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Aircraft proximity warning device


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I think a device like this certainly helps pilots to be more aware of, not only surrounding traffic, but more importantly where they are.

As long as the other aircraft is fitted with a transponder, and has it turned on. Thats the way I understand it to work.


It would be the same setup as installing a FLARM unit (as long as everyone has one and it is turned on), although most GA type aircraft tend to have a transponder fitted.


It wont do anything for you if you were to join the circuit at Natfly. Not many Bantam's out there fitted with transponders although you may have a winscreen full of them (no offence to Bantam drivers ;-) )





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where does it get its altitude reference from? In a high density traffic situation I feel you would be better to make sure you can account for all the traffic you know, or suspect, is in the area, visually. If you are half-in , half -out of the cockpit I can imagine a confusing overload situation happening where you are not sure of anything. Comments? N...



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I personaly feel that there has always been the argument that any type of gadget like this will only be any good if everyone is transmitting where they are i.e. using a transponder or similiar. But like everything else in the cockpit you can't get complacent and depend on them - ASI, ALT, Radio etc.


Offcourse there will always be the odd case that even if everyone did have a transponder that it may not be working without the pilots full knowledge etc. I mean just because the weather report says it is going to be an 8 knot Northerlydoesn't mean that we don't look at the windsock do we. Just because the gadget says there is nothing around us we still look out and around anyway wouldn't we?


BUT, just think how you would feel if you had one of these types of things and you looked around everywhere and couldn't see another aircraft then suddenly this thing went off and told you about one - how would that make you feel - can't be too cautious I suppose because at the moment you only have your eyes and no redundant systems for them;).gif


On the other side of the coin, if you did have one you would have to make sure that you didn'tjust rely on that- I suppose just like any of your instruments - you have to fly knowing not to depend on them as the day may come when your ASI or Alt just may break - you would have to use some other means like your eyes to see your height or your stick to gauge a stall.


The point I am making is that this unit to me seemed a relatively small cost for "some" degree of added security.



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Enroute with a small number of aircraft to contend with, it could be life-saving in an alerting capacity.The pilot has the job of effectively managing the flight. You are right to indicate the availability of this new technology but some training in its interpretation would be prudent. There have been numerous erroneous responses to TCASindications that have been carried out by pilots who thought they could finess the situation and have made it more dangerous.These are full-time professionals, supposedly properly trained , with the best APPROVED equipment.still get it wrong!! Ian, I guess I'm a bit of a devils advocate , but I dont want to upset anyone too much. N....



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You're right Neville, like everything - the GPS, the Auto Pilot, the radio, they can ALL only be considered as backup systems requiring effective training in their use and piloting is all about decision making every step of the way.


A lot of us have heard and seen the TV doco about the Russian and British (???) aircraft that were involved in a mid air collision due to the "professional" pilots making incorrect decisions when listening to ATC and TCAS.



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AOPA are now putting their magazine on the newstand every other month


and calling it GA Pilot. The Nov/Dec issue has a review of a similar


piece of equipment, the ZAON MR6 which they call a PCAS (Portable


Collision Avoidance System).


I can see a few (theoretical) concerns with this equipment.


There was a query above as to where these devices get their altitude,


this comes from the transponders altitude encoder, assuming the other


aircraft has it fitted and in the correct mode (Alt or mode C) to


transmit the altitude. Transponders use pressure altitude or flight


levels not MSL altitude. PCAS units calculate the relative altitude


using the transmitted altitude and your own transponder altitude, if


you have one, what it would do if you don't you would need to


investigate but presumably you would need to mentally convert between


your own altitude and the FL of the 'bandit'.


The range information is based on signal strength. This should also be


treated with some caution, if the signal is partially shielded by the


transmitting aircraft or your own aircraft the reduced signal strength


could mean the 'bandit' is closer than the PCAS says it is.


Transponders are also reactive devices, ie they respond to a radar


signal, so if you are within about 100nm* of a Air Traffic Control


secondary surveillance radar the transponder should transmit a signal


for you to pick up each time it is swept by the radar but if you are


outside that range (Narromine ?) the transponder will have nothing to


respond to and will remain silent.


