| We have all grown up with the idea that airspace | | | | interventions that take into account the need for |
| was the most important single thing aircraft needed. | | | | minimizing the overall distortion to the trajectory. |
| While it is true that aircraft need both air (in which | | | | In other words, precise 4D trajectories enable both |
| the wings can generate lift) and space (the room to | | | | airspace users and the service providers to |
| move around in) but airspace? This word has grown | | | | understand the impact of the trajectories on each |
| over the years and held us hostage to an air traffic | | | | other and the resources being made available so that |
| management (ATM) paradigm that is one of the main | | | | constraints that need resolution can be addressed on |
| causes of inefficiencies and scarce ATM capacity | | | | a timely basis. |
| today. | | | | Flying precise 4D trajectories and TBO doe not mean |
| If we look around, we will see plenty of instances | | | | a "planes on rails" scenario. Far from it. TBO is flexible |
| where the term "airspace" is used in ways that mask | | | | exactly because it is so predictable. This may sound |
| much more essential things, things that need to be | | | | like a contradiction in terms, but it is not. On the one |
| considered first and foremost before we think about | | | | hand, precise trajectories enable precise planning and |
| the space in which those "things" exist. | | | | conflict resolution while predictability enables the early |
| States have their sovereign airspace, airspace | | | | identification of the need for intervention. At the |
| management is an element of the global ICAO ATM | | | | same time, the impact of interventions can be easily |
| operational concept, EUROCONTROL has an Airspace | | | | evaluated and minimum impact solutions sought. |
| and Navigation Team, and there is the concept of | | | | The legacy ATC paradigm is often referred to as |
| flexible use of airspace... Even the quarterly publication | | | | "clearance based" and this is set off against the new |
| of CANSO, the Civil Air Navigation Services | | | | paradigm of TBO. This does not mean that there will |
| Organization is called "Airspace". Air traffic control | | | | be no clearances in the future system. The |
| centers have their airspace... Airspace is the magic | | | | difference is really in the trajectory attaining such a |
| term we all grew up with and think we understand. | | | | central role whereas in the legacy system clearances |
| We also tried to solve ATM problems by "improving" | | | | were issued with a much more limited overall |
| airspace. When those efforts did not quite work out | | | | knowledge of their effect on the trajectory further |
| the way we had hoped, we pronounced airspace to | | | | downstream. |
| be a scarce resource almost saying that it was | | | | The benefits of TBO |
| airspace that actually put a limit on how many aircraft | | | | Precise management of trajectories dramatically |
| there may fly around at any given moment. | | | | reduces the volume of airspace needed for a given |
| In fact, airspace is an almost limitless resort. It | | | | flight and this translates into more flights per unit of |
| appears to be limited only because of the way we | | | | airspace on the one hand (increased capacity) and a |
| use it. | | | | reduced need for intervention with a given trajectory |
| Precise airspace with imprecise trajectories | | | | on the other, resulting in less deviation from the |
| It is telling to consider how the legacy process goes... | | | | original intent of the airspace user. Even when an |
| We design the airspace to serve a given purpose, be | | | | intervention becomes inevitable, this can be much |
| it the containment of flights or allocating | | | | smaller and of shorter duration than is the case in the |
| responsibilities to control units. The airspace design | | | | legacy system. |
| process is a precision exercise and when the | | | | TBO also enables the introduction of much more |
| designers are done, they put forward a product | | | | powerful and effective queue management and |
| characterized by a very high precision in terms of all | | | | separation assistance tools that reduce controller task |
| dimensions of the airspace concerned. It is then | | | | load and hence the inherent capacity in TBO based |
| published and we can wait for aircraft to come... | | | | airspace can be exploited even further. |
| And they do and what happens? ATC has only | | | | The nature of the trajectory |
| rudimentary information on the intention of the | | | | With a bit of exaggeration we could say that an |
| flights, receiving only an extract (the filed flight plan) | | | | aircraft's trajectory begins when it first rolls out from |
| of the carefully crafted trajectory description the | | | | the manufacturing plant and ends when she finally |
