Data… Information… Power

On 07/01/2016, in Buzzwords explained, by steve

informationThat information is power has been known for ages. It is not by accident that various religions, among others, have tried to keep their subjects in the dark. Knowledge acquired from information was dangerous. People with access to information tended to get all kinds of ideas that were better be left alone. In our connected world, keeping information from people is not that easy any more (though some countries will try to do just that…) and if anything, there is too much information around, we hear some folks complaining.

But is there such a thing as too much information? And what does this all mean in the world of aviation?

First of all, we need to clarify something. What do we mean by information? Is data and information synonymous? To fully understand the power of information we need to understand these concepts and also agree on their meaning.

Data is what we generate when, for example, we measure something. Take the position of an aircraft in flight. The position at any given moment in time can be expressed in five dimensions. There are the three spatial dimensions (geographical coordinates plus level), the time dimension (shows the time the other three dimensions are true) and the fifth dimension is the economic value of the flight for the aircraft operator. Though not always used as yet, this last is an expression of the costs and revenues the flight represents compared to other flights in the network of the operator. A flight with lots of connecting passengers represents a higher economic value than one with no connection passengers. If the former is late, it incurs costs that have to be avoided… you get the picture?

Of course when we take a given point representing the position of an aircraft, the five dimensions are nothing more than a heap of numbers.

This is data, not information.

Information is data put in context. Put the same data into different contexts and you will see that the information that emerges is very different, in other words it is context dependent. What does not change is that the different information resulting from the same data will always refer to the same reality.

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Understanding Controller Pilot Digital Link Communications (CPDLC)

On 08/12/2015, in Buzzwords explained, by steve

Reading this article, you may have spotted already that I prefer to talk about digital link rather than “data” link. This comes from an old debate where we tried to find a term that covered any type of digital link between the ground and the air, i.e. digital voice as well as data in the traditional sense of the word. In the end, it was agreed more or less that the D in CPDLC should stand for digital as opposed to data.


Anyway, all this does not change the basic fact that CPDLC is a method of communication between the pilot and air traffic controllers where spoken word is replaced by what are essentially text messages, addressed individually to the aircraft or air traffic control unit concerned. While it is possible to send free text (like you do in an SMS…), most of the messages exchanged in CPDLC are composed of pre-defined elements so that controllers and pilots do not have to type everything letter by letter or even word by word.

Communicating like this has several advantages. Misunderstandings due to language issues or improper use of the phraseology are eliminated, the stuck microphone phenomenon or wrong frequency selection disappear and the legacy linear way of talking to aircraft is replaced by a capability where messages can be sent in rapid succession to several aircraft, with more than one conversation open at the same time. All in all, more information can be sent in a given unit of time than is the case with the legacy, voice based system.

CPDLC lines up nicely with the modern graphical user interface of the air traffic controller. In a voice based system, issuing a new level clearance involves feeding the information into the ATC system by the appropriate manual input (via the keyboard or the screen) and then telling the pilot about it. With CPDLC, the input to the ATC system can generate the corresponding CPDLC message that is then sent to the cockpit automatically. Depending on the level of avionics integration, the new clearance may arrive to the pilot in the form of a command to be approved and once this has been done, the aircraft will climb or descend to the new level, as appropriate. With fewer opportunities to mistype things, safety is enhanced and overall workload is decreased.

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Airport Cities (no, not the game) – What is this?

On 04/07/2014, in Buzzwords explained, by steve

airport city belgradeAt the risk of saying the obvious, I will start by claiming that airfields were invented for the purpose of aircraft landing and taking off. The definition of an “aerodrome” used to this day by the International Civil Aviation Organization actually says so. Of course as airfields evolved to aerodromes and airports, many things changed, some for the better, some not.

