Passing through an area of ISA+ 15-18 in the PMDG 777 and I think I’ve found an issue. Currently seeing fuel flows above 108% of simbrief predictions. It appears more normal ISA’s are within 2-3% of predictions but flight at higher ISA’s is considerably more off. Not sure yet if this is a PMDG or SB issue. I have run the numbers through PFPX as a double check and it is also showing a grater than 108% bias. Not sure if this is a limited charts available issue of if PMDG has incorrect charts themselves for these conditions.
Not sure, but 8% higher than SimBrief predictions seems high.
SimBrief is already applying around 5% higher fuel flow at ISA +15, so if PMDG is 8% higher than that, their ISA+15 burn is somewhere around 13% higher than at ISA. Much too high in my opinion, even if you just compare it to the ISA ratios of most other modern jets.
But I stand to be corrected, presumably they have access to better data than us. But if you are seeing the same discrepancy when comparing to PFPX, it does seem to hint that the issue might be on PMDG’s side. Or maybe with MSFS, I believe it’s quite difficult to match this sort of thing in MSFS. Not sure if PMDG is using an external fuel model or not.
Best regards,