366 Midair Collision at Reagan National - Tragedy Over the Potomac
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This is not the episode I had planned to bring you this week, because, sadly, as I was watching the news last night, reports started coming in shortly after 9 p.m. Eastern of an accident at the Ronald Reagan Washington National Airport. The first report I recall hearing was that a regional jet had gone off the runway into the water. That seemed plausible, as a high percentage of business jet accidents involve aircraft that land long and fast and go off the end of the runway.

Later, it was confirmed that there was a tragic mid-air collision between a regional jet and a U.S. Army Sikorsky H-60 Black Hawk helicopter. Hello again, and welcome to Aviation News Talk. I'm Max Rescott. Footage from a live webcam operated by the Kennedy Center appears to show the collision over the Potomac River. When the landing lights from the two aircraft merge, there's a large explosion and both aircraft drop into the river.

When I saw the video, I commented that it was unlikely that there were any survivors. As of this morning, there are still no reports of any survivors. I've pulled the ATC audio courtesy of liveatc.net, and I'll play that for you. And I've reviewed the flight tracks for the two aircraft that were posted on Twitter by ADSB Exchange, and we'll talk about that as well.

While we don't know all of the factors involved in the accident, and there probably will be many, we do know that the Army helicopter was instructed to pass behind the regional jet and follow it to land on runway 33. The helicopter clearly did not follow those instructions, and that failure to do so will most likely be included in the NTSB's probable cause, though they are sure to cite many other factors as well. This accident is a watershed event.

Midair collisions involving airliners are extremely rare, and when they do occur, there are lots of lessons learned and many changes to rules and regulations to try and prevent the type of accident from occurring again. You may recall the midair collision near San Diego involving an airliner that occurred in September 1978.

In that accident, Pacific Southwest Airlines PSA Flight 182, a Boeing 727, collided with a Cessna 172 over a residential area of San Diego. Following that accident, TCAs, now called Class B Airspace, were implemented to increase separation between commercial and GA aircraft. The FAA also began requiring all aircraft flying in TCAs to be equipped with Mode C transponders.

Ironically, this midair collision also involved an airline called PSA, but it's not the same one that was involved in the San Diego crash. PSA Airlines is a regional airline that's wholly owned by American Airlines. Flight 5342, a Bombardier CRJ-700 regional jet, had departed from Wichita, Kansas, carrying 60 passengers and four crew members.

It was flying the Mount Vernon Visual Runway 1 approach, which follows the Potomac River northbound. It's essentially a straight-in approach to Runway 1 with some minor bends to follow the river. Meanwhile, PAT-25, a U.S. Army Sikorsky H-60 Black Hawk helicopter, was also following the Potomac River, however it was approaching Reagan National from the northwest. It had been flying along at about 800 feet, but descended as low as 200 feet as it approached the airport.

As it passed to beam the runway 19 number, it climbed back up to 300 feet. Meanwhile, flight 5342 was descending along the river northbound. To circle to runway 33, it turned a little to the northeast, flying just east of the river, and finally made a small turn to the left across the river to land on runway 33.

It had been descending steadily and had reached 330 feet MSL. However, the last data point showed it at 380 feet. So it's possible the airplane climbed at the last moment.

At the point of impact, flight 5342 was about 0.4 nautical miles from the runway threshold and about midway over the river. The Black Hawk was on a right base leg to the same runway and was approaching from the airliner's 3 o'clock position, which would have made it difficult for the airliner crew to spot the helicopter, as it would have been initially lower and back-lifted by the lights of downtown Washington, D.C. The last ground speeds recorded were 106 knots for the airliner and 71 knots for the helicopter.

12 seconds before the crash, the two aircraft were about 0.6 nautical miles apart and pointed almost straight at each other, so you would think it would have been easy for the pilots to spot the landing lights of the other aircraft. ADSBExchange.com posted the ground tracks of the two aircraft on Twitter and commented that the Army helicopter was not transmitting ADS-B out. Now, that's a requirement in Class B airspace, though perhaps military aircraft are exempt.