Most airports to-day are competitive companies that edge out a living from the fact that there is an increasing propensity among people to fly. Fly for business, fly for leisure… millions take to the skies every year and they all need to go through an airport. The opportunity to make money from this is there for all to see and take. Of course there are also aircraft still in the picture but, with a bit of exaggeration, we could say that they are more a pain in the six o’clock for an airport than anything else. Aircraft need a lot of space, they make a lot of noise and dirty the environment while their willingness to pay for all that is famously low. I guess airports would just love to have a world where passengers would just come to the airport, eat, shop and then go home again…

Of course this world is not realistic but airports nevertheless try to get as close to it as possible. You cannot have failed to notice how the part of the airport seen by the passengers has turned into shopping centers at many places. You cannot get to the boarding gate unless you walk through the shopping and dining areas… It is a bit like hotel lobbies in Las Vegas… the only way in and out is through the swarm of one armed bandits and roulette tables.

With some airports earning close to 60 % of their revenue from non-aviation sources, it is easy to guess where their investment priorities are.

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UTM – What is this?

On 02/07/2014, in Buzzwords explained, by steve

uasThe controversy about operating UAS or Unmanned Aerial Systems in airspace also used by traditional aircraft has been raging for some time and different States have come up with different solutions, ranging from a total ban to cautious co-existence. Most experts fret however that the longer comprehensive and acceptable rule making takes to materialize, the more of a jungle this whole affair will become and the more difficult it will be to put things back to a semblance of order.

Come to think of it, however, one cannot fail to realize that most of the UAS in fact operate in an airspace not typically used also by commercial aviation. Low altitude airspace is there for all to use and except for areas close to aerodromes, it can be the ideal playground of various UAS services. Amazon wants to deliver packages, others bring your pizza via quadcopters… There is no reason this should not be allowed, however, it cannot be a free-for-all scene. Those machines, even the small ones, pack a substantial punch if they collide or fall from the sky and without proper management, they can soon become an insurance nightmare or simply just kill this new and promising industry.

NASA in the United States is now working on developing a system that will prevent this from happening.

UTM stands for Unmanned Aerial System Traffic Management.

Yes, you heard right. NASA wants to develop an ATM system for the low altitude airspace that will ensure the safe and efficient operation of UASs of all kinds in that airspace. We are primarily talking about Class G airspace here… at least to begin with. Once the concept is validated and operationally proven, it can be gradually extended.

For us, old hands who had fought hard to bring things like SWIM and trajectory based operations to traditional air traffic management, it is extremely satisfying to see that the birth of a totally new dimension in air traffic management, that of low altitude unmanned system operations, is in fact being envisaged with all those advanced concepts taking center stage.

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SBAS, GBAS – What is this? The technical aspects.

On 28/05/2014, in Buzzwords explained, by steve

Those who are familiar with approach procedures feel free to skip this post… I am not going to disclose anything new ore revolutionary. However, with Performance Based Navigation (PBN) and as part of it, GPS based approach procedures become more and more common, I thought it a good idea to summarize what a Space Based Augmentation System (SBAS) and a Ground Based Augmentation System (GBAS) is, what they are used for and why they are required at all. I think there are readers out there who have not dug themsevles into the mysteries of satellite based navigation and for them a bit of background knowledge might come handy.

To understand the issue at hand, first we need to go back to our well known and well trusted current approach and landing aid, ILS (Instrument Landing System). ILS provides precision vertical and horizontal guidance to aircraft on final approach to a runway. The system can provide this guidance with three distinct levels or Categories as they are called. CAT 1 means that the pilot may descend on the ILS glideslope to a minimum of 200 feet above the runway where he must have the runway in sight visually and if not, he must initiate a go-around. The same minimum is 100 feet for CAT II. CAT three has not vertical limit and only a certain Runway Visual Range (RVR) must exist for aircraft to land (usually in full automatic mode).

ILS is relatively expensive to buy and deploy and its cost of ownership is also substantial, not least because of the need to fly regular calibration flights checking out the system every year. Another shortcoming is that when the weather really socks in and CAT II/III landing operations are in progress, departing aircraft need to hold relatively far from the runway to avoid interference with the radio signals. This has a marked negative effect on the departure rate of an airport. Finally, but not insignificantly, you need a separate ILS installation for each runway end to be served.

