Fuel Quantity Display in MobiFlight

[sisoffi]

Hi Pete,

I'm trying to configure the maddogX fuel quantity displays (I always interface with mobiflight which reads the values from fsuipc). From my lvars list there inst lvars fro fqty

so i assume that fqty is readed from prepar offsets.

The problem seems to be in the conversion of the fsuipc data.

My system is set to Hybrid (feet, meters) and the fuel paylow as fuel quantity as weight (I see the kilos correctly). Reading the fsuipc manual, the values that read the fuel are:
0B80 4 Fuel: left main tank capacity: US Gallons
0B98 4 Fuel: right main tank capacity: US Gallons
0B78 4 Fuel: center tank capacity: US Gallons (see also offsets 1244–
for extra fuel tanks)
126C 4 Total Fuel
1334 Gross weight

In my case I have                       Virtual cockpit          Fuel & Payload        Mobiflight
left main tank capacity                       3200                          3199                       1383
right main tank capacity:                    3200                          3199                      1383
center tank capacity:                             500                            499                       3074
126C 4 Total Fuel                                 6900                          6900                     15213
1334 Gross weight                            52,400                      52,496                              0

Could you point me where I'm wrong?
thanks Simone

[John Dowson]

8 minutes ago, sisoffi said:

I'm trying to configure the maddogX fuel quantity displays

Ok, but those offsets are 'capacity', not quantity.

10 minutes ago, sisoffi said:

From my lvars list there inst lvars fro fqty

so i assume that fqty is readed from prepar offsets.

No - the offsets are populated from the sim (using simvars), not lvars. If the maddogX uses lvars for this (and not the simvars), then you will need to read these and write them to a free offset, and then use that offset.

John  

[sisoffi]

i rememebred from the past that old developper read the offsets from fsuipc. 

For the quantities there are offsets?

 

thanks

Simone

[John Dowson]

4 minutes ago, sisoffi said:

For the quantities there are offsets?

Check the documentation! See offsets 1264, 1268 and 126C, and you can also calculate from the tank level offsets (0B74, 0B7C, etc) using the capacity.

Check what those offsets contain first, to see if they look reasonable. As I said, if the add-on aircraft implements its own system via lvars, you may need to use them.

[sisoffi]

Thank you John,

we had just mapped all lvars from maddog and there is no lvars refferring to Fuel quantity display.

In the past old software we had was based on fsuipc offsets ( for this i assumed that is still no change also in the new aircraft software).

I will try soon the offsets.

 

Simone

[John Dowson]

Hi Simone,

1 hour ago, sisoffi said:

In the past old software we had was based on fsuipc offsets ( for this i assumed that is still no change also in the new aircraft software).

I don't think there has been any changes in FSUIPC for those offsets either....

[sisoffi]

6 hours ago, John Dowson said:

Check the documentation! See offsets 1264, 1268 and 126C, and you can also calculate from the tank level offsets (0B74, 0B7C, etc) using the capacity.

Check what those offsets contain first, to see if they look reasonable. As I said, if the add-on aircraft implements its own system via lvars, you may need to use them.

John, i checed the documentation. Examlpe Central Fuel Thanks:

0B74 4 Fuel: centre tank level, % * 128 * 65536 Ok-SimC Ok-SimC
0B78 4 Fuel: centre tank capacity: US Gallons (see also offsets 1244–
for extra fuel tanks)

by setting first offset i have correct 99%

by setting second offset the result is 3074 (i suppose is Gallons because in my sim is 9300)

by settings 1244 = 0 

can you please explain why cannot see the kilograms?

% its ok, capacity also but how to obtain kilograms?

[John Dowson]

54 minutes ago, sisoffi said:

by setting second offset

But you cannot write to the 'capacity' offsets - they are read-only.

 

1 hour ago, sisoffi said:

can you please explain why cannot see the kilograms?

