

On Tuesday, December 10, 2013 12:19:07 PM UTC-6, Dan Marotta wrote:
Maybe someone should develop a device like the MRX PCAS which detects

transponders and includes azimuth in addition to range and elevation.


Hmm, that's exactly what PowerFlarm does with ADS-B/mode S targets. Which are becoming more and more common, and includes pretty much all fast movers and advanced GA planes. Plus PF gives you the same data as an MRX (I have both - now use the MRX for towplanes and club gliders). And you get really good (as in Link-16 good) glider to glider cooperative data.

So lets see - I believe you have a transponder in your glider (about $2k) and a MRX $500 and I assume a parachute (about $2k). So you see the risk is airliners (transponder for TCAS), lightplanes (MRX), and something that will make you need to make a nylon letdown. But by your own statistics, the PowerFLARM is more useful than the parachute, replaces the MRX, and lets you see airliners BEFORE they run you down or have to maneuver around you ("Hey, FSDO, get that clown in the glider out of our approach path!"

To me it's a no-brainer. Where I fly, the transponder provides the least protection, so I haven't yet tried to squeeze one into my '6. But having experienced the SA that the PF provides in a glider-rich environment, and the SA it gives on nearby power traffic, I don't like flying without it anymore!

Of course, we all have to make decisions based on our perceived risk - but i find your dismissal of PF a bit perplexing, especially since you use the much more limited MRX and count on your xponder to keep from getting run over by a fast mover!

Oh, yeah, see and avoid. Right. How about BIG SKY theory - that's really what keeps the midairs down to a tolerable level in the US. In France they finally realized that they no longer have the luxury of a big sky, and now FLARM is mandated for all gliders.

Not so dumb, those cheese-eating surrender monkeys!

Kirk

OT, I just spent 9 months working in France. Sure was nice being in a civilized, modern country. Coming back to St Louis was like being sent off to a third world country! But hey, at least we have more cable channels!
  #14  
Old December 11th 13, 02:27 AM posted to rec.aviation.soaring
son_of_flubber
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Default "Do It Yourself" airborne proximity warning device

This project lends "Blue Screen of Death" an entirely new dimension of meaning http://en.wikipedia.org/wiki/Blue_Screen_of_Death

I'm an enthusiastic supporter and participant in the whole Open Software/Hardware and Maker movement, but given the stakes, I have very mixed feelings about this project. A collision warning system that you cannot trust can potentially cause more harm than good. What if the system tells you to "turn right" when you should "turn left"?

A collision warning system needs to be about as reliable and trustworthy as the software and hardware that implements the ABS in your car. Implementing an ABS system properly is a whole order of difficulty beyond developing something like the very wonderful and amazing XCSoar. A defect in XCSoar is unlikely to kill you.

One thing that can in some cases make open source software and hardware more reliable and trustworthy than proprietary systems is the effect of having a large developer community scrutinizing the source code and hardware. Linar's project presently has one developer. It also helps to have a large and diverse group of users banging on the system and reporting defects.

It is an exciting time when individuals like Linar can pull together a bunch of existing building blocks and rapidly prototype a new idea. But there is an inherent fragility in any system that relies on multiple "black boxes" and a collision warning system needs to be extremely robust. Black boxes often do not do what they are advertised to do, when you use them in unanticipated ways. Just because something works when you turn it on does not mean that it is reliable.

If Linar's approach has a real potential to deliver a collision warning system at lower cost and/or higher reliability than PowerFlarm, then I hope that he obtains the funding that will allow him to pursue this project in earnest. An opensource collision avoidance system has the potential to be superior to PowerFlarm. PowerFlarm might be more reliable and better functioning if they made the software open source (but their business model does not allow that).
  #15  
Old December 11th 13, 05:13 PM posted to rec.aviation.soaring
kirk.stant
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Default "Do It Yourself" airborne proximity warning device

Ok, lets get real here. This sounds like a nice little club project, and if the intent is to have all the club gliders equipped (as opposed to none with Flarm) then it has some value.

However, in the big scheme of things, it would have to be orders of magnitude less expensive and better performing to be able to overcome Flarm's lead (see France, Australia, etc.). And let's face it - most glider pilots are not going to cobble together a piece of kit like that - we'll pay extra for the fancy bells and whistles!

Let's take another example: I'm sure we can come up with a less expensive, better quality radio communications system to replace the old VHF system we now use for aircraft/ATC communications. But until everybody has a compatible system, you can only talk to the others who have the same system - so is your new system that much better? So we are stuck with an archaic AM radio system that you have to have, and it's good enough.

Now, what would be nice is an inexpensive ADS-B "out" box that would let gliders broadcast their position into the ADS-B "system" without needing a full up UAT/Mode S/WAAS IFR certified GPS setup. One of those, plus a PowerFLARM, would be a really nice setup.

Kirk
66
  #16  
Old December 11th 13, 05:51 PM posted to rec.aviation.soaring
Dan Marotta
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Default "Do It Yourself" airborne proximity warning device

Excellent reply!

