MartinRichards 4 Posted September 3, 2018 Share Posted September 3, 2018 Hi all, I've seen a couple of old threads about this regarding the old versions of the Airbus, and have just discovered the same issue myself. To summarise: When flying the CFM Airbus (in this particular case the A318), fuel consumption does not appear to be consistent, instead showing near sieve-like fuel-burn qualities. I've attached a flight plan a flight plan (very) similar to the one I used in order to potentially aid in replication. Also to Clarify: My flights are currently planned with PFPX (Active Sky Providing the weather), with the subsequent weights then inputted into the options mcdu. It is obvious that even with the IAE aircraft that the fuel burn data does not match up exactly, however normally relatively long flights in the IAE and shorter flights in the CFM can be made easily with what PFPX provides, with the CFM on longer flights fuel performance appears to degrade significantly over time. At the start of the flight, the MCDU shows a rather sensible EFOB for the destination, not as high as with other aircraft in my fleet, but workable nonetheless. As hours pass by in cruise however, the value gradually decreases, this is also with a tailwind on pretty much the entire route. More than half of the 18.6k kg of fuel I loaded on board had burnt off by the time I left the coast of Canada, which does not seem right at all. The flight cruised at FL370 with CI30, climbing to 390 and/ or decreasing the CI did little to remedy this. Anyway, the initial conclusion one can draw is that extra fuel should be loaded when flying the AIrbus on long-haul routes. Although fuel is tight on the JFK-LCY route, with the plan attached one has room for another 1-2k of fuel which can make all the difference. Nonetheless, I would reccomend that for SP1 or another update, that the Fuel Performance is given another look at, particularly in cruise. It's possible that the Autopilot in it's current state may not also be flying the Aircraft as efficiently as it could be. Thanks, Martin. BAW2 KJFK-EGLC (03 Sep 2018) #1.txt Link to comment Share on other sites More sharing options...
Aerosoft Aerosoft Team [Inactive Account] 51558 Posted September 3, 2018 Aerosoft Share Posted September 3, 2018 Thanks for that report. Link to comment Share on other sites More sharing options...
Fragged^2 40 Posted September 3, 2018 Share Posted September 3, 2018 I did the KJFK - EGLC flight tonight with about 3100 nm total route planned on Simbrief with current AIRAC and today's NAT. I was at -100 kg fuel vs estimated on the Canadian side of the pond and crossed over to Ireland at -600 kg vs estimated. I landed with 2.2 tons, which was about a ton less than planned. Wind average was 278/040 with average 30 knots tailwind. Fuel / Weight similar to OP, speed was a bit higher. I don't use the built in fuel planner, but I checked what it would've suggested for the trip with today's weight, wind etc. I would've ended up in the pond. Stats: Block fuel - 18 tons ZFW - 44.4 tons CI - 80 FL - 390 IAS - mach .80 Simbrief: PLANNED FUEL --------------------------------- FUEL ARPT FUEL TIME --------------------------------- TRIP LCY 14530 0646 CONT 5% 727 0020 ALTN CDG 1667 0048 FINRES 871 0030 ETOPS/ETP 0 0000 --------------------------------- MINIMUM T/OFF FUEL 17795 0825 --------------------------------- EXTRA 0 0000 --------------------------------- T/OFF FUEL 17795 0825 TAXI JFK 200 0020 --------------------------------- BLOCK FUEL JFK 17995 Fuel planner: Please login to display this image. Link to comment Share on other sites More sharing options...
