CPAN loading of Q400 - minor inconsistencies
Hi,
After some experiments I have some questions to the aircraft loading via CPAN. Maybe these observations are helpful for others and hopefully for the developers for the next fix.
(1) My Setup
Simulator: P3D 4.5 and Q400 latest version
Aircraft: OE-LGM with parameters received from my VA
- Basic weight 17.638 kg
- Max. gross weight 28.998 kg
- DOI 68,93
- Delta BW to DOW 600 kg -> DOW 18.238 kg
I adopted the aircraft.cfg to reflect these figures:
[WEIGHT_AND_BALANCE]
max_gross_weight = 63929.6 // 28.998 kg OE-LGM
empty_weight = 38885.1 // 17.638 kg OE-LGM
I created a PFPX profile with these values:
(2) The Flight
I planned with PFPX a flight LOWW to LOWG (RUPE2C RUPET RUPE2M)
- 70 passengers
- 910 kg baggage
As you can see, the DOW is calculated correctly (BW+600) and for the PAX weight 84kg per PAX were calculated.
(3) Loading with CPAN
Now I have to load these figures as exactly as possible into the Q400. I monitor this loading with a tool called FlightSimManager, which reads the values via FSUIPC.
And here some tricks are necessary to get the desired result, as the CPAN loads the aircraft with slightly different numbers compared to what you see on the screen.
One obvious flaw is just a wording issue:
You don't load here the T/O fuel (which is release fuel minus taxi fuel) but of course your release fuel. So if in the next fix this caption could be chaned to "release" or "ramp" it would be more clear.
Anyhow: The value you are inserting here (1.602 kg) is correctly transferred to the simulator, as the check with FSM shows:
Another interesting thing is the passenger weight: CPAN calculates with 84,8 kg/pax. Therefore it shows 5.936 kg as passenger weight and 6.846 kg as traffic load.
Sending these values to the simulator, loads the passengers only with 84 kg, as you can check with FSM:
The passenger weights from the 4 station sum up to 5.880 kg (=70x84). This again fits exactly to my calculation done in PFPX (see above). The baggage is loaded correctly as entered in CPAN.
Now the really tricky one - the DOW. The Q400 has a load station 0, which should get the 600 kg difference between basic weight and DOW:
As you can see, this has been loaded correctly. But how can this be achieved. The DOM field has a strange behaviour. Whatever you enter here: The difference to 16.982 kg is loaded into station 0. I didn't find a reference in the configuration files, where you can change this base value. So if you want to have a certain DOW delta to BW (eg 600 kg) loaded, add your desired value to 16.982 and enter this calculated value into the DOM field.
With this trick you are able to load, what you have calculated before exactly into your Q400.
So there remain some questions to the developers:
- Why is there a difference in the PAX weight in the CPAN (84.8 kg) vs. the weight loaded into the stations (84 kg)?
- Where does the magic 16.982 kg come from, which you have to use to load the DOW delta correctly into station 0?
- As you have your own simulator engine: are the values as loaded into the sim exactly transferred to your own simulation engine?
It would be great, if you can provide some inside details to us. And as I am not an expert and flightsim is just a hobby for me, some assumptions I made might be wrong. Any additional information is appreciated.
Best regards
Reinhard
Comments
Hello Reinhard,
You are absolutely right about 2 points, which I agree with you, are minors discrepancies.
The TOFF FUEL on te CPL should be labelled as BLOCK FUEL or RAMP FUEL.
Regarding the PAX weight, it was discussed some years ago and I think it is coming from the conversion between Lbs and Kg as originally the operator where the MJC Q400 is based from works in Lbs.
That does not create a big problem as for 70 PAX the difference is only 56 Kg. When we consider 84 Kg per PAX it is already an average between men, women, "little" and "big" persons. On a smaller plane you would have to be more precise and usually we were weighting the PAX individually and the luggage as well to avoid over weight or wrong balance.
The CPL transfers these values to the Sim as weight and balance but, regarding the payload, you adjust it exactly in the FMS.
I do not know FlightSimManager but there is something strange in your example as the results given for the PAYLOAD is 7390 Kg instead of 6790 Kg so it is taking the 600 Kg in the payload which is not correct.
These 600 Kg are the difference between the empty aircraft and the BASIC or EMPTY OPERATING WEIGHT (MASS). What we usually do is to consider the DOM inclusive of the crew, the oil, crew luggage, technical books, first aid kit and few bit and pieces. You could directly consider the DOM as to be, in your example: 18238 Kg. My personal DOM is 17895 Kg.
I use PFPX as well and I computed with your values and found out more or less the same results as we did plan with the same wind.
If you are interested, I did an OFP designed for the Q400 where I included the PAX sections and the cargo to be used with the table that I enclosed in my other post.
I enclose the OFP example of your flight LOWW to LOWG and if it is of any use I can post the PFPX file on this forum as I do not think there would be no copyright problems.
Just one last thing, I think you are using the HIGH SPEED CRUISE and I did the same to match your results.
Regards,
JP
Hi JP,
Thanks for your valuable input. The 600 kg additional payload weight in FSM exists, as it's defined in that way in in the aircraft definition file of the Q400. Have a look into the aircraft.cfg. In the [WEIGHT_AND_BALANCE] section you will find a station.0 entry, which has to be filled with the difference operating minus empty according to the title. FSM therefore counts these 600 kg as "normal" payload, because it is defined in a normal load station. And therefore it shows 7390 in FSM.
