What causes Propwash and how Betaflight Dynamic Idle can help! 

Wow we all talk about propwash so much and know what it feels like when flying but no one, that I've heard, has explained it so well. Nicely done Chris Rosser.

After making a tutorial about dynamic idle, I got a lot of feedback from users and from in-the-know experts, and long story short, I concluded there is not a consistent agreement about how to correctly tune the feature, nor is there consistent advantage from using the feature according to commonly given "best practices". Personally I don't use it and just go with a fixed idle percent per usual. As long as you keep the idle percent high enough to prevent the prop from stalling, all is well. In theory you can get lower idle speed by using dynamic idle, but like with many dynamic elements of Betaflight, it introduces uncertainty and it's not always helpful. It'll be interesting to see if Chris Rosser's recommendations can finally make this feature beneficial for a majority of people.

Late to the party. I simply added the recommended number of 29 for my 3.5" quad(was on 35) and got a big improvement in prop wash and inverted hang time. Thanks!

great insight.I iwsh i could get all your powerpoints instead of spending hours writing them . Thanks a lot for the video

Thanks for all of your helpful input We appreciate you sharing your knowledge !

EXTRA INFORMATION: 1. When using steeper pitch props you may need a DI value 1.5-2x what I give in the table at the end of the video to control propwash (e.g. up to ~ 40 for 5"). I fly very light pitch props (Ethis S3, 5.5x2.2 etc.) which do not stall as easily so can have a relatively low DI value. 2. For inverted hang time a light pitch prop is very helpful as you can run a lower DI value and it makes less thrust at any given RPM.

Just gave your advice a go, and it's - as per, btw - spot-friggin'-on! I was getting serious propwash from my first outdoor flyer, and thought "Well, ya buy the cheapest 3" toothpick on offer and ya gotta expect to compromise." Earlier, I tried raising the master sliders, and lowering the filtering. Both helped, but this put the chef's kiss on my efforts. Thanks again, Chris! My drones wouldn't be what they are today without your expert guidance.

I'm a newb and haven't gotten too deep into tuning yet, but this makes a lot of sense for why I was getting such bad handling pulling out of fast drops. I'll definitely be trying this out tomorrow.

Very interesting and informative video. I'll give it a shot on one my micros. See what happens.

Awesome video, Chris! Great explanation on why prop wash happens and how you can use the dynamic idling to reduce. So so helpful as always

Numbers related to quads! Perfect. Will try on 3, 5 and 7”.

Really good explanations

The way you explain dynamic idle definitely makes it seem like a good thing to try. It's 10pm, but I will test dynamic idle tomorrow (if I have time.) Thank you, Chris!

PSA: So, after doing a ton of research on the subject, if you are on 4.3, you DO NOT want your dshot idle percent to be over your dynamic rpm value. In fact, a dshot idle percentage of 1% is desirable (per Chris Thompson). The values in the table are a fantastic starting point for Dynamic RPM values, but if you end up with poor low throttle stability for some reason (unlikely) or wish to have a bit better propwash performance at the expense of inverted hangtime, you can raise your dynamic rpm value (NOT THE DHSOT IDLE PERCENTAGE) to about double what chris has in the table in the video.

Hi great tutorial 👍 learned something, many thnx. Didn’t know to setup dynamic idle like this. Stay safe, happy fly’n & take care 🤓😉😘

Thank you for coming to the hobby I feel like a aeronautical engineer now 😀

New subscriber here Chris! Loving the AOS 3.5'' and 5'' quads I have so far 😃👌

I'm excited to try it

Chris . Thanks brother👍

Thank you, thank you, thank you for this video and all of your videos!!! This was extremely helpful in my 4" toothpick. I'm having trouble with severe oscillations, like an audible and visual shaking especially after bumping something (a branch, tapping the ground) and the quad violently shaking (oscillations?) while in an almost fly-a-way state until I drop the throttle and apply throttle again after a second (and yes some prop wash). It's a BNF, the GepRC Dolphin HD 4" and mechanically it's all new and sound (new undamaged motors, proper firmware including RPM filtering via Bluejay and all the screws and arms are secure). Only have a couple of packs after the changes, this certainly helped even though my main issue wasn't prop wash, this seemed to have a positive effect. If you have any suggestions, I'm open for an education and always appreciate your time and efforts. Have a blessed day!

