Optimum FL on the 345
 

Hi, does anyone have a definitive answer on why the opt FL differs greatly sometimes between the QRH table values and the MCDU? It can vary by as much as 5000 ft at times, thanks Pudd.
I have tried precise winds and temp entries, tropopause etc,

maybe its the CI youll use?

ASSUMING YOU MEAN BOEING??

As wh says, Opt is based on LRC in the QRP. Wind has no effect on it. It will possibly ONLY affect 'Trip' level. When are you looking at the figures - on the ground or in the cruise?

Assuming you mean Airbus, QRH OPT ALTITUDES don't take account of winds, when MCDU OPT ALTITUDE mainly takes account of your wind entries at different FLs.
Next time, try an hypothetic very good tail component at a much lower FL and check out the resulting MCDU OPT ...

I was told by an Airbus test pilot that the optimum should be approximately 3000ft below Max Alt assuming that the winds are the same at all levels and temperature changes are normal with altitude. However CONF iture is correct. If you enter a crazy tailwind away from your level the FMGS will show an immediate change of optimun alt to take advantage of it. Try it next time you fly.

Many Thanks, Pudd

...and the answers were.......?