Realistic Propeller Effects (flight model)

Vmca demonstration:

Beechcraft Baron
One engine full power, the critical engine windmilling (despite prop lever in feathered position the engine is windmilling)
Take-off flaps, gear-up
ISA conditions
Max. TOW, aft CG

Seems the aircraft stalls before losing control due to asymmetric thrust and drag, full rudder input required around 85 kts. Can anybody with experience on the Baron confirm this is correct? Is it still climbing this well on one engine with flaps at take-off at speed way below Vyse?

By the way the rudder axis on my joystick is seriously borked…

It’s been a long time so a little fuzzier, but the first thing is that flaps weren’t used for take-off, and were immediately retracted during a go-around or engine failure during climb.

In the actual plane we never actually did simulated cuts below blue line so it’s hard to judge how accurate the responses you’re seeing are. In the old Frasca sim though you did basically run out of rudder around 84KIAS, If you let it get slower below 500’ AGL you were rolling inverted and eating simulated dirt.

It did climb surprisingly well on one engine though.

This might help with some of that testing.


This is using my mobile, if it’s too small I’ll re-upload next time I’m at my desktop.

The Beechcraft Kingair is an absolute joke.

Max. take-off weight, speed 140 kts on FLC:

Power idle: -300 ft/min
Full reverse: -1150 ft/min
Engines shutdown, props full forward: -850 ft/min
Props feathered: -850 ft/min

I didn’t note the RPMs but the RPM drops significantly when selecting feather, but with no effect on the aircraft drag. The difference between flight idle and engines shutdown is likely not a drag problem but rather a way too high flight idle power setting…

When shutting down the critical engine (windmilling) and adding full power on the life engine, the aircraft stalls way before running out of rudder to counter the asymmetric thrust and drag. Second try with flaps in landing position to lower the stall speed, able to fly 77 kts with the joke full back, rudder full in just keeping the slip indicator centered, again no departure from controlled flight below Vmca.

I know but it stalls way before running out of rudder authority, I just can’t let it depart controlled flight below Vmca before stalling even with flaps landing.

That’s definitely not accurate, even at blue line you shouldn’t expect much in the way of excess available rudder control.

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Cessna Caravan:

Max. take-off weight, 110 kts on FLC (no idea what best glide speed is).

Power idle: -650 ft/min
Full reverse: -1050 ft/min
Engine shutdown, prop full forward: -900 ft/min
Prop feathered: -900 ft/min

On the Cessna Caravan the prop RPM does not respond when selecting feather. RPM remains the same. Conclusion, the three turbo props seem to suffer the most from incorrect (completely missing) propeller drag.

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Thanks for your definition. This is my definition:
What is propeller drag? If you set full thrust, you have first a mismatch between how fast the air around the airplane moves and how fast the propeller wants to move this air. You get acceleration until this mismatch is resolved. If you set thrust to idle, you have another mismatch. The air moves faster then the propeller wants to move the air. This results in a deceleration that we call “propeller drag”.

Seb Wloch spoke about engine friction. I found the parameters max_rpm_friction_scalar, idle_rpm_friction_scalar, engine_friction_table, recip_stop_arc_friction_factor, power_absorbed_cf, prop_power_cf. For me, the last two parameters looks most interesting (C172 values):
power_absorbed_cf = 0.0 ; Coefficient of friction for power absorbed by propeller
prop_power_cf = 0.0:0.000:0.200:0.400:0.600:0.800:1.000:1.200:1.400:1.600:1.800:2.000:2.200:2.400, 15.0:0.032:0.029:0.025:0.022:0.009:-0.057:-0.188:-0.338:-0.522:-0.705:-0.915:-1.092:-1.220, 20.0:0.084:0.075:0.066:0.058:0.045:0.010:-0.074:-0.188:-0.338:-0.525:-0.726:-0.942:-1.120, 25.0:0.098:0.094:0.088:0.080:0.070:0.050:0.020:-0.040:-0.134:-0.272:-0.468:-0.717:-0.933, 30.0:0.138:0.132:0.128:0.120:0.110:0.099:0.078:0.040:-0.017:-0.110:-0.248:-0.468:-0.741, 35.0:0.206:0.198:0.188:0.178:0.163:0.150:0.130:0.105:0.070:0.023:-0.074:-0.254:-0.510, 40.0:0.250:0.242:0.233:0.223:0.214:0.204:0.190:0.175:0.150:0.118:0.072:0.019:-0.059

It is in the [PROPELLER] section. But at the moment I am happy with my “missing propeller drag workaround” and I work in other areas of flight model - right now on improving FSX conversion flight model.

