PDA

View Full Version : ECON Speed & Cost Index - B777


Parkbremse
22nd Feb 2010, 15:27
During my performance questionnaire i stumbled upon the following question:

During cruise aircraft weight decreases and thus optimum flight level increases. If however, due to ATC restrictions, a climb to the higher level is not possible, ECON Speed will be higher in the actual level than in the higher level. True or False?

My gut feeling is that the statement is correct, as with an increasing cost index optimum altitude will decrease, so if you cannot get the higher optimum level, you can increase your cost index to lower your optimum altitude to the actual level and thus, you would fly faster.

Coming from the CRJ Series the whole concept of ECON Speed and Cost Index is new to me and my explanation (if it is even correct...) sounds a bit weak... Especially as it really doesn't explain why flying faster should be more economical...

Could anybody shed a bit more light on this one? Thanks very much for taking the time :ok:

Spencer-T-Rover
22nd Feb 2010, 15:39
For the same cost index speed will be lower both above and below optimum alt.

Parkbremse
23rd Feb 2010, 10:26
thanks for the reply... there goes my explanation

Could you (or somebody) explain please why the the speed is slower?