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Trip fuel on Simbrief


Luis Landa

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Luis Landa

When I generate my OFP on Simbrief I get a planned trip fuel that frequently doesn't match with the trip fuel that appears on the INIT B page of the MCDU on the A320X.

I've tried to solve this issue increasing the Fuel Factor on simbrief (P02) but even with this sometimes it doesn't work.

Because of that difference when I order the fuel that is indicated on the Simbrief OFP sometimes I get a negative Extra Fuel on the INIT B page. I'm sure that with this negative extra fuel IRL I shouldn't start my flight.

¿Any idea about how I can solve this?

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John Price

I too have experienced this, mainly on the SL aircraft. What I found, Luis, was that the fuel prediction updated and I did end up in excess of the CNR (FINAL RES + diversion fuel), but I did wonder whether in real life I’d have been happy to take off in the real world with minus figures on the FUEL PRED page - I don’t think I would be. Would be interested to see what others say about this. 

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James Harker

One thing to keep in mind is that Simbrief doesn't (yet at least) plan the trip fuel taking the SID/STAR altitude constraints into consideration like they do in reality.  Some SIDs for example can keep you low for a long way out which will be in the FMGS predictions when you select them (even if in reality ATC will normally climb you higher a lot earlier).  To compensate for this I normally increase my minimum contigency fuel from say 5%/5 min to 5%/10 min to ensure it adds an extra 200 kg or whatever for the above mentioned constraints on the shorter flights and so on.

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Phil Tereny

There has to be an error at simbrief, my OFP today showed a T/O Fuel of 6.9 tons and at the first waypoint 26 nm after Takeoff, the OFP says I'm supposed to have 5.6 tons onboard, thats impossible. I was flying the A320SL CFM with a fuel correction of M04.

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STEFAN DORDEVIC
21 minutes ago, Phil Tereny said:

There has to be an error at simbrief, my OFP today showed a T/O Fuel of 6.9 tons and at the first waypoint 26 nm after Takeoff, the OFP says I'm supposed to have 5.6 tons onboard, thats impossible. I was flying the A320SL CFM with a fuel correction of M04.

Simbrief isn't quite optimized for Sharkies as of yet...

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Just adding that you can insert fuel by your own, as captain fuel.

When I'm going in a very busy area in vatsim with a queue for takeoff or have bad wheater I add more minutes in taxi and sometimes I add up to 1ton of captain fuel when meteorological conditions are not great at destination.

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Alexander Polcher
1 hour ago, Phil Tereny said:

Yesterday the fuel planning again was way off with simbrief, I attached my OFP as pdf, what is wrong with that calculation?

LGRPEDDM_PDF_1634222989.pdf 508.9 kB · 7 downloads

Hey Phil,

we can't really help you and say what's wrong just based on your OFP. There are so much more figures which are required:

  • Wind data used? NOAA? Hifi?
  • Mass & Balance used in your sim (ZFW, ZFWCG, TOW, TOWCG, INIT A & B Page)
  • Routing like in your OFP? SID / STAR changed?
  • Flightlevels matching?

Initally I can tell you that your Performance BIAS (M004) is simply unrealistic. Working in dispatch and producing Airframe Configs on real data + Simbrief profiles, I can tell you that plus 5% (P005) for wingtip-fence (WTF) and plus 4% (P004) for Sharklets (SL) is way more realistic and matching the real figures.

But, at least, your arrival fuel seems to be good. Calculated was FINRES + ALTN + EXTRA which was calculated with 1349 + 1063 + 670 which makes exactly 3.082 kg and you had 3.100 kg. An interesting fact in your OFP is that your EFOB and actual Fuel on Board starts to mismatch between FSK and RASTA which looks like a computation problem from Simbrief because you can't be overhead RASTA with 2.7 REFU while calculated on ground is 3.100 kg.

 

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40 minutes ago, Alexander Polcher said:

Hey Phil,

we can't really help you and say what's wrong just based on your OFP. There are so much more figures which are required:

  • Wind data used? NOAA? Hifi?
  • Mass & Balance used in your sim (ZFW, ZFWCG, TOW, TOWCG, INIT A & B Page)
  • Routing like in your OFP? SID / STAR changed?
  • Flightlevels matching?

Initally I can tell you that your Performance BIAS (M004) is simply unrealistic. Working in dispatch and producing Airframe Configs on real data + Simbrief profiles, I can tell you that plus 5% (P005) for wingtip-fence (WTF) and plus 4% (P004) for Sharklets (SL) is way more realistic and matching the real figures.

But, at least, your arrival fuel seems to be good. Calculated was FINRES + ALTN + EXTRA which was calculated with 1349 + 1063 + 670 which makes exactly 3.082 kg and you had 3.100 kg. An interesting fact in your OFP is that your EFOB and actual Fuel on Board starts to mismatch between FSK and RASTA which looks like a computation problem from Simbrief because you can't be overhead RASTA with 2.7 REFU while calculated on ground is 3.100 kg.

