Self-separation

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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, [1] in the case of human-piloted aircraft, or sense and avoid, [2] 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, [3] communication technologies and protocols, air traffic management and others.

Contents

Context and historical background

Pilots of modern aircraft cannot rely only on visual abilities and piloting skills to maintain acceptably safe separation from other aircraft, thus a considerable proportion of contemporary flights are 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 [4] [5] [6] [7] is straining the ATC capacity, and pilot shortages become an ongoing issues, 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. [8]

Self-separation started being considered as a potentially feasible operational concept within the Free Flight initiative. [9] 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, [10] 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, [11] [12] and the results show that the concept is well acceptable from the pilot point of view without imposing unreasonable workload.

An aligned but less radical and more implementable approach was later proposed and named as Distributed Air-Ground Traffic Management (DAG-TM), [13] keeping ATC still with a significant role, but allowing more freedom in en-route airspace. [14] Besides, other relevant aspects in a wider context have been studied in the Mediterranean Free Flight project [15] [16] (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. [17]

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 [18] (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 subsequent studies such as the series from Consiglio et al., [19] [20] [21] [22] which went deeper in the human factor aspects and set the foundations for separating strategic and tactical conflict management processes in self-separation.

Other projects provided complementary contributions, such as the Advanced Safe Separation Technologies and Algorithms [23] (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) [24] [25] and the U.S. Next Generation Air Transportation System [26] (NextGen), even if limited to certain conditions and airspaces.

Recent developments

More recently, the iFly project [27] defined a new concept of operations of self-separation in higher density airspace, based on the works described above, and evaluated it quantitatively using advanced stochastic simulation methods. [28] The results obtained from these studies indicate that self-separation can be safely used in an airspace with thrice the density of European en-route airspace as of in the year of 2005, if the ADS-B dependability level improves by a factor of five or if the TCAS dependability improves by the same factor.

Outstanding issues

Some of the most relevant issues to be solved for Self-separation are:

Although these topics have been researched and there are some solutions proposed for them, the complexity of the problem have prevented to achieve definitive responses.

Related Research Articles

<span class="mw-page-title-main">Avionics</span> Electronic systems used on aircraft

Avionics are the electronic systems used on aircraft. Avionic systems include communications, navigation, the display and management of multiple systems, and the hundreds of systems that are fitted to aircraft to perform individual functions. These can be as simple as a searchlight for a police helicopter or as complicated as the tactical system for an airborne early warning platform.

<span class="mw-page-title-main">Instrument flight rules</span> Civil aviation regulations for flight on instruments

In aviation, instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR).

In aviation, visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minima, i.e., in visual meteorological conditions (VMC), as specified in the rules of the relevant aviation authority. The pilot must be able to operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft.

<span class="mw-page-title-main">Air traffic control</span> Public service provided for the purpose of maintaining the safe and orderly flow of air traffic

Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots.

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 into the U.S. air traffic control system in the next decade. Its potential impact on the operations of the national airspace system is disputed, however.

Airspace is 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. It is not the same as outer space which is the expanse or space outside the Earth and aerospace which is the general term for Earth's atmosphere and the outer space within the planet's vicinity. History:

<span class="mw-page-title-main">2002 Überlingen mid-air collision</span> Fatal collision over Germany

On the night of Monday, 1 July 2002, BALBashkirian Airlines Flight 2937, a Tupolev Tu-154 passenger jet, and DHL International Aviation ME Flight 611, a Boeing 757 cargo jet, collided in midair over Überlingen, a southern German town on Lake Constance, near the Swiss border. All of the passengers and crew aboard both planes were killed, resulting in a total death toll of 71.

<span class="mw-page-title-main">Traffic collision avoidance system</span> Aircraft collision avoidance system

A traffic collision avoidance system, also known as a traffic alert and collision avoidance system, is an aircraft collision avoidance system designed to reduce the incidence of mid-air collision (MAC) between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of MAC. It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg (12,600 lb) or authorized to carry more than 19 passengers. CFR 14, Ch I, part 135 requires that TCAS I be installed for aircraft with 10-30 passengers and TCAS II for aircraft with more than 30 passengers. ACAS/TCAS is based on secondary surveillance radar (SSR) transponder signals, but operates independently of ground-based equipment to provide advice to the pilot on potentially conflicting aircraft.

The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization (ICAO) and described below, though they might use only some of the classes defined below, and significantly alter the exact rules and requirements. Similarly, individual nations may also designate special use airspace (SUA) with further rules for reasons of national security or safety.