I tried several keywords and the midairs I found in the NTSB database were
those that I listed. I will accept your assertion that there are more - I
just couldn't find them.

While reading your response regarding Flarm being better than a transponder,
it occurred to me that, where I fly that is just not the case. Due to the
altitudes that we fly, pretty much all powered aircraft have to have
transponders (above 10,000' MSL), and there are probably less than a dozen
of us that venture far from the airport. Our airport is also very lightly
used by power traffic and the cross country pilots usually return late in
the day after all hangars are closed. Our only major concerns are the IFR
arrival and departure routes which are near the airport. So, speaking
purely from my flying situation, a transponder is a far better solution than
a Flarm.

Your situation is, of course, different.

wrote in message
...
On Tuesday, December 10, 2013 10:19:07 AM UTC-8, Dan Marotta wrote:

I used the keywords "midair" and "glider" in my search but there may well
be
others which I missed. My point is that, considering the number of glider
flights conducted in the US, the risk of a midair is extremely low and, in
my opinion, does not warrant the expense, complexity, or distraction of a
collision warning device for most of the glider flying done in the US.
Competition flying is different, of course, as it concentrates so many
gliders in the same airspace. Europe is much more congested and has far
more glider flights than we do and I can see more of a benefit for them.


And, finally, for a good many of us glider pilots, we cannot simply lay
down
for an ASG-29, full panel, and Cobra trailer. For us, the sport is
somewhat
cost driven.



For some reason it is hard to get the NTSB database to cough up all the
incidents. You missed several midairs I know of in the past 5 years or so
including one requiring a bailout and one where one pilot tried to bailout
but was unable to and thankfully was able to land without injury. That
doesn't include a number of scary near misses.

I believe the data shows that midair is the second leading cause of fatality
next to stall-spin/collision with terrain. Glider-glider collision is at
least ten times likely as glider-GA collision and (by the data) infinitely
more likely than glider-air transport collision. If we ever got one of those
it would be ugly and bring the stats up to making glider-glider 100 times
more likely than glider-air transport.

Yes, contests gather gliders and concentrate traffic but if you look at the
some of the work that has been done to accumulate OLC traces into glider
flight path "heat maps" you discover that the combination of topography,
airports, airspace and (especially) lift sources puts gliders in much closer
proximity to each other than you might otherwise think. Gliders tend to
occupy a small, common proportion of the available airspace, even though we
think we are flying just anywhere. This explains why we see more
glider-to-glider collisions than any other kind of glider involved
collision. It raises the question as to whether if forced to trade off
transponder vs Flarm for cost reasons the most bang for the buck really
might be Flarm, even for non-contest flying near terminal areas. The midair
collision data suggests this might well be true since the penetration of
Flarm and transponders in gliders are both low. The equation would only flip
for very small numbers of gliders (5) flying right up against a busy
international airport - though there aren't many of these. I carry both
Flarm and a Mode S, but I realize others feel they can't afford both, just
the way some feel a parachute isn't worth the cost (I believe there also are
fewer successful bailouts than glider-glider midairs - so selling one's
parachute to buy a Flarm may also be a statistically superior solution -
though emotionally I can't imagine anyone making the switch).

In any case, having two, incompatible, Flarm-like technologies is a terrible
idea for the reasons already articulated.

9B

  #17  
Old December 11th 13, 05:54 PM posted to rec.aviation.soaring
Dan Marotta
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Default "Do It Yourself" airborne proximity warning device

Sorry, Steve.

I misinterpreted your use of the term "avionics" to mean certified. Please
see my recent post concerning those statistics and flight environment and
how they led me to my conclusion.

Dan


"Steve Koerner" wrote in message
...
Hey Dan,

There is actually nothing in my posts that implies that PowerFlarm is FAA
certified. I know that it's not and I have no concern that it's not.

Moreover, though your collision statistics are incomplete, your data would
in itself drive me to an entirely different conclusion than the one that
you prefer.

GW


  #18  
Old December 11th 13, 06:07 PM posted to rec.aviation.soaring
Dan Marotta
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Default "Do It Yourself" airborne proximity warning device

Sorry, but you got incomplete information. I checked your link and the
Raytheon radar is just a part of one of the systems produced by Sensis Corp.
(now Saab-Sensis).

The rotating antenna on top of the control tower is either an FAA ASDE-3
radar or an ASDE-X (Raytheon) radar. ASDE-X and ASDE-3X (using the FAA
radar) fuse data from radar and transponders, both airborne and on the
ground, into a position/altitude. The radar is an adjunct to TDOA and FDOA
(time and frequency difference of arrival of signals) geopositioning and
aids in position accuracy, but is not required to generate a position.

My statements come from prior work as Test Director during acceptance of the
ASDE-3X system at Louisville, KY (SDF). There are 30+ of these systems
worldwide at major and second tier airports.

The company that produced ASDE-X and -3X also setup systems in Colorado and
Alaska which allowed ATC to derive aircraft positions in remote areas which
have no radar coverage.

