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inlovewithBoeing

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Posts posted by inlovewithBoeing


  1. On 10/3/2018 at 3:20 PM, Skyrock said:

    I'm struggling with the 787 profiles since I've already set the bias to -4.0 and I'm still using way less fuel than calculated. I assume it has something to do with the ISA deviation. In the .txt files, I got rid of any ISA deviations in order to achieve a more precise calculation, but the 787 profiles are all .per files, so I can't edit them.

     

    I confirm the problem: these B787 profiles calculate 4 to 6% more fuel than required.


  2. On 18.06.2017 at 4:31 PM, petkez said:

    Thanks for your many excellent profiles. The 717 profile has an error with the engines type BR700-715C1. The profile has a Max ZFW of only 10,500 lbs and a max take off 12,100 lbs so it is unusable.

     

    Thanks

    Pete

    I confirm my mistyping, disregard that above.

     

    I'll reupload it.

     

    Regards

    Mykyta


  3. On 18.06.2017 at 4:31 PM, petkez said:

    Thanks for your many excellent profiles. The 717 profile has an error with the engines type BR700-715C1. The profile has a Max ZFW of only 10,500 lbs and a max take off 12,100 lbs so it is unusable.

     

    Thanks

    Pete

    Hi, Pete.

     

    I've tested the profile in PFPX before release and it worked well.

    The weights were taken from a real-world FCOM directly. I'll check it once again.

     

    Mykyta


  4. 2 hours ago, Emanuel Hagen said:

    During beta testing we tested our Airbus with real world OFPs brought along by our fellow real life A320 pilots.
    The results were within a +-300kg fuel remaining using real weather and flights up to 6 hours. We couldn't get any real life OFP with flight lenghs of more than 6 hours, so anything beyond that can not be confirmed by flight tests.

     

    We can not really assure that fuel usage will remain realistic at fuel loads exceeding the maximum of 20t which we programmed. Theoretically it should remain realistic, but we never confirmed this with flighttests as it was simply too far away from what we expect the typical user to do with our bus.

    Thank you for your response, Emanuel. :)


  5. 12 hours ago, CS-TMT said:

    Alright! All clarified now!
    Didn't know about that of the drag bias.

    Thanks a lot for your help and congrats for your wonderful job regarding these profiles!

    Start with +3% and record the flight data.

    And you may contact the developers and tell them about the problem.

    It would be also important to check this bug out on the rest of Aerosoft A32x Family aircrafts.

     

    Cheers!


  6. 12 hours ago, CS-TMT said:

    Regarding 2. after descending from FL390 to FL380 I had an imbalance of ~300kg between left and right engine (Aerosoft Airbus' known bug of one engine consuming +50kg/h than the other), so I used X-Feed to get things a bit more balanced. X-Feed is also known to consume some extra fuel in this Airbus pack. However I had X-Feed activated for only a couple of minutes (1 or 2 max).

    Extra fuel consumption can be set in form of drag bias. It can compensate the extra fuel flow. It's pretty common in real life because engines have their own bugs in real life. :)

     

    12 hours ago, CS-TMT said:

    Now, after KOMUT, besides of descending from FL390 > 380 I should also maintain a constant speed of M.78 as I was entering oceanic airspace, as oposed to a speed calculated in accordance with CI35. So, in short, the only "event" after KOMUT was the use of X-Feed, as both the descent and speed adjustmen was included and calculated by PFPX.

    When you would like to change the cruise mode you ought to plan it so in PFPX.

     

    12 hours ago, CS-TMT said:

    The flight continued on CI35 and the EFOB kept decreasing by 0,1t every once in a while. I ended up landing with about only 1,5t as opposed to the PFPX calculated 4,5t.
    One thing I noted during the whole flight: the fuel page on the lower ECAM showed a consumption of 39-43kg/min. Shouldn't this be 35kg/min according to a CI35? A 5kg/min discrepancy would give 5*60=300kg/h, which, on a 10h flight would give the 3000kg of difference between the PFPX calculated 4,5t and the actual 1,5t landing fuel.

    It's alright.

    In headwind condtions actual Cost Index increases (approx. +0.18 indeces per 1 kt of headwind component on A319 CFM). So, the formula is:

     

    Corrected CI = MCDU CI + (Wind Comp. * CI Adjust)

     

    Taking into account your conditions (50 kt headwind comp) the actual CI is going to be somewhere of 40-45 kg/min.

     

    12 hours ago, CS-TMT said:

    Side note: Before discovering your exhaustively detailed profiles for the A320-family, I used another profile which I downloaded here in the downloads page if I remember it well. However I had these discrepancies with it as well, so I believe this is not an issue with your profiles. I just came here trying to find a sollution to this. Haven't tried other models (A318, A320, A321) nor have I tried other engine types (IAE) so I don't know whether this is an issue particularly associated with the A319CFM or not.

    That's an interesting subject for a research.


