Abstract : This paper highlights the user-centered design concept, studies the basic theories of human-computer interface (HCI) design, and proposes design principles for HCIs of airborne information systems. Following these principles in interface design helps improve the human-computer interaction capabilities of airborne information systems. Keywords : Airborne information system, human-computer interface design. Airborne information systems are a special type of human-computer interaction system, and the HCI is a crucial component. The functions and performance of airborne information systems are reflected and realized through the HCI. Good HCI design and technical implementation can fully leverage the capabilities of airborne information systems. In traditional information system HCI design, system designers often focus only on the realization of product functions, striving for broad coverage, complete functionality, and strong integration, neglecting the harmony of human-computer interaction. They mainly consider how to make users adapt to the machine, without systematically considering human factors. For HCI design of airborne information systems, it is necessary not only to systematically consider human factors but also to emphasize the physiological and psychological characteristics of humans in flight, and to meet the requirements of ergonomics. Only by adopting a user-centered design philosophy, selecting reasonable interaction methods, and scientifically distinguishing human-machine tasks can we fully leverage the characteristics of humans and machines, and develop a concise, efficient, friendly, and easy-to-use human-machine interface for airborne information systems. I. Human-Machine Interface Design Philosophy 1. The Concept of Three Models Donald A. Norman first proposed the three concepts of mental model, implementation model, and system model in human-machine interface design in his book "The Design of Everyday Things". (1) A mental model is the knowledge of concepts and behaviors that a product should have in the user's mind. This knowledge may come from the user's previous experience using similar products, or it may be the user's expectation of the product's concepts and behaviors based on the goals to be achieved by using the product. (2) The implementation model is the internal structure and working principle of the product, which exists in the mind of the product designer. (3) The system model refers to the final appearance of the product and the knowledge that the user forms about how to use and work the product after viewing or using it. 2. Relationship among the three models: Among these three models, the mental model pertains to the user level and domain, which designers cannot change; the implementation model is constrained by current technological levels and is unlikely to undergo significant changes within a certain period; only the system model possesses great plasticity and can be refined and improved by product designers. The system model lies somewhere between the mental model and the implementation model. The closer the system model is to the mental model, the less the user needs to learn and remember, and the closer the product is to the user's expectations. If the system model is closer to the implementation model, the user needs to map some expected concepts and behaviors onto some interface elements and operations represented in the system model. This mapping manifests as a memory burden in cognitive psychology, and it is this memory burden that makes people feel the product is difficult to use. 3. Problems in Human-Computer Interface Design: As can be seen from the relationship among the three models, the system model, located between the mental model and the implementation model, determines the ease of use and complexity of the product. Traditional software design often focuses solely on making the system model more closely resemble the implementation model, concentrating on increasing product complexity and technical difficulty. This neglects the relationship between system model design and mental model, viewing human-computer interface design as a low-level activity to please users, devoid of practical value. The sole criterion for evaluating application software is its powerful functionality and ability to smoothly assist users in completing their tasks. However, in recent years, with the rapid development of computer hardware technology, a new generation of computer users has placed higher demands on application software in terms of operability and ease of operation. Besides expecting powerful functions, they also desire a relaxed, pleasant, and comfortable operating environment. Due to the special nature of military software, military users have even higher requirements for operability. In traditional military software, usability issues caused by the mismatch between the system model and the mental model are widespread; therefore, user-friendly human-computer interface design has become an important component of military software development. The quality of the human-machine interface in an airborne information system determines the ease of use of the software and the user's evaluation of the overall system function. In order to make the human-machine interface design of the airborne information system better adapt to the user, the idea of ​​"user-centered" should be valued by software designers and run through the software design. II. General principles of human-machine interface design Principles are overall, nature-related design guidelines for the inherent characteristics of the software, and are necessary work to be done. Based on the design idea of ​​"user-centered", the human-machine interface design should follow the following design principles. 1. User compatibility The user is the end user of the system's interactive interface. There should be compatibility between the user's expectations and the reality of the interface design, and it should be based on the user's previous experience. 2. User control Only when the user is in a controlling position can he/she express his/her own needs and control the system himself/herself, rather than being controlled by the system. (1) The user should play an active role in the human-machine interaction of the system and can choose the interaction method and steps to complete the interaction task as needed. (2) Different users have different requirements for the human-machine interface. Therefore, interface elements such as color and font can provide human-machine interaction options according to the user's personality. (3) The interaction tasks should be reasonably distinguished and the process divided so that the user does not need to load the entire application module to perform a certain operation. 