Operational Concept and Validation of a New Airport Low-Level Wind Information System

OPERATIONAL CONCEPT AND VALIDATION OF A NEW AIRPORT LOW-LEVEL WIND INFORMATION SYSTEM

Tomoko Iijima, Naoki Matayoshi and Shoh Ueda *Japan Aerospace Exploration Agency (JAXA)

Keywords: Windshear, Turbulence, Wind Disturbance, Aircraft Operation, ACARS Abstract Pilots are sometimes not provided with sufficient information to avoid go-arounds or other operational disruptions that result from low- level wind disturbances. We identified issues with existing windshear alerting systems, and developed three types of airport low-level wind information systems to enhance pilot situation awareness of wind conditions by providing Figure 1. Causes of go-arounds at Narita landing aircraft with quantitative and visualized International Airport (2008). wind information, ultimately to mitigate air service disruptions due to low-level wind headwind change of more than 20kt is observed (3) disturbances. The three systems, ALWIN (Airport by an airport-based Doppler radar / lidar sensor . Low-level Wind Information) and LOTAS (Low- Although present low-level windshear alert level Turbulence Advisory System) that use systems contribute to the goal of preventing Doppler radar/lidar, and SOLWIN (Sodar-based accidents, they do not always provide sufficient Low-level Wind INformation) that uses Doppler information on wind disturbances to prevent SODAR (SOnic Detection And Ranging), have operational disturbances such as go-arounds. At different costs and capabilities which allow the Narita International Airport (Japan’s largest most cost-effective system to be selected for an international airport), for example, more than airport according to its scale and local weather 90% of go-arounds occur due to wind characteristics. This paper presents the disturbances such as windshear, turbulence, and operational concepts of our newly-developed strong headwinds or crosswinds, as shown in airport low-level wind information systems and Figure 1. describes their validation. On investigating this situation, we found that existing windshear alerting systems provide windshear alerts only when the windshear is 1 Introduction severe enough to pose a high accident risk. In Low-level wind disturbances, such as other words, even if the alerting systems detect windshear and turbulence, near airports can less severe windshear which could nevertheless present hazards to take-offs and landings since still cause a go-around or other air service they disturb aircraft flight paths and attitudes. disruption, this information is not provided to Following several tragic accidents due to strong pilots. We have therefore developed a new windshear (1), the International Civil Aviation airport low-level wind information system to Organization (ICAO) recommended that airport provide landing aircraft with quantitative meteorological services provide windshear (numerical) and visualized (graphical) wind warnings for aircraft flying below 1,600ft above information to enhance pilot situation awareness the runway elevation (2). In Japan, the Japan of wind conditions and ultimately mitigate air Meteorological Agency (JMA) provides service disruption due to low-level wind windshear alerts at major airports when a disturbances. Newly developed graphical and