Thank you, I'll try this

Great tutorial as always :)

Great video. I hope you can make a emuflight tune tutorial too because sone settings are different.

Amazing content

Excellent explanation of the topic! One little remark: It's important to tune the FC for propwash but it's equally important to know how to avoid it as a pilot (line-choice & throttle management).

Thanks so much Chris!

Hi , Chris. this is very interesting and useful information. I will definitely try it the next time I fly. on a copter 80mm and 5". You said that there will be a link in the description for instructions on how to include bi-derectional d-shot.

Thx Chris 🙏🏼

I have tested this back and forth many times now, and I can honestly say that I don't like dynamic idle. I understand the idea behind it. but I don't think it quite works how people perceive it to. I feel like I constantly have to reposition the sticks during a long, smooth, slow banking turn. smooth stick input should equal smooth flight path. I'm pretty sure I can feel those moments that motor power is increased to meet min rpm after motor braking, and it's causing shifts in the flight path.

What never occurred to me until I saw the graphs is with dynamic idle Betaflight must have placed the min-throttle in a closed control loop using eRPM as feedback. Initially I couldn't see why this would be significantly better for prop wash handling given that DSHOT updates (and eRPM telemetry) are usually locked in at the PID loop rate (e.g. 4 khz). But then I realised the control loop using eRPM would have much lower latency in detecting and correcting a stalled prop vs the PID loop having to gyro inertial measurements to correct for the slower oscillating prop wash which resulted from the initial stall. Brilliant, thanks for sharing this.

Excellent explanation, as always. Been using dynamic idle for a long time and it really helps prop wash; set correct;y, similar to your explanation, it allows reduced prop wash without the adverse effect of too high a Dshot %age idle creating too much float. Simple calc to set dshot idle at 20% higher being (D.Idle X 1.2)/(batt volt x motor kv) which is a lot less than simply using dshot idle at a high enough percentage to give same effect

Interesting how educational movies from the 40's are still the best. I remember watching this aerodinamics animation before. Training films!

Lemme get my tea Edit: Ok. I've watched it. At your previous tuning video you gave a calculation for determining this value. My 5.1 inch prop quad calculations were about 18. Maybe it was a tad low. I will try 20 to see if i can notice any difference. Thanks for this video. I'm sure it will help to many people

Thank you

Perfect 👏🏼🙌🏼

Thanks Chris R

I had to stop the video 20s in cos I was laughing at the intro 🤣 U got a like for that 🤣🤙 - now I'll continue watching 🤓 Edit: Nice vid! I love dynamic idle. It's just the cream on top of a good tune

I put the Dynamic idle (50) on my Moblite7 drone and it flies completely different, i mean great! Thanks! Next will be my 5 and 6 inch drones

yeah I have a 2" CineRace 20 from flywoo and its propwash city. I have the dynamic idle up and still can't get the wobbles out. Going to try a higher idle percentage as well

Hi, thanks for the wonderful video Mr. Chris. I have a cinerace20, I love how it flies but it goes into terrible prop wash after some power loops. Do you think upgrading motors from 1203 5500kv to 1303.5 5500kv will help maintain higher torque and reduce prop wash?

Great video Chris! Would enabling dynamic idle help eliminate propwash on ducted quads just the same as explained here? Or would there be a different process to follow for a small ducted quad? I'm fighting very bad propwash on the cetus x and I'm hoping to eliminate that some. Watching a lot of your videos now for some ideas! Thanks for all the great content!

I liked this video👍, but I'm new. I would like to know in more detail how to set the idle speed?

Hi chris. This was a phenomenal explanation - sorry i'm late to the party! could one in theory use the current throttle position as a cutoff/indicator for the minimum motor RPM? For example, if i know my cinewhoop can descend at 30% throttle straight down without stalling (any more is bad) - can i interpret this information and use it to my advantage? I'm struggling a bit with cinematic shots where people wants me to descent straight down with a cinewhoop. In theory would bi-blades help reduce this effect because there is less drag on the prop? (an actual application for a sinusoidal prop maybe??) thanks again for putting this into visuals. I understood intuitively that some sort of feedback loop was happening, but I never fully understood it.

