Although I have considered it I have not bought a PCAS unit - not all of us have unlimited flying budgets - I am with Captain Staple on this one. Flying VFR you should be able to see converging aircraft in time to take avoiding action. The exception is an aircraft converging directly ahead at 12 o'clock. I consider the chances of another aircraft being on a direct heading at exactly the same height very low indeed. Is there any recorded instance of this actually happening?
A few days ago I was on the downwind leg at Swansee when I saw an aircraft far ahead, seemingly outside the ATZ and heading off in a different direction. As I turned on to base leg it was suddenly in front of me and I turned to the right to move behind it.
Swansee is A/G radio but they obviously take their job seriously. I did hear them give airfield information to an aircraft AFTER I had begun my downwind leg and didn't hear any a/c call downwind or the A/G mention anything about other traffic in the circuit.
At this time A/G was strongly advising another a/c about to line up to hold as that pilot seemed not to be bothered looking for traffic on final.
Which makes me think the other airborne a/c was doing a straight-in approach or else a right hand circuit (A/G had notified a left hand circuit). It's pilot also seemed completely unaware of my presence behind and seemed to take forever to evacuate the runway!
So a lot of less than perfect airmanship - and I include myself in that!
By the way, is it acceptable to go and talk to staff in the tower after the event to get more information about what happened? I had no intention with fighting with anyone but it would be of interest.