You need to calculate this. Google tells me that aviation fuel weighs 6lb per gallon (https://www.flight-mechanic.com/standard-weights-used-for-aircraft-weight-and-balance/) which is approx 2.72Kg per Gallon. So given you have the capacity and %age full, you should easily be able to calculate the weight, ie. 2.72 *capacity = capacity in kg, then (2.72*capacity) * %age full would be the fuel weight. Try that and see if it makes sense with your numbers.

 

[sisoffi]

so the offset for left fuel thank is 0x0B7C

the transform formula of default is $*100/(128*65536)

with this is correct i have 100% of capacity (in gallons).

I tried: (2,72*($*100/(128*65536))*$

nothing remain the capacity 😞

[John Dowson]

32 minutes ago, sisoffi said:

nothing remain the capacity

Sorry, I don't understand. And what is '$'?

Offset 0x126C has the total fuel weight (but in pounds), which you can use to cross-check your calculations from capacity and

I'm pretty busy at the moment (on FSUIPC7/MSFS), but I'll take a look at this in more detail over the weekend if you are still having problems.

[Thomas Richter]

Hi,

i.e. for Left Tank

Quote

level1 = 0x0B7C /128/65536
fuelweight = 0x0AF4 / 256
capacity = 0x0B80
capacity_KG = capcity * fuelweight * 0.4536
level_KG = level1 * capacity_KG

Thomas

[John Dowson]

Thanks Thomas - I had missed the fuel weight offset!

[sisoffi]

Sorry but i dont understand nothing.

I attach one pic in order to see what mobiflight produce me. The default for the left thanks is in % and its correct (with the default formula) in transform.

I need now to add to this formula the calculating of your suggestions. Can you help me to correct the formula so that the Vcockpit can display the same value 2400?

 

 

[sisoffi]

I tries this but in the transform data the offset are not consider ( the result remain 57)

($*100/(128*65536))*(0x0B80*(0x0AF4/256)*0.4536)

[John Dowson]

Maybe you should try Mobiflight support for this? We are very busy and cannot support other products that use FSUIPC, we only support FSUIPC.

Maybe there are other Mobiflight users that can help, but not having or knowing their software I cannot advise, sorry.

P.S. I'll update the title of this topic to include Mobiflight, which may attract attention from other users.

[John Dowson]

Btw, what does 'FGCP 1.2 SPD digits' mean for the '$' sign (which I did not understand before)?

[John Dowson]

Another possibility to consider, if you are using a complex add-on aircraft such as PMDG or FSLabs, is that they may not be using the standard FS model for fuel/weight, and implement their own system (in which case those offsets may not be relevant). Do the values in the FSUIPC offsets make sense for your aircraft (without your MobiFlight software)? Or is it just a case of configuring your MobiFlight software correctly? In either case, I think you need help from MobiFlight support or other MobiFlight users. You can monitor the relevant offsets and, for example, see what they contain when your fuel tanks are full, then with 50% capacity. This would at least verify that they are being used.

later... Ah, maddogX - sorry I don't know what that uses

even later....ok, I see you have already reported in the maddog forums...btw, I'm John, not Pete!

[sisoffi]

45 minutes ago, John Dowson said:

Maybe you should try Mobiflight support for this? We are very busy and cannot support other products that use FSUIPC, we only support FSUIPC.

Maybe there are other Mobiflight users that can help, but not having or knowing their software I cannot advise, sorry.

P.S. I'll update the title of this topic to include Mobiflight, which may attract attention from other users.

thannk you, actually not the mobiflight team not reply.

