Joking apart, using an altitude filter of +/- 100 ft could minimise the problem and would automatically take account of the airfield elevation as 'you' would be on the ground (thus automatically setting the datum) - or if on final, warnings would cease during the final approach /round-out and hold-off phase. And all this without needing to manually switch anything![/b
I'm not sure I like the idea of disabling the warning of aircraft within 100ft of mine - they're the ones I'm most likely to hit while flying! Witness my airprox where I was head-on, same altitude and only avoided a collision by pushing -2G at the last second. Literally
Believe me, I fully appreciate your concerns.
You were very lucky and are a terrific 'advert' for why systems like PAW are so important. I too have been there, though didn't get it on video (though I do have a snatched still shot as I banked hard left to avoid the oncoming aircraft - I just happened to have my camera in my hand), so fully appreciate where you are coming from. But remember, what we are discussing here is 'What is the best way of trying to reduce the number of what become nuisance alerts
when you are on the ground, without compromising safety
in the air.I don't like the idea of deliberately excluding warnings of any sort, but having experienced continual alerts from high powered transponders while on the ground at busy airports during Mode S testing, I can appreciate the strain that this places on the pilot and hence why the need to reduce such 'nuisance' alerts was asked for. Before I got involved in the testing, I didn't for example appreciate that CAT traffic in Ground Radar mode can bump out a massive 'mode S' signal while taxiing or queueing waiting for departure, and GA transponders, though less powerful, still cause the same problems.
If Lee agrees to it, the filter would be set for mode S only - ADSB and P3i use a different trigger system which generates far fewer alerts because they are generated from the aircraft's actual position and only occur as it approaches you and breaks one of 3 clearly defined 'physical' boundaries. Because Mode S alerts are not generated from physical boundaries, but from received signal strength at 3 different trigger levels, they repeat every time the signal drops below and then returns above
any of these triggers - which can happen several times when the aircraft is in the circuit - especially if it 'disappears' from your antenna behind hangers or terrain for example, or simply because the distance between you increases, then shortens again, generating repeat warnings each time this occurs. The same thing can happen with aircraft taxiing on the ground. These then become 'nuisance' alerts, because you should already be aware of the presence of the aircraft.
In the air, these multiple mode S alerts are far less likely to occur (unless you are flying in very close formation with other mode S aircraft) and the chances of a mode S aircraft getting within +/- 100 ft of your altitude in normal flight without breaking all 3 trigger thresholds as it approaches (thus alerting you to its presence in sufficient time for you to lookout for it) would be extremely low. But of course mode S can only tell you an aircraft is approaching - it can't tell you where it is - that I'm afraid is down to the pilot. To help reduce 'nuisance alerts' and give some user choice, Lee has already introduced 'user selectable' Mode S Detection Range settings in 'Configuration' in the current software release. As part of ongoing development, these are being continually tested and refined and an improved version will be included in a forthcoming update. What we are discussing here is simply a relatively minor adjustment to address a specific ground issue.
Trust me, we are well aware of the dangers and wouldn't suggest - and Lee certainly wouldn't make - any changes which might in any way affect safety without extensive thought, discussion, testing and due consideration of the risk. Hopefully this will help to alleviate your concerns.
Regards
Peter