Another great video! Thanks Chris. I have been flying props-out on all my quads for years for all the reasons you mentioned. I fly everything from whoops to 5" drones and I fly both freestyle and racing, at all sizes. I agree with your points, but I think there is actually more that could be said on the topic. Here are a few things that might be interesting to expound upon if you ever feel inclined: 1) You showed the combined effect of roll and yaw, but not pitch. The ratio of each will depend on the maneuver and on the amount of camera tilt. If you ever have a coordinated turn that involves all three axes at once, the effect can be even more dramatic (a single motor can be tripple-slowed or tripple-accelerated to accomplish change on 3 axes at once). 2) In my experience, micro drones are affected by prop direction even more than larger quads. I believe one reason is that micros are often flown at higher throttle (using most or all the thrust that is available), whereas larger drones have so much thrust on full throttle that most people use full throttle more sparingly. If a micro drone is already in a high throttle maneuver then it may not have a lot more torque in reserve. Thus, the FC might ask it to speed up to accomplish double or triple duty in a coordinated turn, but it might fail to do so. 3) In my 65mm whoops are affected by prop direction the most. I believe the reason is that the props are tucked in very close to the canopy and the canopy typically rises high above the props (relative to the distance). In a fast forward turn, the canopy badly disturbs the airflow over one of the back props, especially on the inner side of the prop. Everyone I know who races whoops runs props-out. We have even had new pilots show up with props-in whoops that struggled on the turns, and we helped them switch to props out, and even the new pilots could feel the difference in stability. 4) All the assumptions here assume airflow is coming from the front. That is true more than any other direction, but certain moves might involve significant airflow from the side, or even airflow from underneath (such as pulling out of a dive). It would be interesting to discuss how those situations are affected by prop direction. 5) I have seen one case where props-in was clearly better. If you have a whoop that is heavy for its size (like a 2-3S whoop, or a whoop with an HD camera), and you fly props-out, then you might find that it experience yaw "wash outs" (undesired yaw spin and wobbles) while pulling out of dives or power loops. If the drone is light enough, it won't happen at all. In that situation, I have found that switching back to props-in significantly improved stability. Unfortunately, switching to props-in makes those fast forward turns worse, so I still choose props-out. Side note: adding a carbon stiffener also reduces yaw washouts (heavy whoops flex more than people think in high G maneuvers). Nothing contradicting what you said, just some interesting cases to consider. Cheers.

Props out is my preferred setup. Started with props in, made the switched never looked back👍🏻

FPV meets science - thanks again Chris.

I'm going to try props out today! EDIT: I'm back after absolutely amazing flights! For my 2.5", switching to props out improved throttle response and significant prop wash reduction. I typically have trouble keeping altitude doing a tight orbit around a post/flag. With props out, the quad felt like it was able to keep altitude by responding closely to stick input.

Excellent video Chris - The 'Aerodynamic Efficiency' you refer to is commonly known as the Asymmetric Blade Effect among General Aviation. This is one of the reasons why a propeller driven aircraft will yaw to the right upon rotation. An interesting point to note is that when the quad is flying in fast-forward flight (straight and level), the outboard phase of the propeller will be generating more lift than the inboard (assuming props in), thus moving the effective point through which the torque (relative to point zero - for this we shall define as the centre of the frame) acts on the frame, further out. This increases responsiveness and authority as proven by T = f.d as the moment arm has increased in distance from the fulcrum. Contrary to this, when operating in a props out scenario, this moves the effective point through which the torque acts in the opposite direction (as the propeller generates differing amounts of lift throughout the cycle due to the asymmetric blade effect) which, logically, reduces responsiveness and authority. A common misconception is that the rear motors are working harder due to the 'rear section of the quad being pushed down by the oncoming air'. This is not always true. This is purely dependent on the position of the centre of pressure (COP) and centre of gravity (COG). If the COP is forwards of the COG, this will push the nose down, requiring the front motors to work harder. If the COP is rear of the COG, this will push the tail down, requiring the rear motors to do more work. The COP can change depending on the relative profile (effectively the angle) of the multirotor to the oncoming airflow and will not always be constant. I'm surprised that manufacturers haven't started developing forms of natural aerodynamic stability or instability into their airframes like they do in aviation (look at dihedral on a passenger jet and then the anhedral of a fighter jet). Take this with a grain of salt, I do not have an Aerospace Engineering degree, I only have a Commercial Pilots License with a thick interest in aerodynamics and physics.

