ADS-B might actually have prevented a collision today

[RobertE]

I don’t want to get overly dramatic because the fact is it’s very, very unusual for two aircraft to occupy the same space at the same instant.  Three dimensions work in our favor.  But this morning I think it was at least 50/50 that, absent the heads up my GTX 345 gave me, I might have become a statistic.  

I departed Palo Alto just below SFO’s class B, turned in a direction that would allow a climb and commenced a climb.  This was just prior to a hand off from the tower to nor cal and in an area where lots of aircraft squeeze into the airspace below class B.  Well, a King Air was at 9 o’clock 200 feet above me a mile away on an T-bone heading when my ads-b started flashing yellow.  I quit climbing and got a call from the tower just as it passed 200 feet overhead alerting me to the traffic.  Tough to say if had I sustained a climb whether I’d have slowed enough to pass behind it.  But that flashing yellow (and, maybe, audio alert.  Can’t remember) sure helped.  I do know that tower and ATC were of no help in that airspace.

[cbarry]

I’m glad you were paying attention and took corrective action to save your hide!   Your story reminds me to ask if anyone is seeing a variance in altitude reporting from TIS A, B traffic and ADS-B trafffic?  I regularly see a 400-500 feet difference on the same traffic.  It makes me stop and question which is more accurate when you share a story about only a 200 feet separating being the difference between a near miss and a mid air?

[RobertE]

I don’t know the accuracy of TIS A and B but on the half dozen or so times I’ve been able to visually judge ADS-B accuracy it’s accuracy has been at least within 100 feet, maybe better.

[David Lloyd]

At times, I am almost mesmerized by all the traffic showing on the ADSB display.  That time I am not looking for traffic out the window.

There is a large area of spotty coverage east of Charlotte northeast to Greensboro.  I made a sudden and hard turn to avoid nose-to-nose traffic.  As I was turning, less than 1/4 mile, the Garmin lady (I was in a Bo) gave a traffic alert.  With the turn we missed by a couple hundred feet.  Bonanza and Caravan, closure rate was over 300 knots.

As good as technology is, we still need to look out the window.  Don't let the machine do all our thinking for us.