LRC vs ECON (B757 Style)
 

Are there any general guidelines about which will save more gas? Is one better on a shorter leg vs longer leg? Any references or thoughts appreciated.

'Econ' is driven by cost index, so LRC will always be better that 'normal' econ cruise. CI 0 is pretty much LRC I believe. There is a thread here somewhere about it.

Gotcha!

MRC is basically the greatest distance per kg fuel.

LRC is approximately 99% of this distance and is generally a more stable cruising speed than MRC.

Now lets look at Cost Index, this is designed to save MONEY, its a trade off between the aircraft cost and fuel. In our case fuel is cheap so we should fly as fast as possible, using more fuel and saving time!

So i can truthfully say that in our theoretical case, LRC saves more fuel than Cost Index!!!!

For a reference, look at the top of this thread for the J_T list of useful sites, then look for the "Airbus, getting to grips with Cost Index"...


Mutt

Thanks Mutt, I'll have a look.

I think this is the perfect aviation topic where the answeer is, "Well, it depends". Came up the other night flying in LRC at FL360 with over 90 knots on the nose. Slowing down into that wind can't save money.

Big Boeing FMC Guide suggests that ECON will save more gas than LRC.