COMSOFT Safety Nets
COMSOFT’s ground based Safety Nets C-S/N are attentive
supporters of Air Traffic Controllers. Usually unnoticeable,
C-S/N continuously assess the air situation in order to identify potential infringements of air safety. Critical situations are faithfully identified and reported to the ATCO well in advance to allow the implementation of countermeasures and to resolve potential safety threats.

C-S/N provide an extraordinary flexibility and can be optimally integrated and most favourably tuned for the use in all ATC environments. Using different parameter sets for individual parts of the air space, C-S/N support even heterogeneous airspaces with mixed profiles. As an integrated solution, they serve different applications simultaneously.

Short-term trajectory prediction and situation assessment based on surveillance data are fundamental subjects underlying the safety nets. Actually, C-S/N are introducing a novel stochastic approach modelling the uncertainty of trajectory and situation assessment. This stochastic approach has proven to provide the optimal trade-off between in-time conflict prediction and nuisance alert rate.

• Integrated Safety Net Solution providing STCA, MSAW including APM, APW
• Innovative probabilistic approach for conflict prediction
• Optimal trade-off between in-time conflict prediction and nuisance alert rate
• Extensively site-configurable, supporting all operational ATC environments
• Support for different region types and detailed airspace profiles
• Open interfaces supporting the integration into the operational environment
• Extensive information about nature, severity and probability of conflicts

The C-S/N modules receive track data from an SDPS and report alarms to a connected Controller Display. C-S/N also provide an interface to receive meteorological data as well as flight plan details, which are considered for trajectory prediction and situation assessment.

All received information contributes in real-time to a probabilistic model for trajectory prediction, in which the uncertainty of the predicted aircraft location is represented as a function of the prediction time. The predicted trajectory is then used to identify potential infringements of separation margins, either between aircraft or terrain and aircraft. All
critical situations are categorized according to severity, probability and geometry.

A coarse filter is applied to quickly eliminate situations that may not necessarily lead to conflicts within the prediction time frame.

A conflict confirmation and repetition mechanisms are introduced in order to take into account erroneous track data or transient track values.

Patents

The fundamental and patented innovative concept of C-S/N is the introduction of desirability of an alarm. This novel concept is used to model the ATCO’s interest in an alarm, by comparing the probability of a safety threat with the urgency to implement a resolution for the situation. This modelling scheme using a probabilistic approach can be applied to all predictive Safety Net Functions.

C-STCA

The Short Term Conflict Alert C-STCA identify traffic situations that possibly lead to the violation of defined separation criteria between two aircrafts in a near future. This requires simultaneous assessment of horizontal and vertical manoeuvres of multiple aircraft as well as geometric properties of the potential conflict.

C-APW

The Area Proximity Warning C-APW protects aircraft from entering restricted airspaces. Entry to such airspaces may be sanctioned by the system for aircraft with specific mission codes. Featuring dynamic activation of restricted areas, C-APW supports the flexible use of airspace.

C-MSAW

The Minimum Safe Altitude Warning C-MSAW modules monitor the vertical separation of aircraft and terrain as well as obstacles. For this purpose, MSAW uses digital terrain
elevation data (DTED) as well as obstacles definitions. Providing an interface for meteorological data, C-MSAW automatically adjusts altitude information for QNH and temperature. An integrated Approach Path Monitor (APM) enables C-MSAW to be applied in approach units.

Safe Safety Nets

Safety Net Functions form a critical part of today’s ATC automation systems and contribute to the safety of air traffic. C-S/N comply to development standards for safety critical systems supporting an ESARR conformant implementation. C-S/N comply to ESARR 4 on system level and ESARR 6 for the software development, and substantially support an ESARR 3 compliant safety process.

Non Predictive Safety Nets

In addition to the predictive safety net functions, COMSOFT provides situational safety nets that monitor aircraft movements as to their adherence to given clearances. In conjunction with an automated FDPS system, Route Adherence Monitoring and Cleared Level Adherence Monitoring enable the ATCO to immediately detect any divergence from given clearances.

System Architecture

Probability Threshold vs. prediction time

CLAM

RAM

• Adjustable confidence and confirmation level for conflict declaration, depending on conflict urgency and the configured airspace regions
• Possibility to use aircraft intention information to increase quality of trajectory prediction (e.g. cleared flight levels, from flight plan or controller input)
• Prediction of aircraft manoeuvres based on configured airspace regions
• Split tracks detection
• Conflict categories expressing the severity of conflicts
• Identification of the nature of conflict (major/minor separation infringements) and geometry (crossing and divergence attributes)
• Mode 3/A code and/or callsign
  selection to restrict the set of
  aircraft that need to be protected
  by the Safety Net function
• Capability to inhibit conflict prediction for specified regions
  or aircraft
• Capability to activate/de-activate group of regions online
• Conflict confirmation and repetition mechanisms for an optimal stability of the conflict
  output