RPM runaway?

[eduardo]

Hello, greetings from Chile.

I purchased RealSimGear's DA40 NG some days ago and I have been playing around with it. I discovered something that called my attention: retarding the throttle many times causes RPMs to increase into the yellow or even the red zone for some seconds —with the corresponding propeller and engine sound pitch going higher too— before decreasing again.

Lets say I´m flying level at 1500 ft with 75% load which gives an IAS of 127 kts and 2030 rpm. Then, I retard the throttle to idle to start descent and slow down and RPMs go up to 2130 in the yellow zone for about 5 or 6 seconds before going down.
The same happens when landing upon retarding to touch down, which is a little upsetting due to the increase in the propeller sound pitch which one usually associates with an increase in power.

Is this normal?

Edited February 27, 2024 by eduardo

[Coop]

That is normal behavior, here is an image of the engine's propeller target RPM curve: 

The propeller acts as a speed-brake in a way with the engine at low throttle settings, and the drop in RPM after the initial surge is due to the decrease in speed of the aircraft.

[eduardo]

Thank you. I think I'll have to get used to it .

[khazz]

it doesn't work so in real life

https://www.youtube.com/watch?v=50hZamZfYjQ
check this video. there is no grow of RPM on flare

Edited November 11, 2024 by khazz