How I see modern Air Traffic Control

17 02 08 - 01:24 Used tags: , , ,

A few years ago I started expanding and overlapping my hobbies. Obvious overlap between being a system administrator (and integrator and architect) and flying is Air traffic control or ATC. I joined the virtual flying community and observed the procedures there and visited Slovenia Control and Ljubljana airport with them. I'm also reading AeroSafety world online magazine and am following and flightglobal rss feeds. If it is worth anything, I've also seen all AirCrash Investigation tv documentaries and IVTV dvds. I also asked our ATC for their SOP documents but was understandably denied the request as they're internal documents.

The most pressing problem of ATC today is how to increase the capacity of airways to safely carry more planes (=passengers) from point A to point B. Based on the little information I have available, I put together a sysadmin's view on how I think it should be done.

While one obvious answer to that is to build larger planes like A380, this cannot satisfy all needs as not everyone will be flying around in those large planes. We need something else.

What is the main job of ATC today? ATC business is to provide separation between planes to allow safe flying. Of course this separation is just the opposite of squeezing as many planes as possible into the same air way between two points, so the workload and the stress of ATC folks increases. So the question is how to increase the density of airplanes in the sky while decrease the load of the controllers?

Spacing between the planes is largely determined by the delay by which the controller gets the status updates on his screen and the speed he is able to communicate his instructions to the pilot in relation to the speed airplanes fly at, plus all the necessary safety margins. Radars spin only so fast, atc radar picture is composed of information from many radars and it needs a few consequtive updates to calculate airplane vectors ... then processing also takes some time ... At the end it looked painfully slow and sufficiently outdated to me that I thought "this could and should be done better".

I'd say give the freedom to the planes. Don't tie them strictly to corridors from waypoint x to waypoint y. Let them fly as straight as possible from their origin to their destination.

Oh my! The chaos!

Yes. There can be a lot of order in chaos :)

What I would like to see is better integration of TCAS and ADS-B with FMC. Both already "hear" properly equipped airplanes from over 100 miles away, why is then FMC not told about these planes? Next step, when FMC is aware of them, planes should be able to automatically negotiate each their own optimal flight path to prevent not only colisions, but close encounters as well.

When I read about TCAS on wikipedia, I was very suprised to see that TCAS by itself is not aware of the current performance envelope of the airplane nor the terrain over which the plane flies. Thus it is theoretically possible for TCAS to issue a RA of climb when the plane is not capable of climb or to issue a RA of descend when the ground is dangerously close. This clearly shows that there is no proper interaction with TCAS and other airplane systems. In sysadmin speak we say that the unit is not efficiently integrated into the system. I find this interesting, as there is so much time and energy spent in crew coordination procedures, how the PF and PNF share their workload and cross check each other ... and then the instruments are not treated in the same way and are allowed to work one over the other. This is something that clearly needs to be taken care of, the sooner the better.

The other interesting thing I read about TCAS on wikipedia is that it is basically limited to about 1MBit/s of bandwith to communicate with other planes and that this limit is already a problem around some of the bussiest airports in the world. Whoever designed it that way, I can only hope they left enough flexibility in the packet format to upgrade it painlessly to higer bandwith.

ADS-B is the next interesting piece of equipment that is being introduced into planes. It extends mode-s info with "state vector" so that other airplanes "hear" not only where a certain ADS-B equipped plane is, but also where it is pointed at and how fast it is moving in that direction. This improves situational awarness a lot, but in order to decrease ATC load as I see it, it should also broadcast the plane's intentions of where it wants to be in lets say the next 5, 10 and 30 minutes. That way other airplanes would be able to identify them as potential threat. When two airplanes would find out that they are going to cross, they would enter negotiations on how to avoid eachother while taking into account everybody else, aircraft performance (how they're able to perform the avoid maneuvre), weather and ground situation (in which direction they can avoid). All that fully automatically and long before the TCAS would even issue a traffic warning.

When all this becomes mandatory and the density of the metal (and composites;) flying over our heads increase, there will come a situation where two planes will figure out that there is no way to perform avoidance without crossing someone else flight path. That will create a whole storm of negotiations, which can hit time or bandwith bottlenecks just by the nature of complexity of these algorithms. By then I expect swarm algorithms, which are currently being studied in the fields of micro robotics and crowd modeling, will be understood well enough to be ready for implementation into this system. Basically someone needs to say "I will perform such avoidance maneuvre and all others must adopt to me" in a way that is the most efficient for the whole group.

Testing of such system would be very easy to perform in the virtual skies. Design a funcional model of such "next gen TCAS", put them on each virtual plane and then slowly increase the density of flights over a certain area and observe the results. It should be pretty interesting experiment :)

The final question is always "how to implement this?" I'm sorry to say that, but ATC folks will be sweating for some more years. Even if this is mandated by some regulatory agency (which afaik does not exist because of the democracy and free market b*****it), it is going to take years to adopt to the new ways. But the sooner the whole system starts to reorganize, the better for all.


Update: after a chat with a few pilots and folks from ATC they explained that systems for this are in development for at least 15 years now and that the problem is not technical but political in nature. Basically, who's to blame if things go wrong. Bah.

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