getting to grips with the cost index(20)

曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者

80  142  14,6  92  210  16,3  .800 / 342 
A 330  0  449  23,5  135  449  23,5  .774 / 270 
(PW 4168)  50  444  22,7  134  463  22,9  .809 / 281 
(170 000 Kg)  80  427  20,5  125  540  21,9  .819 / 307 
v100  420  19,6  121  580  21,4  .823 / 320 
A 340  ≤50  550  23,2  133  550  23,2  .767 / 273 
(CFM56)  80  524  21  125  620  22  .799 / 301 
(180 000 Kg)  100  509  19,7  120  620  21,4  .811 / 323 
v150  501  19,1  117  663  21,2  .817 / 323 

Values for time, distance, Mach, fuel consumption do vary much with flight conditions such as TOD flight level temperature and wind but are less variable with respect to gross weight.
Similar to the climb, delta values with regard to time and distance are largely the same whatever the initial flight conditions.

 

 

First of all, we note that time to descent between low and high cost indices is more sensitive than for the climb varying from 4 minutes (A300, A330 and A340) up to 7 minutes for the A310.
However, in order to have a representative comparison of these different types of descent, we have to take into consideration the short cruise segments between the "low cost index TOD" and the "high cost index TOD" (see descent profiles in Section 8.1)
The following table provides parameters and differences in terms of time and fuel from a similar geographical point (TOD corresponding to cost index=0) to summarize descent laws between CI=0 (0 to 50 for the A340) and high cost indices (i.e. cost indices from which descent laws are the same : >60 for A320, >100 for A300, A310 and A330, >150 for A340).
Table 16. Descent from FL 370

Time (min) / Fuel (kg)from 1st TOD (CI = 0)  Difference between low and high cost index 
Cl = 0  High cost index  Time gain  Fuel increment 
A300-600  19.3  317  17.0  427  2 min 20 s  110 
A310  21.4  284  18.0  406  3 min 20 s  120 
A320  19.0  138  16.3  210  2 min 40 s  70 
A330  23.5  449  21.4  580  2 min 10 s  130 
A340  23.2  550  21.2  663  2 min  110 

However, in order to obtain the best TOD computation by the FMS and in order to avoid a nominal flight path overshoot (embarassing especially with high cost indices), a good insertion of descent winds is of vital importance even if the FMS adjusts the descent speed in a 20kt range according to the winds encountered.

 
　
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：getting to grips with the cost index(20)