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textual information provide tactical and strategic such as runway thresholds. Sensor wind data are information on low-level turbulence and processed into graphical / textual representations windshear to flight crews, airline dispatchers and useful for aircraft operations, and may be other ground-based operations staff is intended to transmitted to flight crews in the cockpit via increase operational efficiency (by reducing the ACARS data link text message (e.g., Figure 3) or number of go-arounds) as well as to prevent to ground users (airline dispatcher/operations accidents. Flight crews can obtain the officers) via the Internet to provide a graphical information by ACARS (Aircraft and textual web display, as we have described Communications Addressing and Reporting previously (5), (6), (4). System) datalink text message. This is the first Although there are differences in the wind system in the world that provides quantitative sensors used by the three systems, their wind information to the cockpit. architecture, that is windshear / turbulence Based on this concept, we have developed detection and information provision methods, are three types of airport low-level wind information very similar. Table 1 shows the operational system with different capabilities and costs: concept of each system. Although the three ALWIN (Airport Low-level Wind INformation) systems all aim to provide tactical and strategic (4) and LOTAS (Low-level Turbulence Advisory information on low-level turbulence and System) (5) that use Doppler radar/lidar sensors, windshear, the type and cost of the wind sensor and SOLWIN (Sodar-based Low-level Wind and the information content of the web display INformation) that uses Doppler SODAR (SOnic and ACARS message text differ according to the Detection And Ranging). This allows the system airport’s scale and the characteristics of its local with the best cost benefit for an airport to be weather environment. selected according to the airport’s scale and local The main method for obtaining wind weather characteristics. In this paper, airport information also differs among the three systems. scale refers to traffic volume (the number of daily ALWIN is used mainly in a “pull” (request- scheduled flights) and the number of runways. response) mode of operation, while LOTAS and The ALWIN system has been implemented and SOLWIN are used mainly in a “push” mode. operated officially by the JMA at Tokyo’s two With a “pull” operation (4), flight crews can international airports, Narita and Haneda, since obtain low-level wind information from the 2017. cockpit at any time on request using ACARS. To To verify the effectiveness of our concept, an implement this type of operation, airlines have to operational evaluation was carried out by a modify their ACARS ground systems to respond questionnaire usability survey of flight crews and automatically to flight crew requests by ground-based flight operations support staff. retrieving the latest ALWIN / LOTAS / This paper presents the operational concept SOLWIN text information from the server and of our newly-developed airport low-level wind uplinking it. This automated response to flight information systems and describes their crew requests can improve flight crews’ wind validation. situation awareness and enable them to more effectively conduct approach briefings and plan flight control strategy such as determining the 2 Operational Concepts target approach speed, as shown in Figure 4. The newly-developed system architectures Flight crews typically obtain wind information of the ALWIN, LOTAS and SOLWIN systems via ACARS datalink during cruise as part of their are shown in Figure 2. ALWIN and LOTAS preparations for arrival, and use it to plan the automatically detect wind disturbances on approach and landing. In cases where the low- approach flight paths, including disturbances level wind information indicates turbulent with small-scale spatial structures, using Doppler conditions, flight crews can also obtain the most radar/lidar, while SOLWIN automatically up-to-date information during the approach to detects disturbances directly above Doppler allow them to monitor changes in the wind SODAR sensors to monitor discrete locations situation. 2 OPERATIONAL CONCEPT AND VALIDATION OF A NEW AIRPORT LOW-LEVEL WIND INFORMATION SYSTEM

Figure 2-a. System architecture of implemented ALWIN (Airport Low-level Wind INformation).

Figure 2-b. System architecture of LOTAS (Low-level Turbulence Advisory System). On the other hand, with a “push” operation ALWIN / LOTAS / SOLWIN text information to (4), ground-based dispatchers or operations staff the aircraft over ACARS, or verbally monitor the wind situation using a web display communicate the wind information indicated in screen, and transmit the information to aircraft in information area of the display over the company flight when notable wind disturbances are radio frequency. To facilitate push mode observed. Operations staff can either uplink the operations, we designed a function to generate an

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Figure 2-c. System architecture of SOLWIN (SOdar-based Wind INformation).

(1) FNL (Final) text <- ->: wind speed variance (2) APT (Airport) text Figure 3. Example of ALWIN text display .

ACARS text message when the user clicks the Haneda, and on a trial basis with the SOLWIN “ACARS text conversion” button in web system at Oita, a regional airport with about displaye.g. (5). This type of operation does not fourteen daily scheduled flights. At the start of require any modifications to existing airline development, push operation was used with the systems. LOTAS system at Shonai airport, but pull At present, pull operation is used by Japan operation with LOTAS is also possible with Airlines (JAL) with the ALWIN system at modifications to the ACARS ground system. Japan’s largest international airports, Narita and 4 OPERATIONAL CONCEPT AND VALIDATION OF A NEW AIRPORT LOW-LEVEL WIND INFORMATION SYSTEM

Table 1. Operational Concepts of ALWIN, LOTAS and SOLWIN.

We now describe the main operating volume, such as international airports. Since high characteristics of each system in the following. traffic means that low-level turbulence or windshear could affect many flights, and the 2.1 ALWIN impact of an accident or go- around will be high in such an operational environment, detailed ALWIN is intended for airports with wind information with a high update rate is multiple runways and a high daily airline traffic needed. This requires a wind sensor that can