 

Hi Alex,

 

why do you think my Perf BIAS is unrealistic? Since the actual fuel consumption almost matches the planned fuel?

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Alexander Polcher
5 hours ago, Phil Tereny said:

Hi Alex,

 

why do you think my Perf BIAS is unrealistic? Since the actual fuel consumption almost matches the planned fuel?

Didn't you state one post above that the planning was offset?

Quote

Yesterday the fuel planning again was way off with simbrief, I attached my OFP as pdf, what is wrong with that calculation?

As I said, there seems to be a general problem with Simbrief in different phases (Climb, Cruise, Descend) and especially:

  • Taxi Fuel
  • Flightlevel Calculation

I am currently doing testflights with a revised Airframe Config on D-AIDM (A321 IAE WTF) on MUC-PMI-MUC-LHR with a revised Aircraft Profile as well and I could see that the climb sector has a mismatch of around -400 kg. I've noticed as well that Flightlevels are too high which led me to decrease the planned Flightlevel (Cruise Level Offset) to -1000 Feet (M1000). Performance Factors of M004 are in general, as I already said, not what I would recommend or expect.

We are flying with CondorVirtual a fleet of mainly A320 and A321 on midrange sectors (2-4 hours) and have around 55 active pilots. With our settings, we are experiencing on point fuel calculations as it should be.

Fuel.PNG.753ce22f04aac88cd01768742ed4e643.PNG

The current evaluation on PMI-MUC (Tankering Sector to LHR) is good as well. Haven't checked the values during climb, but they seemed to be off as well and need 15-20min in cruise to match the calculation once again. Flightlevel with M1000 Cruise Level Offset was as well better in planning.

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Alexander Polcher

MUC-LHR on Airbus A321-231 D-AIDM (IAE) vom Gate B302 to Runway 08L.

Taxi Fuel seems unrealistic as 150 kg have been shown for 00:15 (15min). I haven't touched the Thrs Levers until the runway and could barely reach it with 170 kg. If Simbrief would implement a value for Taxi Fuel instead of time, values would match better in this case.

Following what I've stated above, there seems to be a gap of 400 kg during climb which closes after reaching final cruise level after 20-30min. Other than this, INIT B page usually shows the correct amount of Trip Fuel (+/- 400 kg) after adjusting the ALTN fuel to the value shown in my OFP.

Fuel_2.thumb.png.2ae583b1871443347cfde4aa7850e38e.png

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Phil Tereny
16 hours ago, Alexander Polcher said:

Didn't you state one post above that the planning was offset?

I did, but even with M004 the actual fuel consumption isn't as high as calculated by simbrief, so with P004 the gap is going to be greater, isn't it?

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Alexander Polcher
46 minutes ago, Phil Tereny said:

I did, but even with M004 the actual fuel consumption isn't as high as calculated by simbrief, so with P004 the gap is going to be greater, isn't it?

No. Performance BIAS 100 means, that your fuel consumption is equal to the data imported from the Airplane Flight Manual (AFM), Flight Planning and Performance Manual (FPPM), Performance Inflight and other fuel consumption data derived from the OM-B.

A minus factor reduces the fuel consumption - e.g. you will have lower required fuel and you will have a lack of fuel.

A plus factor increases the fuel consumption - e.g. usually aircraft have dents, are not build correctly 100% according to the manual, the skin and fuselage is askew, painting is old, ...

Additionally, I've reduced the Cruise Level Offset by M1000 so the calculation will be adjusted.

I've had nearly new Boeing 787-8 in my dispatch while working and they had as well plus factors which were pretty high.

Long story short, here's a link for my aircraft profile for D-AIDV (A321 IAE Retro), the livery can be found in the download section:

https://www.simbrief.com/system/dispatch.php?sharefleet=191112_1634222286979

The Airframe Configuration is attached to my post. Give it a try and maybe give me a feedback if your fuel figures match?

Keep in mind for DLH operations:

  • Set Contingency Fuel to "EASA" (5min; 5%, 3% + ERA, 20min)
  • Set Final Reserve Fuel to "30min"
  • Select at least one Alternate Aerodrome

Would be interesting if you have matching figures with this. As well keep in mind to update the INIT B page after initializing and enter the correct Alternate Fuel from the OFP.

 

D-AIDV.cfg

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Phil Tereny
2 hours ago, Alexander Polcher said:

Keep in mind for DLH operations:

  • Set Contingency Fuel to "EASA" (5min; 5%, 3% + ERA, 20min)
  • Set Final Reserve Fuel to "30min"

Up until now I left those two values on AUTO.

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