Background Information About Last Night's Horrific Crash: Air Traffic Control

Sample TCAS display, red is the "threat aircraft"
From: Rockwell-Collins

During the last couple of hours, I have been asked by the news media about certain aspects of last night's horrific crash near Washington's Reagan National Airport. I have decided to share this information with you. I am taking the statements made by Washington officials that the helicopter was in the wrong place at their word and using that in my analysis. I want to emphasize that the National Transportation Safety Board (NTSB) are the experts for whom I have a great deal of respect and it is their job and not the job of politicians or the FAA to investigate this crash.

I am posting this with a goal of counteracting some of the horrible misinformation about this event. As someone who absolutely loves Wichita, I recommend reading Dion Lefler's excellent essay about how we are feeling today. It gives the non-technical side of the story. 


The last U.S. mid-air collision involving a U.S. airliner was in 1961 over New York City. These are extremely rare and I'll explain why in a moment. Also, the news reports saying this is the "worst since September 11" are incorrect. Two months later, in November, 2011, an American Airlines jumbo jet lost part of its tail after takeoff and crashed in NYC. Two hundred sixty-five were killed, including five residents of Queens on the ground.

TCAS. TCAS ("traffic collision avoidance system") is truly a miracle of modern technology. Installed in the cockpit, it talks to the TCAS systems on other aircraft in an area and sounds an alarm and flashes a display indicating the emergency measures (climb or dive) needed to avoid a crash. Because the TCAS systems "talk" to each other, only one says to go down and only one says up. 

The problem last night was that, as I understand it, military helicopters don't have TCAS. This is understandable as those radio signals could be detected by a foreign enemy. But, the TCAS in the American Eagle jet would not have have been able to flash an alert because there was no TCAS in the Blackhawk for it to "talk" to. TCAS is why mid-air collisions are so rare. More info on TCAS is here

Air Traffic Control "Collision Alerts"  The air traffic controllers see a schematic diagram of the aircraft in the airspace they are controlling. It is updated every few seconds. 

Below is the screen the air traffic controllers were seeing, courtesy of RAWSALERTS. We'll call it the "ATC Display" with ATC = air traffic control. 
  • [6pm Thursday] We have a well-produced video of the sequence of events. The audio is cleaned up. It is here. The aviation schematic map is different than the simplified version I present (above). 
  • The lines and circle left of center on the ATC Display is the runway diagram from the air traffic control screen. The American Eagle jet was going to land on the shorter runway, the line oriented northwest to southeast. 
  • "PAT" is the helicopter and JIA 5342 is the American Eagle jet. You see them getting closer together as the helicopter is flying toward the south and the American Eagle is flying north.  
  • The red CA appears 26 seconds before the crash, which means "collision alert." I have listened to an audio of the controllers telling the helicopter to look for the "traffic" (the American Eagle plane) and the helicopter said they saw it. Below, I will compare this to video of the crash but it is possible (the NTSB will figure this out) that the helicopter may have seen an American Airlines plane taking off toward the northwest which appears toward the end of the video. 
  • We don't know, at this point (the NTSB will listen to the audio tapes from the tower and the American Eagle's black box) what the tower said to the Eagle. It was on a different communications channel than the helicopter. That is normal.
  • This flight was marketed and painted as American Airlines, actually American "Eagle." The flight was operated by PSA Airlines. Its "call sign" is Blue Streak. See my note at the bottom. 
  • What usually occurs in a situation like this is the tower would urgently say, "Blue Streak  5342*, go around!" That is enough for the pilots to know to abort the landing and ascend to an altitude of 3,000 feet (the standard go-around altitude). After the urgent warning, the tower would probably have elaborated, "American 5342, fly runway heading, ascend to 3,000 feet and contact departure (since the plane would be rising in the vicinity of the airport)." It is possible this all occurred, we don't yet know. 

Video of the Crash: Below is the video of the crash as taken from the Kennedy Center which is on the Potomac looking south toward Reagan Airport (also on the Potomac). The bright lights are the landing lights of American (AA) 5342. The dim light moving from left to right (north to south) is the Blackhawk. We can compare it to the ATC Display.

Just before the crash in the video, you see departing from Reagan a separate American Airlines flight which shows up on the ATC display just about the time of the crash. It is in the upper right part of the screen.


It is within the realm of possibility that the helicopter mistakenly thought the departing American Airlines jet was the plane the crew was being warned of, in part because he was told to fly "behind" the American jet. Again, the NTSB will fully investigate this.

Before being critical of either flight crew, the visibility from a helicopter's cockpit is limited and from an airliner is extremely limited. There are no rear view mirrors, etc. And, it was night. Picking out each other's navigation lights in a bright light nighttime environment like Washington's is difficult, at best. 

There are terrible people spreading all kinds of conspiracy theories, etc., online. I've investigated dozens of airline accidents and there is zero evidence of anything pointing to something unusual. 

I have worked with the NTSB on accident investigations on several occasions. Even spent the day together with them on one of those investigations. Again, I have great respect for the NTSB. Congress and successive administrations have preserved the agency's expertise and independence and for that they deserve great credit.

One final thing: it is typical that a final NTSB report, including the "probable cause," will take a year. 

* It is likely the ATC used a different "call sign" last night because the plane was actually operated by PSA Airlines. United's call sign is "United." But British Airways is "speed bird." The PSA Airlines' (which was operating the flight) "call sign" is "Blue Streak." 

Comments

  1. Thanks for your explanation of what is known so far about this crash. Susan and I will be checking in on your blog for further updates. It's good to have a friend with such expertise in this subject.

    ReplyDelete
  2. Thanks for the information Mike. Have followed your reports for years. Fellow Kansan, grew up in Odin. Have you seen the reports the Black Hawk pilots were flying using night vision on a check out run? Keep up your great work.

    ReplyDelete
    Replies
    1. I am not familiar with the latest night vision technology, which is why I haven't commented. Thank you for the c9ompliment.

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  3. Two points of clarification:
    The blackhawk likely had TCAS - even if it didn't - TCAS can provide an RA when the target aircraft has a Mode C or S transponder. Its more likely they were just at a low enough altitude that an RA was inhibited.
    Also a controllers collision alert doesn't necessarily dictate a Go Around. Visual separation is adequate.

    Would like to hear more about your work with the NTSB. Always interests me to see weather and aviation together.

    ReplyDelete

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