getting to grips with the cost index(32)

2. Recalibrating the Cost Index
Curves representating specific range variation versus Mach Number being quite flat, the original computation software of the cost index in the FMS led to the following :
- cost index 0 or MRC corresponds to slower than anticipated cruise speed ;
- the new MRC-calculation process increases the Mach Number, thus resulting in a recalibrated Cost Index ;
- when calculated for low Cost Index (see Figure 44 for CI=70), original software led to speeds that could be lower than the real Specific Range optimum ;
- a new software was defined as from April 1996, in order to achieve a result close to the real SR optimum.

In the meantime, airlines were provided with Cost Index corrective charts that were to be furnished in the form of a temporary revision of the FCOM .
Altogether, improvements are staggered as follows :
.  
The modified definition of MRC and hence of LRC (1% off) was to be introduced in the IFP with subsequent distribution to the airlines.

.  
Customers were provided with a modified table of the Cost Index, converting the old value to a new one, thereby allowing the use of higher Mach Numbers ; Figures 42 and 43 represent these correction charts for, respectively, A340-311 and -211 (CFM56-5C2) and A340-313 (E) (CFM56-5C4).

Pending Load 7, the corrections of Figures 42 and 43 are necessary. Thereafter they will be obsolete and use will then be made of the Table 3, in Section 3 of this brochure.

A340-313/CFM56-5C4 High Cross Weight

.  The next version of the FMGEC, Load 7, will be modified so as to integrate the above modifications; the default value of the cost index will be modified accordingly, shifted from 0 to a value corresponding to a more representative cruise speed ; Figure 44 illustrates the improvement.
Example : 210t 37 000 ft CI-70kg/min

3. Transforming cost index brackets
Using Figures 42 and 43, Table 3 transforms into Tables 4 and 5 for, respectively, A340-311 (and -211), (CFM56-5C2 and C4) and A340-313(E) (CFM56-5C4).
These tables provide typical industry values covering the low to the high cost brackets for both fuel- and time-related costs.
Following integration of the above-mentioned modifications, Tables 4 and 5 will become obsolete. Use will then be made of Table 3, now also still valid for the A330.

APPENDIX 4

A340-200 AND -300 CLIMB IAS PRESELECTION PROCEDURES FOR LOAD 6
PENDING LOAD 7 RELEASE

The following are the recommended procedures pending the release of FMS Load 7, after which corrected climb speeds will be fully integrated.
1. Aircraft is not in climb phase
.  
The preselected CLIMB IAS may be entered on the MCDU PERF-CLIMB page on the PRESEL field. It is displayed in large font.
　
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