* See '6.3 Aircraft radar beacon transponders' of 'Safety and emergency


communication procedures' on the RAA website




Given these concerns it is possible that these units could be


misleading if not interpreted correctly and should never be relied




When I was in the marine game we had all sorts of toys like radar, Sat


Nav (pre GPS), Loran, Decca, VHF radio etc and lumped them all under


one heading, they were AIDs to navigation, nothing more. Treated as


such these units probably work very well. (Primary navigation tool was


Mk I eyeball).


Me, I'd be concerned about distractions from the toys and the mental


gymnastics working out the altitudes, I'll pass for the moment.


Would love to hear from someone with practical experience of one of these units.



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  • 11 months later...

A refresh on PCAS


Hi All,


I have been searching for some user based info on the Zaon MRX PCAS.


I have read the recent Digitalreview on them and they sound quiet good as an entry level unit for around $700 AUD.


In response to the last contributor to this thread, and others curious.


This portable or dash mounted unit the size of a pack of cards will pick up the 1090 Mhz interrogated response from any txpndr (turned on of course) whether it is interrogated from ground based radar up to 200nm and by TCAS interrogation up to 100nm. It will then advise of traffic within 5nm, nearest threat only but tracking up to 10 I believe. Alerts 2 types of alert warnings, displays distance and altitude up or down and whether or not the threat is climbing or descending.


Altitude from either your txpndr or its own internal baro unit if a large discrepancy exist.


Range accuracy is apparently under 10% and much better at closer rangers, <3nm.


I would be interested to know if the ground based and tcas distances are accurate as I have read conflicting reports, particularly with TCAS range, one report stated you needed to be within 40nm, quiet a difference.


Love to hear from any one with user experience or second hand user experience.


Otherwise I'll try and write a review myself in 6 months, pretty much committed to the concept and benefit.







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Could be good idea to talk to glder pilots who have used the "Flarm" anti collision unit.


This unit has become mandatory in a couple of gliding competitions in Australia and will probably become mandatory for all competitions in the future.


It is designed to rapidly indicate which way a pilot should instinctively look for any closing or converging aircraft and unlike the Monroy device, you don't have to mentally translate which direction to look from some digital readout that may be hard to read in some conditions.


I am not neccessarily suggesting that the Flarm is the way to go in power aviation but both the human interface and the technology are already sorted out by the gliding fraternity so why reinvent the wheel?


The swiss design Flarm site;




The Australian built and fully compatible OzFlarm site;





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Guest High Plains Drifter

For VFR I'd recomend the Eye ball mark 1 anti collision unit. It has been in aviation use since 1903 - even though it's old tech, when properly used it is still efective.



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Guest Flyer40

Smokey, to expand on one of the points that Mick made, the passive traffic systems used in light aircraft rely as much on the active traffic systems in heavy aircraft as they do on the SSR to obtain position info from nearby traffic. Any heavy in the same area you're flying is compulsorily TCAS equipped, and will also be pinging nearby transponders. Thanks to the heavies, passive traffic systems often work when there's no SSR coverage, especially around the high density air routes.


Traffic systems are an aid to looking out, not an alternative to looking out. No traffic system manufacturer has ever advocated that their system is an alternative to keeping a proper lookout. The aircraft that is on a collision course with you is the hardest one to spot because there is no relative movement. In my view, anything that increases the chance of spotting that one high-value target has to be a good thing. And it only has to do it once in its life to make it worthwhile.



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Thanks ROM,


I'm reasonably familiar with FLARM and yes it is I suspect a superior system and credit to the GFA for quickly adopting the available technologies.


However whilst I acknowledge the high density of glider traffic on certain days in certain locations, for broad scale PCAS it is probably not as well suited as 5th generation txpndr based units.


Which in turn will become obsolete 5 years or so with the role out of ADS-B.


The MRX's big brother the XRX which is unfortunately not dash mountable due to the internal aerial does give a direction to look much like the FLARM, but does cost $1800


My philosophy on the MRX is it is simply a heads up unit, if I've got my head down attending to another item for a moment and I get an audio visual warning I've got a good head start for the scan, up or down, and distance. No one is selling them or buying them other than for that I guess.


I'll have another look at the Monroy again in case I missed something.


