The Traffic Alert and Collision Avoidance System - Research Paper

Introduction

Civil air traffic is likely to increase due to high passenger demand thereby putting more stress on the system to provide safety measures to avoid accidents. There is a range of initiatives in Air Traffic Management (ATM) and aviation generally that offer safety, and these include controller computerized assistance tools, modern ways of structuring airspace and controlling traffic flows, and the invention of delegation separation assurance between the cockpit crew and systems. Aviation, in general, is therefore under a lot of pressure and is continually undergoing extended periods of fundamental changes. The need for a severe safety system must be in place to avoid an increase in safety-related incidents and accidents. Aviation procedures provide that there should be a structured process that ensures safety is built into conceptualization, design phases and the overall lifecycle of aircraft systems (Strohmeier, Schafer, Lenders & Martinovic, 2014).

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The safety concepts of aviation also referred as 'implicit safety' relies heavily on the culture of operations rather than the safety formal procedures and policies that exist such as the alarm systems, even though these safety policies must be provided. The study indicates that aviation also benefits heavily from the 'explicit safety' measures. Aviation safety refers to the freedom from unacceptable risks either by elimination or control through the application of safety system concepts and principles (Strohmeier et al., 2014). This essay seeks to address the collision avoidance systems in real-world situations that have been introduced based on fatal accidents. This essay will further how maintenance, aircraft design and development, repair and general maintenance programs are incorporated in safety measures.

Questions that are often asked after serious accidents are how to stop such accidents from happening. Many incidents and accidents in the past have led to safer flying conditions due to the improvements and changes to protocol, laws, and technology embraced in the design of airplanes. For instance, the development of The Traffic Alert and Collision Avoidance System (TCAS) and the next generation collision avoidance systems such as Airborne Collision Avoidance Systems (ACAS X) were influenced by fatal accidents that occurred in mid-air collisions. Over the years, there have been substantial improvement and development based on technological advancement to help reduce the collision of aircraft.

In 1956, a TWA plane crashed into a United Airlines flight above the Grand Canyon, and it triggered the need for increased communication between planes. The Federal Aviation Administration was later formed to give directions and set regulations for aviation in relation to collision avoidance systems, but this did not solve the issue as other plane accidents including the 1996 collision near New Delhi that resulted in 349 casualties emphasized the need for an advanced and up to speed anti-collision technology (Kodama & Nakatani, 2018). Other accidents cause due to mid-air collisions include Syrian Arab Airlines Flight RB-501 and the Syrian Air Force Mil Mi-8 helicopter, Zlin 242L and the Cessna 172, Air Tractor AT-502B and the US Air Force Cessna T-37B to mention a few. The FAA implemented the Traffic Alert and Collision Avoidance System to control and monitor the airspace around an aircraft. This system was introduced to reduce the risk of mid-air collisions between aircraft, and it is based on transponder (SSR) signals (von Essen & Giannakopoulou, 2014). This accident gave birth to the Federal Aviation Agency that was later transformed to Federal Aviation Administration that took control of all American airways under a single control.

The Airborne Collision Avoidance System interrogates the Mode C and Mode S transponders of nearby aircraft and alerts the pilots of the altitude and range. The system works independently of the flight management system, air traffic controls ground systems and aircraft navigation, and offers traffic advisory (TA) and resolution advisory (RA) (von Essen & Giannakopoulou, 2014). The traffic advisory is intended to aid the pilot on visual acquisition of any different aircraft and prepare him for appropriate resolution advisory. Resolution advisory alerts the pilot of the range and vertical speed at which the aircraft should be flown to avoid colliding with a threat aircraft (Julian et al., 2016).

Designing Safer Collision Avoidance Systems

A new approach for developing safer collision avoidance systems has significantly helped to reduce the risk of mid-air collision and is currently mandated worldwide on all large transport aircraft. The concept of air collision avoidance systems was a very costly undertaking that spanned several decades. The development of air collision systems has gone through an iterative process where the logic was specified using pseudocode, evaluation based on simulation and later revised based on performance against a set of metrics (Julian et al., 2016). The development of air collision systems has spurred challenging conditions to maintain the Traffic Alert and Collision Avoidance System (TCAS). This has led to the introduction of next-generation air traffic control procedures and surveillance systems. The aviation industry has been working on designs that have the potential to shorten the development cycle, improve maintainability and enhance the safety of the air collision systems (Holland, Kochenderfer & Olson, 2013). Recent technological advancement involves leveraging advances in the computation to automatically derive optimized collision avoidance logic that links encounter models and performance metrics.