Someone asked me how ADS-B Exchange was able to plot the helicopter's position without ADS-B data. So I exchanged a couple of emails with their CEO, Dan Storifert. He explained that the helicopter data was obtained through their volunteer network of Mode S receivers. Then they used multilateration to triangulate the helicopter's approximate position. So the helicopter was squawking Mode C or Mode S, which means that it certainly appeared on the airliner's traffic screen.

But perhaps the airline pilots were relying on TCAS alerts instead and were not looking at the traffic screen. While that may be a safe strategy at higher altitudes, it doesn't work well at low altitudes as TCAS alerts are inhibited at the altitude they were at. As you can imagine, when an airliner is landing and gets close to an airport, they could receive lots of nuisance alerts from other aircraft that are close to the ground, perhaps landing on other runways.

Per the FAA's AC20-151A, resolution advisories are inhibited below 900 feet AGL while descending, and TCAS automatically reverts to just traffic advisories . However, all TCAS oral and visual traffic alerts, including TAs, are inhibited below 400 feet AGL while descending.

ADS-B data shows the crash occurred at 350 feet MSL. The actual altitude was closer to 330 feet MSL since the local altimeter setting was 29.90 and ADS-B data is referenced to pressure altitude 29.92.

So the airliner was so low that all of its TCAS alerts were inhibited. And when they're inhibited, the only way the air crew can spot traffic is by the same way you and I do, which is looking out the window or looking at a traffic screen. Here's the relevant ATC audio courtesy of liveatc.net.

At 8.43 p.m., five minutes before the accident, Flight 5342 checks in with the tower on the Mount Vernon Visual using the callsign BLUESTREAK 5342. 20 seconds later, Flight 5342 responds.

About a minute and a half later, the tower gets a call from the Army helicopter using the call sign PAT-25. We can't hear the helicopter side of the conversation since they're transmitting on a military frequency.

The tower, which is simultaneously transmitting on both the civilian and the military frequency, responds to PAT-25. 45 seconds later, the tower notifies PAT-25 of the airliner's position. About a minute and a half later, and just 20 seconds before the crash, the tower gives the helicopter this instruction.

The tower seems to be saying visual separation and is apparently repeating what the helicopter had said.

Six seconds later, we hear this transmission, and you can hear other people in the tower cab reacting to the explosion that occurred when the aircraft collided. The tower then issues a series of instructions to get aircraft to exit the airspace. American, 3132, go around, turn left, and 250, climb Anthony 3000.

KLX heading 350, 3000, American 3130 Tower, Blue Streak, 5347 is on final, request runway 33, circle to 33 Take in the heading from American 3130 American 3130, go around, select band 270, respond maintain 3000 270 on the heading, 3000, American 3130 American 472, Council landing, cleared for runway 122

While the helicopter apparently indicated that it had the airliner in sight, it's clear that they didn't. One possibility could have been that they had a preceding aircraft in sight. However, as I played back the data, I can see that the preceding aircraft landed on runway 33 about two minutes before the accident. So when the tower asked the helicopter if they had the airliner in sight, flight 5342 was number one for the runway.

I have a presentation on night flying that I gave at AirVenture for eight years in a row, and in it I talk about the difficulty pilots sometimes have avoiding other aircraft at night. My recollection is that years ago there have been some night accidents that occurred when an airliner could see the lights of another aircraft, but because of limits to our perception at night, couldn't figure out exactly where the other aircraft was located and how to avoid it, even though they could see the aircraft.

So at night, accurately perceiving the location, motion, and trajectory of another aircraft based on its landing light can be surprisingly difficult due to some of these factors. One, lack of depth perception. In darkness, our eyes rely more on monocular depth cues than stereoscopic vision, making it hard to judge distances accurately.

2. Size and distance illusion. A bright landing light can appear as a point source, making it difficult to determine whether the aircraft is far away and approaching or close but moving laterally. 3. Lack of relative motion cues. If an approaching aircraft is coming directly at you, it may appear motionless, a condition known as constant bearing decreasing range or CBDR effect.

