ECON SPD in CRZ seems to be broken (Cost Index has no effect in CRZ)

[marius1411]

Hey,

done 2 flights with the A350 now, first of all: brilliant work! Love that bird!

One thing I have noticed though: when editing the Cost Index, the speed values on the CLB and DES Page change. As they should, perfect!
-->But the CRZ page always stays at .85 ECON.  When in Cruise and CRZ mode, I noticed, that once I pull the speed selector, I can see the magenta diamond showing the predefined ECON Speed (it was around .84 in my case with CI15 today... if I push back to managed SPD / ECON mode, plane would have accelerated to .850)

Could someone please confirm that and have a look into it? The Cost Index Data seems to be implemented and available (as I can see it on the magenta diamond once I pull the speed selector in cruise+ CLB and DES pick up the Cost Index and change accordingly), but someohow the AC overrides it in MACH ALT CRZ and always cruises with .850

Thanks a lot! Cheers!

[richboy2307]

On 3/3/2025 at 6:05 AM, marius1411 said:

Could someone please confirm that and have a look into it? The Cost Index Data seems to be implemented and available (as I can see it on the magenta diamond once I pull the speed selector in cruise+ CLB and DES pick up the Cost Index and change accordingly), but someohow the AC overrides it in MACH ALT CRZ and always cruises with .850

Hi,

As replied on another post, It does have an effect, but its nowhere near to the same extent as some of the other aircraft, especially at the upper levels (~FL310+).

The optimum CRZ MACH range is very narrow, 0.85-0.86 at its narrowest between CI 0 and 999. The 787 is quite similar in that regard, so a narrow margins in CRZ MACH is expected behaviour for this aircraft. 

As for discrepancies between planned and actual CRZ IAS at lower alts (below FL300), the report is acknowledged and we're looking into it.

Thanks!