3. Guidance Function: Users are inevitably unfamiliar with different software, especially complex systems. The human-computer interface (HCI) should provide a context-sensitive help system to ensure users receive timely assistance, using concise verbs and verb phrases to prompt commands. The user help mechanism should be integrated to avoid a layered system where users have to browse a lot of irrelevant information to find a specific guide. Error and warning messages must use clear and accurate terminology and should also provide suggestions for error recovery whenever possible. 4. Strong System Stability and Fault Tolerance: User errors are unavoidable. The HCI should have strong fault tolerance to prevent irrecoverable or catastrophic consequences from erroneous operations. The HCI should have data backup and recovery capabilities. The HCI design should prevent errors and provide protection against damage to the system's operation and information storage caused by misoperation. The system should provide necessary error information that is clear, easy to understand, and consistent. 5. Timely feedback and evaluation Timely feedback and evaluation of human-computer interface use is essential. After the interface prototype is designed, it needs to be delivered to users. Through user participation, designers should also organize users to evaluate and verify the functionality and usability of the interface, identify problems in the human-computer interface prototype, and make targeted modifications to the interface in conjunction with the maintenance and modification of the software platform. The evaluation of human-computer interaction system software can be considered from the following main aspects: (1) User satisfaction with the human-computer interface. (2) Standardization of the human-computer interface. (3) Adaptability and coordination of the human-computer interface. (4) Stability and fault tolerance of the human-computer interface. In the process of evaluating the human-computer interface, it should be noted that the main principle of evaluating the user interface is whether the interface meets the user's needs well and whether it improves the usability of the interface. III. Basic principles of human-computer interface design for airborne information systems 1. For military users Airborne information systems are mainly provided to military users, who are the end users of the system's interactive interface. There should be harmony and unity between user expectations and the reality of interface design, and it should conform to the thinking habits and interactive experience of military users. In order to cater to military users, military users should be actively invited to participate in the initial interface design process. There are two ways to participate: First, during the system design phase, military users should work with system designers to complete the user interaction characteristic requirements analysis and interaction task requirements analysis of the system, and do a good job in the necessary preliminary preparations for the human-computer interface design; Second, after the system human-computer interface prototype design is completed, a test version should be made, and representative military users should be selected to test and evaluate the human-computer interface prototype, find out the defects and errors in the interface design, and then make further modifications as appropriate. 2. The system is simple and easy to use. The design concept of "user-centered" requires users to be in a controlling position and to be able to easily control the software. Therefore, the human-computer interface software of the airborne information system should be as simple and easy to use as possible, conform to the user's usage habits, and be able to operate correctly without special training. (1) Provide a variety of help services The human-computer interface software of the airborne information system has a rich set of functions, especially some commands that are highly professional and complex to operate, which puts forward relatively high requirements for users. For airborne information system human-machine interface software, it is not enough for the system to only provide a user manual, because it is difficult for unfamiliar users to read the complete manual, especially in specific combat environments, which causes a lot of inconvenience to users. The interface design should guide users through task prompts and feedback information, and provide various forms of help such as contextual help and process help, so as to minimize the time users spend guessing and searching. (2) Provide multiple information input methods In airborne information systems, information input is the main operation method. Whether the operator's operation can be quickly and accurately reflected to the system and responded to is an important evaluation of the performance of airborne information systems. Using multiple information input methods can give users more choices and make the software more flexible. Based on the usage habits of military users and the experience of human-machine interface design, the airborne information system human-machine interface software should adopt the following information input methods: ① Command language: directly operate the system by inputting specific commands. This method is flexible and convenient for users to exert their creativity. It has high work efficiency for skilled users, but it requires users to undergo prior training. It is not user-friendly and difficult to learn. Its error handling ability is also weak. However, due to the usage habits of military users, this operation method can be considered to meet their needs. ② Menu Options: Compared to the command-line method, this method is less prone to errors and can significantly shorten user training time. It also allows for the use of dialogue management tools, greatly improving error handling capabilities. However, during use, there may be situations with too many menu levels and complex menu options, requiring selection step-by-step rather than a single