Jaun Browne did a good job covering what is known so far on the Instructor and Student in the 172 and single pilot in the Sonex midair in the busy airspace just outside DEN class B airspace. He mentioned the audio some of you have mentioned on Foreflight that gives a audio warning of nearby aircraft while our eyes are in see and avoid mode. I had my first experience with ADS-B the other day without Foreflight or audio and was not impressed. I looked out while Damon checked his ADS-B screen and we were unable to turn to get a view and see a target. We did not find one a mile away same altitude.

When Soy Anarchisco and I flew his J-3 Cub in the area working on energy management turns, we were never more than a thousand feet up and not in Bolder traffic, so not as crowded. I understand the need for a higher altitude to practice stalls, but why are so many training a couple or three thousand feet AGL? Flying through D below (200' AGL) many Bs and usually along and then across busy runways, I found no traffic down there except when crossing the main runway or parallel runways. Nor have I seen much up at legal for others low altitudes. What would prevent instructors from using those less dense altitudes?

The number of pilots has remained stable for many years. It is the reduction in the number of airports and their most common location around B that is the problem. When we didn't have to go so fast, most towns of some size had an airport. Most were grass and less than 3,000' long, but the same number of pilots had a lot more airport space to spread out in.

Around B, there is limited airspace under the layers of the cake for VFR operations. The lower altitudes that are hardly used are perhaps a place of greater safety for those willing to learn safe maneuvering flight techniques.

Ok ...... care to add anything to that second paragraph ? . That is a classic

Sorry. I have posted about flying pipeline patrol below B airspace before so I didn't want to bore you'all. Patrols have a waiver for 200' AGL. That is the best patrol altitude and also the safest escape from midair exposure. Congested areas are minimum 2,000' AGL I think for normal operations, but few fly there. So outside the traffic pattern, both D and uncontrolled, I would think 2,000' AGL would be a safe practice altitude except for stall practice. Most of my students were Ag, so over a couple hundred feet up was outer space. Stalls was a fatal event so we taught energy management turns of 1g regardless of bank. The unloaded wing will not stall. Even around B and other high traffic areas, we worked in a world free of other than Ag and pipeline patrol aircraft. 2,000' AGL is the beginning of nose bleed altitude in our world, but I would think other training schools would take advantage of that less traffic dense altitude. I flew all over the US on pipelines, including the front range, and did not see much traffic up at 2,000' AGL. Most aircraft I saw were little dots much higher or in a traffic pattern.

There are no altitude cops looking for those below the layers of B airspace. Only the pilots around the airport who think someone is flying too low. C Class controllers will fuss about climbing to get you on radar. Decline radar services. Hopefully they will eventually use GPS and quit fussing. The whole idea of the upside down wedding cake of B Class is to keep VFR separated from IFR. C radio call requirement seems to counter that idea.

The need to get up high is high altitude orientation. It is not safer in every situation, and certainly not around the edges of Class B airspace.

ADS-B has little to no value in mid air reduction. Likely makes things worse by providing a false sense of security and sending everyone's eyes inside to screens when it starts beeping.
https://www.youtube.com/watch?v=IGQmdoK_ZfY
How'dyall do?

Another thing in visual reconnaissance is the intent to see. We used the technique with aerial scouts in Vietnam looking for Charlie and with pipeline patrol here looking for leaks, equipment, etc. The pilot leaning into his work with expectation will call in twice as many spot reports as the pilot just flying the patrol. We can't lean into the outside visual scan while leaning into the video screen. We can't wait for the video or audio trigger to initiate the lean into the visual scan.

A bit more about leaning in and about low density down low. There was a tower controller at Cincinnati Northern Kentucky that would fuss with airline pilots calling, "I got TCAS." He would answer in a Texan drawl, "He's fifty feet off the trees. He is not traffic." The airline pilot was leaning into his TCAS.

I am very, very familiar with this area and I dont' think Juan is correct about this being related to Class B shelf. The issue here is the confluence of 4-5 airports and a victor airway, and the choice of the high volume141 schools out of KBJC to conduct training maneuvers right at that exact spot that we refer to as the "striped fields"

This exact spot is the exact approach for KBDU, KLMO, KEIK, 76O0 airports and is on the victor airway for approach transitions and all the practice IFR traffic to/fro KBJC, KFNL and all parts north/south along the front range. It's also in an extremely sensitive area for noise abatement - proximity to the niwot and gunbarrrel where we get a ton of noise complaints. It's frankly the mother of all hot spots.

I'm pretty sure this 141 pilot is brand new at 22 years old - and the sonex is quite a bit faster than the 172. I'm pretty sure the sonex was setting up to enter the 45 downwind at LMO. I really wish the striped fields were not used for maneuvers and training - and if they are the instructors make a much, much greater effort to perform clearing turns before conducting them. I'm sure that first circle they did was a lip service clearing turn. I'm also not sure if they had stratus - but they both could have and should have used ADSB in to alert them of each others presence. But you still have to do pilot shit and move to de-conflict. I believe until I see more evidence that the sonex driver was looking to set up his approach and not paying attention to his ipad - as he should. And the CFI which had 2 people in it should have had a greater chance to see what was happening and avoid it. We will know more in 2 years when the NTSB report comes out.

ADSB is not a complete solution - and itself is not the problem. It's much easier to spot traffic with ADSB than in the days when Contact and I flew here without it. Most of these planes (except gliders and the no-electric exceptions) are reporting their positions with working ADSB out inside the mode-C veil. Just because you saw a blip on the fish finder and couldn't see it out the window is not a reason to conclude that ADSB doesn't work. It should highlight to you just how close we were always operating before and just never knew it because it's actually very, very hard to see aircraft - especially flying in the rising sun, or a mix of speeds and altitudes.

To be frank and honest, for the last 10 years and even more so now - I depart and arrive through this spot almost daily - and I now choose to come in VERY low - like 500-1000 AGL to try and stay under all the yahoos. And there are a LOT of them now. They plow through the glider box while we are towing gliders almost every day. You can't get a lap in the pattern any more at LMO without some dingleberry doing a 12 mile straight in on the RNAV expecting everyone to get-out-the-way. Planes intentionally flying within 1/4 mile of me are an almost daily occurrence now. It's terrifying really. But I can't stop flying.