Thanks ROM



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The following is a long post but I thought it might be interesting to anyone considering these technologies. It was posted on the PocketFMS Forum by a European user as his first experience of the ZAON XRX. Other posts suggest that FLARM is becoming increasingly popular for GA in Europe.










Yes, I was able to take her out on my flight from EHHO to EDWJ and back again, so here are my first impressions based on some basic questions that I had before we took off.




A: YES, it certainly is!


During this first flight, I found two reasons for this (maybe there's more?):


(1) The aircraft we were flying with is an older type Socata Rally with an almost fully curved dashboard; not having an anti-slip mat caused the thing to slide and turn on the little flat piece in the middle, the power- and headphone wires pulling on it being the main reason for turning. With only that one flat surface available in the Socata, convenience of operation was out the door...


(2) Another effect that I observed was the indication of the own plane's heading, which I believe was caused by the position relative to the avionics and compass: on certain positions in the cockpit the heading was off as much as 140 degrees (!), moving it some 30 centimeters sideways resulted in a correct indication.




A: (this part of my PiREP might be a little premature, since I only tested the XRX during this one flight; so this piece has to be taken with reservations!)


First some known facts, that are also mentioned in the manual:


- transponder-equipped aircraft that are not triggered into responses are BY DEFINTION not detected (this includes traffic flying below radar)


- transponder-equipped aircraft flying in your own plane's cone of silence are not (or barely) detectable


- configurable thresholds can be set to limit relative distance and relative altitude


My observations:


- detection on lower altitudes is significantly worse than higher up; not only detection is worse, also the indication of distance seems to be of lesser quality (the manual has a FYI mentioning about a distance indication being up to twice the real distance while on the ground, but this also seems to be the case while flying below 1000 feet). During this first flight only 1 out of 4 other planes that we saw was detected (both we ourselves and the other traffic flying below 1000-1300 feet AGL), quite a poor score IMHO!


- detection of traffic higher than roughly 1500 feet AGL seems to be excellent (all other traffic that we spotted was also detected by the XRX)


- setting a high threshold on relative distance (6NM) and relative altitude (+/- 2500 feet) makes the XRX to be be 'really present' in the cockpit, drawing too much attention to itself (I found myself to be glancing over at the XRX in sort of a reflex with every beep it gave, which I feel takes too much of my attention away from scanning the skies - this certainly is not to be ignored!). Setting relative distance to 3NM and relative altitude to 1500 feet improved that 'pitfall' significantly.


- indication of direction: the traffic the XRX detected was usually in the indicated quadrant. When an airplane departing EDWJ immediately after we did was crossing our path a few hundred feet above from right-behind to left-behind, I was able to observe when the XRX was changing the indication accordingly. I was in for my biggest disappointment of the day: only when the crossing plane was at our 7-8 o'clock it changed the quadrant Maybe it had to do with the PA28 that -at that same moment- was flying about 2NM + 600 feet of us, that it was 'paying less attention to the crossing plane behing'. I just don't know, but if this behaviour also applies to the other quadrants and to traffic considered to be 'primary threat'......... (hmmm, don't want to think about that just yet)




A: Yes, I found one: regarding callibrating the internal altimeter while being on the ground: not being able to callibrate using negative alitudes (called Flight Levels by the XRX) there's limitations based on airport elevation and QNH. Yesterday QNH at EHHO was 1029, field elevation 40 feet; the XRX showed FL001 (100 feet), so recallibration (actually initial callibration was required. The XRX however does not allow you to put in negative FL's.


Instead, I had to callibrated in-flight, subtracting 30 feet for every hPa from the indicated altitude (I can't imagine this to be the best way to callibrate when you're flying alone, so I will put in a change-request for this with Zaon, asking them to allow negative FL's during callibration)


My first (maybe premature) conclusions:


- cockpit-design and positioning of avianocs does greatly affect the readouts of the XRX's built-in compass that indicates your own plane's heading


- the XRX cannot be trusted to detect traffic equally well in all situations, my first impression is that when flying below 1300 feet AGL it's to better turn it off completely (the readouts that we got were incorrect, so no use to even consider the XRX in those situations, is there?).


