DA40NG FADEC RPM Scheduling

[Alec246]

Hey guys!

After checking sources, and asking a real DA40NG pilot about correct behavior, I am confident the Prop RPM behavior controlled by the FADEC is in need of a fix.

After Takeoff, when I reduced power to 92%, the RPM should have gone to 2100RPM, instead it stayed around 2250RPM, and to reach 2100RPM, I needed around 80~85%.
That behavior is controlled supposedly by the Throttle Lever position, and not influenced by the load on the prop, etc. So, basically a fixed schedule between throttle position and Prop RPM. 

This Throttle Position vs RPM Scheduling was posted also, It shows perfectly how these two behave across all power range


Hope it helps!!

 

Regards

 

Alexis

Edited June 19, 2023 by Alec246

[Coop]

Hi Alexis,

I've heard conflicting information both ways on this. From the docs, it is pretty clear as you mention that the x-axis of the RPM schedule is not % Load, but the physical power level %. The propeller controller is already scheduled to the chart referenced above based on this. 

[Alec246]

Hey Coop!

Indeed it makes sense your point. I decided to chase down the rabbit hole, and I found these graphs which brings us more data to solve this question.

 

This shows that the Power Lever Position (PL) will exactly target PowerLoad% in flight, so 92% of Power Lever must mean 92% indicated Load%. It looks to me as a linear relationship across the entire power position range. Around 800mbar pressure altitude though, Load% starts to drop, around 70% PL keeps the Load% through all altitudes

What is also interesting, is that I learned that the Austro AE300 Diesel needs a Low Power Correction, starting at 800mbar. So, Bringing the Power Lever to 0 above roughly 6000feet, you will not get Idle Power anymore, a Low Power Correction is incrementally added, the higher you are. 

Some nice 100% - 2300RPM and 92% - 2100RPM Power Load% relationship with Altitude as well in this one, also including Manifold Intake Temperature influence. Too bad they dont give straight OAT for easier match with the Sim.

 

Edited June 27, 2023 by Alec246

[Coop]

Good catch! I'll get this logged and see how we can get this integrated.

[khazz]

the fact is that when we set idle thrust on flare in real life the rpm doesn't grow and then decrease but decreases slightly
however in the model we see that rpm increases on flare and then decreases sharply

 

Edited October 21 by khazz