ADS-B and MLAT – No technology war
On 19/05/2010, in Buzzwords explained, by steve
There will still be people who remember what a VHS cassette looked like and a few who remember the epic technology war between Betamax, System2000 and VHS. More recently, the Blu-Ray disc won in a similar battle in the consumer electronics field only to face quick extinction as the world moves towards on-line entertainment distribution.
In air traffic management such an epic battle was raging a few years ago between VDL Mode 2 and VDL Mode 4. They were vying for the privilege of becoming the prime technology for air/ground digital link, one of the most important enablers of the new air traffic management system. VDL Mode 2 won in the end mainly for practical reasons and certainly not because of technical superiority.
A cursory glance at the surveillance landscape shows that yet again there are two technologies aiming to replace expensive and cumbersome radar and one might conclude that a new technology war is in the offing.
The technologies concerned are Automatic Dependent Surveillance-Broadcast (ADS-B) and Multi-lateration (MLAT). Just to recap, ADS-B is a surveillance solution where
aircraft broadcast their GPS-derived position (ADS-B out) and the messages received on the ground are used to create air situation displays for air traffic controllers. When aircraft are able to receive the same messages (ADS-B in), these enable them to do airborne separation assurance, among other things.
Multi-lateration uses the replies from SSR transponders, timing their arrival at ground receiving antennas and calculating aircraft position from those time differences. WAM is Wide Area Multilateration, in effect the MLAT technology applied for surveillance in a given area.
The potential accuracy of both technologies is phenomenal and is far better than that of conventional radar. The icing on the cake is that the cost of implementation and ownership is a fraction of those outdated monsters.
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Is an aircraft an aeroplane or the other way round? The importance of proper terminology.
On 12/03/2010, in Buzzwords explained, by steve
The word game
A lot of air traffic management related material passes through our hands, usually to be checked with a view to ensuring quality of content and consistency of the terminology. There is a disturbing trend that is becoming more and more evident with the passage of time. The documents show a deteriorating level of quality in respect of terminology use.
Why is this a problem? Unless they have been sensitized to the issue, the authors of those documents may not feel particularly disturbed by the fact that they use the terms aircraft, aeroplane or airplane interchangeably in their text, they may even feel that the varied use of words reflects better writing style. But in technical documents, the terms used must all have their precise definition and it is not enough to find a given word in a Webster’s Dictionary.
Let’s have a look at these three words, aircraft, aeroplane, and airplane. They are all English words and they all mean something that flies. Very true. But
there are many things that “fly”, from hot air balloons to helicopters and, depending on how you define “fly”, even hovercraft. So how do we know which exactly a given text refers to if it is not clear from the context?
If you see a piece of text that says “a flashing white light shall be displayed on all aircraft” and then another one that says “a flashing white light shall be displayed on all aeroplanes” and you own a helicopter, a glider and a hot air balloon, which one would you need to equip based on the first requirement? And the second?
Although I assume you know the answer without the explanation that follows, it is still interesting to look at these terms in more detail.
First and foremost, we have to say good-by to the term “airplane”, at least in the international context. Only aircraft and aeroplane have been defined by the International Civil Aviation Organization (ICAO).
An aircraft is any machine that can derive support in the atmosphere from the reaction of the air other than the reactions of the air against the earth’s surface.
A aeroplane is a power-driven heavier-than-air aircraft, deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight.
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Performance Based Navigation (PBN) – Why the “N” should be an “O”
On 11/03/2010, in Buzzwords explained, by steve
The abbreviations game
In aviation we seem to be creating abbreviations at a rate that raises the specter of our grandchildren not having any usable combinations left any more. This remark from a well respected colleague of mine who used to work for UPS airlines does in fact indicate a few problems that go beyond the scarcity of available unique letter combinations and which, as we will see, affect our daily work in all kinds of unexpected ways.
This is not aviation CNS...
Consider the well known CNS formation which, we all know, stands for Communications, Navigation and Surveillance. Whoever came up with the abbreviation CNS probably had no idea how much damage their invention would cause in air traffic management by perpetuating the kind of silo mentality that keeps many organizations hopelessly divided and some experts retreating into their respective ivory towers.
