See and Avoid
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See and Avoid ( Engl. "See and avoid") refers to measures for safety in air traffic , particularly around collisions in the air to avoid. Due to technical progress, the term changes to Sense and Avoid (scanning / recognizing by sensors and automatically avoiding). This also includes unmanned aircraft ( UAV ), which are increasingly involved in military air traffic. The term includes not only the pure observation and reacting of the pilot (s) in the aircraft, but also all other measures for safety in air traffic on the ground and in the air, for the preparation and execution of the flight, technically and organizationally.
background
Until the 1930s, the airspace was largely unannounced and unrestricted for pilots. They were only restricted by topographical conditions, sovereign or political regulations or overflight bans.
With the increase in air traffic, the risk of collisions in the air increased. Therefore, air traffic was monitored and regulated from the ground through a system of regulations and air traffic controllers. Other reasons were the increasing size and speed of the aircraft and better instruments with which it was possible to fly even in poor visibility and at night ( IFR ). Air traffic was limited to selected areas and airways and followed strict rules. This should reduce the risk of flying off (deviating from course) and collisions.
As a result of further developments in the field of airspace monitoring and flight navigation, controlled flights are no longer limited to fixed airways, but can be guided largely freely according to requirements in the so-called "Free Route Airspace". Due to the strong increase in air traffic, however, the flight density continues to increase, especially in the vicinity of major airports. Visual flights in uncontrolled airspace by general aviation aircraft such as gliders , light aircraft , business jets , rescue helicopters and military flights must also be taken into account . The risk of collisions in the arrival and departure areas of the airports and in the waiting corridors must also be controlled. Despite increasing flight density, the spatial conditions on the ground and in the air can usually not be adapted.
Human factor, man-machine system
Even after good training, pilots reach their limits ( human factor ). Example: The time from when a visual stimulus hits the retina to processing in the brain is 0.1 seconds. In addition, in the ideal case there is a reaction time of 0.3 seconds until countermeasures are initiated. In this total of 0.4 seconds, two commercial aircraft move 200 meters towards each other.
The human eye no longer resolves objects less than 0.6 meters at a distance of 2 kilometers. This corresponds e.g. B. the fuselage diameter of a glider. It is difficult for the eye to recognize slow objects and everyone has a blind spot where they cannot see anything. The eye has to focus on a recognized object, while other objects become blurred. The brain also loses consciousness of other objects when it focuses on individual objects.
After a maximum of three hours of concentration, human attention drops, but long-haul flights today take 10 hours and more. Routine and getting used to dangers lower your attention even further. In addition, pilots have to monitor on-board systems and thus cannot look in the direction of flight for a relatively long time and observe the airspace.
The same factors apply analogously to people involved in air surveillance on the ground.
These examples show that the maximum level of safety cannot only depend on the people involved in air traffic, but must be supported by a series of technical measures on the ground and in the air and must be continuously further developed according to the technical possibilities. The human being remains the responsible part of the system and remains fully challenged in the event of technical failures.
Technical measures on the aircraft
Passive systems / elements on the aircraft
These measures improve the perceptibility of the aircraft by other pilots. They also include systems for recognizing other aircraft and obstacles, the use of autopilot systems, and avoiding areas with less flown.
Transponders serve as an essential element for better identification of aircraft . These are response devices installed in the aircraft that actively respond to the signals from a secondary radar . In Germany, since 2008, flights in the airspace Charlie (altitude over 10,000 feet / 3000 meters), Delta (not control zone) and for flights in areas with high traffic (TMZ / Transponder Mandatory Zones) as well as all flights with motor-powered aircraft (except in the glider operating mode ) above 5000 feet above sea level or 3500 feet above ground, a Mode-S transponder is required, which not only transmits the transponder code and the flight altitude but also the identification of the aircraft.
In addition to air traffic control , these transponder signals can also be actively queried by the TCAS systems of the commercial aircraft.
Important elements of passive flight safety are the flight management system (FMS), autopilot ) and the use and classification in the monitored air traffic. It should plan the flight path precisely in advance, comply with it automatically and relieve the pilot so that he can observe the nearby airspace more closely. The pilot can also avoid zones with a high volume of flights. Modern flight planning systems can suggest alternatives with less air traffic and avoid military training areas and catchment areas of major airports . This also requires an update during the flight, especially in the event of delays and loss of the slot at the destination.
The color scheme of the aircraft should provide a lot of contrast against backgrounds in the sky and the ground. This can be achieved through large-scale multicolor of a maximum of three colors. The color scheme must not break the contours, a camouflage effect must be prevented. The visibility can be further increased by reflections (shiny lacquers / polishes) from the sun and moon.
Crash warning lights (strobe lights) further increase visibility and must be in operation day and night. The standardized colors of the position lights make it possible to assess the flight direction from a great distance and to initiate any necessary evasive maneuvers.
Larger cockpit windows create a better view of the outside. Video cameras for an all-round view of the aircraft are already standard on the Airbus A380 .
Due to their high cost, size and energy requirements, FMS and active warning systems can mostly only be used in commercial aircraft.
Other passive measures are receivers on board that receive and evaluate electromagnetic emissions from other aircraft. If the distance and direction are appropriate, they can warn their own pilots without informing the other pilots. The latter is only possible if both aircraft are equipped with these systems.
Active elements on the aircraft
Active elements are sensors and systems that actively scan the area (using ultrasound , microwaves ( radar ) or lasers ). The Traffic Alert and Collision Avoidance System (TCAS / ACAS) in its various expansion stages should be mentioned here. These systems receive flight data from other aircraft, evaluate it and can warn of approaching. In a further expansion stage, they send their own identifiers and data. In the highest expansion stage, they warn when approaching and automatically change the flight path. Both expansion stages are in use. The former are used in smaller aircraft and helicopters because of their lower weight and lower energy consumption. The higher level of expansion is mandatory in commercial flights. The aim must be to introduce TCAS / ACAS in the highest expansion stage in all aircraft, including those for small aircraft. However, this requires further miniaturization, low power consumption with a long range and lower procurement costs.
The FLARM collision warning is particularly widespread in gliding . Unfortunately, the TCAS systems cannot evaluate the FLARM signals. Conversely, the newer versions of this system can also evaluate transponder signals and thus warn of approaching aircraft equipped with FLARM and transponders, but they are not able to actively query transponders. For hang gliders and paragliders there are inexpensive so-called passive FLARM modules.
Problem area UAV
Even if the pilot stays on the ground here, the aircraft moves on the planned flight path, which in the case of large UAVs such as Global Hawk and EuroHawk does not differ from modern commercial aircraft in terms of equipment and procedures. These UAVs have transponders and TCAS II on board and react automatically, like commercial aircraft in an emergency. Another aid is that the view in the direction of flight / around the aircraft can be recorded by video cameras and transmitted to the ground. Here, however, there are time delays due to the transmission path, which entails further automation through appropriate detecting sensors / automatic image processing as a further development to Sense & Avoid, from which manned aviation can draw another advantage.
Individual evidence
- ↑ Eurocontrol - As the crow flies - Free route airspace Maastricht (Brochure) . Retrieved November 9, 2012.
- ^ German air traffic control : Aviation Handbook Germany , GEN 1-13 as of November 2012
Web links
- Site for preparing flights under See & Avoid
- Article in Avionics Magazine (English)
- Article on image recognition (English, PDF, 277 KiB) ( Memento from May 28, 2010 in the Internet Archive )
- Contribution to Sense & Avoid at UAV (PDF, 454 KiB)