Great video! I've always wanted to learn where propwash is comming from. I don't use dynamic idle until now. But I'll definitely give it a try! Should I include it into my tune now or after I've finished following your BF4.3 tuning series?

What do you do in the case of a cinelifter? I would think you have to have a high idle value from the standpoint of load and responsiveness. I find if I make too much a drop in throttle position the bird comes down like a rock with low pitched props vs high pitched props. The low pitched props give me the best video, so I increase my idle value accordingly. I personally keep my moves to have long drawn out movements for the purpose of smoothness, but I can see that dynamic idle can help with smoothing those moves. I think with cinelifters it can be used, but the dshot idle percent value (critical to get right) has to be high enough to support the weight of the quad with respect to the prop being used. Great stuff Chris I really enjoy your channel.

Hi Chriss. Thanks for your videos. I have a doubt about Dynamic Idle. For more aggresive props we need to set dynamic idle rpm higher? That seems counter-intuitive. I'm using BF4.3 and Hurricane 51466 and found zero throttle problems that I solved rising Dyn Idle to 40. With a prop like Ethix S3 the quad flies well with Dyn Idle at 30. Can you give some clue about that?

Great explanation! I was wondering if the x8 offset motors is a good idea? Seems like a lot of dirty air.

Hi Chris, thanks for the good videos. What is the right DI for the AOS5 with iflight 2207 1850KV and s3 props?

Hello Chris, for me PropWash is mainly due the propeller going though its own wake, and turbulences. I'm not sure about your vicious circle, I think the FC is only accomodating with the air turbulences it faces. when piloting, you get propwash in turns and when going down flat. you can easily avoid propwash in turns by managing thrust efficiently: in turns, you have to counter the centrifugal force by increasing thrust so that your quad doesn't slide in the turn, and doesn't meet its own wake: easy, efficient, and doesn't require any tunning ;-) keep the good work.

I'd probably put a big disclaimer on just going with preset values. Most my 5inch quads are at about 19-20 when tuning via motors tab which is inline with what you say, but my AF227 are at 24 at 4% idle. Attempted to preset them at 20 and got a desync first flip.

In the 4.3 tuning notes, CT has some interesting ideas around putting the idle value below the dynamic rpm value. I believe to allow the separate PID controller on Dyn idle to do its thing at low RPM. Any thoughts on this setup?

I tried dynamic idle when it was first added. It was working OK initially but when I tried to fly a quad with a motor output limit, I got a desync. I could feel that much of a difference when using it and I think there may be a bug with using it combined with motor output limit. The recommendations on what value to set seem to be different depending on where you look for the information, at least it was the last time I looked. I can’t remember what value I had used but it was towards the higher end of the recommended range.

thanks as always, chris! I'm still a complete noob when it comes to tuning a quad, and still VERY confused about all the parameters and settings. for example, what's the interplay between "dynamic idle" and "motor boost"? thanks

I look forward to installing 4.3 and trying this. Could you help me understand a similar concept at full throttle? It seems to me that 1 or 2 motors will hit 100%, which means the FC can only provide stability control by decreasing other motors. Is it true to say that stability control at full throttle is inherently diminished, or is there some kind of dynamic full throttle pid loop that keeps all the motors hovering above and below 90%? I'm developing a quad that uses prolonged full throttle punch outs, so I am curious to find out if scaling the throttle to 90% allows The flight controller to act like a dynamic high throttle pid loop.

I turned this on my shendrones squirt V2 a week ago and it's made a large improvement. Do you know if the 4.2 implementation works the same as the 4.3 release candidates?

I personally like idle value a bit higher then default as it gives me longer and smoother drops when spit-s or powerloop, and a this movements it is easy to get in to the propwash. Setting up my main idle value to around or above 6% was great in reducing propwash in this movements but after adding dynamic idle (in my case at or under 25% less then main idle) it gave me almost no propwash at all. Everyone should at least try what Master Chris is suggesting and I promise you will get what you expect :) LESS PROPWASH :)

lift is greatest just before the stall but also drag is increased which would try to slow the props there will be an ideal relative airflow angle of attack like say 15 degrees where lift and drag are at there ideal compromise for best performance also giving better battery life... If you @Chris Rosser could elaborate on the pitch and blade amount assuming 3 blades used for the 30 mph tip speed used in the table this may further increase peoples better understanding to more accurately set there dynamic idle. heavier quads will have a greater reverse flow!!!! the thrust triangles are what is used in aerodynamic design but there is another triangle effect called whirl speed that is effected by pitch. also the raynolds number of each aerofoil which is not shown by each prop manufacturer will also have a small effect a nice feature from betaflight would be to have a dropdown like we do with the flight controller for props and motor choices with a preset that would adjust with quad weight would be asking maybe far too much lol

Are there any changes to the way you set this up in 4.3?

what setting to use for getting more inverted hangtime?