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Figure 4. Use of ALWIN text display in the cockpit. cover a wide area, as shown in Table 1, which system at regional airports with only light inevitably has a high cost. The leads to ALWIN scheduled traffic. potentially having the greatest installation and Considering these factors, in order to satisfy maintenance costs of our three systems. the conflicting demands of low cost and the need However, the ALWIN systems that have for strategic information under rapidly changing been operated by the JMA at Tokyo’s Narita and weather conditions, LOTAS provides not only Haneda airports since 2017 use the existing information on low-level wind conditions during Doppler-radar and lidar sensors used for the approach and landing phases, but also conventional windshear alerting, so only the directly provides a measure of flight control ALWIN software development cost and the difficulty, in addition to radar echo information recurring sensor maintenance costs are incurred. to support landing timing decisions in dynamic weather situations (5). 2.2 LOTAS 2.3 SOLWIN Although the LOTAS wind sensor is assumed to be smaller and cheaper than that used SOLWIN is targeted at regional airports by the ALWIN system (4), (6), LOTAS can be with small budgets, and therefore uses a lower considered as having the greatest functional cost, less capable wind sensor than the other two capability of our three proposed systems since it systems, Doppler SODAR, as shown in Figure 2- provides novel information on flight control c. Doppler SODAR measures upper-air winds by difficulty and landing timing decision support, acoustic signals, has limited observation range listed as one of its advantages in Table 1. and its valid wind information is limited to below LOTAS is intended to be best suited to approximately 300ft. airports with only a few scheduled daily flights but where the weather environment is prone to changing rapidly, with strong precipitation and 3 Operational Evaluations low visibility, as shown in Table 1. Although Evaluations of the operational usability of strong windshear in low visibility is a difficult the ALWIN, LOTAS and SOLWIN systems environment for aircraft operations, system were carried out with a number of airlines during installation and maintenance costs must be system development as shown in Table 2. reduced due to the lower cost benefit of the Although the development of each system started

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Table 2. Operational evaluations of ALWIN / LOTAS / SOLWIN.

previous to the operational evaluation described who responded considered ALWIN to be in this paper, we focus here on the final “slightly useful” or “useful” shown in Figure 5-a. operational evaluation period of the system Figure 5-b shows that 94% of flight crews who design in Table 2. Since the evaluation of the responded considered the LOTAS ACARS general utility of the LOTAS system and requests message information to be useful. Figure 5-c for improvement have been presented previously shows that more than 70% of flight crew who (5), (6), these discussions are omitted from this responded considered SOLWIN to be useful. paper. In summary, more than 70~80% of flight Participants in the evaluation (pilots and crew who responded to the questionnaires rated ground-based operations staff from several our proposed new airport low-level wind Japanese airlines) were asked to rate the information systems as useful, and we therefore effectiveness and usability o f each system in consider that they are effective for supporting questionnaires, and to provide comments. normal aircraft operations. Information was gathered on which aspects of the system participants found to be useful or Flight crew comments on which aspects of appraised positively, and which they did not find the ACARS messages were found to be useful useful or appraised negatively. are summarized in Table 3. A “○” in a table cell indicates that obtain comments were made supporting the usefulness of an aspect, while 4 Results and Discussion “N/A” indicates that no such comments were Figure 5 shows overall pilot evaluation obtained. results of each system at each airport where it As shown in Table 3, the information was deployed. It should be noted that rating provided by each system was considered to be scales used in the questionnaires differed among applicable to improving situation awareness of each system due to modifications to improve the low-level wind disturbances and enabling their usability questionnaire after each evaluation. The prediction, and for flight control planning. rating scale of ALWIN had four points, “Not It is therefore possible that the provided useful”, “Slightly not useful”, “Slightly useful, information might contribute not only to greater “Useful”, while those of LOTAS and SOLWIN safety but might also reduce the number of go- had only two points, “Not useful” and “Useful”. around events that disrupt smooth operations, particularly because crews will be able to predict More than 80% of the flight crews at Narita the reduction of airspeed due to windshear, plan and more than 70% of the flight crews at Haneda

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a. ALWIN

b. LOTAS c. SOLWIN

Figure 5. Overall flight crew usability ratings

flight control strategy and make runway airports, although some issues remain to be selections accordingly. addressed in the future. From the result of “difficult to understand As shown in Figures 6, the aspects that were info. (information)” in SOLWIN, it is considered found not be useful or were negatively appraised that the presentation of up and down draft with the ALWIN system also received the same information is novel and crews had no experience appraisal in the SOLWIN evaluation; that is, as to how it could be applied, and that ACARS “difference between flight path (actual wind the message text itself may also be hard for flight situation) and SOLWIN” and “not getting info. crews to understand. A method for presenting the (information) just before landing”. Since new severity metric message and how to apply it SOLWIN cannot measure wind data on the are future issues. approach flight path, unlike ALWIN, a We obtained many flight crew comments in difference between the actual encountered wind the category “others” relating to SOLWIN’s situation and SOLWIN wind information is limited observation range. Typical comments considered unavoidable. show that providing wind information only Nevertheless, there were almost unanimous below 300ft is insufficient, and flight crews flight crew requests for SOLWIN requested wind information above 300ft as an implementation, and we obtained positive improvement. comments shown in Table 3. These results indicate that SOLWIN will be useful for regional

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Table 3. Useful aspects of system ACARS messages.