If at least the inventors had the good sense of putting those letters into some kind of logical order, like history, which would have given us NCS… We did navigate first (as in trying to find our way by reading the names of train stations and flying along highways), then communicated, initially with lights and hand signals and later via radio and most recently we do surveillance also. Not that NCS would have been any better at driving the silo mentality from the face of the earth.
Of course in the old days there was some logic in looking at navigating and communicating as something totally different from each other. You trained for one or the other, aircraft carried separate navigators and radio operators and when radar came along, the wizards of that kit were a completely new breed yet again. It was only logical also that separate fiefdoms should grow up along the letters NCS with hardly any horizontal contact between them. That they should fiercely protect their respective domains was perfectly natural…
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8.33 kHz Channel spacing – what is this?
On 04/03/2010, in Buzzwords explained, by steve
The radio spectrum, a scarce resort
One of the most basic activities in a cockpit is tuning the radio to the assigned frequency of whoever we want to talk to. Contacting ground control, the tower or one’s own company is done by turning a few knobs until the right numbers show in the radio control panel display and we can talk.
Air traffic controllers see the same thing slightly differently. They do not normally have to tune their radios. The proper frequencies for their sector or other working position are pre-set and need no further attention.
With the matter being so pedestrian and the actions so routine, few of us realize that the ability of pilots and controllers to talk to each other is in fact dependent on one of the scarcest resources in aviation, namely the radio spectrum allocated to aviation use.
Many other disciplines have their own radio spectrum and we all guard jealously what we have been given and for good reason. With so many users wanting to use the radio waves, the incumbents better watch or the use it or lose it principle kicks in. Luckily, the frequencies most widely used by aviation (118 – 137 MHz) are not coveted so strongly by others. Our problem is different but not in the least less serious.
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The ICAO Flight Plan – changes are coming!
On 17/02/2010, in Buzzwords explained, by steve
The basics
If you are working in aviation, chances are you have seen an ICAO Flight Plan. Something that looks like the example here. It is a strange looking document showing clearly its origins in a world where clattering teletype machines were considered modern communications means. The double chevrons pointing left indicate “carriage return” and the three dashes above each other indicate line feeds… Yes, the ICAO Flight Plan form is a hybrid of text parts and instructions to the old teletype machines (and the modern computers that have replaced them) as to how the information is to be formatted on displays and hard copies of the flight plan. When transmitted via the Aeronautical Fixed telecommunications Network (AFTN), the flight plan takes the form of the famous FPL message.
Flight Plans are of vital importance for flights in managed airspace. This is basically the only means an airspace user has to tell air traffic control what they are planning to do. You either file your flight plan before departure or you file it from the air if you did not need a flight plan for the first part of your operation (if you flew in unmanaged airspace and then decide to go into managed airspace for example). The content must be accurate and it must be in the hands of air traffic control on a timely basis.
The International Civil Aviation Organization (ICAO) has defined a number of so called standard field types, each identified by a number. Each field type
contains defined information and the various air traffic services messages must contain the prescribed field types in the order specified for the given message. Message types in turn are identified by 3 letters. A message with message type designator CHG is a flight plan modification message and one with designator FPL is… well, you guessed it, a Flight Plan Message.
On the flight plan form you will find Items and not field types. Items are also numbered and they correspond to the numbers allocated to the field types. So both a field type 7 and an Item 7 will contain information on aircraft identification and SSR mode and code.
The rules for composing the messages and their content are very strict and are also globally standardized. This way ATS messages can be handled manually or by computers, irrespective of where they come from or whom they are addressed to.
Why the change?
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The transition from AIS through AIM to IM – What is this?
On 26/01/2010, in Buzzwords explained, by steve
A global congress with this title will make even the aficionados of abbreviations shiver… AIS, AIM, IM… What is next? UR? Well, the funny thing is, the title is perfectly correct and abbreviations or not, it reflects one of the most profound changes ever in the way information is collected, promulgated and used in international aviation.
Let’s have a look at what is meant by those abbreviations and what their significance really is.
What is AIS?