There were additions in the concept stage when I left the company that
included in-cockpit displays of traffic detected by the system but that was
over 5 years ago and I have no idea of whether they ever came to fruition.
But, like anything aviation related, it would probably cost both arms and
legs.

wrote in message
...
On Tuesday, December 10, 2013 10:19:07 AM UTC-8, Dan Marotta wrote:

Maybe someone should develop a device like the MRX PCAS which detects
transponders and includes azimuth in addition to range and elevation.
Most
of the algorithms have already been developed. There are well established
methods for very accurately locating a transponder. Look up ASDE-X, for
example (LAT/LON/ALT derived from transponder replies). Alas, I suspect
development cost would far outweigh expected return on investment.


I looked it up - ADSE-X is an active radar system that uses either a
rotating or phased array antenna (apparently normally mounted on top of the
control tower). It's not the sort of thing you'd find you could fit in a
glider - even if it were legal. Here's a long to a schematic of the
Raytheon version:

http://avstop.com/stories/asde.html

I am not aware of any system you could even adapt to put in a glider that
would allow you to get accurate azimuth information off of transponder
returns - even in theory.

9B



  #19  
Old December 11th 13, 06:12 PM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,335
Default "Do It Yourself" airborne proximity warning device

You don't need directional antennae. Without getting too long winded (I
know, I know...) you monitor the arrival times and frequencies of the
interrogation signals and the replies and combining that with your known
position, you can mathematically determine the positions of all the
emitters. Multiple samples enable the system to determine velocity (a
vector of direction and speed).


wrote in message
...
On Tuesday, December 10, 2013 1:41:26 PM UTC-8, Sarah wrote:

Well, define "accurate", and "could put in a glider".


Fair enough.

If you were able to put TCAS in a glider that would do it, but trying to get
azimuth information off of passive monitoring of radar returns (like PCAS
does) has to be a hit-or-miss proposition (pun intended) since you don't
have the ability to actively interrogate other transponder-equipped aircraft
to string together enough bits of information to get good direction. You are
dependent on ground radar or TCAS-equipped aircraft to do the interrogating
for you which is no always reliable. Some sort of directional antenna added
to a PCAS might help in the way you describe (showing quadrants), but I have
to believe it's not the sort of thing you could really count on and would
totally suck for glider-glider scenarios.

I'd also add that the research shows that no matter how diligent the scan,
see-and-avoid detects not more than half the targets that are collision
threats. Non-threats are much easier to pick up because of the angular
movement of non-collision targets. So, the fact that you see other aircraft
when you are flying to some extent generates a false sense of security -
your are much less likely to see the one that's going to actually hit you.
There are scenarios in the research where successful detection in time to
act is on the order of 10-20%. That gave me some pause.

9B



  #20  
Old December 11th 13, 09:07 PM posted to rec.aviation.soaring
[email protected]
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Posts: 220
Default "Do It Yourself" airborne proximity warning device

On Wednesday, December 11, 2013 9:07:33 AM UTC-8, Dan Marotta wrote:

But, like anything aviation related, it would probably cost both arms and
legs.


Maybe someone should develop a device like the MRX PCAS which detects
transponders and includes azimuth in addition to range and elevation.


Thanks for the info on the ASDE-X system Dan - I think you are right that it's unlikely to make a cost-effective anti-collision system in the end.

I think Sarah's link to the Zaon XRX represents an attempt at what you are talking about that only costs one arm. It carried a retail price of $1395.. Even if it were in production today I'd still rather carry a PowerFlarm for that kind of money because you'd get actual 1090ES GPS fixes plus PCAS plus glider Flarm traffic for about the same price. I think in general the idea of trying to interpret radar returns - even with a lot of calculus of variations math - is by now antiquated and far inferior to more modern GPS-based solutions. The review on the XRX seemed to confirm this - it only sometimes worked.

I looked up ABQ in the FAA's Air Traffic Activity System. On an average summer weekend soaring day it handles about 100 total airport operations during the active soaring day, which places it at #116 among airports in the US - a reasonably busy airport. Even so, I'd bet dollars to donuts that if you took all the IGC traces and all the radar traces and compared them you'd find on a typical glider flight that more than 9 out of 10 of the closest approaches to another aircraft would be another glider or towplane, not a commercial jet.

That's not to say I'm advising against a transponder - I often fly near Reno (#197 in summer weekend airport operations) and I carry one. Yes there are differences across airports in terms of how the jet approaches mix with glider flights. However - if we take it back to actual statistics, I expect ABQ is not so atypical a traffic situation to overcome the more than 10x difference in the statistics on average - that is, you are more than 10x as likely to run into another glider or local traffic at your home airport than a jet. The big jets are certainly more obvious and scarier and would make a bigger headline if you actually hit one, but the outcome for you is the same whether you smash into one of those or your soaring buddy. For that reason I consider carrying a transponder more of a public service than my primary device for personal safety - my PowerFlarm, InReach, parachute and extra drinking water all rank ahead of my transponder in terms of personal safety - more or less in that order.

9B
 




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