Realistic Propeller Effects (flight model)

Dear all,

The propeller effects in FS2020 are not realistic or even completely missing. Just to give you some examples before giving a comprehensive breakdown of each effect:

The TBM and Kingair just won’t slow down when you slam the power to idle, I haven’t flown the TBM myself but I did fly the Kingair in real life. I can tell you, as soon as you kill the power its like throwing out the anchors. It must be a piece of cake to fly 160 kts until 4 nm with any turboprop and be stabilished at 1000 ft, not so in MSFS. Same is true for basically all propeller driven aircraft in FS2020, deceleration is not accurate.

I did recently test the TBM rate of descent with the engine OFF and throttle idle versus throttle feather with no change in rate of descent to maintain 120 kts. Even when selecting the throttle into full reverse in flight (again with the engine OFF) the RPM goes up significantly but remains within limits (in real life it would overspeed and get destroyed by centrifugal forces) but absolutely no change in rate of descent to maintain glide speed. This for me is the ultimate proof that no propeller drag is simulated.

During take-off roll, some right rudder is needed to stay on centerline, when airborne however these effects seem to disappear completely. On any single engine piston aircraft continuous rudder input (or rudder trim) is need to compensate for the propeller slipstream effect and P-factor.

  • Torque Effect - According Newtons 3rd law, every action has an equal and opposite reaction. If the propeller turns clockwise seen in the direction of flight (as is the case for most aircraft) the whole aircraft tends to rotate anti-clockwise. I’m not convinced the torque effects are simulated at all, this effect is most noticeable when applying full power at low speed. It is definitely not accurate, on the Kingair for example a lot of right rudder is required at the beginning of the take-off roll to compensate for torque effect in the real world.

  • Propeller Slipstream Effect - The air leaving the propeller picks up a swirl, rotating around the aircraft and creating a slightly different angle of attack on the wings roots causing a difference in lift, this effect is very small. The air also creates a different angle of attack on the vertical stabilizer, creating a yaw to the left (right rudder required). This effect is 100% missing in FS2020 which is a shame really as this is a very important characteristic of propeller driven aircraft. During flight no rudder input is required at all for coordinated flight is FS2020.

  • P-factor - This is not a very strong effect on single engine aircraft and is more a concern on multi-engine aircraft in determining the critical engine. This effect is only present at positive angle of attacks creating different AOAs on the up and down going propeller blades. The result is when pitching up the uneven thrust built-up creates a yaw to the left (again right rudder required). I’m not convinced this effect is present in FS2020, its not very noticeable at least.

  • Propeller Drag - A windmilling propeller (for example power selected to idle in flight) is a condition where the angle of attack on the propeller is negative due to low rotational speed and / or blad angle (constant speed propeller). A windmilling condition creates a ton of drag and therefore a lot of deceleration. In FS2020, unfortunately this is completely absent. Just try to reduce speed with the TBM or Kingair while on approach, the deceleration is even slower than a jet. This does not only affect turboprops though. The deceleration on all aircraft I’m able to compare to real life is considerably slower than the real deal, also glide ratios are unrealistically high because of this.

  • Propeller feathering - Non of the multi-engine piston aircraft and single / multi-engine turboprop aircraft in FS2020 have the ability to feather the propeller in flight. On the Kingair and TBM the ITT gets as hot as the sun when selecting feather on the ground indicating a problem in the turboprop engine logic but I guess that is a different subject. The Cessna caravan just doesn’t react to selecting the prop to feather at all.

  • Gyroscopic Precession - Mainly a problem on taildraggers where the aircraft yaws strongly to the left when lowering the nose during take-off roll. I haven’t noticed this in FS2020 so far, if it is there its definitely not realistically represented. Taildraggers also don’t have the tendency to ground loop in FS2020 but that is is not just because of missing propeller effects, different topic.

Its unfortunate that FSX and even FS9 were able to represent propeller effects more realistically. On top of other flight model fixes, this one needs to be fixed so please vote this one up! For people not interested in accurate flight dynamics I guess there could be an autorudder function as was the case in FS9 and FSX?

Do you find these in your D sims?

I haven’t flown any single engine level D sims and I’m not sure if they even exist. Multi-engine turboprop level D sims I have flown are pretty accurate, the Kingair really pulls off the runway at the beginning of the take-off roll just like in real life. But FS9, FSX and X-plane do a far greater job in this respect so it must be possible.