AIS is of course the abbreviation of Aeronautical Information Service. This is the traditional, product based service concept that brings you vital information in the form of Notices to Airmen (NOTAM), the Aeronautical Information Publication (AIP), Aeronautical Information Circulars (AIC), the AIRAC system of information publication and of course the loads of standards and practices that come with them.
Over the years, AIS has grown into a worldwide system of aeronautical information provision that is both indispensable and for a long time was also a hindrance to progress in aeronautical information management.
How come? Well, let’s state right here and now that AIS is a wonder of global cooperation. It went global and worked well decades before the term “globalization” was invented (albeit in a different context). So, as far is it went, AIS was and still is in many respects an example to be followed. The problems came as a result of its product based nature. Raw data is collected, checked and collated, then published in “products” that represent a best-guess of what users of aeronautical information want most. In the simpler world of yesteryear, those guesses were not even so bad.
In to-day’s much more complex environment an AIS that serves everyone does not in fact fully satisfy anyone. OK, there are some really simple operations that are exceptions but they are really a minority.
Why was AIS a hindrance to change? As you can imagine, global AIS was not built overnight and they had had their share of troubles. Also, being State monopolies, AIS offices were not exactly reared to embrace change, even necessary change. So, even when the need for change was staring everyone in the face, AIS in some parts of the world pretended that everything was just fine. Change this well balanced system and face the consequences, they seemed to suggest…
Enter AIM…
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Trajectory Based Operations (TBO) – what is this?
On 16/11/2009, in Buzzwords explained, by steve
We have all grown up with the idea that airspace was the most important single thing aircraft needed. While it is true that aircraft need both air (in which the wings can generate lift) and space (the room to move around in) but airspace? This word has grown over the years and held us hostage to an air traffic management (ATM) paradigm that is one of the main causes of inefficiencies and scarce ATM capacity to-day.
If we look around, we will see plenty of instances where the term “airspace” is used in ways that mask much more essential things, things that need to be considered first and foremost before we think about the space in which those “things” exist.
States have their sovereign airspace, airspace management is an element of the global ICAO ATM operational concept, EUROCONTROL has an Airspace and Navigation Team, and there is the concept of flexible use of airspace… Even the quarterly publication of CANSO, the Civil Air Navigation Services Organization is called “Airspace”. Air traffic control centers have their airspace… Airspace is the magic term we all grew up with and think we understand.
We also tried to solve ATM problems by “improving” airspace. When those efforts did not quite work out the way we had hoped, we pronounced airspace to be a scarce resource almost saying that it was airspace that actually put a limit on how many aircraft there may fly around at any given moment.
In fact, airspace is an almost limitless resort. It appears to be limited only because of the way we use it.
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Enterprise Architecture and service orientation – what is this?
On 03/11/2009, in Buzzwords explained, by steve
Few abbreviations connected with the future air traffic management system have given rise to so many questions and misunderstandings as EA (Enterprise Architecture) and SOA (Service Oriented Architecture). In the United States both concepts are part and parcel of air traffic management system development since the marching orders were given by the Federal Government. In Europe, however, it was only during the SESAR development phase that EA and SOA were first introduced into the ATM context and the reception was at first mixed.
To-day there is probably no doubt any more that EA and SOA are the way to go but the fact remains: to many in the air traffic management family the exact meaning of both remains a puzzle.
Let’s try to set out the pieces and see what picture emerges.
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A short (unofficial) history of air/ground digital link – 3
On 24/10/2009, in Buzzwords explained, by steve
Pioneers to the rescue
In spite of the positive business case, airspace users were not exactly rushing to equip with air/ground digital link. Because of the slow down of traffic growth in the wake of 9/11, the expected ACARS problems did not materialize and the ATC frequency congestion was also pushed far into the future. In other industries, such a period of respite might have been used to prepare for the times when business recovery would once again make air//ground digital link essential. But that is not how aviation works. With the immediate threat receding and even some of the big carriers fighting for survival, enthusiasm for investing in things that would generate benefits only many years down the road cooled.
Of course for the planners of the ATM system this was a situation that spelled trouble for later. The frequency congestion problems were not a mirage even if for the time being those problems slipped into the future. The need to put together a comprehensive kit of capacity enablers had not become less important, only the urgency had changed somewhat. For LINK2000+ the big question was: how to jump start equipage? The question was not self serving at all. If Maastricht UAC controllers did not get digital link equipped aircraft to work with, it would be impossible to build and maintain proficiency and to shake down the system in real operational circumstances.
