Menu Sign In Contact FAQ
Banner
Welcome to our forums

Misc. electronic conspicuity boxes: Garrecht / Air Avionics / TRX-1500A / Air Connect / PAW / PilotAware / LXnav / PowerMouse / FlarmMouse / Flarm / Uavionix / SkyEcho / SafeSky

With TCAS you pull/push

That’s nonsense. Done to death already, however.

You are describing “airliner” TCAS2.

Administrator
Shoreham EGKA, United Kingdom

mooney75 wrote:

and with FLARM you normally turn. Immediately.

That is the most profound BS I’ve ever read. Do you really believe that you should immediately turn when a target shows up on the 12 o’clock position on your FLARM? Do you actually do that?

FLARM ist, btw. not at all a collision avoidance system. It is a situational awareness support system. And therefore I don’t know about a single checklist that says “When dot shows up then turn immediately”.
btw: Turning is a bad idea because if two planes really approach each other frontally at 100kt, turning is too slow and odds are to high that they are (given the intrinsic error margins of such devices) actually turning towards each other. That is exactly the reason, why with TCAS-II (with happens to be a collision avoidance system) you don’t turn but descent/climb

mooney75 wrote:

FLARM also tells you when somebody comes within range, usually minutes prior

For relevant traffic – that is the opposing one – it’s never minutes proior

mooney75 wrote:

I will, obviously, not post any private IGC files, nor would that imply anything. If your range is below at least 5-10 km, there is probably something wrong with your installation.

1.) It’s always about privacy when one doesn’t want to prove ones point. But now problem: You can also share the range analysis that is totally anonymous.
2.) Fundamental misunderstanding of the system: 2/3 of the problem is not due to my installation but with the installation of the potential targets. And it would not be my installation anyways, as there is no legal way to “install” it in my plane.

Peter wrote:

you are kidding yourself.

Problem is, that these kind of devices create the impression of safety not by actually avoiding any collisions (despite gliders in competition these are too rare events to statistically show any effect at all) but by showing blinking dots on displays. Many people like blinking dots on displays! And somehow people feel more safe if they see many dots that relate to airplanes that would never cross their path in the fist place.

Having said that, I love my GTS. Not because I think it will safe my life, but because it has nice practical applications in many situations e.g. it is great to estimate how fast I catch up with a slower plane in the pattern and if it will work out ..

Germany

That’s nonsense. Done to death already, however. You are describing “airliner” TCAS2.

No, I’m just describing TCAS II. Not any airliner version.

United Kingdom

Indeed, 100% irrelevant to GA.

Administrator
Shoreham EGKA, United Kingdom
That is the most profound BS I’ve ever read. Do you really believe that you should immediately turn when a target shows up on the 12 o’clock position on your FLARM? Do you actually do that?

That’s not at all what I said. I said when you get a collision warning. When the aircraft shows up on the 12 o’clock position 40 seconds before the collision (if both aircraft are travelling at 250 kt, assuming 10 km range), then you can start contemplating. For most GA aircraft speeds, it’s also more like 90 seconds before, even more if not exactly head-on.

United Kingdom

I’m rather sorry I asked my question!!

UK, United Kingdom

Peter wrote:

Clearly there are loads of really crappy transponder installations

There probably are, but there are also some quite big antenna nulls (e.g. if you’re above the other traffic, since your TAS506 antenna is on the roof and most simple transponder installations have the antenna underneath). I’ll have to see if I can dig it out again, but there was something I was reading showing something on the potential of 30dB attenuation in certain situations. So the other aircraft could have a perfectly decent transponder installation, but just the combination of your antenna nulls and theirs means you’ll not get much range.

Airliners and bizjets on the other hand typically have multiple transponder antennas (and are more likely to be higher than you, meaning you’re avoiding attenuation from your own antenna installation).

Andreas IOM

Yes; that’s correct, sort of. Actually there are two antennae, each 2-blade, one on top and one on bottom. Described here. And yes there is a conical blind spot above and below – illustrated in the writeup. But it is only pretty well directly above and below, and any relative movement quickly produces a suitable lateral displacement.

The bigger stuff will have dual txp antennae (“diversity”) but the TCAS will be the same principle.

In practice, the scenario where somebody descends above you at exactly the same speed and hits you from above, or same from below, is extremely rare. In general you will have noticed them beforehand, long before they ended up vertically aligned. I have seen it, and then one has to descend, or climb, respectively. One was at Zell am See (weird circuit procedures, disregarded by some) and one was at Shoreham (possibly a glider). Neither was ever seen. But I never lost the relative altitude in such cases. Only the bearing became useless.

Active TAS works very well in the by far most common scenario which is somebody at roughly your height and heading in your direction

ADS-B would solve these cases.

Another thing one needs to ask is whether traffic warnings are presented with audio and into the headset. If this can’t be achieved, the thingy is close to useless, because nobody will be staring at their Ipad while flying. It’s like car satnav systems which have speed cameras but no audio off them – totally useless. I have one – Satnav Systems RNS510

Administrator
Shoreham EGKA, United Kingdom
mooney75 wrote:
When the aircraft shows up on the 12 o’clock position 40 seconds before the collision (if both aircraft are travelling at 250 kt, assuming 10 km range), then you can start contemplating.

Not really – at 10km range (which would be extremely good given that all range diagrams I have seen so far show a considerably shorter reliable range – but let’s assume both planes in this example have a perfect FLARM installation – which btw many airplanes in that speed range can’t have as there is no legal way (I’m aware of) to have an outside FLARM antenna in a pressurized cabin…) 38 Seconds (the first 5% reduction of what you claim) is the theoretical first point in time where it would be physically possible that the Flarm boxes show a point. But FLARM doesn’t send continuously that is where you loose your next at least half second.

Then – under ideal circumstances – you have a dot. No direction of flight and no speed yet. Therefore even theoretically no collision warning. We now needed to go very deep into the mechanics and algorithms of FLARM to figure out quite quickly: For that case of a heads on collision with 500kt difference speed it is absolutely useless!

That doesn’t mean that FLARM is useless – it is a great tool for gliders! For everything in between gliders and 250kt flights one has to evaluate it’s own mission profile.

Germany

Peter wrote:

Another thing one needs to ask is whether traffic warnings are presented with audio and into the headset

Mine do. I use the aux in on the radio for it. The display is also between the ASI and the bottom of the windscreen, so I only have to glance down slightly to see it (in other words, easy to incorporate into the normal scan), I use a Samsung XCover 4 which is big enough for the job, but not so big to be inconvenient.

Andreas IOM
Sign in to add your message

Back to Top