How to Use a Cost Index to Your Advantage:
I had the great opportunity to fly with an instructor a couple weeks ago who was conducting training. When we pay attention lessons come from many places.
Cost Index Lesson:
Example of MCDU page values:
Cost Index UTC time /EFOB
100 1738Z / 20.9
75 1740Z / 21.2
50 1743Z / 21.9
25 1745Z / 22.0
0 1748Z / 22.1
(Flight plan cost index can be used instead, that is closest to above 25 increment C/I)
Example of MCDU page values:
Mach UTC time/ EFOB
.82M 1743Z / 21.6
.81M 1745Z / 22.2
.80M 1748Z / 22.3
.79M 1750Z / 22.2
I had the great opportunity to fly with an instructor a couple weeks ago who was conducting training. When we pay attention lessons come from many places.
Cost Index Lesson:
"The PERF descent page is hard tuned for .81/300 (variable) as I reach top of climb, and am not expecting a change in course (this will cause a change in fuel burns/times) all step climbs per flight plan are entered and constant mach entries are not entered at this time for a more pure fuel burn. I set up the following template on the right side of the flight plan:
Example of MCDU page values:
Cost Index UTC time /EFOB
100 1738Z / 20.9
75 1740Z / 21.2
50 1743Z / 21.9
25 1745Z / 22.0
0 1748Z / 22.1
(Flight plan cost index can be used instead, that is closest to above 25 increment C/I)
Depending in your interpretation, and needs (target landing window) Cost Index (CI) of 50 appears to give a 1000# fuel savings for an added +5 min as compared to CI 100, and a 700# savings for only a +3 min increase. CI of 25 and 0 do not appear to be that advantageous for the small fuel savings regarding increased time.
After a CI is determined for the flight i.e.. 50 in this case, I go to Flt plan page and a Mach template is set up to see what computer is showing for crossing mach segment, and note the Mach/UTC/EFOB in this case .81M 1745Z / 22.2 appears to be best for this scenario:
After a CI is determined for the flight i.e.. 50 in this case, I go to Flt plan page and a Mach template is set up to see what computer is showing for crossing mach segment, and note the Mach/UTC/EFOB in this case .81M 1745Z / 22.2 appears to be best for this scenario:
Example of MCDU page values:
Mach UTC time/ EFOB
.82M 1743Z / 21.6
.81M 1745Z / 22.2
.80M 1748Z / 22.3
.79M 1750Z / 22.2
Again, depending on your interpretation and needs (target landing window) .81M appears to be most cost effective for this flight. Also note that there sometimes is a change in time/EFOB when a hard Mach is entered for the constant mach segment. Trying to do better than Flight plan values, as we know they will not be the same.
The above procedure is a little time consuming, but in most cases I have been able to average 1500 to 5000 lbs of extra fuel on arrival. I also try to climb to a higher altitude when it shows beneficial in the step climb computer."
The above procedure is a little time consuming, but in most cases I have been able to average 1500 to 5000 lbs of extra fuel on arrival. I also try to climb to a higher altitude when it shows beneficial in the step climb computer."
Enjoy the Journey!
XO Karlene
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