This helped me a lot with my 4 inch but I am getting some low throttle wobble. In Betaflgith 4.3 when you use dynamic idle you can't use Motor Idle Throttle Value anymore is there another way to address the low throttle wobble in Betaflight 4.3?

Я "молодой" пилот пришел в это Хобби 3 года назад, хотя в этом году "стукнуло" - 66 годков. По научному обосновать и объяснить физику процесс Вам ЗДЕСЬ!! нет равных. Joshua Bardwell - один из "ветеранов", но его научно - технические познания скудны, а исследовательская работа не его профиль, подергать стики да полетать в комфортных условиях его стезя. Ну и конечно долгие разговоры перед камерой. Ваша лаборатория повергает меня в "ужас"!!!))) а фильм про объяснения особенностей работы двигателей смотрел как захватывающий ВЕСТЕРН!!+++. Только выйдя на пенсию можно отдаться этому ХОББИ по "САМЫЕ УШИ" не боясь проспать работу или захрапеть в офисЕ))). Продолжайте делать ВАШУ учительско - просвятительную работу. С большой благодарность - Соколов Андрей. I'm a "young" pilot came to this hobby 3 years ago, although this year it "knocked" - 66 years old. To scientifically substantiate and explain the physics of the process to you HERE !! no equal. Joshua Bardwell is one of the "veterans", but his scientific and technical knowledge is meager, and research work is not his profile, twitch sticks and fly in comfortable conditions in his path. And of course long conversations in front of the camera. Your laboratory plunges me into "horror" !!!))) and the film about explaining the features of the operation of engines looked like an exciting WESTERN !! +++. Only when you retire you can give yourself up to this HOBBY according to "THE MOST EARS" without fear of oversleeping work or snoring in the office))). Keep doing YOUR teaching and enlightenment work. With great gratitude - Andrey Sokolov.🤠

I'm about to try dynamic idle for the first time on a 4" apex a value of 25

From someone with no clue: these values seem kinda high? Setting DI of around 67 for a 1.5inch (approx. my whoop with 40mm props) I'd have to increase the motor idle throttle value by so much, that it would be too floaty for my liking... good chance that I misunderstood something though. My thought process right now: Does the "idle throttle value" even do anything with DI enabled? You explained that the FC, with DI enabled, can command down to 0 throttle (so go below the motor idle value) and then controls the RPM according to the DI-value that I entered, correct? So, if it is controlling the motor according to its RPM, "motor idle value" now only acts as a trigger for activating Dynamic idle whenever my throttle-channel goes below the idle setting? In my understanding now: Whenever I move to idle power, Dynamic Idle determines the power to the motor to keep the minimum RPM as set in the "dynamic idle value". The "motor idle throttle" does nothing except trigger dynamic idle to control the RPM as soon as my throttle-stick moves below that value... but I'm sure there is a mistake in my thinking somewhere..

How about for tiny whoops? I struggle with a balance of min idle, inverted hangtime, and propwash/washout. If i try dyn idle at 67 on a 75mm whoop i have to increase min idle to about 15 from 5.5 to get rid of low throttle issues and then that kills any indoor inverted tricks. Secondly what about different blade counts? Logically it looks like a quad blade would have worse performance because of the unstable air coming of tail effecting the following prop.

Hi Chris, Thx a lot for the video.I followed your advise and propwash is gone. I've got one problem left.On full punch out, i am getting oscillations.I increased the throttle boost from 5 to 10, it made it worst.Do u have any quick tip on the full throttle punch out issue? Thanks.

I've actually not tried dyn idle yet would it also help with inverted tricks ?

