Never that close but was with a friend a couple of months ago and a Barron would have. He never saw us. He was IFR. We were flight following. We volunteered to descend. Both planes ADSB but the Barron was not looking out the window. Clear day. Don’t think ADSB is going to save you. Just means they can get real close and still feel comfortable not changing direction.
Had a Bonanza go under me once JUST like this, albeit about 30-50' more vertical separation, as I was thermalling an SGS 2-33 over the Ortega Ridge at Lake Elsinore, CA. I could see him in the cockpit as he went by, with his head down, and never saw me. Never knew I was even there. This, despite him flying within a half-mile of a chart-marked parachuting jump-zone, and IN a chart-marked area of glider activity. I was turning into him as he went under, so the view of my aircraft as he approached would've been the entire 50' span of the very white wings of the glider banked towards him. Clearly he hadn't been looking up for a while. I saw him coming in just as I was clearing my turn in that direction. I'd cleared it that way on the previous circle, but this guy was moving fast.
Soaring at less than 80 feet over a ridge, had a helicopter pass directly under me in the same direction- less than 2 wing spans distance; looking down to see whirling blades was not fun.
As passenger on a commercial jet into nighttime San Diego circa 1979, a fighter jet shot vertically past our wing tip, within about one of our wingspans- I was just looking in the right direction at the right moment. There, then gone into the darkness, the lights of the city bellow resembling the Death Star. Highly cinematic.
Flying an early morning search grid over vineyards in the Central Valley for the Sheriff’s Department looking for a six year old girl that had just been abducted. Circling an area of interest in a Champ at 500’ AGL. I was searching while my friend was flying. I spotted a brief glint in the far distance, so I kept an eye on that area of the sky while searching. The glint hit a few more times, and the last time I could make out the head-on view of a low wing plane moving fast. I advised the pilot, but he couldn’t hit get the right focal distance to see it. It closed very fast Headed straight for us, I shouted “MY PLANE” as I grabbed the stick and did a quick yank’n’bank to show our wings and get out of the flight path. I watched it go by about 100’ away (same 500’ AGL altitude) right where we had been just a second or two earlier. It was a business jet of some kind, flying up the valley at 500’ and there was no indication that he ever saw us.
Ridge soaring a hang glider again, focus downward to the forest canopy, looking for signs of lift, unknowingly on a collision course with a redtail hawk coming from the opposite direction, also looking down, probably for something to eat. We both looked up at the same moment, eyes at the same level, about to collide- the hawk cries out, flips up into a wing-over to present it's claws to my face, rounding out under my base bar, disappearing below and behind me.