In this video, an airline captain does a fantastic breakdown of the radio communications/radar screen from this incident, (VIDEO OF THE COLLISION IS SHOWN) helping translate all the chatter and offer his insight. Basically, the Army Blackhawk helicopter was asking for "visual separation" from the tower, meaning it's all on the chopper to look out the window and not hit anything (in sky right-of-way, helicopters must yield to airplanes), and the tower let them do this while asking, "Hey you see that plane that's trying to land, right? Go behind him, ok?" and the chopper said they had the traffic in sight, but it seemed as if they were looking at a whole different plane, much further away. After all, these Army choppers are used to just kinda...doing whatever, and the controllers at DCA know this.

What gives this tragedy a sordid twist is when you see this series of events literally the day before, in which a (different) US Army helicopter very nearly does the same thing to a landing airliner at DCA, triggering the TCAS system on each plane... and then they do it twice more.

TCAS is basically an airplane's "if(goingToCrash){ dont(); }" system, which, if flying planes get close enough, feeds the pilots of both planes on a collision course opposing evasive maneuvers, called an RA. An RA occurring at all is cause for serious scrutiny in any event, because it means something else went terribly wrong. It also sets off alarm bells in the actual control tower. This shit has saved many lives.

In the video from the night before though, you can see the military helicopter ask for visual separation (familiar), fly so close to an airliner that they get an RA, continue flying right up the line of approaching planes, buzz past, and trigger an RA on TWO MORE landing airliners. That's three RAs from the TCAS system, almost like the army guys were playing connect-the-dots.

The following fateful night, this CRJ-700 was exactly where it was supposed to be: turning on a weird short final, focused on the runway, making sure the plane is landing safely without worrying about anyone getting in the way. Once you get low enough to the ground, TCAS shuts off (for complicated but pretty sound reasons) so these helicopter pilots did not have that last line of defense to lean against when they got as close as they did. If what I see is what I think I saw, I am disgusted at the cavalier mentality and behavior of these Army pilots. In the video with the three RAs the helicopter didn't even acknowledge what they'd done (over civilian radio, at least) as three airliners had to fly off and reset their approaches.