Re: [Flightgear-devel] Incorrect conversion used for lbs to gallon of fuel

[Bertrand C. <bco...@gm...>]

A better improved patch that supersedes the previous FuelDensity.diff
I sent to this list.
This one takes /consumables/fuel/tank[n]/density-ppg into account in the calcs.

Cheers,

Bertrand.

2011/1/29 Bertrand Coconnier <bco...@gm...>:
> 2011/1/28 Hal V. Engel <hv...@gm...>:
>> A thread was opened on the forum about how the C172P appeared to be
>> incorrectly calculating the amount of fuel in gallons based on the weight of
>> the fuel.  It appears that the conversion is using 6.6 lbs/gal when it should
>> be using something close to 6.0.  That is
>>
>> /fdm/jsbsim/propulsion/tank[n]/contents-lbs divided by
>> /consumables/fuel/tank[n]/level-us_gal == 6.6
>>
>> I also had an issue with this for the p51d-jsbsim model and I had to use 6.6
>> as the conversion factor when setting up the fuel tanks in order to get
>> /consumables/fuel/tank[n]/level-us_gal to report the correct amount of fuel.
>> What is really strange is that /consumables/fuel/tank[n]/density-ppg = 6.0.
>> Is this a bug or is there some other issue that aircraft developers need to be
>> aware of to get this to work correctly?
>>
>> Hal
>>
>
> Hi Hal,
>
> This is somehow a bug since the fuel density is hardcoded to 6.6
> lbs/gal in src/FDM/JSBSim/JSBSim.cxx. Enclosed patch reads the fuel
> density from JSBSim to make conversion between volume and density.
>
> Note that JSBSim allows different sort of fuel density to be used (see
> JSBSim reference manual chapter 3.1.7.1 pp. 39-40). Most of the fuels
> seem to be around 6.6 lbs/gal with the notable exception of AVGAS and
> HYDRAZINE.
>
> Cheers,
>
> Bertrand.
>