本文從幾何觀點出發，提出“飛航安全裕度”的觀念，來解釋航機之飛航情境的安全性變化。本文首先定義飛航組員操作飛機的情境空間，所謂的情境空間，是指SHELL模型中，除了人(L)以外的所有其它參數所構成的抽象空間，包含來自軟體、硬體、與環境等，各種與飛航安全有關之參數所構成。每一次的飛航，均假想成在情境空間中之一條隨時間變動的連續曲線。完全符合標準操作的飛航，假設為情境中之中心線，發生事故的相關情境用事故邊界來代表，而飛航的當下情境到事故邊界的距離即為安全裕度。依此定義，飛航安全裕度即代表當下情境偏離正常標準情境多遠，也就是所剩下之安全空間還有多少。由於安全認知的見仁見智，引用專家的知識與經驗是必需的。在給定情境之下，本研究以飛行員需要多大的綜合飛行能力，才能把飛機飛回正常標準情境，來表現該情境有多嚴重。情境偏離標準越遠，所需之綜合飛行能力也越高，表示飛航安全裕度被壓縮得越嚴重。本研究以大園事件以及一個正常飛行為例，各選取十個瞬間，分別收集相關的情境參數，再透過專家訪談，請資深機師提供，將各該情境飛回標準正常情境，所需之綜合飛行能力，換算成飛航安全裕度，再透過類神經網路的學習，建立任意情境與飛航安全裕度的因果關係。本研究並針對正常航班、異常航班、大霧、重飛、風切、單發動機失效、名古屋事件與大園事件等，以飛航安全裕度，呈現其相關安全性之連續變化。結果顯示，本方法可以跨越認知的限制，以量化方式呈現飛航安全狀況的變化，初步確定飛航安全裕度理論的可行性，如能與模擬機結合，將可進一步驗證本法的正確性與實用性。

The goal of this research is to propose a quantitative theory for flight safety：flight safety margin from a geometrical point of view. Firstly, the abstract situation space is defined using all the parameters in the SHELL model excluding the liveware. Each flight is viewed as a continuous curve in the situation space. If the flight situation of the plane follow the standard strictly, it can be represented as the center line. The accident boundary is defined as any combination of the situation parameters causing accident of the flight. Hence, the distance between the flight situation and the accident boundary is defined as the flight safety margin. Since safety is a perception problem, different from person to person, expert system is used in this research. A questionnaire is designed to extract the expertise from the captains given different flight situations both from a normal flight and the Taoyuan accident. The required flight perform once for the pilots to recover from the situation back to the standard defines the distance between them. Consequently, the training examples are then created and the causal relation between the flight situation and safety margin can be established using neural network. Eight real flight cases including Nagoya and Taoyuan accidents are used to check the feasibility of the theory of flight safety margin. From the results, if is reasonable to say that the proposed flight safety margin can supply logical, scientific, and quantitative measure about the flight safety. If is also expected that the simulation capability can be established with flight simulator.

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