願你經歷再多，都不忘初心；
願你難過再多，都不忘微笑；
願你能披荊斬棘，做到自己想要做到的事
一、為什麼需要CI（cost index）？
Used appropriately, the cost index (CI) feature of the flight management computer (FMC) can
help airlines significantly reduce operating costs. However, many operators don’t take full
advantage of this powerful tool.
使用合適的CI能夠幫助航空公司節約成本，但是確實存在一些航空公司不能完全利用這個有效的工具。
二、什麼是CI，有什麼作用？
the CI is the ratio of the time-related cost of an airplane operation and the cost of fuel. the value of the CI reflects the relative effects of fuel cost on overall trip cost as compared to time-related direct operating costs。
CI是航空器運行成本和燃油成本和時間的比率。
CI = 單位時間(小時)成本(美元) Time cost / 單位燃油(磅)成本(美分) Fuel cost
分子部分的時間成本也就是與飛行時間有關的費用，比如很容易聯想到機組成員的薪金，再比如飛行時間長的話，飛機的維護費用也會增加，總之"時間就是金錢"，這些費用都可以歸入固定成本的範圍。
分母的燃油成本就是單位重量的使用燃油費用。
The range of allowable cost indices is shown in Figure 1. the flight crew enters the company-calculated CI into the control display unit (CDU) of the Fmc. the FMC then uses this number and other performance parameters to calculate econ-omy (econ) climb, cruise, and descent speeds.
飛行管理計算機根據飛行員輸入的CI值和其他性能參數計算經濟(ECOM)爬升速度，經濟巡航速度和經濟下降速度等指標。
For all models, entering zero for the CI results in maximum range airspeed and minimum trip fuel. this speed schedule ignores the cost of time.
對於所有機型來說，輸入0往往意味著最大航程速度和最小航程耗油，這個速度忽略了時間成本。
Conversely, if the maximum value for CI is entered, the FMC uses a minimum time speed schedule. this speed schedule calls for maximum flight envelope speeds, and ignores the cost of fuel。
CI值大的話，時間成本優先於燃油成本，因此經濟速度也就相應增大。
CI值為0時，時間成本完全被忽視，燃油消費最小，範圍空速最大，航程最長。
CI值為最大值時，燃油成本完全被忽視，飛行包線速度最快，航行時間最短。
In practice, neither of the extreme CI values is used; instead, many operators use values basedon their specific cost structure, modified if necessary for individual route requirements. As a result, CI will typically vary among models, and may also vary for individual routes.
實際上，基本不會使用極端的CI值，相反，很多公司都會使用他們自身特定的成本結構得出的成本指數，一些特殊航線可以更改，也就是說CI可以在不同機型不同航路上更改。
Clearly, a low CI should be used when fuel costs are high compared to other operating costs.
當燃油成本高於運行成本時，要採用低的CI。
The FMC calculates coordinated ECON climb (see fig. 5), cruise, and descent speeds (see fig. 6) from the entered CI. To comply with Air Traffic Control requirements, the airspeed used during descent tends to be the most restricted of the three flight phases. The descent may be planned at ECON Mach/Calibrated Air Speed (CAS) (based on the CI) or a manually entered Mach/CAS. Vertical Navigation (VNAV) limits the maximum target speed as follows:
Figure 5表現的是CI值對於ECON CLIMB模式的影響，可以看到CI為0時將會獲得最大爬升角度。
注意最大爬升角的意思不代表飛機能夠最快爬升到初始巡航高度，而是指出發點A點到到達巡航高度時的距離最短，因此在巡航高度上的飛行距離也就最長，此時的速度反而是最低的。
隨著CI增加時間成本被重視，燃油成本被忽視，因此飛行速度更高，以上面的757的數字，從0.778增加到0.847馬赫，如此同時爬升角也就變小，飛到巡航高度的距離越長。
Figure 6表現的是CI值對下降模式的影響，CI為0時下降角最為平緩，可以聯想成最大限度的利用高度能量，緩慢滑翔下降的感覺。隨著CI的增加，下降角度也就更為傾斜，飛到目標地B點的距離也就最短，因此飛行速度也就最大。以上面的757的數字，速度從250節會增加到334節。
The cost of fuel is the denominator of the CI ratio. Although this seems straight forward, issues such as highly variable fuel prices among the operating locations, fuel tankering, and fuel hedging can make this calculation complicated.
燃料成本是CI比率的分母。雖然這看起來很簡單，但是諸如操作地點之間的燃料價格高度可變、燃料補給和燃料對衝等問題會使計算變得複雜。
A recent evaluation at an airline yielded some very interesting results, some of which are summarized in Figure 4. A rigorous study was made of the optimal CI for the 737 and MD-80 fleets for this particular operator. The optimal CI was determined to be 12 for all 737 models, and 22 for the MD-80.
最近對一家航空公司的評估產生了一些非常有趣的結果，其中一些總結在圖4中。對737型和MD-80型飛機的最佳CI進行了嚴格的研究。最佳CI被確定為12為所有737型號，22為MD-80。
The table (see fig. 4) shows the impact on trip time and potential savings over the course of a year of changing the CI for a typical 1,000-mile trip. The potential annual savings to the airline of changing the CI is between US$4 million and $5 million a year with a negligible effect on schedule.
表(見圖4)顯示了在一個典型的1000英裡旅程中，更改CI對旅行時間的影響以及在一年內的潛在節省。航空公司每年可能節省400萬至500萬美元的費用，但對時間表的影響微乎其微。
三、總結？
CI can be an extremely useful way to manage operating costs. Because CI is a function of
both fuel and nonfuel costs, it is important to use it appropriately to gain the greatest benefit.Appropriate use varies with each airline, and perhaps for each flight. Boeing Flight OperationsEngineering assists airlines』 flight operations departments in computing an accurate CI thatwill enable them to minimize costs on their routes.
CI是一種非常有用的管理運營成本的方法。因為CI是無論是燃料成本還是非燃料成本，為了獲得最大的效益，正確使用燃料都是非常重要的。適當的使用方法因航空公司而異，也許也因航班的不同而異。波音公司飛行操作工程學幫助航空公司的航班運營部門計算一個準確的CI將使他們的航線成本降到最低。
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To Be Continued..