- even with the directional indication down to a single quadrant, about half of the sky remains to be scanned (which of course is a lot better than not receiving any indication at all)


- if the XRX is getting onto your nerves by it's detections and alerts, decrease the tresholds for relative distance and altitude immediately! (as we all know: flying the plane remains THE most important thing to do, don't let any device endanger that - including PocketFMS)


- my next flight with the XRX I will ignore the detection-beeps, and just pay attention to the advisories and alerts; I found my regular scanning of the skies to be degrading a little, but maybe that had to do with me being anxious to find out how well the XRX performs.






From the previous you might get the impression that I was in for a major disappointment.


Fortunatley this is not the case, because there are a number of important positive qualities as well:


- First and most importantly: during this first flight the XRX did detect other traffic before we did on at least three occasions.


- It also once detected traffic that we never even saw (the XRX indicated the traffic to crossing behind and 600 feet below and descending at 2NM distance)


- It correctly ignored traffic with relative distance and altitudes beyond the set threshold (that is: we did spot some distant traffic that seemed beyond the threshold, and also a rescue-helicopter flying at least 2000 voet below that it disregarded)


- Battery pack that bought with it (the small one) does indeed have the advertised capacity: earlier this week I kept the XRX running on my desk for about 8 and a half hours straight!


Well, you got my message I presume: I'm not all Halleluja just yet, but am certainly not disappointed either!


Some lessons learned today, and some new experiments need to be conducted to find out how the XRX can be best used from a technology point of view, and how to effectively incorporate working with the XRX in my normal flying routine.


I guess the most important lesson that I learned today is that the XRX has a strong tendancy of providing you with a false sens of safety and comfort, which holds the risk of decreased See-and-Avoid skills over time! (similar to GPS-es drawing people away from basic navigation skills using only a paper chart). In my opinion, this fact alone should be the basis for a strong discussion on whether an integration with PocketFMS should be developed, because such an integration would greatly increase the false feeling of safety by presenting an accuracy on a moving map that really does not exist!


Hope this preliminary PiRep will help others.


Blue skies,








PocketFMS running on: HP 4700 with Windows Mobile 6


(Zaon PCAS XRX hopefully filling in the gaps





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Great Post Rong, thanks for that.


That was the sought of onfo I was seeking, I spent the money the other day for better or worse ($650.00) for the XRX's little brother the MRX, so it should arrive in the post soon. I'll give it a try in the work plane to see how it goes, and then fit it in the panel of my eze when I get home.


The author of the PiRep pretty much confirmed my perceived thoughts on them.


I am curious to know weather they pick up the transponder return from an aircraft that is fitted with TCAS.







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I like the mark 1 eyeball for several reasons.


When looking at something inside the cockpit, you can't see outside.


It is more reliable, doesn't need volts to run.


If used in conjunction with a radio it usually allows me to keep a check on other planes.


It can spot planes without a transponder.


In a cramped cockpit there is little room for "gizmos"


If you use the radio on area frequency, you will hear planes from hundreds of miles away, you can work out who is near or heading your way, even the parachute droppers. Change to CTAF frequencies when near and you will have a good idea of what is happening, but of course you won't know where I am doing steep turns and other practice stuff, but I don't have a transponder anyway, so an eyeball will work well.


With about 40 passenger flights per day passing near my home strip I am yet to be surprised by another plane.



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I like the Mark 1 eyeball to, in fact I am now using the Mark II eyeballs, both left and right, makes me less one eyed about the world around me. The Mark 1 or II is and I agree, still the best primary guard in most VMC conditions.


Unfortunately though even my Mark II eyeballs aren't that reliable, they don't do so well when looking into the sun, they also struggle when in heavy haze, smoke, rain, or in IMC or at night, not to mention empty field focus issues.


Apparently both Mark 1's and Mark II's seem to suffer degradation with age, which can be mitigated to an extent but they can't be replaced, the PCAS doesn't and can be.


Since position broadcast are now discouraged on area frequencies by VFR aircraft the radio has lost a degree of collision avoidance ability, so the TCAS/PCAS helps out.


I love the concept of the Zaon MRX because it is so small (smaller than a pack of cards) it easily fits into smaller panels.


I love the concept that the range for alerts from the PCAS can be adjusted so as to eliminate those aircraft that aren't a threat. Unlike a radio where every call has to be listened to determine its relevance.


