today I took a look on 737, these two speeds are different but i can't figure out which one is better . can anybody tell? THX.
Cost index :0 = MAX Range Cruise and Max L/D during descent(239kt on NG).
LRC is a good compromise if you need to go somewhere fast but still save fuel (airport closing/engine failure...).
LRC does not correct for wind(ie you fly into tailwind and your target speed will be the same),it uses 1% more than ECON CI:0.
On the NG,LRC is about CI 40-45.
Source:Boeing