I’ve noticed that activating Prop Low Speed in cruise impacts the RPM and the engine noise, but it has no impact in fuel flow. Is this expected or is it a bug? I think that lowering the prop speed would reduce the fuel needed and this is a way to optimize fuel.
The POH doesn’t give different performance charts for high and low rpm, it only depends on torque. As I understand it, low rpm is used to lower the noise level, but gives worse performance (because you need higher torque).
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Is this on the ground or in flight? Or both?
In cruise. I haven’t tried in ground as I assumed it was an option to save fuel in long trips.
If you want to save fuel you’ll have to cruise slower. The PC12 already has a pretty good endurance and range at max cruise speed. I don’t believe moving the prop to low rpm makes much difference in flight. On the ground it’ll reduce noise and idle thrust for taxi but never seen anything about it saving fuel in flight. I always leave my turbo props in the high idle position in flight.
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torque is better correlated to/affects fuel flow more than prop RPM. reducing rpm not always lowers fuel flow, it depends on the shape of the prop itself, does it extract as much energy out of the air at every angle, or at specific angles only? is it optimized for takeoff, climb or cruise, or is it a very smart shape that can pull air perfectly at any angle? etc etc.
I dont know specifics of the PC-12 prop+turbine design to know, but safe to say the MSFS model probably does not model the prop and turbine and FADEC faithfully to the real one.
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Idle thrust in taxi is a nightmare with this aircraft, so I’ll try this on ground, thanks.
IRL it’s low rpm mixed with beta thrust to manage taxi. Beta isn’t modeled very well or sometimes at all in the sim. So I with toggle reverse let the speed bleed off then toggle out of reverse and keep doing that to manage my speed