The last few flights I did on the fenix A320 gave cruise altitudes that were significantly higher than the optimal level indicated in the FMC. E.g. currently going from KLAS to KSTS, with a pretty full load (1,600 lb less than max ZFW) the plane says optimal cruise is FL350 but simbrief planned for FL380. The FMC “recommended max” is FL383
Hi, this happens all the time in the real world. FMGS computed optimum altitudes can be different from the flight planned values for any number of reasons, especially on shorter legs like the ones you’ve been flying. Main factors can include different underlying calculations to determine the altitudes in the first place, differences in upper level winds, differences in TOC/TOD due to SID/STAR restrictions, etc.
Pilots often request a different altitude than flight planned if the PROG page indicates something different.
In the sim you have the added (massive) uncertainties caused by differences in the simulated engine types or MSNs, or even differences in the data used to program the add-on in question.
As far as I can recall, Fenix is simulating quite an old MSN (based on the MTOW they are using), which likely also means using less powerful engines. It would make sense that the calculated altitudes would be lower in this case.
If it’s routinely 2-4000 ft off, then I recommend creating a custom airframe and adjusting the “Cruise Level Offset” appropriately. But your STS-LAS turns are not long enough to tune this in my opinion, the cruise portion is too short and the FMGS optimum altitude can vary widely as a result. I recommend flying a trans-con or something at least 2:30 or longer in the air when testing.
Best regards,
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