Hi, I don't see the link you promised about enabling bi-directional d-shot. :(

I'm of the understanding Dyn Idle was basically rewritten in 4.3. setting it up should be the same, but it should perform better.

Is this still applicable for 4.3?

Nice Video. But at my BF 4.3 there is Motor idle gray, so I can't set this value when I use Dynamic idle. Is that new in BF 4.3?

interesting! using dynamic idle versus a variable pitch blade (heli's)?

When using Dynamic Idle my motors initially can't spin up. After giving it a throttle burst, they remain spinning. Is this normal, should I go back to regular DSHOT idle?

OK so, I have 5.22" props. I set my dynamic idle to 19. I then spun a motor until I got 20% more. For me it was 4.8 idle value at an RPM of 2300. So only thing throwing me off if I lowered my idle value but then I have bigger then 5.0" props. Am I on track here?

Just I wonder if Dynamic I. settings work for EDF quads as well?

Propwash is in its effects much like turbocharger surging or sudden unloading of an engine.

But with higher throttle idle the quad often becomes too floaty and I personally felt like as if it created sort of a deadband in low throttle control making it a bit tough to control the quad through tight gaps or even hovering it before a landing. Lastly i dont know for sure if dyn idle was the culprit but one of my lightweight 5" racers tend to bob up and down at low throttle and when i disabled dyn idle i got rid of it.

Great video The part of how to set it I disagree it should be as dev recommend it is related to motor kv and size (rpm) and not the prop size The start of the process should be the max idle value you find is suitable to your like and bring you great prop wash and floaty feel ,with not too much for efficiency , and then tune with proper motors tabs , sorry but not all features can be converted to simple user , there is some advanced user features , That needed to be handle carefully

Hello, an important question for me, when activating Dynamic idle can I have the Airmode activated? I don't know if I should do it in case it cancels the Airmode to Dynamic idle

My dynamic idle sits at 40 on a 5 inch eberything lower and its just dropping like a stone

My idle at 7% is 20 dynamic idle amount.. so i set it to 12 on one profile and 15 on another to test

So if the whole point of dynamic idle was to increase stability, but it ruins stability at 0% throttle, then is it worth it at all? I've been using it to try to help my low- throttle wobbles, and have had to set idle % values at like 14% on 6" to 10" rigs, which has been totally ridiculous and has ruined my inverted hangtime and dive abilities. If what you say is true, then I'm going to go back and turn off dynamic idle on all my quads, because it seems like a losing proposition. Why does it result in the need for super high idle %, anyway?

I experience wobbling when the throttle is at zero after using the 'Dynamic Idle Value [* 100RPM],' but in BF 4.4, I can't change the 'Motor Idle Throttle Value [percent].' How can I fix the wobbling issue?

This is interesting, but I must admit that I'm like JB and have written off attempting to tune dyn idle long ago... IIRC it occasionally introduced desyncs or tuning issues that I would have rather avoided entirely. I'm curious, however, to plug in these values and see how they work with some idle tuning. Do you think your table would apply to 4.2.x fine?

In betaflight 4.1.7 works fine without any tunning, due that not appear and I suppose that is with cli. All my quads still in 4.1.7... Except the 4" iflight whit this feature turns off

I am having some serious bounce back when I chop the throttle on roll and pitch , and I just can't figure this out

Has anyone here encountered uncontrolled altitude gain when the only variable they’ve changed from stock BF settings is dynamic idle? I have a light 3” Roma L3, fresh build, and as soon as I add dynamic idle it just takes off at 1/4 throttle and keeps climbing until disarm.

Look at my flippy floppy vtx antenna, it's so flippy floppy 🤣👍

5:00 lol i just tried this on a 5 inch and it didnt budge

Lola now I have to actually watch the videos 😬

just so u know when u activate dynamic idle, dshot idle is disable

How does this relate to airmode?

I am not sure I agree with the stall point/flow separation explanation as the root cause but interesting none the less.

So what about 31mm props? That’s not listed in your board. And tip speed means what for whoops, or anything? No offence but seems your video creates more problems than solutions. Relax before you drown in fpv delusions of grandeur, like so many.. hint hint next commenter

quá hay. ngày mai tôi sẽ thử :D Rất cảm ơn. Trân trọng từ Việt Nam.