Not as important as everyone seems to think.

Not as important as everyone seems to think.

I think my VNAV overshooting the descent path one the NGX was due to me using a very high cost index (80). When I use less than 30 it works fine.

Shouldnt be. Maybe it just made another thing (like missing des wind forecast) more pronounced.Diego: Cost Index is a number that airline would calculate, ideally for every flight, how important are flight time dependent costs (part maintenance, crew costs, etc.) versus fuel costs.Basically you divide your time-based costs by your fuel costs. This should then tell FMC how should it calculate speeds to make sure you have an overall best distribution of costs.

Not as important as everyone seems to think.

I think my VNAV overshooting the descent path one the NGX was due to me using a very high cost index (80). When I use less than 30 it works fine.

you see its very important, in RW it's very important don't underestimate.(:

Well, pilot's job is just to enter value in FMC, some economists does that calculations. Really do not care what cost index I should use, just enter a random number.

Don't use the Qantas indices. They are all incorrect. Search for Qantas Cost Indices in this forum. They are available to anyone who look hard enough.

you see its very important, in RW it's very important don't underestimate.(:

Matt is a 737 pilot. I wouldn't be so dismissive of what he shares. My experience by riding the jump suggests that his statement holds truth.Ash Frew.

Is 25 a good number?

Its a high number these days, but its your sim, use whatever you like :)

9 or 10? 27 or 30? 13 or 14? You'll see a bigger difference due to tailwind or headwind. I think because it's a bit nebulous, so people ascribe mystical powers to CI. If it's low, you'll come down a bit slow, say .76/256. If its high, you'll come down fast, I just did .789/290 at CI of 45. Operationally, that's really the only difference you'll need to account for. Otherwise, you're just spending a few more or less minutes in cruise - two sips of coffee. We generally manually enter .78/280 for our descents. It's fast but it's fixable. When you start getting above 280, you need to be thinking about how to account for turbulence, and that comes from PIREPS and weather briefs. That might affect your crossing restrictions if you need to slow. 20? Sure. 30, why not. 15? Great. 60 - Will it be bumpy?

It's a simulation, so it really doesn't matter as you're not paying the bills; however, if you fly for a VA that has economics built-in then you'll want to conserve fuel, so add a lower CI. If they also happen to have a timer, so you have to get there on time as well as try and conserve fuel, then I have found that 15-25 seems the best happy medium, but up to 55 if I'm running late due to whatever reason. I've never needed higher than that.

Cost Index = Cost of time/Cost of fuelIt's as simple as that!Where the red and green lines are intersecting, we have ECON mode on a specific cost index. Moving further left on the x-axis decreases the Cost Index. Moving right will make the Cost Index increase.

Transavia uses 11 all fleet, Euro Atlantic uses 25 for 737

In the tutorial Ryan used 36? Why 36 specifically?

I bet if you did a search on this forum alone there would be about ten or more topics just about CI.Why is this? Is it that important?High=high and fast; low=more measured flight and descent in my (very limited) experience. That's good enough for me..I never change mine (25 for anyone remotely interested) I'm more interested in flying cool approaches than how much gas I'm (not) burning..each to their own...By the way, what are the PSI of the tyres in an NG? :wink:jake

Awesome Chris. thanks