After having tried several modifications on the engines.cfg, it turns out that several parameters are not having any impact on the engine performance. Especially prop_efficiency_table and prop_power_cf. After checking with the debug engine pages of the aircraft editor in dev mode, changing these tables that are crucial in the tuning process have no impact on the live values of these very same coefficents displayed (and no impact on performance. You can even delete these tables, it loads anyway.
It seems Asobo uses internal generic tables, proabbly thoese beautifuls curves display in green and red in the debug window (but with no figures). Maybe these entries are reserved for legacy mode, but then it’s very sad because, developpers have very limited options to fine tune an aircraft in the modern flight model.
It’s the same problem with lift_coef_aoa_table that lists CL vs AOA. As sdk mentions, it uses a “subset” of this table. In fact it uses probably CL max and CL0 to scale a generic lift curve profile mathematicaly. You can still adjust height of this pre profiled lift curve with another parameter but that’s all.
As a consequence, post stall lift is not modifiable. In the case of the DA40 model, the post stall dip is too strong, leading to a mush and a spin. In reality it’s just parachuting and remain controllable and stable. It’s a pity that in Legacy mode we can adjust this and in modern we are so limited. I mean if we could have more freedom to adjust the models we could show the modern flight model in all its glory.
Frankly after having spent hours fine tuning the model, I am convinced it gives a huge benefit in terms of realism and handling once properly tuned. It’s very convincing. I hope Asobo will consider this opinion and open up a litlle more modeling capabilities.