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Remaining fuel on board


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I just setup a flight from EGPH to LPMA in the 737NGX 800W.

 

I'm using latest update on PFPX and using ASN also for weather.

 

This is the first time i have seen such a split between PFPX fuel at dest and the NGX FMS prediction.

 

PFPX OFP says i'll arrive with 2555 and the NGX shows 3800kg or 3.8t

 

I'm using CI 6 climb/des profile is 250/280/300

 

i setup the PERF INIT with CI of 6 and CRZ WIND.

 

My weights match - ZFW 55226kg

 

just can't find why the reason?

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Doesn't solve my problem.

 

it seems using 100 for fuel bias on short sectors i'm arriving under the PFPX fuel prediction at dest. However using 103 and on long sectors like 2+ hrs i'm arriving with far more fuel than PFPX predicts.

 

anyone?

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Ok i will hold off thanks.

 

I'm finding 103 is perfect for short sectors less than an hour. But for long sectors i'm finding my remaining fuel on the NGX at dest is way more than PFPX predicted.

 

I done a test flight with 100 as the Bias and the predicted fuel on the NGX and PFPX matched perfect. Even every waypoint fuel burn and remainjng was matched. BUT this was only when i disabled the weather in PFPX?

 

why is it matching when i fly in zero wind?

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If i use fuel bias 100 on short sectors like 1hr or less i'm finding that my arrival fuel is much lower than what PFPX predicts and i get the using reserve fuel warning on the FMC.

 

I done a flight in zero wind 1 hr sector, EGPH to EGKK and all fuel burn and fuel on board matches perfect within 100kg.

 

Not sure what is going on here seems like PFPX burn against TW or HW is computed different to what the NGX computes?

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On 24/04/2016 at 9:39 PM, Driver170 said:

 

This is the first time i have seen such a split between PFPX fuel at dest and the NGX FMS prediction.

 

Confirm PFPX v1.26 now in use.

 

Have there been any other changes at all?

 

Confirm ASN integration with PFPX.

 

If you have a subscription try planning with PFPX weather.

 

Is ASN correctly injecting to the sim, FSX or P3D?

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If i plan a flight in TWs for example i done a flight from, EGPH to EGSS in a TW. I use ASN and P3D V3.2 And also the 737 800W NGX.

It seems like doing a flight in a TW is leaving me short of fuel and putting me into reserves before reaching the DEST. However if i do the flight from EGSS to EGPH in a HW both PFPX fuel is sufficient to complete the flight without going into reserves and i land with 2100kg unlike the flight to EGSS where i landed with 1500kg.

So seems like the TW is the culprit in the calculations but i can't figure it out why?

I hope this makes sense, but something is wrong here.

I have setup my NGX 800W weights per that guys topic on aerosoft matching weights. I use the same CI6 and FL.

I've even had a real world pilot Ryanair check this and he said something is not right.

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I have just computed a plan for EGPH-LPMA and get a similar result to yourself in that the NGX predicted fuel remaining is 4.4 tonnes whereas PFPX lists 3.8 tonnes, however I don't have time to actually fly the route.

 

Last weekend I flew ENGM-EIDW where PFPX v1.26 predicted fuel remaining at 3392kg and I actually landed with 3443 kg, so 51kg difference was highly accurate. This with a PFPX forecasting TL014 KT.

 

I shall try to find time the next couple of days to actually fly the route.

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Flown a round trip EGSS-EGPH-EGSS with no issues regarding fuel predictions or burn.

 

For the outbound PFPX predicted 3.2t remaining, the FMC 3.3t and landed with 3.1t. Flight was planned with PFPX wind data and average headwind of 21kt, ASN used for inflight weather.

 

Return trip gave similar figures and an average tailwind of 15kt.

 

May try the LPMA run over the weekend.

 

EDIT: CI=35

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Flew the route with your posted setup Vernon, I modified the descent speed which with CI-6 gave 250/0.772 to 280/0.776 in keeping with the PFPX plan.

 

At EGPH the FMS indicated 4.0t remaining ( before taxi ), PFPX 3.6t and actually landed with 3.9t.

 

The FMS prediction varied inflight between 3.8 & 4.1t.

 

The enroute waypoint figures matched PFPX perfectly with a small drift in the descent giving a difference of around 250kg above the landing prediction, a very good result.

 

Flight again planned with PFPX weather and flown with ASN.

 

egph-lpma.jpg

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Ok, EGPH-EGSS @ FL390 with your setup, CI=6 descent adjusted 280/0.776. Default EU fuel policy.

 

Fuel remaining:

 

FMS at gate 2.1t

PFPX           2.1t

Landed        2.0t

 

Waypoint fuel matched exactly.

 

No issue at all Vernon in any of the flights.

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19 minutes ago, Driver170 said:

I'm getting a FL410 and not FL390

Vernon

 

Try the flight with a fuel bias of 103.5 and a climb/descent speed using PFPX default of 280/.78. Don't use whatever CI6 comes up with for climb/descent speed. How can you expect the FMC in the NGX and PFPX to agree if one uses apples and the other oranges to arrive at a reserve.

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