A possibility would be, to add the 600 kg to the empty weight and set station.0 to zero. Then the payload will be the same value as calculated by PFPX. But then you lose the functionality, that you can simulate several DOW configurations without changing the aircraft.cfg each time.
According to adjusting the payload in the FMS: I don't think, that values entered there influence anything in the actual loading of the plane. It's just for calculating ZFW, reserve fuel, etc. You can enter here what you want - it doesn't change anything in the actual load in the sim as far as I know.
Of course the difference at the pax weights are not big - but if you don't adopt the DOW field to the calculation described here, you might get quite big differences. If you enter 18.238 into the DOM field, the CPAN will load 1.256 kg in station.0 which adds to your basic weight. And that might be a problem. Check this in your sim after sending it to the Q400.
I raised this topic here in the hope, that in upcoming updates these minor things can be corrected in the CPAN so that we really get loaded, what is shown in the CPAN. I know, how to overcome it and by that I have exactly the same figures in PFPX and in the sim.
And I wanted to know, if the values loaded into the simulator are also taken into account in the simulation engine used by Majestic. The reason why I ask this is, as you can find the same load stations in the XML file for this simulator engine. And I want to know, how these values are synced.
And yes: I am interested in your template, as it contains some elements, which I can reuse in my templates.
Best regards
Reinhard
Hello Reinhard,
Good points regarding the acft.cfg if you have different DOM. I have the same DOM all the time so in PFPX I enter directly the DOM.
However, I think it should have been more near the RW if FSM would have shown the empty Mass, then the value entered to have the aircraft to be operational and the DOM.
I agree that the values entered in the FMS do not change a thing in the Sim, they just allow to check these values against the OFP.
A bit out of topic: I know that some people do it that way but I think it is a mistake to transfer directly the PFPX results to the Sim. The OFP values (route, fuel, weights) should be entered manuallly in the FMS otherwise no check is possible.
Here enclosed is the PFPX file that I use for the Q400. Feel free to change it as you wish. It is based on different operators, on LIDO for the fuel and personal experience (long time ago). It is calibrated to be printed on continuous listing paper. So may be some changes would have to be made to print it on normal A4 paper.
Regards,
JP
Hi JP,
Thanks for sharing your template. Very useful.
For empty weight and operating weight: Majestic did not completely follow the SDK by moedelling this delta weight as normal payload (although you will find this also in other aircrafts done in that way). Why? If yo look at the definition for the aircraft.cfg parameter "empty_weight" you find in the SDK:
empty_weight
Total weight (in pounds) of the aircraft minus usable fuel, passengers, and cargo. If not specified, the value previously set in the .air file will be used.
So in fact this is the DOW. But in the Q400 we have to configure the empty weight (and the delta to DOW is loaded in station.0).
If you want to have the correct weight by specifying the DOM in the CPAN, then you have the option to set the empty_weight to 16.982 kg or 37.438.9 lbs. as the CPAN always loads the difference between your specified DOM to 16.982 kg into station.0, your weight will then be correct.
Any information, if this is hard-coded into the application or if this is configurable somewhere, is appreciated.
Rgds
Reinhard
Hello Reinhard,
I am not too good with computers but I did a bit of searching and I found this in the aircraft.cfg:
[WEIGHT_AND_BALANCE]
max_gross_weight = 66000.0
empty_weight = 37572.48 // This is in fact DOM
I am not sure but it would appear that the DOM is in the right place ; however the mass in Kg beeing 17042( if I am not mistaken) does not look correct.
When I change the figures in the CPAN and send it to the Sim, it does not affect the aircraft.cfg. May be it is normal but I do not know what does it change and maybe it is not accessible to the user.
Do we have to change the mass in the aircraft.cfg if we use a different DOM?
Quite a few questions. Do you know the answer?
Regards,
JP
Hello JP,
If you are loading the Q400 via the CPAN, the following method is the best way to get the Q400 correctly loaded:
(1) AIRCRAFT.CFG
max_gross_weight = 64130.3 // which is the max ramp weight 29089 kg
empty_weight = 37438.9 // This is the magic number used by the CPAN to calculate station.0 load with the DOM delta; don't set the correct empty weight here !!!
(2) PFPX aircraft profile
Here you can specify the correct basic weight and the correction to DOM in the airline specific configuration weight according to your airline
OE-LGM
empty weight 17.638 kg
Config. AUA +600kg
(3) CPAN
Here you set the actual DOM (=empty+config)
OE-LGM: 18.238 kg with DOI 68.9
With these values you get the correct loading, as empty_weight from aircraft.cfg and the value in station.0 load (difference between DOM and 37438.9) together result in your DOM.
Passengers are loaded with 84 kg each and the cargo is loaded as specified.
So the trick is to specify empty_weight = 37438.9 in the aircraft.cfg.
I also needed some time to find this out.
Rgds
Reinhard
Hello Reinhard,
Sorry for the delay in responding but I was a bit busy.
Thank you so much for your explanation. I did not know how it works within the Sim. Very interesting.
Regards,
JP