The Future Aircraft Systems in Commercial Aviation
Currently, many commercial aircraft carriers have trouble with the current aircraft navigation and communication systems because of the continuous increase in air traffic around the world. This calls for the development of advanced navigation systems such as PBN that pave way for automated flight paths a concept that will change the airspace traffic, design, and access to runways. New advanced communication systems such as ADS-B can handle the increasing traffic and synchronization of ground and onboard communications. This paper will discuss PBN navigation and ADS-B communication system and explore ways which they handle challenges in the future aircraft systems.
Purpose of the system PBN and ADS-B systems
The PBN navigation system developed for commercial aircraft industry comprises of the Area Navigation System (RNAV) and the Required Navigation Performance System (RNP). PBN system provides specifications that aircraft adhere to in accord with the International Civil Authority Organization terms and conditions. ICAO specifies the functional requirements, integrity, accuracy, continuity, availability, and appropriate navigation infrastructure for RNAV and RNP systems for aircraft (Strohmeier, Schäfer, Lenders, & Martinovic, 2014). The PBN gives navigation specification to the pilot, issue infrastructure specification to manufacturers, and general navigation application for all aircrafts using performance standards.
Contrary, the Automatic Dependent Surveillance-Broadcast System (ADS-B) has completely transformed the commercial aircraft communication system. The ADS-B system is equipped with technologies that make possible real-time precision monitoring of position and location responsiveness. Like the PBN system, the ADS-B system also utilizes satellite navigation that makes it possible to track the aircraft. Additionally, periodic broadcast received from the ADS-B system in ground stations and by other aircraft provide the precise location of the aircraft. This technology enables the aircraft (pilot) to determine its exact location.
Components of PBN and ADS-B systems
The PBN has an advantage of flexibility because it encompasses both the Area Navigation (RNAV) and Required Navigation Performance (RNP). Area Navigation permits commercial aircraft to fly any desired path provided it lies within the coverage of Navaids, RNP, on the other hand, is RNAV but with additional board performance monitoring such as GNSS and GPS (Glonass and in future Galileo). The Onboard performance monitoring and alerting system components include Advanced RNP (A-RNP), RNAV-GPS, RNAV-RNP, RNP1, RNP2, and many more system approaches(Haynes, 2014).
Figure 1 PBN comprise of both RNAV and RNP that enable automated flight paths
The main components of the Automatic Dependent Surveillance-Broadcast (ADS-B) system are the airborne component, ground infrastructure, and its operational procedures. The “ADS-B In” and “ADS-B Out” have gradually replaced the use of radars in many parts of the world. The system is fitted with a highly integrated GPS system and a data-links (Haynes, 2014). The GPS system identifies aircraft location, altitude, cruising speed, and signals from nearby aircraft. The data-link (ADS-B unit) is a broadcasting channel; the most common ones operate between 978 MHz and 1090 MHz frequencies. Even so, the 1090 MHz is more efficient due to its features that carry Mode-S transponders and easily accommodate new technological changes; it is likely to be the standard communication system for commercial aircraft in future (Haynes, 2014).
Figure 2 illustration of ADS-B communication system
How they operate (PBN and ADS-B systems)
PBN use Global navigation Satellite System (GNSS) and computerized onboard systems, unlike the traditional navigation systems that used sensor-specific navigation based on fixed ground stations to guide commercial aircraft through predefined routes. This provides “absolute navigation” because of the onboard performance monitoring and alerting utility warrants integrity in navigation at all times. It uses longitudes and latitudes to determine the aircraft position in relation to their destined location and flight path, this way, the airplane meets its requirements accurately all the time. The GNSS provide information from a satellite view and warns the pilot to discontinue if the aircraft’ position falls outside the acceptable limit (Nakamura and Royce, 2008).
The ADS-B system provides unified surveillance to both ground and airborne parties; it receives customized data from the ADS-B ground station. The ADS-B system has two elements, ADS-B Out, and ADS- B In. These frequencies transmit and receive information in the aircraft. As the name suggest, the ADS-B In is the receiver while the ADS-B Out sends signals to the ground station and other aircraft in the same wavelength (Strohmeier, Schäfer, Lenders, & Martinovic, 2014). This way the Automatic Traffic Control (ATC) and other aircrafts know the exact position of an aircraft. The ATC designed two special frequencies for commercial aircrafts to avoid frequency overload, aircrafts above 18000 feet use 1090 MHz while those below this altitude can use 978 MHz frequency.