| airspace user had put together. Very often even this | | | | goes to rest in a scrap yard. While we do not need |
| extract is further removed from the original (it | | | | to use this extreme view of the trajectory when |
| becomes the current flight plan) as clearances | | | | designing TBO, it is important to remember that each |
| demanded by the traffic situation are implemented. | | | | section of the trajectory (whether the aircraft is |
| As if to add insult to injury, a given control center | | | | moving on the ground or in the air) actually impacts all |
| and the sector controllers within it only see and really | | | | subsequent ones. We should not forget that if an |
| care about that stretch of the flight trajectory that | | | | aircraft is stationary on the ground, docked at the |
| is inside their airspace and possibly a bit further down | | | | gate or waiting on a remote stand, the trajectory is |
| the route... Finally, the precision with which this | | | | not broken. It is in an idle state but it is still consuming |
| trajectory is flown and known is not exactly | | | | resources. There may be a security guard there; |
| spectacular. Longitudinally, we talk about minutes. | | | | others will be working on the plans for the next |
| This is not something we should blame air traffic | | | | flight... Clearly, the contention that the trajectory, |
| control for. They are doing their best in the system | | | | rather than airspace, is central to the life and |
| that grew up around them. A system where airspace | | | | operation of an aircraft is easy to prove. The next |
| is designed to a very small tolerance while inside it, | | | | step, that the trajectory must be central to air |
| the all important aircraft trajectories are accepted | | | | traffic management, is a logical and unavoidable |
| with tolerances that have improved very little since | | | | conclusion. |
| the earliest times. The result is low predictability and a | | | | The extreme proof of the cake |
| huge waste of the airspace resource, which combine | | | | Originally, at this point I was planning to bring some |
| to create inefficiencies that are avoidable to a very | | | | kind of snappy example from civilian air traffic |
| large extent. | | | | management to make the point of this article. In the |
| Instead of starting by managing the airspace, we | | | | meantime however, our colleagues in uniform have |
| must manage the trajectories and then ensure that | | | | produced an introductory video that talks about |
| the airspace is there to accommodate them | | | | trajectories and trajectory management. They have |
| The concept of Trajectory Based Operations (TBO) | | | | provided the best possible example for me to use |
| Of course it is not realistic to envisage that it will | | | | and believe me, when the military sign up for |
| ever be possible to adjust airspace to the | | | | trajectory based operations, the thing needs no |
| trajectories without there being any airspace imposed | | | | more proof of its value. |
| constraints. But by shifting the balance towards | | | | Imagine the old, airspace based system where you |
| trajectories, it is possible to achieve a situation where | | | | have two fighters in an exercise area that will need |
| it is mainly the trajectories that influence airspace | | | | to be refueled. The military have blocked off the |
| rather than vice versa. | | | | exercise area plus a biggish volume of airspace where |
| TBO requires that the trajectories be expressed in | | | | the tanker is circling, waiting for its charges to find it... |
| four dimensions (3 spatial and 1 time) = 4D with a | | | | Wasteful in terms of airspace as well as fuel |
| very high precision, which is then carried over into | | | | consumption. Change now to a trajectory based |
| actual execution of the trajectories. The SESAR | | | | operation where the precise 4D trajectory of the |
| Concept of Operations for example talks about | | | | tanker is designed to arrive where the fighters are at |
| navigation accuracy improving to +/- 10 seconds | | | | just the right time and while the babies are slurping, |
| longitudinally. | | | | mama flies with the minimum of restrictions to other |
| This very precise trajectory is then shared between | | | | traffic. Instead of trying to segregate everything on |
| all the partners concerned via System Wide | | | | an airspace basis, the trajectories are managed to |
| Information Management (SWIM) resulting in common | | | | ensure minimum interference and maximum |
| situational awareness and knowledge of the | | | | compliance with the user intent, both civil and military. |
| consequences of all interventions, end-to-end. It | | | | Won't we just love TBO? |
| becomes possible to make decisions on required ATC | | | | |