bill3810 109 Posted September 4, 2018 Share Posted September 4, 2018 14 hours ago, Fragged^2 said: I did the KJFK - EGLC flight tonight with about 3100 nm total route planned on Simbrief with current AIRAC and today's NAT. I was at -100 kg fuel vs estimated on the Canadian side of the pond and crossed over to Ireland at -600 kg vs estimated. I landed with 2.2 tons, which was about a ton less than planned. Wind average was 278/040 with average 30 knots tailwind. Fuel / Weight similar to OP, speed was a bit higher. I don't use the built in fuel planner, but I checked what it would've suggested for the trip with today's weight, wind etc. I would've ended up in the pond. Stats: Block fuel - 18 tons ZFW - 44.4 tons CI - 80 FL - 390 IAS - mach .80 Simbrief: PLANNED FUEL --------------------------------- FUEL ARPT FUEL TIME --------------------------------- TRIP LCY 14530 0646 CONT 5% 727 0020 ALTN CDG 1667 0048 FINRES 871 0030 ETOPS/ETP 0 0000 --------------------------------- MINIMUM T/OFF FUEL 17795 0825 --------------------------------- EXTRA 0 0000 --------------------------------- T/OFF FUEL 17795 0825 TAXI JFK 200 0020 --------------------------------- BLOCK FUEL JFK 17995 Fuel planner: So I just want to make sure I understand your numbers here correctly and nothing was left out. According to what you posted above I have noted specifics Below.... M 0.80 / FL390 / ZFW 44.4 T Actual Block Fuel: 18.0 T EST Take Off Fuel (-taxi) = 17.8 T Actual Landing Fuel = 2.2 T No Route Changes, Short Cuts, Holding, Climbed Directly up to Optimal and stepped up to FL390 when appropriate (Max Altitude Prog Page >390 + Optimal = 380) Is this correct? Now looking at your numbers above and plugging those same numbers into Sim Brief, using the Plan and Alternate Plan it spit out, I get a trip burn of 15.6. My Trip Distance: 3215 Ground (270@41 / ISA+3) Every thing else the same. I just ran your numbers using Sim Brief and Came up with a Burn of 15.6. (A319) According to your numbers above. Takeoff Fuel (Actual) of 17.8 - 15.6 (Actual Trip Burn) = 2.2 Remaining (Almost right on with my Sim Brief) Of Course the AS Fuel Planner shows much less if you plug these exact numbers in and calculate. So if what I posted above matches your data then Sim Brief and the actual Burn of the aircraft are very close and could be adjusted simply with a Fuel Bias. We do this Real World as the planning doesn't match the actual as the engines age and are switched out etc... If you have the time I would like to see another example with exact details to get better info. Please use the A319 or A320 if you can plan it with Sim Brief and load it accordingly and post the data. If you're not interested in that I would say just go with sim brief, always take a little extra for mamma and the kids and record your burn data over a set of flights and then use a Fuel Bias and that's it, wallah. BTW: I used RW Flight Planning charts and came up with the same numbers as MY Sim Brief using A319 Performance data. Edit: And lastly the Fuel Planner needs some work and we will look into that. Thanks for your report. Disclaimer: If you see any mistakes in here let me know, lots of numbers and charts so yah... Link to comment Share on other sites More sharing options...
Fragged^2 40 Posted September 4, 2018 Share Posted September 4, 2018 Yep. Straight climb to FL390, no shortcuts, optimal was FL385 when I reached top of climb. Ended up using 1000 kg more fuel than planned, which isn't that big of a deal, it's just a bit sketchy as we are close to max range of the aircraft. Overall Simbrief seems to be quite close with it's prediction. With my plan / actual flight the biggest thing I noticed was EFOB shown by the plane going from 1.8 initially to 2.2 closer to destination. It's still a small change, but I saw an increase in EFOB while I believe OP mentioned it dropping as he went on. So I saw the complete opposite than what happened to him. I might try another long flight in the A319 later this week and will record fuel stats again. Link to comment Share on other sites More sharing options...
bill3810 109 Posted September 4, 2018 Share Posted September 4, 2018 Ok thanks for your input, I think the fuel predictions can use some shoring up as well. Remember this is the initial release and there will be SP's coming up along with regular updates so I'm hoping we can fine tune this. The Fuel Planner is on the list but again if the plane is burning close to what Sim Brief has then we're pretty good just use the Fuel Bias with Sim Brief and you should be spot on. I will post when I have more info. I will be checking my numbers as well. Thanks again. EDIT: BTW we see fuel burns vs actual off quite a bit after engine changes, and other maintenance that's why we keep a monthly fuel burn report so we can adjust the numbers in the MCDU for predictions etc.. AKA: PERF Factor Link to comment Share on other sites More sharing options...
bill3810 109 Posted September 4, 2018 Share Posted September 4, 2018 5 hours ago, Fragged^2 said: With my plan / actual flight the biggest thing I noticed was EFOB shown by the plane going from 1.8 initially to 2.2 closer to destination. It's still a small change, but I saw an increase in EFOB while I believe OP mentioned it dropping as he went on. So I saw the complete opposite than what happened to him. One thing to note on this is weather programs and how they transition from one area to another concerning winds. I am doing a test flight from KORD to KSFO right now but steady winds at cruise and ISA deviation per the planning so there will be no jump from one reporting station to the other which depending on what weather program you use can be drastic. I'll report my numbers here and let you know how it went. So far cruise burn numbers, TAS, N1 % all matching pretty close to Cruise data charts (RW). Link to comment Share on other sites More sharing options...
bill3810 109 Posted September 4, 2018 Share Posted September 4, 2018 Test Results from KORD - KSFO. Planned Burn and Actual Burn both - 9.7 Tons Flight Time - Within 2 minutes Weather - as planned. So for a flight up to 4 hours using the exact weather and performance as planned, netted me the exact data as Sim Brief. Of course the Fuel Planner is way off but this will be worked on. Regards Link to comment Share on other sites More sharing options...
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