I love the PCAS concept because when your looking at something inside the cockpit you can't see outside, the PCAS can, and will then alert you by a TA or RA audio alert into your headphones. Then you can use your Mark 1's or Mark II's to find the aircraft. And instead of having to scan the whole sky you have some indication of where to look first, before resuming your normal full scan.


I love the benefits that PCAS affords when installed into an aircraft with restrictive outside vision.


The greatest proponents of see and be seen, the gliding fraternity seemed to have no problem adopting this type of technology even mandating it in certain comps I believe.


Those with the most at risk, RPT ops mandated its use.


Call me greedy but I think I'll have both, eyeballs and PCAS





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Guest High Plains Drifter

There's a lot of money going to be made by the manufacturer's and suppliers of this collision avoidance gadgetry if it is mandated for Ultralights. I guess that might explain why some of the threads are for it.


The aviation print media are certainly being romanced by the gadgett suppliers - I wonder what the dollar value is of all the gadgett advertising.


Re the "problems" with a pilot useing their eye's to look for traffic, I would point out that the visual flight rules for OCTA op's is written emphasizing the "V" in VFR - For those who like to look at panel's, CASA has the IFR.


To the average Ultralight pilot, ( considering most fly below 5,000') if they fly within the reg's for visibilitie requirements the Mk 1 eye ball is all they will need. Keep in mind that apart from other aircraft, a pilot is also looking for non transponder equiped large birds, plus tera firma.


My personal experience with (VFR legal) flight in smoke, haze and rain, is close traffic becomes easyier to spot because of the blurring of distant objects. If you intend to fly in heavy smoke I would recomend reading the Notams first, otherwise you may get to meet Elvis in there (Elvis the helicopter that is)


Empty field myopia is addressed in basic training.


If an Ultralight pilot intends to flock with a dozen other Ultralights in the one thermal, there may be a use for a warning buzzer. Probably would'nt hurt to have a parachute as well.





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Please don't interpret anything I have written as being an endorsement for mandating TCAS/PCAS systems to recreational VFR operations. This would be a ridiculous impost for little gain.


With reference to heavy smoke, I was typically referring to operations in the top half of Oz during the burn off season rather than Fire Bombing ops.


I have just completed a months worth of survey flying in the top end in smoke haze at times at or below VMC and for the life of me I cannot see how you could possibly interpret those conditions as beneficial to see and be seen.


Flying around NSW and Vic. during the bushfires of the early 2000's was nothing short of nerve wracking due to poor visibility. That is one reason Fire Ops put a Bird Dog above Bombing operations to coordinate the attack in restricted visibility.


And what about the occasional VFR aircraft operating in less than VMC and not wishing to admit his/her presences, it is not that uncommon. Surely PCAS use under these circumstances would be advantages.


PCAS/TCAS is an enhancement to lookout not a replacement!!





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Guest High Plains Drifter

Mick, after re-reading many of your posts very closely, you come across as a very genuine and concerned aviator.


I did have a concern with your 6/11/07 post, and other posters, in this thread and how it ties to the current ADSB debate. I think some of the posts might give the impression that there is some sort of a vision problem with RAAus aircraft and pilots. I was pointing out that a RAAus pilot, flying within the reg's, has a very low risk profile.


Obviously it is my fault for not being more clear about where I was coming from. (my extremely poor writing skills don't help either)


The first two paragraphs of my 7/11/07 post refer to how all these PCAS, Transponder and pro ADSB threads seem to add to the collision risk hysteria/hype that I think some are trying to build up. All that hype does is support the pro ADSB profiteers.





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  • 1 month later...



The new version of PocketFMS can display traffic reported by ZAON or FLARM on their moving map display.


An undocumented pre-release of the PC version is available from the discussion forum


http://www.pocketfms.com/phpBB3/viewtopic.php?f=26&t=4163 and a brief setup guide for the ZAON is at









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Thanks for the update on pocket FMS's.


I must admit I am not all that up to speed on these things but get the impression from looking over the shoulders of others that these units will be a big player in future.


I haven't quite worked out how they work with the XRX or if they will work at all with it's little brother the MRX. At the moment I can only dedicate about 2.8 seconds daily to other tasks outside of trying to fix the eze's radio so I can get home for xmas. Mother is not happy.


Plastic aeroplanes and radios :;)1:







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