Improve Light A/C Separation
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PCAS for traffic spotting
I know it is by no means 100%, but many times I have been flying along, looking out to the best of my abilities - and also many times, head down looking at maps etc. - when my little portable PCAS unit goes off and warns me of another aircraft.
Just a few weeks ago I was flying along maybe 500-1,000ft below a broken cloud base, and the unit went off - warned me of an aircraft ahead, same level. I had been looking out but just had not seen it. I quickly descended by a few hundred feet and very shortly after saw a twin only a few hundred yards away, pretty much nose-on to me, which passed a few hundred feet overhead. Based on the 'big sky' we probably would not have hit each other, but it would have been close.
The unit itself is pretty small, very light, sits easily on top of the panel, and uses 12V power from the panel (or a battery unit I carry) so is no problem to use in the club aircraft that I rent.
It doesn't necessarily give peace of mind, but at least it helps a lot to spot aircraft that are transponding Mode C (or S) and which are a 'threat'. (Of course not all aircraft have Mode C/S, like perhaps the smaller aircraft in the Coventry accident, but it tends to be most of the faster ones, where you would have less time to avoid.)
It was pretty expensive - over £1,200 - but having used a PCAS unit I would be pretty reluctant to fly without.
Just a few weeks ago I was flying along maybe 500-1,000ft below a broken cloud base, and the unit went off - warned me of an aircraft ahead, same level. I had been looking out but just had not seen it. I quickly descended by a few hundred feet and very shortly after saw a twin only a few hundred yards away, pretty much nose-on to me, which passed a few hundred feet overhead. Based on the 'big sky' we probably would not have hit each other, but it would have been close.
The unit itself is pretty small, very light, sits easily on top of the panel, and uses 12V power from the panel (or a battery unit I carry) so is no problem to use in the club aircraft that I rent.
It doesn't necessarily give peace of mind, but at least it helps a lot to spot aircraft that are transponding Mode C (or S) and which are a 'threat'. (Of course not all aircraft have Mode C/S, like perhaps the smaller aircraft in the Coventry accident, but it tends to be most of the faster ones, where you would have less time to avoid.)
It was pretty expensive - over £1,200 - but having used a PCAS unit I would be pretty reluctant to fly without.
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"Of course not all aircraft have Mode C/S, like perhaps the smaller aircraft in the Coventry accident, but it tends to be most of the faster ones, where you would have less time to avoid."
Thanks for the info. A Rotax or a IO540 makes little difference landing on your lap.
Thanks for the info. A Rotax or a IO540 makes little difference landing on your lap.
Last edited by Robin400; 26th Aug 2008 at 15:54.
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So by way of resume, and to solicit peoples views, one aspect of this discussion which I find particularly interesting was developing as follows:
Very few light aircraft have "full" TCAS. Full TCAS, in addition to actively interrogating other aircraft, will provide the pilot with an RA, in other words what action to take if a collision becomes likely. (This is a simplistic explanation for the purpose of this discussion).
To keep down the price GA typically uses two different types of systems. The first (such as Skywatch) also actively interrogates traffic which is then displayed on a PFD (moving map) or stormscope showing the relative position of the traffic, its height, its change in height (relative to you) and the trend in its position relative to you.
PCAS on the other hand relies on piggybacking traffic information from ground based radar returns (in other words it is passive, and would not work in an environment without any other interrogators). In its simplest version it indicates range and altitude relative to you. In its more "advanced" version it also indicates direction, but only to the extent of the four quadrants relative to you.
PCAS has some other limitations. A return may not be received because it relies on a single antenna, whereas Skywatch has two antennas above and below the aircraft and mounted externally. PCAS is not approved and it is unclear how well the technology has been tested.
Skyforce typically offers the following level of accuracy:
Range accuracy 0.05nm (typical)
Bearing accuracy 5d rms (typical), 30d peak error
Altitude accuracy +/- 200 feet
I haven’t looked up the figures for PCAS.
FLAME is also used, particularly by the glider community, but very little within powered aircraft. It has some similarities with ADS-B.