step, resulting in slow interaction speed. This inevitably affects user operation time and the interaction time of the airborne information system. A better solution is to change the menu mode and selection method, limiting menu levels when necessary, and adopting Fitts's Law from human-computer interface design. Frequently used menu items can be summarized and categorized to reduce mouse positioning time and be converted into shortcut menus for easier user location and selection. ③ Keyboard Shortcuts: Keyboard shortcuts use keys or key combinations on the keyboard to replace menu command selection. Therefore, the shortcut key usage schemes for each functional module of the information system should be uniformly designed and allocated, and the following issues should be noted: Shortcut keys should only be used for important and frequently used functions; the setting of shortcut keys should conform to software development habits, generally using "CTRL + key" combinations, "SHIFT + key" combinations, or "F1~F12" to perform some quick operations, avoiding the use of shortcut key combinations of more than three keys and shortcut key combinations already defined by the system; avoid assigning one shortcut key or combination to multiple operations. 3. Rapid System Response Excessive system response time is the most frequently complained-about problem in interactive systems. Airborne information system human-machine interface software, due to military use requirements, has high requirements for system responsiveness. If user operations cannot be responded to in a timely manner, it will lead to delays in important commands. In addition to the absolute length of response time, users are also very concerned about the difference in response time between different commands; if the difference is too large, users will find it unacceptable. 4. Strong System Real-Time Performance Airborne information system human-machine interface software needs to meet the needs of military operations. The information display of the human-machine interface must be periodically refreshed according to changes in real-time data on site, reflecting the changes in the monitored and controlled objects in real time. Therefore, in the process of human-computer interface design, under the premise of ensuring system stability, a multi-task processing method is adopted, the algorithm is improved, and the real-time display efficiency of the system is improved. 5. The system is compact and simple. The airborne information system human-computer interface software is software that is run in the airborne environment. Due to the special nature of the hardware environment and operating environment, the design of the airborne information system software human-computer interface does not need to be too fancy. It should be as compact, simple, and natural as possible. A human-computer interface with a consistent style will give people a sense of simplicity and harmony. Therefore, in the design of human-computer interface, it is necessary to pay attention to the following aspects of style consistency. (1) Consistency in color use. Color itself is an auxiliary form of information. It can attract the user's attention and generate associations. Because the airborne information system screen display is relatively rich, in order to avoid causing difficulties in the user's visual cognition, the airborne information system human-computer interface should use a limited number of colors. The color selection must meet the needs of interaction and adapt to the user's psychological cognition. The color matching should be as beautiful and harmonious as possible and make it easy for the user to concentrate. (2) All menu selection, command input, and data display functions should maintain a consistent style. (3) Maintain consistency in font and character size. (4) Maintain consistency in the display of specific symbols. Since airborne information system software is military software, considering user habits and traditional regulations, some specific symbols need to be consistent with other military software to avoid ambiguity. (5) Consistency in shortcut operations. Although airborne information system software has its own special characteristics, some commonly used shortcut operations should be consistent with the user's daily usage habits, which can reduce the learning and training time for operators. (6) Consistency in the use of controls. Controls are the basic elements that make up the interface, and the combination, layout, arrangement and size of controls need to be specified in detail. First, the combination of controls and the control set of the system human-computer interface should be reasonably determined according to the needs of the system interaction tasks. Second, the arrangement and layout between controls should conform to the user's operating habits and interaction needs: there should be a certain distance between controls and between controls and forms to prevent hidden and overlapping controls; the arrangement and display of controls on the interface should have a certain hierarchy and logic; attention should be paid to the consistency of control layout and arrangement. IV. Conclusion The human-computer interface of airborne information system is the bridge between airborne information system and the outside world, and is the main channel for human-computer interaction. Human-computer interaction systems should take human factors into account as much as possible and serve users. Only by fully considering the requirements of system operators and their airborne environment can the human-computer interface better reflect the system functions and complete the system tasks in a high-quality and efficient manner. Following the above principles will help the development of airborne information systems and improve the overall quality of airborne information system software. References : [1] Li Leshan. Human-computer interface design [M]. Beijing: Science Press, 2004. [2] Microsoft Press. Windows user interface design [M]. Beijing: Peking University Press, 2000. [3] Luo Shijian, Zhu Shangshang, Sun Shouqian. Human-computer interface design [M]. Beijing: Machinery Industry Press, 2002. [4] Zhang Liang. “Easy to use” user interface design ideas [J]. Programmer, 2006 (1). [5] RJ Torres. User interface design and development in detail [M]. Translated by Zhang Lingang and Liang Haihua. Beijing: Tsinghua University Press, 2002.