This illusion can result in a collision because the other aircraft does not appear to move across the pilot's field of vision. 4. Autokinesis At night, a single bright light against a dark background can seem to move unpredictably due to small involuntary eye movements, leading pilots to misjudge the actual motion of another aircraft.

And five, glare and blooming. A bright landing light can create glare or halo effects, making it harder to determine an aircraft's shape or orientation. So the advice I give in the presentation is to start avoiding other aircraft at night as early as possible, as it may become more difficult to avoid them when you get close. Also, if you have a traffic screen in your aircraft, use it, especially at night when it's harder to visually perceive the exact location of another aircraft.

And if you're flying with late model Garmin avionics, check your traffic screen to see if you can turn on vectors, which stick out in front of other traffic to show where those aircraft are pointed. Then see if you can select between absolute vectors and relative vectors. You want to choose relative vectors and use that all the time as it shows you not where the other aircraft are pointed, which is irrelevant, but where those other aircraft will pass relative to you.

And if the green line, the relative vector of another aircraft, crosses your aircraft, you are on a collision course with that aircraft. Oddly, I found myself in a similar situation to this mid-air collision when landing a Vision Jet in Kentucky at night.

We were number one to the runway, and there was a fast twin that was approaching us from our two o'clock position that had been told to follow us. But when I checked on the traffic screen, the relative vector was crossing our plane, so I knew we were on a collision course. When I informed the tower of this, they said not to worry as the plane would follow me. So I had to call them again and tell them that my avionics showed us on a collision course. The controller then had the twin widen out to his left to pass behind us.

So sometimes we need to help controllers out with separation from other aircraft. Let's talk briefly about Professor James Reason's Swiss cheese model. In his book, Managing the Risks of Organizational Accidents, he talks about how organizations build defenses to try to prevent accidents. Each defense could be a policy or regulation or maybe even a piece of equipment meant to guard against a possible accident. When one of these lines of defense doesn't work, it's called an escape.

The idea behind the Swiss cheese model is that each slice of cheese represents a line of defense, but that there are holes in each of these defenses through which escapes can occur. The slices of the cheese rotate somewhat randomly, and on rare occasions, the holes in all of the slices of cheese will line up. An event occurs in which there is an escape for every layer of defense. When this occurs, you have an accident.

Let's talk generally about the lines of defenses associated with this accident and where escapes may have occurred. As we already mentioned, the U.S. Army crew apparently failed to follow the controller's instruction for reasons that are unknown. Also, both crews failed to see and avoid each other, but I believe that see and avoid is a very weak defense as it's difficult to spot other traffic visually.

In-cockpet traffic screens are an excellent defense, and I rely on them heavily, especially when flying in busy metro areas. We don't know for sure whether either aircraft had a traffic screen, but it's highly likely the airliner did. Failing to notice the traffic on a traffic screen is another escape in a line of defense. The design parameters of TCAS equipment was also an escape from a line of defense. Since the aircraft was below 400 feet AGL, it likely didn't generate any alerts for the crew.

Another possible factor was that the tower didn't alert the airliner to the presence of the helicopter. I don't know whether FAA rules would have required them to make that notification, but if they had, the airline crew might have searched more actively for the helicopter. There was also a post on Twitter that showed a short video that the poster said had been sent to them by a friend who worked for the FAA. Now, there's no way to verify if the video is real.

It shows a computer screen with two aircraft starting to merge. About 30 seconds before the accident, the screen shows red CAs or collision alerts next to both aircraft. So if the tower had access to this radar feed, which they probably would have, they could have warned the pilots of the impending collision. So it appears that the radar collision alerts were another escape in a line of defense.

We will learn much more about this accident in the days and years ahead. If you want to learn more about midair collisions, you may want to listen to episode 109 called Avoiding Midair and Near Midair Collisions. You can find that episode at aviationnewstalk.com slash 109.

undoubtedly we're going to learn many lessons from this accident and there are sure to be changes in the rules and regulations as a result in the meantime please fly defensively and use all of the tools at your disposal to avoid a mid-air collision

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