Self-separation
Encyclopedia
Aircraft Self Separation is the capability of an aircraft
maintaining acceptably safe separation
from other aircraft without following instructions or guidance from a referee agent for this purpose, such as air traffic control
. In its simplest forms, it can be described by the concept of see and avoid, in the case of human-piloted aircraft, or sense and avoid, in the case of non-human piloted aircraft (such as UAVs
). However, because of several factors such as weather, instrument flight rules
and air traffic complexity, the self separation capability involves other elements and aspects such as rules of the air, communication technologies and protocols, air traffic management and others.
from other aircraft, thus a considerable proportion of nowadays flights is performed under instrument flight rules
with the responsibility for separation
belonging to air traffic control
(ATC). However, as the air traffic growth in the end of the 20th century and in the beginning of the 21st is straining the ATC
capacity, researchers on aviation and air transport are trying to propose operational and technological improvements in order to cope with this strain, one of which is self-separation.
Self-separation started being considered as a potentially feasible operational concept within the Free Flight
initiative. Its key technological enabler is automatic dependent surveillance-broadcast
(ADS-B), in which aircraft spontaneously transmit periodic position and state reports, including absolute horizontal position information, which is not used as information source for the pre-existing Traffic Collision Avoidance System
(TCAS). In relation to the current implementations of TCAS, which is intended only for collision avoidance, self separation requires a leap in processing logic, time anticipation and procedure changes. Its feasibility is dependent on confidence in automation and its co-existence with the human role in the cockpit. Some studies have been conducted to assess this relationship, and the results show that the concept is well acceptable from the pilot point of view without imposing unreasonable workload. Besides, other relevant aspects in a wider context have been studied in the Mediterranean Free Flight project(MFF) which had, as one of the main conclusions, that self-separation would be overall beneficial, but it should have to be limited to low- or medium-density airspace
.
Since the beginning of the association between self separation and ADS-B
, it has been also associated with another technical concept called Airborne Separation Assistance System(ASAS) which, in short words, performs the core logic of self separation and other related applications. With this association, the concept of aircraft self separation in the full technological and operational context is more clearly distinguishable from the already cited see and avoid and sense and avoid basic concepts. ASAS was an assumption in the MFF project and also in further projects as the Advanced Safe Separation Technologies and Algorithms(ASSTAR), which carried out performance, safety and cost-benefit analyses for ASAS applications, including a limited version of self separation, resulting in positive findings. Based on the above mentioned and other studies, ASAS-based self-separation has been selected as one of the goals to be pursued by major development programs in air traffic management, such as Single European Sky ATM Research & Development(SESAR) and the U.S. Next Generation Air Transportation System(NextGen), even if limited to certain conditions and airspaces.
Besides, self-separation has also been redefined in a context with assumptions slightly different from free flight, mainly regarding communication capabilities, and is passing through intensive quantitative safety analysis in the iFly project, one of the main aims of which is to evaluate the use of self-separation in higher density airspace.
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
maintaining acceptably safe separation
Separation (air traffic control)
In air traffic control, separation is the name for the concept of keeping an aircraft outside a minimum distance from another aircraft to reduce the risk of those aircraft colliding, as well as prevent accidents due to wake turbulence....
from other aircraft without following instructions or guidance from a referee agent for this purpose, such as air traffic control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
. In its simplest forms, it can be described by the concept of see and avoid, in the case of human-piloted aircraft, or sense and avoid, in the case of non-human piloted aircraft (such as UAVs
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...
). However, because of several factors such as weather, instrument flight rules
Instrument flight rules
Instrument flight rules are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules ....
and air traffic complexity, the self separation capability involves other elements and aspects such as rules of the air, communication technologies and protocols, air traffic management and others.
Context and historical background
Pilots of modern aircraft cannot rely only on visual abilities and piloting skills to maintain acceptably safe separationSeparation (air traffic control)
In air traffic control, separation is the name for the concept of keeping an aircraft outside a minimum distance from another aircraft to reduce the risk of those aircraft colliding, as well as prevent accidents due to wake turbulence....
from other aircraft, thus a considerable proportion of nowadays flights is performed under instrument flight rules
Instrument flight rules
Instrument flight rules are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules ....
with the responsibility for separation
Separation (air traffic control)
In air traffic control, separation is the name for the concept of keeping an aircraft outside a minimum distance from another aircraft to reduce the risk of those aircraft colliding, as well as prevent accidents due to wake turbulence....
belonging to air traffic control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
(ATC). However, as the air traffic growth in the end of the 20th century and in the beginning of the 21st is straining the ATC
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
capacity, researchers on aviation and air transport are trying to propose operational and technological improvements in order to cope with this strain, one of which is self-separation.
Self-separation started being considered as a potentially feasible operational concept within the Free Flight
Free flight (air traffic control)
Free flight is a developing air traffic control method that uses no centralized control . Instead, parts of airspace are reserved dynamically and automatically in a distributed way using computer communication to ensure the required separation between aircraft. This new system may be implemented...
initiative. Its key technological enabler is automatic dependent surveillance-broadcast
Automatic dependent surveillance-broadcast
Automatic Dependent Surveillance-Broadcast is a surveillance technology for tracking aircraft as part of the Next Generation Air Transportation System ...
(ADS-B), in which aircraft spontaneously transmit periodic position and state reports, including absolute horizontal position information, which is not used as information source for the pre-existing Traffic Collision Avoidance System
Traffic Collision Avoidance System
A traffic collision avoidance system or traffic alert and collision avoidance system is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft...
(TCAS). In relation to the current implementations of TCAS, which is intended only for collision avoidance, self separation requires a leap in processing logic, time anticipation and procedure changes. Its feasibility is dependent on confidence in automation and its co-existence with the human role in the cockpit. Some studies have been conducted to assess this relationship, and the results show that the concept is well acceptable from the pilot point of view without imposing unreasonable workload. Besides, other relevant aspects in a wider context have been studied in the Mediterranean Free Flight project(MFF) which had, as one of the main conclusions, that self-separation would be overall beneficial, but it should have to be limited to low- or medium-density airspace
Airspace
Airspace means the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....
.
Since the beginning of the association between self separation and ADS-B
Automatic dependent surveillance-broadcast
Automatic Dependent Surveillance-Broadcast is a surveillance technology for tracking aircraft as part of the Next Generation Air Transportation System ...
, it has been also associated with another technical concept called Airborne Separation Assistance System(ASAS) which, in short words, performs the core logic of self separation and other related applications. With this association, the concept of aircraft self separation in the full technological and operational context is more clearly distinguishable from the already cited see and avoid and sense and avoid basic concepts. ASAS was an assumption in the MFF project and also in further projects as the Advanced Safe Separation Technologies and Algorithms(ASSTAR), which carried out performance, safety and cost-benefit analyses for ASAS applications, including a limited version of self separation, resulting in positive findings. Based on the above mentioned and other studies, ASAS-based self-separation has been selected as one of the goals to be pursued by major development programs in air traffic management, such as Single European Sky ATM Research & Development(SESAR) and the U.S. Next Generation Air Transportation System(NextGen), even if limited to certain conditions and airspaces.
Besides, self-separation has also been redefined in a context with assumptions slightly different from free flight, mainly regarding communication capabilities, and is passing through intensive quantitative safety analysis in the iFly project, one of the main aims of which is to evaluate the use of self-separation in higher density airspace.