Figure 6. Non-useful or negatively appraised aspects of ALWIN (left) and SOLWIN (right). Although SOLWIN’s Doppler SODAR are highly correlated with turbulence or wind wind observation sensor was installed at the shear on the landing path, for example due to runway threshold in this evaluation, it is local topography. It is therefore recommended necessary to install the sensors at locations that that unless the Doppler SODAR observation

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range can be improved, the SOLWIN sensor [3] anon, “Aviation/Marine Weather Services,” locations should be determined at each airport by JMA Web site, investigating the correlation between SOLWIN http://www.jma.go.jp/jma/en/Activities/aws. wind measurement data and flight data on the html (as of May 2016) landing path. [4] Matayoshi, N., Iijima, T, Yamamoto, K. and Fujita, E., Development of Airport Low-level Wind Information (ALWIN), American Institute of 5 Conclusions Aeronautical and Astronautics Aviation 2016, AIAA-2016-3865, June, 2016. This paper describes the design concepts and [5] Iijima, T., Matayoshi, N. and Yoshikawa, E., validations of three types of new airport low- Development and Evaluation of Low-level level wind information system that provide Turbulence Advisory Display for Aircraft landing aircraft with quantitative and visualized Operation, 29th Congress of the International wind information to enhance pilot situation Council of the Aeronautical Sciences, St. awareness of wind conditions and ultimately to Petersburg, Russia, Sep. 7-12, 2014. mitigate air service disruption due to low-level [6] Matayoshi, N., Iijima, T., Yoshikawa, E. and Ushio, T., “Development of Low-level Turbulence wind disturbances. The results of evaluation of Advisory System for Aircraft Operation,” 29th these systems during actual airline flight Congress of the International Council of the operations and issues for future consideration Aeronautical Sciences, St. Petersburg, Russia, that arose are identified. September 2014. Given that 70~80% of flight crew ratings [7] ICAO, “Eleventh Meeting of the evaluated the systems as useful, our proposed Communications/Navigation/Surveillance and new airport low-level wind information systems Meteorology Sub-Group of Apanpirg Uplink and are considered to be effective for supporting Downlink of Weather Information – Recent Development in Hong Kong, China, CNS/MET aircraft operations. The information provided by SG/11-IP/12 Agenda Item 12 (4), Bangkok, the systems is considered to improve situation Thailand, 16-20 July 2007. awareness of low-level wind disturbance, to [8] Iijima, T., Matayoshi, N., Fujita, E. and Yamamoto, enable its prediction and to allow flight control K., “Development and Evaluation of Airport Low- planning. Thus, the information by these systems level Wind Information, 53th Aircraft Symposium, might contribute not only to greater safety but 2015, Japan (in Japanese). might also reduce the number of go-around [9] https://www.metair.go.jp/metair/view/login/index. events that disrupt smooth operations, html particularly because crews will be able to predict [10] Observation by Airport Weather Doppler Radar, http://www.jma.go.jp/jma/kishou/know/kouku/2_k the loss of airspeed due to windshear, plan flight annsoku/23_draw/23_draw.html control strategy and make appropriate runway selection. The method for presenting the new severity Copyright Statement metric message in the SOLWIN system (as up The authors confirm that they, and/or their company or and down draft indications), and how to apply it, organization, hold copyright on all of the original material how to determine the SOLWIN sensor locations included in this paper. The authors also confirm that they are future issues. have obtained permission, from the copyright holder of any We continue to discuss cost benefit analysis third party material included in this paper, to publish it as of all three systems in the future. part of their paper. The authors confirm that they give permission, or have obtained permission from the copyright holder of this paper, for the publication and distribution of this paper as part of the ICAS proceedings References or as individual off-prints from the proceedings. [1] Anon, Aircraft Accident Report: NTSB/AAR- 82/02, NTSB, 1983. [2] Anon, Meteorological Service for International Air 6 Contact Author Email Address Navigation. ICAO Annex 3 to the Convention on Tomoko IIJIMA, [email protected] International Civil Aviation, 16th edition, 2007.