<span class="mw-page-title-main">Airborne collision avoidance system</span> Avionics system to avoid aircraft collision

An airborne collision avoidance system operates independently of ground-based equipment and air traffic control in warning pilots of the presence of other aircraft that may present a threat of collision. If the risk of collision is imminent, the system recommends a maneuver that will reduce the risk of collision. ACAS standards and recommended practices are mainly defined in annex 10, volume IV, of the Convention on International Civil Aviation. Much of the technology being applied to both military and general aviation today has been undergoing development by NASA and other partners since the 1980s.

<span class="mw-page-title-main">Allegheny Airlines Flight 853</span> 1969 mid-air collision

Allegheny Airlines Flight 853 was a regularly scheduled Allegheny Airlines flight from Boston, Massachusetts, to St. Louis, Missouri, with stops in Baltimore, Maryland, Cincinnati, Ohio, and Indianapolis, Indiana. On September 9, 1969, the aircraft serving the flight, a McDonnell Douglas DC-9, collided in mid-air with a Piper PA-28 light aircraft near Fairland, Indiana. The DC-9 was carrying 78 passengers and 4 crew members, and the Piper was leased to a student pilot on a solo cross-country flight. All 83 occupants of both aircraft were killed in the accident and both aircraft were destroyed.

<span class="mw-page-title-main">Non-towered airport</span> Airport without an air traffic control tower

In aviation, a non-towered airport is an airport without a control tower, or air traffic control (ATC) unit. The vast majority of the world's airports are non-towered. In the United States, there are close to 20,000 non-towered airports compared to approximately 500 airports with control towers. Airports with a control tower without 24/7 ATC service follow non-towered airport procedures when the tower is closed but the airport remains open, for example at night.

In aviation, a mid-air collision is an accident in which two or more aircraft come into unplanned contact during flight. Owing to the relatively high velocities involved and the likelihood of subsequent impact with the ground or sea, very severe damage or the total destruction of at least one of the aircraft usually results.

<span class="mw-page-title-main">Transponder (aeronautics)</span> Airborne radio transponder

A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar. Collision avoidance systems have been developed to use transponder transmissions as a means of detecting aircraft at risk of colliding with each other.

The Next Generation Air Transportation System (NextGen) is an ongoing United States Federal Aviation Administration (FAA) project to modernize the National Airspace System (NAS). The FAA began work on NextGen improvements in 2007 and plans to finish the final implementation segment by 2030. The goals of the modernization include using new technologies and procedures to increase the safety, efficiency, capacity, access, flexibility, predictability, and resilience of the NAS while reducing the environmental impact of aviation.

ATC Zero is an official term used by the U.S. Federal Aviation Administration (FAA) that means the FAA is unable to safely provide the published ATC services within the airspace managed by a specific facility. The term is always used in conjunction with a facility reference. FAA ATC facilities include Air Route Traffic Control Centers (ARTCC); Terminal Radar Control facility (TRACON), Air Traffic Control Tower (ATCT), Flight Service Stations (FSS), or the Air Traffic Control System Command Center (ATCSCC). The term is defined in FAA Order JO 1900.47, Air Traffic Control Operational Contingency Plans. It is one of three designations used by the FAA to describe degraded operations and invoke operational contingency plans.

The National Airspace System (NAS) is the airspace, navigation facilities and airports of the United States along with their associated information, services, rules, regulations, policies, procedures, personnel and equipment. It includes components shared jointly with the military. It is one of the most complex aviation systems in the world, and services air travel in the United States and over large portions of the world's oceans.

<span class="mw-page-title-main">Automatic Dependent Surveillance–Broadcast</span> Aircraft surveillance technology

Automatic Dependent Surveillance–Broadcast (ADS-B) is an aviation surveillance technology and form of Electronic Conspicuity in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts its position and other related data, enabling it to be tracked. The information can be received by air traffic control ground-based or satellite-based receivers as a replacement for secondary surveillance radar (SSR). Unlike SSR ADS-B does not require an interrogation signal from the ground or other aircraft to activate its transmissions. ADS-B can also received point-to-point by other nearby equipped "ADS-B In" equipped aircraft to provide traffic situational awareness and support self-separation. ADS-B is "automatic" in that it requires no pilot or external input to trigger its transmissions. It is "dependent" in that it depends on data from the aircraft's navigation system to provide the transmitted data.

Unmanned aircraft system traffic management (UTM) is an air traffic management ecosystem under development for autonomously controlled operations of unmanned aerial systems (UAS) by the FAA, NASA, other federal partner agencies, and industry. They are collaboratively exploring concepts of operation, data exchange requirements, and a supporting framework to enable multiple UAS operations beyond visual line-of-sight at altitudes under 400 ft above ground level in airspace where FAA air traffic services are not provided.