I am familiar with the first two and have used both, but not with FLAME.
This discussion I think is relevant to all these systems.
Skywatch say that the intention of the system is to enable pilots to far more readily visually acquire conflicting traffic. They caution that separation should not be initiated until the traffic has been acquired visually. As far as I recall PCAS don’t say anything in their OM, but I may be mistaken (it is not to hand). I don’t know what FLAME say.
The discussion is should you do nothing until you visually acquire the traffic because of the inherent errors in range and bearing accuracy and because the other pilot might resolve the conflict in the same but opposite way to you. Only in the case of TCAS are expected to carry out an RA even if you have not visually acquired the traffic.
I think it is an interesting discussion as to how this might work in the GA environment giving the differences between TCAS and CAS.
What are the differences in environment.
Well for GA traffic outside CAS the traffic has complete freedom to manoeuver both laterally and vertically as it wishes. In other words as we all know there is no need to tell anyone that you are departing from your heading or altitude. Moreover other traffic often cannot be verified by reference to ground based radar because the traffic is not receiving any ground based service.
So the question is, in short, outside CAS do you make any adjustments to avoid an apparent conflict with other traffic based solely on CAS, or do you always wait until you have acquired the traffic visually however close that may mean you get.
I gave in the previous thread an example. You are enroute, VFR in 4k viz. Traffic at a range of 10k is converging your track at right angles, same height.
Do you:
React immediately either by altering course, height, or course and height,
or
Do you do nothing and wait until you have acquired the traffic visually how ever close that may take you?
Thoughts welcome from anyone using any of these sytems or just interested in how they work in a "non controlled" enviroment with the mix of traffic we are all accustomed to.
Very few light aircraft have "full" TCAS. Full TCAS, in addition to actively interrogating other aircraft, will provide the pilot with an RA, in other words what action to take if a collision becomes likely. (This is a simplistic explanation for the purpose of this discussion).
To keep down the price GA typically uses two different types of systems. The first (such as Skywatch) also actively interrogates traffic which is then displayed on a PFD (moving map) or stormscope showing the relative position of the traffic, its height, its change in height (relative to you) and the trend in its position relative to you.
PCAS on the other hand relies on piggybacking traffic information from ground based radar returns (in other words it is passive, and would not work in an environment without any other interrogators). In its simplest version it indicates range and altitude relative to you. In its more "advanced" version it also indicates direction, but only to the extent of the four quadrants relative to you.
PCAS has some other limitations. A return may not be received because it relies on a single antenna, whereas Skywatch has two antennas above and below the aircraft and mounted externally. PCAS is not approved and it is unclear how well the technology has been tested.
Skyforce typically offers the following level of accuracy:
Range accuracy 0.05nm (typical)
Bearing accuracy 5d rms (typical), 30d peak error
Altitude accuracy +/- 200 feet
I haven’t looked up the figures for PCAS.
FLAME is also used, particularly by the glider community, but very little within powered aircraft. It has some similarities with ADS-B.
I am familiar with the first two and have used both, but not with FLAME.
This discussion I think is relevant to all these systems.
Skywatch say that the intention of the system is to enable pilots to far more readily visually acquire conflicting traffic. They caution that separation should not be initiated until the traffic has been acquired visually. As far as I recall PCAS don’t say anything in their OM, but I may be mistaken (it is not to hand). I don’t know what FLAME say.
The discussion is should you do nothing until you visually acquire the traffic because of the inherent errors in range and bearing accuracy and because the other pilot might resolve the conflict in the same but opposite way to you. Only in the case of TCAS are expected to carry out an RA even if you have not visually acquired the traffic.
I think it is an interesting discussion as to how this might work in the GA environment giving the differences between TCAS and CAS.
What are the differences in environment.
Well for GA traffic outside CAS the traffic has complete freedom to manoeuver both laterally and vertically as it wishes. In other words as we all know there is no need to tell anyone that you are departing from your heading or altitude. Moreover other traffic often cannot be verified by reference to ground based radar because the traffic is not receiving any ground based service.