Benefits of PBN and ADS-B systems over other systems
The PBN is advantageous to other navigation systems especially the sensor-specific systems in numerous ways. The PBN system is cost effective because it systematizes RNAV and RNP and this way, it helps commercial aircraft escape proliferation of costs in achieving standards for certification (Jackson, 2015). This is cost saving to commercial aircraft because there will be no need of maintaining sensors for individual routes (e.g. VOR) and by avoiding the need to develop a new sensor-specific operation, every time technology advances (Nakamura and Royce, 2008).
Additionally, the intervention of ICAO in providing infrastructure and navigation specifications has facilitated and improved operation approval. The PNB has also facilitated flight efficiency; the system is a transition of RNP/RNAV environment that result in optimization of airspace in terms of fuel, noise mitigation, and route placement (Jackson, 2015). Furthermore, PNB has increased the use of area navigation (RNAV) close routes thus clarifying its use. The PBN navigation system also improves commercial aircraft infrastructure; it only requires one dual GNSS (sometimes supported by DME) and therefore there is no need for NDB and VOR (Jackson, 2015).
The main advantages of fitting commercial aircraft with the ADS-B avionic system are that it increases the efficiency and safety of air traffic supervision. This is because aircraft fitted with the ADS-B communication system are easier to track in case of emergencies (search and rescue). In addition, there are policies that require Air-services providers to prioritize their services to aircraft with ADS-B systems; this way commercial airlines with ADS-B systems benefit(Strohmeier, Schäfer, Lenders, & Martinovic, 2014).
Furthermore, aircraft equipped with the ADS-B communication system do not have to report their position since they are visible in most ground radars. The ADS-B communication system also allows ATC to allocate and approve pilot requests for continuous ascending or descending efficiently (Eldredge et al., 2010). Moreover, with the development of ADS-B communication systems, airspaces that previously lacked communication radars can now utilize the ATC communication and surveillance services. Pilots in aircraft fitted with ADS-B systems also receive real-time weather reports and avoid flying into storms or turbulences.
Limitations of the PBN and ADS-B systems
The major limitation of the PBN navigation system is that in order to operate (use) in RNAV/RNP airspace/environment, a commercial aircraft must first subscribe to an ATS Route (routes designed by ICAO). Therefore, a commercial aircraft that has not ascribed to use ATS routes (PBN “airspace”) cannot use the PBN navigation system. This implies that the aircraft will not follow the usual company routes and may follow longer routes. In addition, system maintenance costs may increase because of the high standards enforced by ICAO (Nakamura and Royce, 2008).
Several factors limit the use of ADS-B communication system; these systems rely on secondary surveillance technology and needs the assistance of the targets (aircraft). Therefore, because this system entirely depends on the veracity of the aircraft navigation system and its functional transponder when it fails it will not be able to broadcast its location or may give false location (Strohmeier, Schäfer, Lenders, & Martinovic, 2014). Moreover, these systems are not secure and as such, aircrafts fitted with these systems can easily receive fake broadcasts from ADS-B In (Eldredge et al., 2010). This is because ADS-B messages can be aired by anyone with the right equipment, so unless regulations are passed, hackers can easily gain access to important flight information. Further, the rapid technological changes witnessed every time imply that there are transition periods when ADS-B systems will not be functioning (under maintenance).
PBN navigation system heavily on operations based on Area Navigation system (RNAV), which has been around for more than two decades. Therefore, pilots and operators around the world are familiar with these systems standards. This makes this system effective and efficient because of its ease of use and popularity around the world. “The concept of PBN is intended to better define the use of RNAV systems and provide a means to eventually reach the level of common use as the conventional navigation system” (Eldredge et al., 2010).
The ADS-B communication system is a new invention from the NextGen, it is very efficient because it provides real-time data to control air traffic, enables safer flights because it receives, traffic information, provide ways for faster and accurate search and rescue, and weather reports (greater ability to avoid bad weather). However, if the governments do not pass necessary regulations governing the use of ADS-B system, it will fail to be effective because anyone with the right equipment can broadcast using these frequencies and may confuse pilots and those in ADS-B ground stations.
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