38 minutes ago, John Dowson said:

Btw, what does 'FGCP 1.2 SPD digits' mean for the '$' sign (which I did not understand before)?

not consider this part is only for another application

11 minutes ago, John Dowson said:

Another possibility to consider, if you are using a complex add-on aircraft such as PMDG or FSLabs, is that they may not be using the standard FS model for fuel/weight, and implement their own system (in which case those offsets may not be relevant). Do the values in the FSUIPC offsets make sense for your aircraft (without your MobiFlight software)? Or is it just a case of configuring your MobiFlight software correctly? In either case, I think you need help from MobiFlight support or other MobiFlight users. You can monitor the relevant offsets and, for example, see what they contain when your fuel tanks are full, then with 50% capacity. This would at least verify that they are being used.

later... Ah, maddogX - sorry I don't know what that uses

MaddogX use standard values for these offsets. But one question: possible that there isnt directly an offset that read the value of fuel in each tanks? 

I have never found aircraft (jets) that use capacity indicators, but rather the weight value loaded at the time of tankering and the instant use of it. Why does it have to be so difficult?

sorry to stress you 🙂

 

[John Dowson]

4 minutes ago, sisoffi said:

But one question: possible that there isnt directly an offset that read the value of fuel in each tanks? 

The offsets that hold this information have been there for many years, way before my time, so I don't know the reason why. But with the information that is provided, you could quite easily write a lua script/plugin (for example) to calculate the actual fuel weight for each tank (given the formulas provided) and then write that to a free offset. You can then read that from your mobiflight interface (if thats whats needed). But first of all, you need to be sure that the formulas produce the correct value - but I can't see any reason why this wouldn't be the case. 

[sisoffi]

2 minutes ago, John Dowson said:

The offsets that hold this information have been there for many years, way before my time, so I don't know the reason why. But with the information that is provided, you could quite easily write a lua script/plugin (for example) to calculate the actual fuel weight for each tank (given the formulas provided) and then write that to a free offset. You can then read that from your mobiflight interface (if thats whats needed). But first of all, you need to be sure that the formulas produce the correct value - but I can't see any reason why this wouldn't be the case. 

yes sure is possible to use lua lvars but im not able with lvars scripts plugins.... 😞

[John Dowson]

lua is distinct from lvars...lua can use lvars but doesn't have to, and looks like lvars aren't needed for this. But lua can be complicated for non-programmers, so I understand you point. I would do this for you in quieter times, but I just don't have the time at the moment, sorry. Anyway, it should be possible using the provided offsets, but I'm afraid that you need a mobiflight user to help you configure that.

[sisoffi]

3 minutes ago, John Dowson said:

lua is distinct from lvars...lua can use lvars but doesn't have to, and looks like lvars aren't needed for this. But lua can be complicated for non-programmers, so I understand you point. I would do this for you in quieter times, but I just don't have the time at the moment, sorry. Anyway, it should be possible using the provided offsets, but I'm afraid that you need a mobiflight user to help you configure that.

thanks John, i will attend if somebody of mobiflight can help me.

[Pete Dowson]

4 hours ago, sisoffi said:

I tries this but in the transform data the offset are not consider ( the result remain 57)

($*100/(128*65536))*(0x0B80*(0x0AF4/256)*0.4536)

0x0B80 and 0xAF4 are OFFSET values -- i.e the addresses in FSUIPC which contain the data. They are not the data themselves but fixed numbers, in hexadecimal. 

In other words you need to read the values from those offsets -- making three values you need to read to calculate what you want.

3 hours ago, sisoffi said:

I have never found aircraft (jets) that use capacity indicators, but rather the weight value loaded at the time of tankering

The fuel level provided is in terms of the percentage of tank full, so is based on tank capacity.  All versions of Flight Sim, including the new MSFS, provide the capacities of each tank and the current level as a proportion.

They also supply the current weight per gallon so that the current total weight of fuel can be calculated.

I think you'll find that GA prop aircraft have analog fuel gauges which show capacity and current level, much the same as in motor vehicles. I'm pretty sure that in glass cockpit airliners, and the like, the calculation is done for you -- by software.

There was that famous case where and airliner had the fuel loaded in US Gallons and the pilot had thought it was in Imperial Gallons (20% more), and they ended up crash landing on vapour.

Pete