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A short (unofficial) history of air/ground digital link – 2
On 18/10/2009, in Buzzwords explained, by steve
The clash of VDL Mode 4 and VDL Mode 2
Following years of testing and discussions on countless forums, VDL Mode 2 was emerging as the solution that, combined with the ATN protocol, could support the initial implementation of Controller Pilot Digital Link Communications. There was nothing else it could do but it had a huge advantage over everything else. There was agreement that it would do the trick! Some people tended to consider this virtue as being of little value but in fact it was as important as the link’s ability to perform. Achieving consensus on the scale needed to decide which link to use is an epic hurdle and when agreement is there, it should not be put in danger.
But that is exactly what was being done by the promoters of another technology that goes under the name VDL Mode 4. VDL Mode 4 can do everything, they claimed… It does voice, text messages and also ADS-B! Most of the claims were of course true and the initial hiccups with the system were no reason to discard it. Yet it never made it into the mainstream and the hard push did only one thing: delayed the inevitable, the final agreement on Mode 2. VDL Mode 4 lacked the most important element: industry agreement for implementation.
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A short (unofficial) history of air/ground digital link – 1
On 12/10/2009, in Buzzwords explained, by steve
Introduction
Talking to a group of young controllers the other day I suddenly realized that Controller Pilot Digital Link Communications (CPDLC) and its enabler, air/ground digital link were a kind of given for them… Their centre has either already implemented it or had plans for it and while their opinion diverged on the usefulness of the thing, they certainly did not consider it as anything exciting. In a way this is good. The more everyday air/ground digital link becomes, the more we can consider having cleared a major hurdle in implementing an important capacity enabler.
But not being familiar with the history of a particular development reduces our ability to understand its shortcomings and its future potential.
With this article I would like to put on the table a few, sometimes amusing, sometimes incredible, details from the last 15 years of so about air/ground digital link development in the hope that it will be provide some insight into what is after all a very exciting development in air traffic management.
The story will not be comprehensive; it is only a summary and is based mainly on my recollections. I was pretty close to the fire but possibly for that very reason I may have seen things in a light that was colored differently from the actual reality. If you have better information, do comment on my version of the tale.
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(Before) all else fails… read the Concept! Part 3.
On 24/09/2009, in Buzzwords explained, by steve
What is TMR?
The abbreviation of Trajectory Management Requirements and an item that has been misunderstood in several ways (some quite surprising). Obviously, the CONOPS did not do a very good job of explaining this simplest of elements (mea culpa…). An aircraft flying its 4 dimensional trajectory will do so with an agreed precision and the trajectory to be flown will not deviate from the one agreed by more than prescribed limits. The aircraft system does not need to re-publish its trajectory as long as any deviation that may occur remains within those limits.
TMR is nothing more than an automated instruction to the aircraft containing the applicable limits. In other words all TMR does is set the triggers for re-publishing the trajectory. An aircraft may be given different limits as it flies, depending on the changing requirements along its trajectory, resulting in several TMR messages.
Restricting the number of instances of trajectory publishing to that actually required saves bandwidth and processing resources.
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(Before) all else fails… read the Concept! Part 2.
On 23/09/2009, in Buzzwords explained, by steve
What is a net-centric system?
Net-centric, in its most common definition, refers to “participation as a part of a continuously evolving, complex community of people, devices, information and services interconnected by a communications network to optimise resource management and provide superior information on events and conditions needed to empower decision makers.” It will be clear from the definition that “net-centric” does not refer to a network as such. It is a term that covers all elements constituting the environment referred to as “net-centric”.
Exchanges between members of the community are based not on cumbersome individual interfaces and point to point connections but a flexible network paradigm that is never a hindrance to the evolution of the net-centric community. Net-centricity promotes a “many-to-many” exchange of data, enabling a multiplicity of users and applications to make use of the same data which in itself extends way beyond the traditional, predefined and package oriented data set while still being standardized sufficiently to ensure global interoperability. The aim of a net-centric system is to make all data visible, available and usable, when needed and where needed, to accelerate and improve the decision making process.
