Sure; I was referring to the OCAS scenario where I get a traffic warning from the TAS box. The azimuth is available but if the convergence is anywhere near head-on, one cannot tell precisely enough which way to turn, so climbing is a good option. The assumption is that the other traffic has not seen me, and IMHO usually this is correct.
If everybody (or a large %) had a traffic warning system then the above might not work so well 
That is reportedly true on water already and collisions happen despite both having radar. But that will not happen in GA in my lifetime, simply because in any area where there is significant enough traffic density most of the planes will not have anything like that.
Überlingen was in CAS and it’s extremely unlikely to repeat in a way that involves light GA which is normally vectored many miles away from jet traffic.
Peter wrote:
Überlingen was in CAS and it’s extremely unlikely to repeat in a way that involves light GA …
I am not so sure. They saw each other on TCAS, they say each other visually, the controller saw them. Yet they kept flying straight ahead and changed their altitude instead (which is correct with TCAS, but only if everybody follows his TCAS). If I don’t know whether or not the other aircraft sees me (on radar/TCAS/FLARM/… or visually) then the chances that he will change altitude in the same direction as I do are almost 50/50. At low level they will even be something like 80/20 because no one descends if he is already close to the ground. Therfore I will rather try a lateral escape.
Assuming we were at the same height on a collision course before, I would say a 50/50 chance is not too bad, because keeping your altitude and heading meant a 100 % chance of hitting each other. Any scenario where you weren’t head-on, you don’t win anything, but you don’t lose either. In climbing, you still have a chance to recognize on your TAS system that the other aircraft has initiated a climb as well, and reverse. It just shouldn’t result in both trying to outsmart the other.
When you start turning, you often block the view, be it in a high wing or low wing, so I wouldn’t feel comfortable starting to turn if I think the traffic is close but I haven’t seen it.
And sometimes, you just need to get lucky and it looks like this:
Rwy20 wrote:
Assuming we were at the same height on a collision course before, I would say a 50/50 chance is not too bad, because keeping your altitude and heading meant a 100 % chance of hitting each other.
Normal procedure is to “stay on track”, unless you see the other and need to maneuver. The reason for this is the other person might see you and has already initiated a maneuver to avoid collision. If everybody starts to do unexpected maneuvers all the time, things will only get worse. This is the same in a boats, in gliders, in paragliders, you name it.
bookworm wrote:
That’s the first time I’ve seen a suggestion that such a display might be used to manoeuvre to increase separation before visual acquisition.
Thats’s how a FLARM works. It’s an extension of the eyes for all practical purposes, and increases the situational awareness so you can get proper separation even with no vis.
Peter wrote:
I think the “aid to visual acquisition” is a legal disclaimer to avoid liability.
I agree, though I think there are a lot of people out there who would want you to take the disclaimer literally.
I would tend to manoeuvre in the horizontal plane, BTW. There is the advantage that both aircraft should try to have the other pass down their left side. In the vertical, who climbs and who descends? And there’s the potential complication of TCAS.
Peter wrote:
Why is head movement required for an effective visual scan for traffic?
Moving your head helps also to eliminate a dirty windscreen. Try it out next time your windscreen is full of raindrops. Moving your head will greatly increase your ability to lookout.
OK; I wondered whether there was some more subtle reason why head movement is supposed to help. I could not see any difference between head movement and eyeball movement, for subjects which are distant.
Peter wrote:
Also what about the F16’s radar?
Are the F16s equipted with something different to the “normal” airborn radar which does not “see” other traffic in the round. I know airborne radar for traffic detection is possible, but it would need to be a very large and complex airborne system and perhaps not suited to a small fat jet?
Moving your head will shift the relative position of an object against the background. While this may not be overly important if flying, say, over the sea, it really helps to see traffic that moves over a cluttered area, such as patchwork fields or a city.
I don’t get the geometry of that.
If the background is at say 10 miles, the other aircraft is at say 5 miles, a shift in one’s head of 5 inches will shift the other aircraft by only 5 inches relative to the background.
But the movement of both aircraft is way more than 5 inches… at say 150kt, so the 5 inch head movement can’t do anything useful.