So the question is, in short, outside CAS do you make any adjustments to avoid an apparent conflict with other traffic based solely on CAS, or do you always wait until you have acquired the traffic visually however close that may mean you get.
I gave in the previous thread an example. You are enroute, VFR in 4k viz. Traffic at a range of 10k is converging your track at right angles, same height.
Do you:
React immediately either by altering course, height, or course and height,
or
Do you do nothing and wait until you have acquired the traffic visually how ever close that may take you?
Thoughts welcome from anyone using any of these sytems or just interested in how they work in a "non controlled" enviroment with the mix of traffic we are all accustomed to.
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Tcas will only ever be reliable if all aircraft are forced to be transponding. That is the case flying in the IFR invironment of airways.
The downside out of controlled airspace is that Tcas can give a false sense of security and hence in a certain respect make a collision more likely.
So its really an all or nothing game ie make all aircraft use working transponders ie gliders, microlights light aircraft even balloons before they can legally fly.
Most of us who fly in IMC conditions out of controlled airspace are at risk especially as one poster said when making a cloud break blind to VMC and not knowing what aircraft are circling or flying below the clouds.
Maybe we should consider the possibility of a complete network of radar coverage to be allowed to fly in IMC offering RAS or RIS services but even that is not foolproof especially low level.
The only "almost foolproof system is a combination of both ie TCAS and radar from takeoff to touchdown or controlled airspace.
Pace
The downside out of controlled airspace is that Tcas can give a false sense of security and hence in a certain respect make a collision more likely.
So its really an all or nothing game ie make all aircraft use working transponders ie gliders, microlights light aircraft even balloons before they can legally fly.
Most of us who fly in IMC conditions out of controlled airspace are at risk especially as one poster said when making a cloud break blind to VMC and not knowing what aircraft are circling or flying below the clouds.
Maybe we should consider the possibility of a complete network of radar coverage to be allowed to fly in IMC offering RAS or RIS services but even that is not foolproof especially low level.
The only "almost foolproof system is a combination of both ie TCAS and radar from takeoff to touchdown or controlled airspace.
Pace
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So its really an all or nothing game ie make all aircraft use working transponders ie gliders, microlights light aircraft even balloons before they can legally fly.
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Fuji, you may wish to know it’s “FLARM”, not “Flame”. The Flarm people emphasise in their manuals that it is an aid to lookout and visually acquiring other Flarm carrying aircraft (and/or obstacles in its database – in Switzerland, cable car cables etc.), not a collision avoidance thing in itself.
From their website: “FLARM is designed and built as a non-essential 'situation awareness only' unit to support the pilot, and cannot always provide reliable warnings. In particular, FLARM does not give any guidance on avoiding action. Under no circumstances should a pilot or crewmember adopt different tactics or deviate from the normal principles of safe airmanship.”
My comments are limited to “Original FLARM for gliders and portable use” – I see that they now have other products including one “for GA” – dunno what that does.
It does have algorithms that separate what it deems non-threat (e.g. formation flying, gliders sharing a thermal and on non-intersecting courses) from threats – projected collision paths. So it does not do the same job F-F as Txp-Txp or PCAS-PCAS.
FLARM is the ONLY solution available now and in the foreseeable future that all, or almost all, gliders could use – because its battery requirements are low.
Sorry it’s not interoperable, but that’s a fact. Transponders are also not interoperable – notably, with things that can’t carry enough battery and/or can’t install it, as well as not being interoperable with other transponder-carrying aircraft unless they have TCAS or PCAS or something like it, or ATC and a totally known environment.
I presume other glider pilots who have it believe, like I do, that Flarm is the best available tool for us at present. I leave others to judge whether it could be so for them.
Chris N.
[edited to add points from Flarm website]
From their website: “FLARM is designed and built as a non-essential 'situation awareness only' unit to support the pilot, and cannot always provide reliable warnings. In particular, FLARM does not give any guidance on avoiding action. Under no circumstances should a pilot or crewmember adopt different tactics or deviate from the normal principles of safe airmanship.”
