機場跑道攔截系統經濟分析與決策模式之建立

Abstract

機場安全向來為飛安主要課題之一，致力減少飛安事故之發生之可能性與嚴重程度應為各機場主管機關努力之目標。國內過去曾發生數件衝出/滑出跑道事故，是常發生的飛安事故類型之一。因應此類事故的機場改善方法除拓展機場跑道與相關安全區域外，近年有一新型民航機用攔截系統面世，稱為工程材料阻擋系統(Engineered Material Arresting System, EMAS)。美國FAA不僅認可其效能，甚至為其推出民航指南與相關財務分析文件。但該財務分析文件內容僅就選擇裝設EMAS前提下比較不同方案的價值，並未對裝設EMAS與否進行探討，對有意改善機場現況的管理者或規劃人員無法提供一完整之評估流程供參考。本研究之目標即為建立一完整之評估模式，依序評估機場跑道長度、安全區長度現況，跑道長度不足者務須力即改善，安全區長度不足者應就現況探討不同方案的可能性，再就各種改善方案進行經濟分析，以得出各方案對機場、航空公司、旅客長期之經濟面影響。 為確實了解各民航法規對跑道與安全區之定義及規範，本研究先就FAA與ICAO兩大系統進行法規整理，再整理現有機場攔截系統，並參考前人所提出之機場改建評估方法文獻，建立本研究所提出之評估模式。因國內機場以ICAO系統為準，故法規部分也以ICAO規範為依循。依據ICAO所公布之機場跑道設計法可求得機場跑道長度需求，對照機場現況或近期使用機型即可了解機場跑道現況是否足夠。若跑道不足者應延長跑道或限制載重以策安全。跑道長度充足的前提下再進行安全區域審視，安全區域不足者應進行改善策略的規劃。應用FAA公布的經濟價值資料與本研究整理之歷年衝出/滑出跑道事故損失分佈可估計一機場對此類型事故長期之風險價值，再估計各種改善方案所可能改變的損失期望值，配合攔截系統價位、地價等改善方案代價即可求出各改善方案的經濟要素，再交由據管理單位依據不同考量標準自行決策。 本研究建立模式後針對國內機場現況進行檢核，發現大部分機場跑道長度都符合設計機型需求，但若以最大機型需求估計則可能部分機場跑道稍有不足。安全區檢核部分則發現國內公告安全區資訊不足，許多機場並未公告安全區，但自行以空照圖估計結果發現多數機場仍有充足空間可供使用。 本研究選定台北松山機場做為安全區改善方案比較的試算範例，試算結果發現裝設EMAS之類的攔截系統代價極高，雖有其效益，但仍須考量事故後維修代價；購地延長安全區方案雖可明確減少事故損失，但因代價過高，機場應審慎評估後再行決策。為了解參數改變對計算數值的影響，本研究另以簡單敏感度分析了解攔截系統維修費、地價、事故量等參數改變之影響，發現事故量增加時兩大類型改善方案之效益都明顯增加，攔截系統維修費與地價下降時則方案實施之價值也隨之提升。在機場無地可用時決策必然傾向於裝設攔截系統，但若土地充足且地價低廉時可能決策將傾向於購地延長安全區。 鑒於國內機場現狀，本研究建議各機場應確實公告安全區並確保安全區內無障礙物阻礙，以保持良好航機運行環境。另因本研究之試算有其限制，若機場有安全區改善需求，但又有社會、交通、環境等大範圍長遠考量，應在本研究範圍外另行探討各方案之可能效應以達到更宏觀的決策。

Runway Overruns and Excursions are common accidents in records. The solutions to reduce the severity of such accidents are basically increasing the size of safety area beyond the runway end. In FAA and ICAO regulations, the recommended length of safety area for large airports is about 300 meters. However, there are still airports unable to meet the requirement for safety. Recently a new system called Engineered Material Arresting System (EMAS) that can arrest the overrun aircraft below design speed without damage to structure. Furthermore, FAA published the advisory circular and Order for the system. However, the documents only discuss the circumstances of setting EMAS, and did not explained how to make the decision between EMAS or other solutions, and not applicable for the operators who are interested in improve the insufficient safety areas in aerodromes. This research proposed a general model composed of runway-related areas dimension check and economical analysis of available improving solutions if the current condition does not meet the regulations. The dimensional check should proceed in accordance with the ICAO regulations. With the performance information of different aircraft types the runway length requirements can be calculated. After comparing the common-used aircraft types in current airport, the maximum length required runway length would be obtained. If the runway length is insufficient, the improving measures such as runway extension or aircraft weight limitations must be performed. If the runway length is sufficient but the runway end safety area (RESA) is insufficient, the possible solutions should be compared by economic analysis. This research focus on the airport related groups include airport, passengers and airlines. The analysis calculated the changes of cost, expected loss, and other elements related to the different programs. Because the analysis excluded the external effects, so the economic values calculated in this model only show the worth to specific groups. However, the analysis still can provide airport administrators basis of decision-making. This research also check the airports in ROC, and found almost all airport runway length meet the requirement, but most airports does not provide clear information about RESA, the dimensions estimated by this research showed that several airports cannot provide sufficient safety area length and should be improved. This research chose Taipei International Airport as a sample for economic analysis. Several programs such as arresting system installation, RESA extension, or collocations were purposed. After comparing the economic elements, the result showed that all programs have relatively low benefits and without any financial profit. Nevertheless, the improving programs must be performed for that the safety should not be weighted in money. The sample analysis also showed that the arresting systems are expensive and the repairmen after arresting are valued, but still comparatively cheaper than RESA extension program in those sites lack of certain length. If the land price is so cheap such as in countryside or the extension length is short that the program cost is low so that the programs will be feasible.