With the availability of the Global Positioning System (GPS) came the realization that it should be possible to use GPS also for final approach guidance. A lot of advantages were immediately visible. One could define an instrument approach procedure basically anywhere, even when there was no runway… or conversely, approach procedures could be developed for each runway end for all the runways at an airport without having to deploy anything o the ground. And aircraft equipped to use the GPS system was, in principle, already able to fly a GPS approach. The beauty of such a solution is also that the long, straight final track of the ILS could be replaced by a curved track if required for, as an example, avoiding noise sensitive areas or wildlife preserves or whatever. A straight track was required only in as much as the aircraft needed it to be able to set up a stabilized approach.

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Up close and personal – Mind games with the aircraft trajectory

On 24/05/2014, in Buzzwords explained, by steve

060504_091043The term “trajectory” does not need an introduction to pilots and air traffic controllers. At its simplest, trajectory to the pilot is what the aircraft flies and to the controller the path through the air calculated by his or her system that the aircraft will fly. Hence it is fair to say that if we define trajectory as the series of points in space that the aircraft will occupy as it proceeds to its destination, we are not far from the truth.

In the traditional scheme if things air traffic controllers were looking at a small section of the trajectories, may be something like 10-20 minutes into the future, and moved aircraft around as necessary to avoid conflicts. In other words, they were managing aircraft, not the trajectories.

When the concept of air traffic flow management (ATFM) was defined, we did take the first step towards what is to-day known as Trajectory Based Operations (TBO). After all, ATFM was trying to predict what would be happening in the airspace hours or even months ahead in order to ensure that the resources necessary to handle the demand were made available on a timely basis (or that demand was capped but that is another story).

TBO came into its element when people finally realized that traffic demand expected around the turn of the century would no longer be manageable using traditional methods. The need to switch from managing aircraft to managing trajectories became clear.

If aircraft fly precisely defined trajectories that are described in the three spatial dimensions as well as the time dimension, by managing the trajectories on a timely basis one could make far better use of the available capacity in the airspace while avoiding an overload of the human controllers also. Simulations have shown conclusively the fallacy of the oft repeated argument that airspace was a finite resource… No, airspace appeared to be a finite resource only because of the way it was being used. Managing trajectories unlocks the inherent capacity of the airspace in a safe and efficient manner.

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PNT and RNT. What are these?

On 01/05/2014, in Buzzwords explained, by steve

gpsPNT stands for Positioning, Navigation and Timing and in most cases it refers to the signals from the satellite constellations we know as GPS, Glonass, Galileo or their regional equivalents in India, China and Japan. These days we take it for granted that our smart phones, cars, tablets and so on include a small receiver that can make use of the faint signals from those constellations to tell us where we are. Aircraft in turn use the signals to fly ultra-precise approaches. This is important but for the world at large, even more important is the precise timing that the satellites make possible. Power grids, the cellphone system and other important systems make use of GPS time to operate. Without this timing, the systems would collapse.

You would think that with something as important as the PNT signals, they would be protected from malicious intent. In fact, the signals are totally unprotected. With a box costing just a few hundred euros or even less, it is possible to block GPS signal reception in a substantial area, causing havoc to even safety of life systems. Sometimes you do not even need malicious intent as was demonstrated by the GPS jammers installed in trucks in the US to keep the boss from learning where the vehicle was on the road… Newark Liberty airport has a highway quite close to the runways and the jammers made GPS unusable also for aircraft whenever a truck passed nearby.

Experts have been saying for years that putting all of aviation’s eggs into a single basket called GPS was a bad idea but the prospect of a cheap and efficient system was too much to resist and PNT signals are fast becoming indispensable to aviation.

It is a wonder that no bad guys have yet come to the conclusion that they do not need to blow things up to cause untold economic damage to a country they have a gripe with…

What can be done?

