RCMD FL

[made82 0]

Is there an influence of the CostIndex to the recomend FlighLevel and what else is therefor calculated? Weight, distance, wind?

[dromeascr 1]

The weight and the distance are the most two most importany factors for the FL calculations (as far as my knowledge goes). I doubt that the cost Index is taken into account for that calculation. The cost index is directly releated with the VNAV cruising speed calculations (It is the single most imprortant factor considering cruising speed and fuel predictions).

 

When requesting a route, usually (depends on the airline options, most airline settings do include automatic uplinks along with the route's one) you also get a Perf Init uplink, once you load the Perf Init, you get winds aloft data uplink, and after that you get the descent forecast uplink. 

Judging by that sequence, it is clear that the wind is not taken into account when calcualting cruising altitude. (You get the winds once you loaded the perf Init which includes the Cruing Altitude).

 

The route and the Zero Fuel weight are the most important factors for the Cruising altitude calculations.

[skelsey 765]

Without having checked the manuals, I'm fairly sure that CI does affect the FMC displayed optimum cruise level because TAS varies with altitude (you will get a higher TAS for a given Mach number at a lower altitude). Therefore, I would expect to see slightly lower OPT altitudes with high cost indexes than with low CIs.