All around the world civil aviation is a part of market economy with rare exceptions. No matter who operates aircraft, large air company or small regional air club, everybody tries to reduce operation costs and therefore save money. Reality of aviation business requires a huge amount of factors to be considered on a daily basis: economics, marketing management, crew scheduling, flight operations, engineering and maintenance management, technical condition of aircraft etc. And the most effective way to take all these factors into account is to use the Cost Index (CI).
CI definition
Used appropriately, the CI feature of the flight management computer (FMC) can help airlines significantly reduce operating costs.
Trip cost
Generally, the total cost of a specific trip is the sum of fixed and variable costs:
Since we can’t affect the fixed cost, we need to minimize the variable cost (fuel- and time-related).
Time-related costs
As an example, time-related costs contain the sum of several components:
CI calculation
CI is used to take into account the relationship between fuel-related costs and time-related costs. With time-related costs, the faster the aircraft is flown, the more money is saved in time costs. This is because the faster the aircraft is flown, the more miles can be flown for time-related components. It also means that more miles can be flown between inspections when considering maintenance costs.
However, if the aircraft is flown at such a high speed, the fuel burn increases and total fuel cost for the trip increases.
Let’s take a look on two extreme cases:
1. CI = 0 In this case time cost as low as zero and fuel cost is extremely sufficient (greatest influence of fuel cost in the operating bill). It is the minimum fuel mode for the best range (MRC).
2. CI = MAX In this case fuel cost means nothing compared to the time cost. It is the MINIMUM TIME MODE for Maximum Speed (VMO/MMO)
CI and ECON speed
Looking at the figure above you can see from the total operating cost curve that the speed which gives the minimum total operating cost is the most economical speed to fly.
Increasing CI from zero to maximum will increase the ECON speed from the maximum range speed to maximum operating speed.
Typical cost indexes
Let’s get through some typical CI examples. It will help to make flight planning more precise and accurate.
Aircraft list
(MRC = Maximum Range Cruise; LRC = Long Range Cruise)
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.
VARIABLE FUEL PRICES, FUEL TANKERING, AND FUEL HEDGING MAKE THE COST INDEX CALCULATION COMPLICATED.
by Bill Roberson, Senior Safety Pilot, Flight Operations
This article is the first in a series exploring fuel conservation strategies.
COST INDEX DEFINED
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.
In equation form: CI =
Time cost
The range of allowable cost indices is shown in Figure 1 (see next page). 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 economy (ECON) climb, cruise, and descent speeds.
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.
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 (see fig. 2, on next page).
А откуда Вам на земле известно что нет никакого потолка? Очень интересно было бы узнать. То что передано с бота может иметь массу мотиваций.
Принципы расчета мне хорошо известны.
Ой берут меня сомнения. видимо нет. Зря Вы на Сержа нагоняете, он всё верно расписал тут(конкретно про S7 судить не берусь, тут есть парочка «зелёных» спецов). Не придерёшься, понятия ЛР.
Алексей, а Вы в Тунисе бумагу не писали?
Вот тут зачЁт! И про АФЛ в Питере тоже 🙂
(кавычки в русском языке пишутся так: Французские кавычки («ёлочки»). «ёлочки» Немецкие кавычки («лапки»). „лапки“ Английские двойные кавычки («английские двойные»). “английские двойные” Английские одиночные кавычки («английские одиночные»). ‘английские одиночные’ ) Это так, без обид. Да и другим будет информативно и поучительно.
2 ip: Молоток! Опередил меня 🙂 Красиво сформулировал.
. если они не перестанут посылать к Бениной маме контроль.
Истина. Тут уже ни о какой эффективности и экономичности речи нет.
2 Туилов: Ставь костидекс- 28, или 30- и всё будет ОК.
Кому ответил, что ответил. сам не знаю. Скорее всего и ТС и STAN-не летающие персоны. (Ничего страшного в этом конечно же нет) Правильно Серж спрашивает про обоснования и про тип. Если Вы трудитесь на 737CL, то это ещё далеко не гарантия того, что на больших самолётах и ВС других корпораций CI будет абсолютно аналогичным Вашему по дефолту.
Виктор Константинович, Вы меня огорчили 🙁 Сам хотел выложить сей документ. но вот только сейчас в тему заглянул! Браво! Коротко и ясно.