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Crossing the pond in new and better ways

On 27/03/2014, in Buzzwords explained, by steve

trackEver since I got my controller’s license, I have been fascinated by the way air traffic is managed over the Atlantic Ocean. Why? Well, designated air routes as such are giving way to free route airspace in many parts of the world but flying over the pond has had a very special definition of air routes for a long time which meant that there were no such things yet there existed at the same time the most sophisticated organized track system ever invented. Sounds weird? Let me explain.

Due to the very specific needs of traffic operating between North America and Europe and vice versa as a result of passenger preferences and time-zone differences, airlines fly in two distinct waves: there is a westbound flow departing Europe in the morning and an eastbound flow departing North America in the evening. Although timetables vary by season, the westbound traffic crossing 30W longitude peaks between 1130 and 1900 UTC while the eastbound peak occurs between 0100 and 0800 UTC. More than a 1000 aircraft cross the Atlantic daily.

Most of the North Atlantic (NAT) oceanic airspace lacks surveillance and hence traffic is handled procedurally with separation minima that are far larger than what we are used to in continental airspace (this is going to change now… see below). Things are complicated by the fact that the economical level band is limited (Fl310 – Fl400) and that aircraft prefer to climb as their mass decreases in line with the burn-off of their fuel loads. This results in a major congestion of the airspace during the peak hours.

In order to make things manageable, a system of organized tracks has been put in place with a view to accommodating as many flights as possible in each of the flows on or close to their minimum time tracks and optimum level profiles. This sounds simple, but it is not. Weather patterns, including the position of the jet stream exhibit major swings and the minimum time tracks are seldom located at the same place from one day to the next. In practice this means that a different set of tracks has to be constructed for each of the flows every day. A separate and dedicated track arrangement is published each day for the eastbound and the westbound flows. This is the Organized Track System or OTS.


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NOP – what is this?

On 24/01/2014, in Buzzwords explained, by steve

The abbreviation NOP went through a number of iterations over time, originally we used it to refer to the Network Operations Plan and it now stands for Network Operations Portal.


It is a portal managed and run by EUROCONTROL and it provides a real-time picture of the air traffic flow and capacity management situation over Europe. It is a treasure trove of information and is interesting “reading” for professionals and enthusiasts alike.

A map shows where the current trouble spots are and a section called Network Headline News gives you the… well headline news affecting the network. You can find here information on, among other things, upcoming industrial action.

You want to know how many aircraft are expected on a given day? How many are currently airborne? How many have landed? How many more are still to come? It is all there. Delays in minutes (total, average per flight, en-route, airport…) are also all there for the interested visitor to see.
As if this were not enough, you can request pertinent information for the strategic, pre-tactical and tactical phases of traffic management while a post-operations tab takes you to any day you want to see in the past. Cute.

This is a place well worth a visit or even keeping a tab with this portal open in your browser to check on things every now and again.


Traffic Aware Planner – TAP. What is this?

On 17/12/2013, in Buzzwords explained, by steve

air_trafficIn the traditional scheme of things, an aircraft operator will plan a flight, submit the flight plan and then operate at the “mercy” of air traffic control, a service which will ensure a safe flight in terms of avoiding conflicts with other traffic but which may not always excel at allowing the flight to actually fly what was originally planned. There are many reasons for this and ineptitude of the air traffic controller is not among them. Often, the originally planned trajectory may simply be impossible due to the amount of traffic around. Things get even more complicated if the flight crew requests an in-flight change to the trajectory. The air traffic controller needs to check the consequences of the change before approving it and often there is no time to do this, there is simply too much work. The catch here of course is that the request from the flight crew is based solely on what they consider as best for their flight. Traffic, airspace limitations, weather will all play a role in whether or not a change is feasible from an air traffic management point of view and it is the controller who has to figure it all out. You cannot blame him or her if they balk when the request comes in the middle of intense traffic.

But what if the request sent by the flight crew were of a more considered nature? What if the flight crew did some of the preliminary work, checking traffic, airspace availability and weather in order to generate a request that controllers could approve with a minimum of additional checking?

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