But BusPeeGee wrote in Flight Model mod for the DA40NG - #19 by BusPeeGee
“it turns out that several parameters are not having any impact on the engine performance. Especially prop_efficiency_table and prop_power_cf”

Again we are at the Asobo “dumbed down” topic. Seb talks about we have it already in MSFS 2020. I say this is marketing speech. They may have the parameters, but the flight dynamics engine is not using them (at the moment).

Seems a common theme. This is what Wing42 had to say in their Bleriot release notes:

Meanwhile, Pamela Brooker took a deep dive into the new flight model, and while some aspects
have been improved upon drastically in the new simulator, some other parts of the aerodynamics
simulation seem to have been forgotten.

I confirm your test results with the G36. It seems to behave pretty well with expected changes due to the prop lever movement.

With that, it seems like prop pitch effects are modeled within MSFS, but they don’t present in all aircraft. I tried a couple other piston powered aircraft (Carbon Cub for example), and did not notice the same aerodynamic changes due to prop pitch.

We need this!!! :pray: :pray: :pray:

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It seems like SU5 might have additional improvements. The DV20 seems to have better prop pitch effects. Can someone else confirm?

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I dont fly the DA20 but the prop singles I do fly all seem unchanged, in other words Torque effect is still messed up and prop pitch effects poorly modelled

I honestly doubt Asobo cares to fix this, or even accepts its a problem.

Propeller physics are complex but at least a simple model would suffice for MSFS. I’m fairly sure DCS has already taken a good stab at this.

Possibly, but I hope that’s not true.

There is a lot of noise from users to improvement base content. It is my opinion that Asobo should never have released the game with such a large number of default aircraft, or provided any indication that they would model any avionics package to a significant extent; that they should instead concentrate on developing the environment (including flight model, atmospheric simulation and world scenery/graphics/aeronautical infrastructure), leaving third-party developers to provide high-fidelity aircraft, avionics and airports - taking a cut of the latter via a functional marketplace to sustain the former.

Although Asobo have indicated intentions to address all of the above, I wonder whether it is feasible to obtain sufficient expertise, time and/or money to improve all of these things satisfactorily (regardless of whether it translates to additional sales). That said, I’d happily eat my hat.

On a separate note, my research led me to this: New DCS WWII Propeller Technology - YouTube. Albeit unrelated to physics, it looks bloody amazing.

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Propeller physics are not exactly a DCS strong point. Just check this great Yak 52 comparison video.
In some areas even MSFS is more realistic.

Lets talk about Yak-52 - YouTube

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Interesting.

I did read something about the P-51 oscillating strangely when dived at idle thrust which they proposed might have something to do with abnormal propeller modelling.

Great video by the way, or at least from what Youtube translator could make of it. I’ve got but one hour dual in a Yak-52 and it was a very cool machine.

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Exactly, one or two aircraft in each category would have been fine. One glider, one helicopter, couple of single engine pistons, one multi-engine piston, one single engine turboprop, one multi-engine turboprop and one airliner (maybe a fighter). Now there is a long laundry list of single engine piston planes as long as my arm.

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Completely agree.

Just like with previous versions, of course. Projects which no doubt also had a significant budget yet elected only to model one or two types for each aircraft category very basically.

I fail to understand how consumers expected any of the default aircraft to be anywhere near realistic, but I was at least hoping for a reasonably realistic portrayal of the aviation environment.

Well if they would only take the C172 and ditch the rest they might have been able to use it as a showcase of the new flight model and really show what the new sim can do. On the other hand, most planes are just nice exteriors with a G1000 slapped in, its not like they’ve put a lot of effort in custom avionics or anything, maybe it didn’t take them that long.

That’s true.

An excellent C172 model would be great - perhaps then they would have had a chance at properly simulating the G1000 too. However with only one (albeit very realistic) aircraft, their product would have been almost unmarketable.

I suppose we’ll just have to have faith that they’ll improve the flight/environment models to our satisfaction, or else eventually give up and unlock them to allow third-party improvement like previous versions.

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Well they sort of did but the categories were more like “single engine piston with tail wheel, flaps, fixed gear, glass and fixed prop” , “single engine piston with tricycle gear, flaps, fixed gear, glass and fixed prop” , “single engine piston with tail wheel, no-flaps, fixed gear, glass and fixed prop” etc etc and then doubled down on some iconic ones with identical configuration like the 152s and C172s .

There are differences between the configuration of most of those single engine GA planes, but whether they matter to most people, that is another argument altogether.

Also, not everyone flies the same aircraft from the Asobo choices. I have used the Pipistrel Virus a lot. Lovely plane with amazing visibility from the cockpit. Many people do not know it exists even if they have the pack that contains it. The default twin that I fly the most is the DA62, which again is not a common choice.

Currently most of my time is spent in aftermarket aircraft - the Warrior II and Cessna c140 and the Grob is growing on me.