The Traffic Alert and Collision Avoidance Systems use onboard beacon radar surveillance that monitors local air traffic. The system uses a logic that determines when to alert the pilots of a potential collision and recommends vertical maneuver for pilots. The creation of robust air collision systems is affected by factors such as state uncertainty caused by sensor noise, the risk of future aircraft trajectories, performance constraints of aircraft and pilot response (Lee, Kochenderfer, Mengshoel, Brat, & Owen, 2015). The system needs to be designed in a way that conserves the safety of aircraft and at the same time minimizes the disruption of normal operations. Nuisance alerts impacts negatively on the pilot's compliance resulting in unnecessary course deviation or conflict between aircraft (Lee et al., 2015). Recent development has pursued a new model that is based on optimization approach to developing a logic that shortens the development cycle, improves maintainability and enhance safety with fewer nuisance alerts that affect pilot's compliance and conflicts. This new approach involves using a computer to optimize the logic that identifies encounter models and performance metrics. Since the computer can predict future aircraft trajectories, the system is capable of producing a safer logic with fewer nuisance alerts than the current TCAS (Holland et al., 2013).

The success of any collision avoidance systems depends on the ability of the logic given the current state of the position and velocity of aircraft to predict future trajectories. When issuing an advisory to the possible collision, the logic should take into account all possible future trajectories and their likelihood. The standard safety of TCAS for near mid-air collision is when an intruder comes within 500 feet horizontally and 100 feet vertically (Nussberger, Grabner, & Van Gool, 2014). The alert rate should also be determined to measure how disruptive the system is to normal operations. Experiments of the new approach demonstrate that the logic has helped improve safety while reducing unnecessary alerts compared to the current TCAS systems (Nussberger et al., 2014). This new approach has left the role of optimizing the logic to computers, for instance, predicting future trajectories of airplanes. This new approach incorporates the concepts of new surveillance systems, procedures, and aircraft. This approach, however, faces challenges in terms of software certification and the cost of function development. The new approach is an improvement to the already existing TCAS systems, and it needs to ensure interoperability between the two systems. Before committing to a particular model, aircraft should take into consideration the real encounters and cost parameters to balance the performance considerations adequately.

Maintenance

With the introduction of new procedures, aircraft capabilities, and sensor systems, the aviation industry needs to maintain a high degree of safety by keeping operational acceptability (Olson, 2015). The changes that have been incorporated since the introduction of TCAS have involved the introduction of a new development approach that equips aircraft with new hardware and surveillance systems. The current TCAS does not have the memory capacity to hold logic tables, but aircraft are being equipped with hardware that accommodates a tabular representation of the logic (Olson, 2015). Experiments show that it is much easier to re-optimize the logic in terms of metrics than incorporating changes to the pseudocode.

The Next Generation Collision Avoidance Systems

The Traffic Alert and Collision Avoidance Systems (TCAS) have shown significant improvement in safety and have reduced the risk of mid-air collision. However, the logic used to select methods of pilot advisories is difficult to modify and does not support surveillance inputs prompting the development of the next generation systems (Holland et al., 2013). Airborne Collision Avoidance Systems (ACAS X) has been developed to address some of the design limitations of TCAS. The development of ACAS X is optimized concerning cost function, increase safety and reduce risks, meet operational suitability and pilot acceptability performance metrics (Holland et al., 2013). ACAS X is designed to reduce collision risks and unnecessary and disruptive alerts.

Experiments indicate that ACAS X resolves encounters with more straightforward alert sequences and offers many reversals and altitude crossing advisories unlike TCAS (Holland et al., 2013). In 2009, the FAA TCAS Program Office introduced the ACAS X system to improve on the limitations of TCAS. ACAS X adopts a different methodology design that is based on decision theory by automatically deriving the optimal logic based on probabilistic models and cost functions. The development of ACAS X is based on choosing models and cost parameters to achieve safety and operational performance. This system also incorporates the use of modern sensor systems that enhance new procedures based on user classes. The surveillance systems track the local air traffic and employ a set of weighted samples to represent the estimate of the aircraft state in terms of positions and velocities.

This new approach takes advantage of the recent technological advancement in dynamic programming and computer science techniques that were not invented during the development of TCAS that can generate alerts with the help of off-line optimization of resolution advisories (Zou, Alexander, & McDermid, 2016). The development of ACAS X is intended to replace the TCAS systems completely. The ACAS X will use the same hardware in the form of antennas and displays as the current TCAS systems, with no significant changes in how alerts will be announced to pilots as the new system will be fully compatible with the TCAS systems (Zou et al., 2016). However, there will significant changes in the collision avoidance logic and the sources of surveillance data. TCAS relies on interrogation mechanisms with the help of transponders onboard ai...