Negative Fuelflow

[LuxCayoine]

Hi @junzis

Thanks for maintaining and updating this project.

I wanted to let you know that it was possible to get negative fuelflow:

fuel = FuelFlow(ac="b77l", use_synonym=True) FF = fuel.enroute(mass=316350.0, tas=300, alt=10000, vs=0, acc=0)

After some investigation I think the error could come from FuelFlow._load_fuel_model method, more exactly the following code:

return ( lambda x: c1 - self.sci.exp(-c2 * (x * self.sci.exp(c3 * x) - self.sci.log(c1) / c2)) * scale )

The scale is only apply on the second element from the difference and not on c1 shouldn't the scale be applied over the whole formula?

Thank again,

Antoine