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Different CI for climb and cruise

Started by Richard McDonald Woods, Sun, 5 Jul 2009 13:55

Richard McDonald Woods

Apparently BA require pilots to set a CI of zero for climb and 90 for cruise.

The Boeing article at does not say anything about using a different CI for climb to cruise.

My feeling is that setting CI=90 will obtain from the FMC the required flight path for all phases of a flight.

What do you believe?
Cheers, R
Cheers, Richard

Jeroen Hoppenbrouwers

CI=0 just means "near lowest fuel consumption, at the expense of a bit more time".
CI=90 means "tid bit faster".
In all cases, it also means that BA has sacked some bean counters who "should" provide proper CIs depending on airport pairs.


If a higher CI is used for the climb, it cud mean a lower fuel burn for the rest of the journey enroute, as u get 'on top' faster.  Getting a higher rate of climb (using more fuel) sometimes = savings for the entire flight.
I do beliv some airlines (those who know exactly how to use proper CI) takes some kind of methodology this way.  Again, it depends on city pairs and the total costs needed to operate the flight. Not all lower CI in cruise equates to savings, as turn-round, acft utilization factors play a part too.

I too, am trying to grasp this science :)



There are a few more factors to consider for economics. Depends on company procedures figured into CI,  and which if any are figured externally:
a. Cost of fuel dynamics
b. Arrival time slots
c. Current wind
d. Cargo or passengers
e. Time of day/ date- some might be getting extra pay for night/ weekend/ holiday etc...
f. Landing/ parking fees as functions of time/ date.

El Al utilizes for operations optimization, a cost model in which there are about 1000 variables, each variable dependent on about 1000 variables (lots of room for infinite loop calculations :oops: ). On the other hand, I remember an executive meeting of counselors to the minister; El Al on the Tel Aviv London route was marginally breaking even while BA general manager said it was their most profitable route.
Regards, Zinger