Ay caramba!
The tragedy of loss of life is hard to take. But a close second is observing the "experts" tell their opinions on why it happened and why they are the only ones who know the truth.
Having said that, here I go....
Aircraft: UH-60L Blackhawk. This could have been a VH-60L, but it definitely was not a 60M variant. Wreckage photos do not seem to concur with the "Gold Top" paint scheme assertion, but it is quite possible the unit has aircraft with varying livery. If the aircraft was a 60V conversion, it would have glass cockpit and I believe ADS-B in/out. That's hard to say, since the 60V configuration has been a moving target. The actual configuration of this 60 could be almost anything. As a maintenance test pilot and QC supervisor I had to manage many aircraft configuration changes when the Army moved aircraft from unit to unit. Different aircraft configurations with a company sized unit is not uncommon. I would say more than likely there was no ADS-B IN, and probably only a basic ADS-B OUT which included barometric altitude either directly from the bar-alt or as a pass through from the mode C transponder. Radar video playback showed altitude for the Black Hawk in 100' increments. That means the helicopter could be 150'-249' while reading 200' on the ATC display. The video I saw, after being paused several times, showed the helicopter altitude going from 200', to 300', and then back to 200' just before impact, which would be 150'-249' MSL. This assumes the correct altimeter setting was used and there was no error in the altimeter itself. Of course the Black Hawk was probably using their radar altimeter to fly, so they probably didn't pay attention to what the bar-alt read at all. TLDR: What the altitude the ATC saw may inaccurately represent the actual altitude of the Black Hawk at the time of the collision.
Crew: a 1000 hour CW2 instructor pilot is not "very experienced". Even the best CW2s I flew with lacked the full wisdom to realized that they don't know everything. Conducting an NVG APART with a 450-500 hour copilot can make this a relatively risking mission. A barely experienced IP with a junior (flight time wise) PC who is higher rank (maybe their company commander) is not optimal. It's done, but it is not optimal. An APART requires flight in both the left and right seat. Depending on how the day and instrument APARTS were flown, the NVG eval could have been done with the instructor in either seat. This would have been indicated on the risk assessment. Doing an NVG APART in a congested area like this would require the IP to be WAY ahead of the aircraft, just in case something unusual happened. If this route were part of their normal mission, it would be a necessary part of their APART. Can this PC safely get me through this airspace at night? According to the TC 1-1520-237-10, there is no requirement for a 2nd crew chief under NVG. In fact, some units allow NVG flights that originate and end at an airport to fly with just 2 pilots. It's part of the risk assessment worksheet and hopefully this was at least discussed during the brief.
There are some really good videos out on YouTube, as well as some TERRIBLE ones. Look for some that have a simulation done by expert pilots. One particular, was done with NVG lighting. It scared the crap out of me! The narrator was talking about the how difficult the RJ was to see. He even said, "I didn't have a CRJ, so I used another (bigger) aircraft in the simulation." While talking, I saw a "light" coming from left to right (from Black Hawk cockpit). It barely moved due to constant bearing decreasing range. I didn't realize how close the "light" was until the entire jet filled the screen. I have a lot of time flying Seahawks and Black Hawks. I have had a lot of bird strikes and even a couple of close calls with near mid airs. I know what a close call looks like. The simulation I saw was scary. I knew where to look. I knew what to expect. I saw a faint position light, but I was still surprised at the close proximity and the lack of reaction time. I'll try to link to the video.
Another simulation video showed the CRJ doing the circling approach. With the PAPI on glide slope, the CRJ was between 200-250' at the collision location. IMO, this video showed that if the Black Hawk had actually been 300' or more, they MIGHT have passed above the CRJ on approach glide path. It DEFINITELY showed that there was not adequate vertical separation, whether the H-60 was at their correct altitude or not.
The Black Hawk crew reported visual (without saying "Oh shit!" immediately). I find it extremely hard to believe they had a visual of the collision aircraft. After all, who would see an aircraft and deliberately not avoid a collision? Just my opinion, but I think they had a visual on the wrong aircraft. But, the NVG simulation I mentioned above indicates that they could have had visual on the collision aircraft and thought the CRJ was much further away due to CBDR.
Navy Jax has helos transition 300' and below along the east shore of the St Johns River. This puts you below glide slope on the approach end of runway 28. I have done this transition for most of my flying career and can't remember a single time NAS Jax relied only on vertical separation. I do remember several times being asked to circle south of the Buckman Bridge for traffic spacing. Is the Potomac too narrow to allow for this? Also...where would the Black Hawk gone to pass behind the CRJ had they really had them in sight? Over the city at 200'? Yikes. Looking at the charts there are several towers up to 400-450' in that area. Hit a plane or hit a tower? Hmmm
There are so many other factors, but I just wanted to cover the ones that seem to be represented inaccurately the most and for which I have personal experience.
**** Sorry, I tried to find the two videos I was talking about and couldn't find them. I'll add a post if I find them later
Most of you know my background, but here it is in a nutshell:
Army IP, IE, MTP, ME
3000+ hours in Seahawk and Black Hawk
HAC or PC all of the following... SH-60B, SH-60F, HH-60H, UH-60A/L/M, HH-60M, etc.. as well as various foreign sales 60 configurations)
Commercial CFI, CFII Helo
Commercial Fixed Wing Single/Multi CFI & CFII