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I fear this might be also something they dumbed down for the regular gamer, like they did (and acked in the last Q&A session) with the updrafts in thunderstorms.
If they would implement this, they would get alot of support tickets from these gamers,
complaining about the need to push rudder on start and aileron in cruise all the time.

If they only had thought about this earlier and would have added a Game/Realism Mode switch to the options… :woozy_face:

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They have them for the TBM and the PC12.

I was thinking about single engine piston planes, for single engine turboprops there sure are sims for those, but I haven’t flown them nor flown those planes in real life so I can’t say anything about that. I have flown a lot of single engine piston planes, a couple of multi-engine turboprops, and some airliners.

Oh about all your going to get single engine piston wise are the RedBirds. I can tell you those are far from realistic in terms of flight dynamics and cost $80K. Probably why I don’t expect a whole lot from a consumer product.

I don’t assume it’s ever gonna be as accurate as a Level D simulator, that won’t be realistic to expect. But having fundemental characteristics completely missing is the other end of the spectrum. Copying the FSX code in this regard would already be an improvement.

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I agree with some point however P-factor, Torque, Slipstream and gyroscopic precession are there. At least I can compare with those airplanes I flew in real life and it seems OK

In which aircraft do you experience gyroscopic precession? (With the FDM set to modern)

When you lift tail during take off in Cub

Ok, and in flight?

In flight I get mix of all

On which aircraft do you need continuous rudder input for coordinated flight? Especially at low speed and high power? I don’t need any rudder input after take-off on any airplane for coordinated flight.

Slipstream effect is definitely not there, if I’m flying close to the stall speed and cycle power between full and idle absolutely nothing happens yaw wise. This would also mean P-factor is not there as angle of attack is high in this situation.

Regarding torque effect, try to stall the aircraft with full power, I’m getting about 50% wingdrops to the right and 50% to the left. At some point I thought I did notice something, so I’m not so sure about this.

Propeller driven aircraft in FS2020 are missing their main characteristics, they fly like jets. They fly straight with no input and won’t slow down.

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I’m sure this is all true about the propellers. But even basic aerodynamics aren’t correct. I was flying the King Air at 60 knots and just floating. You know as well as I that as the airspeed decreases lift decreases, so you need a higher angle of attack. I kept the angle of attack the same so the aircraft should have descended to the runway, but it didn’t it just kept floating in a full stall almost 8,000 ft. It just wouldn’t settle down to the ground unless I push the nose down. So it is more than just the propeller physics that are wrong, it’s the entire flight model.

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Well this is supposed to be the ground effect, even when maintaining the pitch constant the effective angle of attack increases. But in FS2020 this is completely overdone. Combined with a lack of propeller drag and therefore low deceleration and you will float forever. Also the props are spoiling the airflow over the wings in real life at idle power, pretty sure this effect isn’t present either.

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Yeah if that is their idea of ground effect then yes they way overdid it. The king air is stalled at 60 knots, whether you’re in ground effect or not you’re hitting the pavement. Honestly you’re hitting the pavement at 90 knots if you pull the powers to idle in a C90 let alone a 350, that thing drops like a piano.

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Well said, thank you

I think this problem is easy to fix by configuration files editing. Just set induced_drag_scalar to 2 or 3. There is a common problem in all Asobo airplane flight models. It is about the following diagram:
back side of power curve
The speed of the powered airplane is between stall speed and cruise speed. In both cases the engine gives full power. The induced drag or lift drag determines stall speed, the parasitic drag determines the cruise speed.
In the Asobo airplane models the parasitic drag is acceptable, but the induced drag is wrong. Everybody can test the flight model: Give full throttle and rise the nose until the airspeed is the stall speed. If the model is correct at the stall speed there is no more vertical speed. This is the same as with cruise speed: this is the speed at which all engine power goes into level flight.
The flight model parameter induced_drag_scalar and parasite_drag_scalar are very important.
After I corrected the drag_scalars, the airplane has a different, in my opinion more realistic, behavior. Important for me is stall and spin behavior of aerobatics airplane. Download my Cap10, Extra 330LT and Pitts S-2S mods at http://www.andreadrian.de/FS_2020_sailplanes/index.html
The diagram is from https://www.aopa.org/news-and-media/all-news/2013/november/pilot/proficiency-behind-the-power-curve
See also https://www.boldmethod.com/learn-to-fly/maneuvers/private-slow-flight-why-do-i/

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This is very interesting. You have all these effects in your FS2020 airplanes? Can you please show us these effects in a Youtube video. I’m sure this is no problem for you. Thanks a lot!