  7. 10 minutes ago, Mklemme said:

    I noticed in the PFPX OFP that the mach speed is .78 at TABAX and KOMUT, but then it starts to decrease to .74 by TIMTO. If the actual flight was flown at constant .78 this could explain the increased fuel burn after KOMUT. It's could also be a conversion issue with how Cost Index 35 translates to TAS/M# in the Aerosoft FMC logic v. what's in the PFPX profile.

    By the way, thank you for this notice, I haven't paid much attention to that because the flight time was almost the same. I'll check it out right away.

     

    The function of cost index also determines lower speeds at lower weights when the cost index is within typical flight ops range (0-40).

     

    Anyway, it is a planning issue because MNPS area requires Mach Number Technique (flying with a determined constant Mach No.).


  8. I've had a look at it.

     

    The facts:

    - the total overconsumption of fuel from takeoff to landing is almost 1100 kg;

    - ZFW is OK according to the OFP;

    - Block Fuel was loaded enough according to the OFP;

    - fuel quantity on takeoff was enough according to the OFP;

    - ISA deviations throughout the route are OK.

     

    What was discovered:

    1. At the first waypoint of the cruise flight (as I have no info about TOC/TOD points location and fuel remaining) the discrepancy has already reached -0.2 t. This discrepancy is acceptable. It is covered by contingency fuel and might be compensated during the flight.

    2. The discrepancy begins to increase rapidly after descent to FL380 and entry into the oceanic airspace. It is:

    -0.5 t at 3820N

    -0.7 t at BEKUN

    -0.8 t at VMG

     

    Was there anything special during this part?

     

    3. The actual winds in flightsim enroute were approximately the same as in OFP in velocity, however their heading appears to be more westerly than calculated resulting in slightly higher headwind component. The cost index function on modern aircrafts is designed that way to increase or decrease economic speed depending on the components to keep the flight time closer to the computed CI.

     

    The winds themselves can play some role, but for more precision in order to compare the directions I'll need the magnetic declinations, as long as all enroute wind data is always provided in true headings.

     

    4. A very early descent into LPHR. 

    OFP reads that the TOD point should have been after TIMTO intsc, however you've started your descent somewhere after VMG. You've also burnt almost thrice more fuel on descent than required (approx 0.7 - 0.8 t instead of calculated 0.3 - 0,4 t).

     

    In conclusion I can say that there could be two contributing factors to our case:

    1. Early descent into destination field. There are plenty of circumstances in flight that may require it (ATC commands, traffic density etc.), but they are all going to the factor of airmanship and not the aircraft model.

    2. Wind directions and velocities, especially at middle and low altitudes during descent. At the cruise segment it looks rather well, but anyway, it doesn't tell us why there is a increasing discrepancy.

     

    I have also to add that I haven't tested the performance of Aerosoft Airbus A32x models so far. You can always make an experiment to check it. You may calculate the flight in ISA and zero wind (option in PFPX weather settings) and complete a flight in ISA and zero wind. When we exclude the weather, we get the model and airmaship factors.


  9. 9 hours ago, CS-TMT said:

    inlovewithBoeing thanks for your kind and complete reply. Just to make things clear, I didn't intend to criticise your exhausting work on making such precise profiles, I posted this so that my doubts could be answered and "misteries" solved.

    It's alright, Duarte, any feedback or critics is welcome. :)

     

    9 hours ago, CS-TMT said:

    That's exactly what [url=https://en.wikipedia.org/wiki/CFM_International_CFM56#CFM56-5B_series]this Wikipedia article[/url] says, but Aerosoft Airbus pack uses the 5B4 variant on the A319 (or at least it's what the MCDU says). Power is the same on the two variants, though 5B4 and 5B7 differ slightly on the pressure ratio. And the pack doesn't bring a CJ version, so any CJ flying with this Aerosoft pack is an "adapted" version of the standard passenger version if I'm not mistaken (which anyway doesn't use the 5B4 variant as per the Wikipedia article mentioned above).

    Alright, we've clarified this moment. 

     

    9 hours ago, CS-TMT said:

    The source used in PFPX was its internal server yearly subscription, P3D weather was from ActiveSky Next with live (real time) weather. I know the two may differ slightly (usually on long 10+ flights with the PMDG 777 for example I ger a discrepancy of around 2000kg, wich I believe its perfecly natural) but 600kg on a < 3h flight...

    Such high discrepancy on B777 is abnormal, too. Normally, it can be in range of several hundred kilos on a 10+ hour segment and is often covered enough by contingency fuel.

     

    9 hours ago, CS-TMT said:

    In the image of the route, the planned route is traced with a continuous green line and the actual route flown is traced with a red dotted line. As you can see, no deviations (only a small one after take-off enroute to BUSEN and the biggest difference that isn't clearly seen in the image is that I took off via LPAR04 instead of LPAR22 which translated into a slightly greater route (950nm planned, 954nm flown).

    One of the images shows the flight plan log with the fuel remaining at each waypoint as logged by FS Flight Keeper.