<span class="mw-page-title-main">1997 Namibia mid-air collision</span> Collision between USAF C-141B and German Air Force Tu-154M

On 13 September 1997, a German Air Force Tupolev Tu-154M observation aircraft and a United States Air Force C-141B Starlifter transport aircraft were destroyed in a mid-air collision while cruising at 35,000 feet (11,000 m) off the coast of Namibia. All 33 people onboard both aircraft were killed. At the time of the collision, the Tupolev was flying on a southerly route from Niamey, Niger, to Cape Town, South Africa, while the C-141 was heading northwest from Windhoek, Namibia, to Ascension Island.

References

  1. ↑ See and Avoid, Skybrary
  2. ↑ Rosenkrans, W. "Detect, Sense and Avoid". FlightTech, pp. 24-29, July 2008.
  3. ↑ Rules of the Air, Annex 2 to the Convention on International Civil Aviation, ICAO.
  4. ↑ EUROCONTROL Long-Term Forecast Flight Movements 2010 - 2030 [ permanent dead link ]
  5. ↑ The world of Civil Aviation 2003-2006. ICAO Circular 307 AT/129, 2005
  6. ↑ Air Transport, Air traffic growth trends and forecasts. UNESCAP Archived 2012-09-24 at the Wayback Machine
  7. ↑ FAA Aerospace Forecast Fiscal Years 2010-2030
  8. ↑ "Airline Pilot Hiring Outlook and Career Information / ATP Flight School". atpflightschool.com. Retrieved 2023-11-10.
  9. ↑ RTCA Task Force 3 Final Report on Free Flight Implementation. October, 1995
  10. ↑ "Federal Aviation Administration - Home Page – TCAS". Archived from the original on 2011-07-21. Retrieved 2011-06-14.
  11. ↑ "NLR Free Flight with Airborne Separation". Archived from the original on 2012-03-25. Retrieved 2011-06-14.
  12. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-27. Retrieved 2011-06-14.{{cite web}}: CS1 maint: archived copy as title (link)
  13. ↑ NASA, Concept definition for distributed air-/ground traffic management (DAG-TM), Version 1.0, Advanced Air Transportation Technologies project, Aviation System Capacity Program, National Aeronautics and Space Administration, NASA, 1999
  14. ↑ NASA. DAG-TM Concept element 5 en-route free maneuvering for user-preferred separation assurance and local TFM conformance operational concept description, AATT Project Milestone 8.503.10, NASA Airspace Systems Program Office, Washington D.C., 2004.
  15. ↑ "Search".
  16. ↑ http://www.medff.it Archived 2005-04-02 at the Wayback Machine
  17. ↑ http://www.asas-tn.org/workshops/2nd-asas-tn2-workshop/session-3-b/1_MFFresults.ppt
  18. ↑ http://www.skybrary.aero/index.php/Airborne_Separation_Assurance_Systems_%28ASAS%29
  19. ↑ M. Consiglio, S. Hoadley, D. Wing and B. Baxley, Safety Performance of Airborne Separation: Preliminary Baseline Testing, Proc. 7th AIAA ATIO Conf., Belfast, Northern Ireland, 2007
  20. ↑ M. Consiglio, S. Hoadley, D. Wing, B. Baxley and D. Allen, Impact of Pilot Delay and Non-Responsiveness on the Safety Performance of Airborne Separation, Proc. 8th AIAA ATIO Conf., September 2008
  21. ↑ M. Consiglio, S. Hoadley and B.D. Allen, Estimation of Separation Buffers for Wind-Prediction Error in an Airborne Separation Assistance System, Proc. USA/Europe ATM Seminar, Nappa, CA, 2009
  22. ↑ M.C. Consiglio, S.R. Wilson, J. Sturdy, J.L. Murdoch, D.J. Wing, Human in the loop simulation measures of pilot response delay in a Self-separation concept of operations, Proc. 27th Int. Congress of the Aeronautical Sciences (ICAS 2010), 2010
  23. ↑ "Archived copy". Archived from the original on 2011-06-24. Retrieved 2011-06-14.{{cite web}}: CS1 maint: archived copy as title (link)
  24. ↑ "SESAR and Research | EUROCONTROL". Archived from the original on 2011-06-12. Retrieved 2011-06-14.
  25. ↑ "SESAR WP4 Projects". Archived from the original on 2012-05-06. Retrieved 2012-05-11.
  26. ↑ https://www.faa.gov/nextgen/ [ bare URL ]
  27. ↑ http://ifly.nlr.nl/
  28. ↑ "H.A.P. Blom, G.J. Bakker, Safety of advanced airborne self-separation under very high en-route traffic demand, SESAR Innovation Days, 2011" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2012-05-11.
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