VHOJT 57 Posted December 22, 2019 Share Posted December 22, 2019 Hello all, I have conducted some statistical analysis on all PMDG aircraft - none of them increase fuel burn 3% per 10 degree ISA increase, and none of them have decreased fuel burn for the reverse. PMDG have been notified and are looking into the problem. In the meantime, I hope this might help a couple of people who might be frustrated by not being able to find a good "bias" number. If you can edit the aircraft file, remove any reference to the increase/decreased burn in varying ISA conditions. Or adjust by average on a per flight basis. Here are some figures for bias to start with that I have obtained by flying the aircraft at different weights in different ISA conditions, and measuring fuel burn (if you're interested in the method, I'll detail that later). All reference the default profiles, which are good profiles: Boeing 737-800 Tested at CI20 NGX: ISA bias -2.47% Drag: +0.74% NGXu: ISA bias: -2.03% Drag: +0.19% Boeing 747-400 RR Tested at CI50 ISA bias: -2.93% Drag: +0.3% Boeing 777-200LR Tested at CI100 ISA bias: +2.73% Drag: 0% Boeing 777-300ER Tested at CI100 ISA bias: +1.28% Drag: +0.13% Now, if you can edit the aircraft files - I would suggest removing any reference to added/decreased fuel burn for ISA deviation. You can post if you need help with this in this post. Or - you can look at the average ISA deviation for the flight, and change the bias accordingly, i.e. if the average ISA deviation is +6, you would get 6/10 = 0.6. Multiply by 3: 0.6*3=1.8. Because the ISA deviation was positive, you will burn more fuel. Add the 1.8 to the ISA 0 bias figure. This method is a little cruder, but it has served me well for a long time with some aircraft. Hope this helps anyone who feels they can't get the right bias for the PMDG aircraft. Any questions let me know. Cheers, Rudy Link to comment Share on other sites More sharing options...
VHOJT 57 Posted December 26, 2019 Author Share Posted December 26, 2019 Looks like, for the NGXu, this has been resolved in the latest update: - 0008251: [General - Engines] ISA Deviation effect on fuel flow model (emvaos) - resolved. Link to comment Share on other sites More sharing options...
danimaestro444 0 Posted May 8, 2020 Share Posted May 8, 2020 to warm up this old post, PMDG has updated its 747. two great items in the changelog: - 0007799: [General - Flight Model] ISA Fuel Burn adjustment (emvaos) - resolved. - 0008525: [General - Flight Model] Separate OPT/MAX ALT tables for -ER and -ERF (emvaos) - resolved. Link to comment Share on other sites More sharing options...
VHOJT 57 Posted May 12, 2020 Author Share Posted May 12, 2020 Yes - I told them about that! Looking forward to testing it out. Link to comment Share on other sites More sharing options...
danimaestro444 0 Posted May 23, 2020 Share Posted May 23, 2020 Have you already tested them? Are they accurate? I haven't had time yet.. Link to comment Share on other sites More sharing options...
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