My comments are limited to “Original FLARM for gliders and portable use” – I see that they now have other products including one “for GA” – dunno what that does.
It does have algorithms that separate what it deems non-threat (e.g. formation flying, gliders sharing a thermal and on non-intersecting courses) from threats – projected collision paths. So it does not do the same job F-F as Txp-Txp or PCAS-PCAS.
FLARM is the ONLY solution available now and in the foreseeable future that all, or almost all, gliders could use – because its battery requirements are low.
Sorry it’s not interoperable, but that’s a fact. Transponders are also not interoperable – notably, with things that can’t carry enough battery and/or can’t install it, as well as not being interoperable with other transponder-carrying aircraft unless they have TCAS or PCAS or something like it, or ATC and a totally known environment.
I presume other glider pilots who have it believe, like I do, that Flarm is the best available tool for us at present. I leave others to judge whether it could be so for them.
Chris N.
[edited to add points from Flarm website]
Last edited by chrisN; 26th Aug 2008 at 18:02.
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Transponders are also not interoperable – notably, with things that can’t carry enough battery and/or can’t install it, as well as not being interoperable with other transponder-carrying aircraft unless they have TCAS or PCAS or something like it, or ATC and a totally known environment.
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TCAS comes in two flavors; TCAS I, and TCAS II. TCAS II provides resolution advisories, whereas TCAS I does not.
Even a professionally installed TCAS II system in a radar environment has it's limitations. It's a tool, but still misses traffic, and collisions still occur with TCAS onboard and functioning.
See and be seen is still the best policy, with everything else serving only to back that up.
Even a professionally installed TCAS II system in a radar environment has it's limitations. It's a tool, but still misses traffic, and collisions still occur with TCAS onboard and functioning.
See and be seen is still the best policy, with everything else serving only to back that up.
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I never said transponders alone would, but if you have TCAS you will not pick up non transponding aircraft.
TCAS is a tool but can give a false sense of security making you believe you have a shield of protection which you do not have.
In the same way an RIS also gives you a false sense of security. How many times do radar miss an aircraft that passes in front of you?
Pace
TCAS is a tool but can give a false sense of security making you believe you have a shield of protection which you do not have.
In the same way an RIS also gives you a false sense of security. How many times do radar miss an aircraft that passes in front of you?
Pace
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This is why TCAS is a dead duck as far as light aircraft/ microlights and gliders are concerned.
The cost alone will prevent most people from installing such a system.
R400
The cost alone will prevent most people from installing such a system.
R400
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The discussion is should you do nothing until you visually acquire the traffic because of the inherent errors in range and bearing accuracy and because the other pilot might resolve the conflict in the same but opposite way to you.
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Robin
It may be a dead duck as far as gliders microlights etc are concerned but transponders fitted to those aircraft will at least allow aircraft fitted with TCAS to see them.
A white glider circling in one spot under a cloud is not very visible especially to a twin prop chopping in and out of cloud, IMC one second VMC another second.
Maybe it should be a choice to have TCAS but compulsory to have at least mode C transponder for all flying machines?
Pace
It may be a dead duck as far as gliders microlights etc are concerned but transponders fitted to those aircraft will at least allow aircraft fitted with TCAS to see them.
A white glider circling in one spot under a cloud is not very visible especially to a twin prop chopping in and out of cloud, IMC one second VMC another second.
Maybe it should be a choice to have TCAS but compulsory to have at least mode C transponder for all flying machines?
Pace
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Pace. Do you have Tcas II or a variation of ?
Robin.
Without doubt that is correct. TCAS II warnings with no level displayed frighten me to death!!!
Robin.
compulsory to have at least mode C transponder for all flying machines?
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I detect the same prejudices in some quarters here as happens with GPS.
TCAS allegedly damages your lookout.
GPS allegedly damages your traditional navigation skills.
Why not just have a long spike in the middle of a steering wheel, and ban the use of seat belts. It would do wonders for road safety - without a shadow of doubt. Mandate crossply tyres, with excellent aquaplaning properties, for good measure.
