Using the 737's, one of the only things I don't understand in the FMC is the cost index. I can't find any mention of how to calculate it or what to enter.Can anyone help?thanks,robert smith

Beancounters calculate CI, not pilots. We just put in whatever CI we're told. Search the forum and you'll find some good posts on that topic.Paul

hello Robert, i have several routes compiled by a real world pilot for the pmdg 737ng, and the point he makes about cost index is it is very complex based on maintenance cost, operating costs, personnel costs, fuel and operative factors. the cost index he uses is 35 as it is a good compromise between low fuel flow and acceptable flight time. i personally feel that the aircraft developers plus flight simulator itself is not able to reproduce cost index factors purely as previously stated due to the complexities and i dont think many simmers would know the differences anyway. richard welsh.

I fly for Thomson Virtual, and pilots there get updated cost indexes regularly via flight crew notices (I think that's how it happens in the real world, too). At the moment pilots are supposed to use the value "9" for the 737-300 and the 737-900.

As others have said, pilots are invariably told what Cost Index to use (although there are exceptions to this, particularly on the NG), but mostly you will have to decide for yourself, so it would help you to understand exactly what Cost Index is...Basically it is a ratio calculation of the average cost of operating the aircraft, versus the cost of fuel, expressed as a figure (which is why the accountants decide much of it). A Cost Index of 0 will make your aircraft fly most economically, saving the most fuel and making your aircraft fly at the most economical settings as far as squeezing maximum range out of the fuel on board is concerned. That would seem to make it the obvious choice, but, you also have to factor in other economics, such as how long the aircraft would be at this or that throttle setting on the climb (higher throttle settings might get you up to cruise altitude quicker, but since higher throttle settings mean higher temps and more vibration, they can also mean more general wear and tear on the engine). Even so, less time at full throttle on a climb means less overall wear and tear, so a high throttle setting on the climb might actually mean less overall wear, since it will be for a shorter period of time (to be fair though, much of this kind of dilemma is factored into Cost Index already).On the other end of the scale a maximum figure in the Cost Index field of the FMC (which is 200 on a Classic 737 and 500 on an NG), means the aircraft is more concerned with speeds rather than economy, and at maximum values in the FMC, the aircraft will fly at Vmo in the climb and cruise (i.e the maximum safe maneuvering speed in both the climb and the cruise), so you can effectively use that setting all the time when flight simming to make the quickest flight without manually keying in cruise speeds, since you are not paying for fuel, that is unless you are using something like Air Hauler where you pay for fuel, in which case you might want to change things.The maximum Cost Index will also limit your descent speed to 330 knots on an NG in order to protect you against overspeeding, so it can have an effect on VNAV Path and VNAV Speed, and that is important on a 737 because the CFM-56 needs to keep some RPMs on when descending through rain squalls, as it is prone to being flamed out in wet weather at descent idle (although theoretically at least, it is not as bad as it was since the spinner cone was modified on more recent CFM engines).In short, Cost Index 0 means save money, Cost Index 500 (or 200 on a Classic 737) means save time; anywhere in between those settings is some sort of compromise figure, depending on what you are after in economic terms, although time is money too remember.I normally put 25 in when flying in Air Hauler.Al

Great explanation Al! I stumbled upon this a while ago, it is a chart showing the typical CIs used in various aircraft, and an explanation on how it works.http://www.boeing.com/commercial/aeromagaz...ticle_05_3.html

Joseph,You made a very good find! Lots of useful information in the article.@ Ryan Maziarz, could you please pin this topic.

thanks people.

Well done Alan. A most useful post - thank you very much.Gerry

I fly for Thomson Virtual, and pilots there get updated cost indexes regularly via flight crew notices (I think that's how it happens in the real world, too). At the moment pilots are supposed to use the value "9" for the 737-300 and the 737-900.

Hello,My VA (GlobeCargo) stated in a NOTAM that we shoud use a CI of 30 for the 747-400F.(Just my 2 cents).Happy landings,Wijnand