John Miller wrote:
So IFLY "screamimg" TERRAIN, TOO LOW ], 500 amd PU:: UP doesn't create a problem?
John M
Good point, John--although I have two different answers: One is that the ADS-B system is still unreliable. Where I generally fly (near Richmond, VA, but outside the KRIC Class C airspace) transponders are not required, and a surprising number of airplanes aren't ADS-B equipped. Also, there are lots of military helicopters that don't transmit ADS-B data. So no matter how good one's ADS-B receiving and displaying equipment is, those aircraft are never going to show up on the screen. So I have to expect frequent false negatives--no indication that those aircraft are nearby--creating a false sense of security. Yes, iFly often displays ADS-B traffic; but I can never know what it doesn't display. What's even worse is that friends' airplanes that I know are transmitting ADS-B data are not always depicted on my iFly display--even when I can see them directly with my eyes. Sometimes they are and sometimes they aren't. (It might be caused by faulty coordination of the UAT and standard ADS-B data, but I don't know that for sure.) In any case, it's very disappointing. So if iFly were announcing "traffic" in my headset, it would be some slight comfort if traffic is really THERE. But it wouldn't be really comforting because I could never be sure.
As for your terrain example: hills and towers aren't at all like airborne traffic. Hills and towers don't move around, ascend, or descend. They're always either there or they're not there. So a terrain-and-obstacle warning device ought to be close to 100% reliable--very unlike ADS-B.
But my other reason is that I usually fly a small amphibian low and therefore have terrain warnings turned off to keep from constantly being warned of flying close to the ground when it's my intention to fly low. So I leave terrain alerts turned off unless I know I'm going to be flying among hills and avoiding water. Granted, I'm probably a special case in this--but constant audio warnings of terrain would--for me--be intolerable.
On the other hand, I'm reasonably comfortable with iFly's "Traffic" instrument--that black square that pops up when iFly detects ADS-B traffic. I usually see it appear, and even when I don't notice it immediately, it stays on the screen for me to notice later. So it depicts the positives it gets but doesn't nag me about them and I know to expect that there almost certainly are false negatives flying all around me.
An effective audio warning would happen once and stop nagging until the situation got really serious. But it would still be a positive, and I'd never know about the false negatives.
What I've come to be most disappointed in is those military helicopters that aren't playing in the ADS-B system. They're often flying at or above my altitude. Or aren't they? (Or are they...)
So maybe Boeing/Foreflight has audio traffic alerts all worked out--but unless they're awfully close to 100% accurate, I'm not tempted to complicate my flying life with yet another steep learning curve and a complete instrument panel rebuild.