    Yes, I see. Such small deviation like different TO runways doesn't make too much difference in fuel consumption. Still, the captain can always make a decision to load a couple hundred of kilos more to clear this if necessary.

     

    I'll study the navlog, the data recorded and tell you the result within this day (Europe time).

     

    9 hours ago, CS-TMT said:

    In my aircraft on PFPX I only made some personal modifications (max fuel capacity 32800kg as I've seen in a document I have here downloaded from Airbus page a few years ago instead of the little lower capacity on your file, as well as altered the Aircraft.cfg with a little bigger empty weight to match some "personal furniture" (instead of the basic 39-so tons, it has an empty weight of 42-something tons of empty weight, which I also took into account when creating my personal aircraft on PFPX (instead of the ~39t, the empty weight on my PFPX aircraft database also says that the empty weight is ~42t).
    Could it be the case that PFPX isn't taking into account that extra 3t of the empty weight and so calculating the fuel consumption assuming that the aircraft has an empry weight lower than the actual one?

    The DOW modification plays no role in our case because the planned and actual ZFW's are almost equal: 43144 kg vs 42939 kg respectively (if the flightsim and model calculate it right, certainly)

     

    BTW, I've noted a misprint: I reckon that the TOW shall be 79 t, but not 89 t.

     

    9 hours ago, CS-TMT said:

    As a final note, I also edited the Aerosoft's fuel planner to match my needs (fuel capacity, passenger capacity and such) and when creating the loadsheet to see the needed take-off trim for the given CG, the CG is always within the limits (33% for this case), so I doubt it is a weight and balance issue.
    Hope you have enough elements now to evaluate what could be wrong.
    Before using your profileI used another one (don't remember if a downloaded one or some standard PFPX one) and on two different occasions I ended up a 10 and 11h flight with less 3-4t of fuel than expected, though still within calculated reserve minimums.

    More that enough elements, Duarte, thank you very much!

     

    I'll come back to you within this day.

     

    Regards

    Mykyta


  10. 7 hours ago, CS-TMT said:

    So why did I land with 1t less than I should (I repeat, I used the X-Feed valve to correct an imbalance, for about 1min or so, which consumes some extra fuel, but from the 2,5t of predicted fuel at the end of using X-Feed the the final fuel left of 1,9t, what went wrong?
    In summary:

     

    1 - Why there's not a profile for the A319 with CFM56-5B4, and 

     

    2 - Why did I land with ~600kg less fuel than predicted on a flight of only less than 3h?

    Thanks for any help or enlightening!

    Best regards from Portugal!

     

    1. As far as I know, A319 never uses -5B4, but uses -5B5, -5B6 and -5B7 engines with 22000 lbf, 23500 lbf and 27000 lbf respectively.

    Anyway, -5B4 equals 27000 lbf.

    A319CJ Business Jet series use the most powerful -5B7 engines available for A319 due to specifics in bizjets operations (short runways and long-range flights).

     

    As I always note in the profile files itself, it is recommended to set a "static_thrust=" parameter to the appropriate power of the modification.

     

    In general, A319-100 CFM56-5B5/6/7 CFM use all the same cruise data, but A319 with -5B7 engines have higher OPT/MAX altitudes.

     

    2. To answer this question, I need some more details like

    a) The source of wind in your FS and PFPX. Not all the weather clients in MSFS/P3D are precise in terms of wind aloft and temperatures.

    b ) Filled (at least, partially) OFP navlog with progress in-flight. This can help us determine at what stage of flight the discrepancy starts and determine the factor: weather, aircraft model or specifics of airmanship (deviations enroute, diffrent modes of climb or descent, speed/altitude constraints enroute etc).

     

    and, as the specifics of your Airbus model

    c) What meaning in "static_thrust=" in your Aircraft.cfg file do you have on your particular A319 model?

    If it has less than "27000" the aircraft will definitely use more thrust at higher altitudes to maintain speed and buffet margin and it definitely results in higher fuel burn.

     

    And I have a belief that c) is the point. :)


  11. 1 hour ago, Sascha17 said:

    I guess I found the problem. You wrote with your profiles on A320-214 you can fly at FL230 at M0.60-M0.71.

     

    So I calculate a flight on FL230 from EDDF to EDDM with speeds at LRC / M.60 / M.65 / M.70 / M.71 / M.72 and M.78 

    The result is with LRC and the Mach between M.60 and M.71 PFPX calculate the speeds correctly. If I set now M.72 or M.78 (this is not in the range in the profile at FL230 as you wrote above) PFPX automatically uses LRC speed for the flight.

     

     

    Yeah, it looks correct now. So, if you wish, I can make some Mach No. for lower altitudes.

     

    When I was making the profiles themselves I defined the minimum altitudes for Mach No. as the altitudes where Mach No. available in LRC mode at the highest aircraft weight given in tables on specific flight level is the closest to the required one.

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