ive noticed that the pmdg 77er used about 15% mnore fuel than simbrief planner predicts using the b777 er profile. Pmdg say that this is caused by the sim having much lower Isa than the realworld prediction however ive not seen this mtself , the isa at the given alt is pretty close to the simbrief predicted isa. my question is about the P factor fuel adjuectment option. the simnbrief quidance on this feature simply says that if you find you are burning more fuel than the simbrief plan estimate then add the P factore percentage.
what exactly does this do other than add more fuel. ive played around with the feature and it appears to just add more fuel , the hourly predicted burn data doesnt seem to be affected in the briefing. in other words the fuel burn predictions at each waypoint in the briefing dont seem to be affected by the p factor adjustment so are still innacurate , (fuel burn much lower than aircraft actual fuel burn at each waypoint)
can you explain to me why this feature does and why the burn rates are still just as innacurate. allyou end up with is more fuel to burn from what i can see rather than increased burn rates?
thank you
i have my own setup and it differs depending on the winds, if im getting major headwinds i use P01 if its not bad headwinds i use P0. i would recommend using these ive created
FAA Summer pax weights:
FAA Winter pax weights:
hi how can p0 or p01 work for me if im finding each flight burning about 15 -20% more than the default simbrief calculations, p01 is 1% unless im mistaken?, ajusting t p factor doesnt appear to make any difference to the hourly fuel burn calculated rate, it just add more fuel from what i can see
Hi, not sure what makes you think this. Looking at 2 of your flight plans (P00 on the left and P15 on the right), you can clearly see higher flight log fuel burns on the flight plan using P15:
Regarding the PMDG fuel burn mismatch in general, I’m not sure. Many users have reported SimBrief is accurate, while a few have reported the same issue as you. PMDG has indicated in their forum that it might be caused by unrealistic OATs at altitude in the simulator, which would explain why it seems to be hit and miss.
In any case, please reach out to them on their forum. Using P15 should also help though in the mean time.
Best regards,
Hi I see your point however even with p15 the sb predictions were still way less than the pmdg 777 so it was hard to notice any difference at each waypoint , I thought p15 equated to 15% added is that right? This is what I couldn’t really understand because by adding 15% I assumed this would solve the issue but within an hour of adding the 15% and adjusting the p factor I was still seeing the same issue , I was already at least 1000 kg down at this point every time .
Pmdg say they think their 777 is accurate so it must be sb , you guys say sb is accurate so it must be pmdg and we are left in the middle .
I ran a comparison of Simbrief and PFPX on an 8hr flight, the figures were not too disimilar which in P3D I use a P01 adjustment and would be accurate enough and never had a shortfall. I really doubt it is a simbrief problem.
Maybe try and use a utility to try and record fuel flows and temps against the flightplan.
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