But seriously, in the GA OCAS context, one uses TCAS to assist in visually spotting the target, and if one cannot visually spot it then one has no option but to take avoiding action based on TCAS alone. It is better than doing nothing.
TCAS allegedly damages your lookout.
GPS allegedly damages your traditional navigation skills.
Why not just have a long spike in the middle of a steering wheel, and ban the use of seat belts. It would do wonders for road safety - without a shadow of doubt. Mandate crossply tyres, with excellent aquaplaning properties, for good measure.
But seriously, in the GA OCAS context, one uses TCAS to assist in visually spotting the target, and if one cannot visually spot it then one has no option but to take avoiding action based on TCAS alone. It is better than doing nothing.
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Just to clarify terminology.. . . .
When we refer to "TCAS" it is only applicable to "TCAS II" equipped flying machines.
Is it possible to fit an error free static source to microlight type aircraft?
If not the mode "C" is of no value.
When we refer to "TCAS" it is only applicable to "TCAS II" equipped flying machines.
Is it possible to fit an error free static source to microlight type aircraft?
If not the mode "C" is of no value.
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Perhaps a little more time looking out of the window rather than playing with the 3285 GPS functions and dreaming of a "magic" bit of kit to relieve us of one more bit of responsibility to avoid hitting another aircraft is the true low cost solution to this problem............... Sorry for the younger pilots that is consulting the large reality display!
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“Is it possible to fit an error free static source to microlight type aircraft?
If not the mode "C" is of no value.”
Yes it is. I have an MCR01 home built (the group a version but the micro would be identical in this case). Despite my kit being entirely self installed it works well (BK76a + encoder). The problem with modern 3X micros is not a technical one it is the regulations. UK micros have a max empty weight. The popular designs are built to come very very close to this limit. The CT for example is 1lb under the max. This makes it almost impossible to install such kit. When the CAA was pushing Mode S for all we pointed this out to stunned disbelief. The CAA types initially thought it would be easy to get their own organisation to increase the limit, but this was ruled out completely. This area of flying is the fastest growing and all 2000 ish of them fly around at normal GA levels, at typical GA speeds – VFR day only.
If you add in the LAA aircraft, the gliders etc then there are more aircraft flying at “normal GA levels” without transponders than with. It often amuses me when people complain that pilots do not turn on transponders that they do not have!!
What we need to do to improve separation is to improve lookout. In the gliding world, if you cannot demonstrate a good lookout to your instructor, all the time, you will not be allowed to fly solo. Some people (particularly ex royal observer types) were trained to be very good at lookout. We need to actively teach lookout to PPL’s and test the lookout of existing pilots. This should take priority over any “black box” solution, unless the solution is going to detect non-transponder aircraft.
Rod1
If not the mode "C" is of no value.”
Yes it is. I have an MCR01 home built (the group a version but the micro would be identical in this case). Despite my kit being entirely self installed it works well (BK76a + encoder). The problem with modern 3X micros is not a technical one it is the regulations. UK micros have a max empty weight. The popular designs are built to come very very close to this limit. The CT for example is 1lb under the max. This makes it almost impossible to install such kit. When the CAA was pushing Mode S for all we pointed this out to stunned disbelief. The CAA types initially thought it would be easy to get their own organisation to increase the limit, but this was ruled out completely. This area of flying is the fastest growing and all 2000 ish of them fly around at normal GA levels, at typical GA speeds – VFR day only.
If you add in the LAA aircraft, the gliders etc then there are more aircraft flying at “normal GA levels” without transponders than with. It often amuses me when people complain that pilots do not turn on transponders that they do not have!!
What we need to do to improve separation is to improve lookout. In the gliding world, if you cannot demonstrate a good lookout to your instructor, all the time, you will not be allowed to fly solo. Some people (particularly ex royal observer types) were trained to be very good at lookout. We need to actively teach lookout to PPL’s and test the lookout of existing pilots. This should take priority over any “black box” solution, unless the solution is going to detect non-transponder aircraft.
Rod1