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(Before) all else fails… read the Concept! Part 1.
On 22/09/2009, in Buzzwords explained, by steve
The birth of the SESAR Concept of Operations (CONOPS), perhaps not unexpectedly, was not an easy process. Although SESAR is claimed to be a user-driven project, when the airspace users tried to drive the development of the CONOPS, the road proved to be anything but smooth. Plenty of natural and artificial obstacles had to be negotiated before the final product was crafted and pronounced airworthy. In the end, the CONOPS had turned out to be much more than the usual representation of the smallest common denominator, agreed and supported by most, criticized by others.
Now, some two years after version 1 of the CONOPS saw the light of day, we still see a worrisome degree of misunderstanding, hesitation and claimed or actual ignorance persist around the concept. Apparently, some people just continue with legacy thinking, pleading ignorance that there is any direction being set that is relevant to them. Ignoring the guidance encapsulated in the CONOPS or giving it a new interpretation not in line with what was originally intended represents a grave danger to the effectiveness of the new air traffic management system and the SESAR project itself.
In this article, I will try to clarify a number of issues still burning around the CONOPS, answering also questions which have been put to us in recent months. Some items may appear trivial to those who have been involved in the SESAR definition phase but will be useful to our worldwide readers many of whom are innocent when it comes to any phase of SESAR.
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Trajectory ownership: dogfight or guiding principle?
On 13/09/2009, in Buzzwords explained, by steve
Few elements of the SESAR Concept of Operations (CONOPS) have generated more controversy than the idea of trajectory ownership did. Regrettably, the controversy still boils. Some experts dismiss the whole thing as a “political dogfight”, others conduct lengthy debates on how trajectory ownership will work (or not work) in daily operations. They are both on the wrong track, revealing a fundamental misunderstanding of what the CONOPS is trying to say. It is time we put the matter out of its misery and recognize trajectory ownership for what it was always meant to be: a strategic guiding principle with a fundamental impact on future air traffic management.
First and foremost, we must realize that, except for the smallest and lightest aircraft, almost all flying machines are in fact business tools of differing sophistication. From rented aircraft to the most modern airliners, they fulfill a mission and are meant to generate revenue for their operators. The Sunday leisure flyers apart, this is true of business jets, crop sprayers, airline transports and even the military.
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Net-centric air traffic management system explained
On 11/08/2009, in Buzzwords explained, by steve
Net-centric, in its most common definition, refers to “participation as a part of a continuously evolving, complex community of people, devices, information and services interconnected by a communications network to optimise resource management and provide superior information on events and conditions needed to empower decision makers.” It will be clear from the definition that “net-centric” does not refer to a network as such. It is a term that covers all elements constituting the environment referred to as “net-centric”.
Exchanges between members of the community are based not on cumbersome individual interfaces and point to point connections but a flexible network paradigm that is never a hindrance to the evolution of the net-centric community. Net-centricity promotes a “many-to-many” exchange of data, enabling a multiplicity of users and applications to make use of the same data which in itself extends way beyond the traditional, predefined and package oriented data set while still being standardised sufficiently to ensure global interoperability. The aim of a net-centric system is to make all data visible, available and usable, when needed and where needed, to accelerate and improve the decision making process.
Click here to read the full article
Towards a net-centric system
On 30/07/2009, in Buzzwords explained, by steve
In the numerous descriptions of the future air traffic management system, the term “net-centric” appears over and over. What does net-centric really mean and how will such a system improve safety and flight efficiency?
Watch this space for a forthcoming post on this fascinating subject, the latest in our series “Buzzwords explained”.
Trajectory based operations
On 26/07/2009, in Buzzwords explained, by steve
Trajectory Based Operations (TBO) is a key element of the operational concept of both SESAR and the US NextGen.
But what is TBO? It is definitely more than giving direct clearances and getting rid of route structures is an element, but not the essence, of Trajectory Based Operations.
We will be publishing a post on this exciting subject soon. In the meantime, why not write to us with your understanding of TBO, its perceived advantages or problems. We will strive to answer your issues as part of the forthcoming article.