Красава, нечего добавить 🙂
Чтобы не коптить в пробках над москвой, сюда нужно прилетать к 3 ночи, а вылетать в 4 утра. В остальное время во Внуково будет хаотичная свалка «Черных плащей» (как дачники в пятницу из города, только они каждый день такое устраивают и на вылет и на прилет) или перекрытие от Богданова до Октября и от Гагарина до Черустей (геи прилетают или вылетают) В Домодедово тоже не сахар, туда все как мухи на.. (и причем все сразу) В Шрм адский-ад! Нац. аэропорт. (мать его. ) Деваться от них там некуда просто!
И тут нечего добавить, только вместе улыбнуться, резко опустить правую руку и сказать: «Ну и **** с ним с плащом».
А поэтому ставим CI рекомендованный, а работаем с максимальной эффективностью.
I’m not sure if it’s just in Boeing aircraft, but I’ve heard that Cost Index has something to do with flight planning but have no idea what it is.
What is it for and how is it calculated? (I’m happy for the simple version of the calculation if it’s too hard to explain)
4 Answers 4
The cost index is a number used in the Flight Management System (FMS) to optimize the aircraft’s speed. It gives the ratio between the unit cost of time and the unit cost of fuel.
With this number, and knowledge about the aircraft’s performance, it is possible to calculate the optimal speed for the aircraft, which results in the lowest total cost.
Speeds slower than the optimal speed will result in less fuel burn, but also in more flying time. The cost of the extra flying time outweighs the fuel savings at speeds below the optimum speed.
Speeds faster than the optimal speed will result in more fuel burn, but also in less flying time. The saving of less flight time do not outweigh the fuel burn at speeds above the optimum speed.
A low cost index means that the cost of time is low or that fuel is expensive. It will result in a low speed. High cost index means high cost of time (e.g. passengers about to miss their flight connection) or low fuel price (rare these days).
At the minimum cost index (0) only fuel counts. This will result in the aircraft flying at Maximum Range Cruise. At the maximum cost index only time counts. This will result in the aircraft flying at Maximum Cruise Speed (Vmo / Mmo with a buffer)
Airlines generally have a standard cost index they use for planning and adjust them on a flight by flight basis.
This document from Airbus explains the cost index in more detail.
Cost index (CI) is a number presenting 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.
The formula may look simple enough but getting the numbers in it isn‘t quite simple.
Each company must determine its fleet CI in order to fly as efficiently as possible. It is work that should be done when forming the basic strategies of the company. It is a lot of work and is not as simple as it looks. Most of the manufacturers provide a default CI based on the average prices of fuel and time related cots but CI for a specific operator may be very different for another. Sometimes the CI of two airplanes of the same type model or variation may have different values.
Time related costs (TRC)
The TRC are basically the costs you can save by saving one hour of flight time.
When determining the type related costs for a trip, you must take into account every cost you pay by time. Such costs are leasing, maintenance, engines, auxiliary power units and all other items you replace by the hours. Also some companies pay their crew by the hour, or provide a bonus by the hours, If this is the case those expenses should be included in the CI.
The leasing of the airplane can be paid by the actual flight time or by fixed period of years. If the first is the case then leasing is directly included in TRC if the case of your company is the second then a more complex calculation based on lease period is required to determine the how it affects the TRC during the lease period. When the lease is paid then this cost can be removed by the formula.
The hourly price of leasing can be determined by dividing the lease price by the hours, you want to fly in order to pay the airplane.
Maintenance price is the price you pay for every scheduled maintenance of the aircrafts and its items. This price can be easily evaluated as most maintenance is hourly scheduled. When there is cycles based maintenance it doesn‘t add value to the TRC as it doesn’t change with changing the flight time between two cycles.
Fuel costs
Fuel costs is the price of fuel your aircraft consumes by the hour during flight. It looks straight forward but in fact this costs are subject for complex calculation. The varying fuel price, fuel tankering and fuel hedging can make a lot of difference when calculating the fuel costs.
Avery simple example is given below
Calculated maintenance 50$/h
Average consumption = 2000 lb/h
Fuel Cost Per Hour = 1000$
This means that if you can save one hour by flying faster and burning 2000lb more you will save 150$
The number of the cost index varies with each manufacturer and a way to determine it is provided in the manuals. Once calculated it can be inserted into the FMC and the computer will do the complex calculation and give you the optimum speeds and performance in order to get most of the airplane resources. CI changes all the time and modifications should be made with each change in costs.
Flying efficiently is very important in commercial aviation and is sign of good airmanship.