You convinced me to switch to props out on all my kwads. I know what I'm doing tomorrow! Great info, Chris!!

All my drones are in Props outs, I always told people that out is pure commonsense in many ways. Like swimming 🏊‍♂️ Front Crawl in witch is most effective just like Props Out! Physics always win over ignorance. Great Job!

thanks for this, its great ;) just want to add for authority in turns: props out is also better because if you fly straight forward the rear motors do work harder than the front ones, so the extra work in turns in props out configuration do not add to the rear ones too, which also leads to the advantage of props out

This is 2 years old and I am not sure if anyone will read this. However I have three AOS T3 quads in different configuration. I asked Chris about tuning because I was having issue with at least one of them. It bobbles a lot. Chris suggested lighter props which I bought. It helps but not the one that bobbles. Then I noticed I was running props in on that particular quad. After changing rotation direction of the motors I am now flying props out on the quad and it is behaving much better.

Can't wait for the tunning content mate. Thanks again for sharing your knowledge.

Awesome video, thank you for doing this! It answered everything I was pondering, and clarified my main sticking point which was reversing props should just "flip" torques. I hadn't thought of the clean vs. dirty air issue with the front props and advancing/retreating blades. Also made me happy that I didn't waste my time swiching quads to props out this week. 😅

I turtle mode so much, with props OUT, turtle mode covers my lens with junk (or pits the lens with rocks) during reverse direction. Therefore I only fly props IN. This way, turtle mode doesn't make it impossible to see (or ruin my camera lens) when I get back upright and flying. I conformal coat everything, and use plugs in my USB ports to keep wet junk from killing my electronics, since turtle mode throws stuff into the flight controller. 🤣 Nothing else matters to me since I claw my way out of pretty much everything using turtle mode. LOL When I crash much much less both racing and freestyle- then I'll go back to props out. Great video, though. Mad props to ya!

An amazing explanation to what can be a daunting subject to get your head around. Nice work.

Awesome Chris. I am so glad we got to chat about asymmetrical loading and glad you included it in your analysis and breakdown in this presentation! Awesome job!

Thank you chris, really the whole explanation is very clear to me. You are on the top of my list for my "Support you on Patreon", when the situation improves. Thanks for all your effort to share your knowledge with the rest of uss, Very Thank you.

I started running props out when people started saying it was better for whoops and I just wanted to keep it the same with all my quads. Thank you for these videos, they're great :)

Thank you Chris. You just answered every question I've had about this topic!

I think one important consideration regarding clipping objects: if you fly around a lot of trees, in my experience, props in is more likely to let you continue your line through things like ghost branches, where as props out will tend to deflect you away. I prefer to just plow through those light obstacles. second consideration: cross-coordinated rolls have the exact opposite effect on authority: front motors work harder props in. this is irrelevant to racing and cinematic, but smewhat relevant to freestyle, considering any roll move when shooting footage you want to cross coordinate, otherwise your shot is just spinning around your camera angle. Of course, throughout the flight, coordinated turns will likely be more present than cross coordinated rolls. third, taking freestyle in to consideration again, Im not sure that forcing the front motors to work harder in turns is advantageous when you consider that the front motors are closer to a gopro, and thus are already working harder than they should be considering they have to work a short torque lever situation with that vertical weight. It seems in that scenario you inch closer to motor saturation sooner. lastly: shouldnt we use some sort of fluid dynamics simulation to determine the difference in advancing/retreating turbulence? I ask because, in your diagram, you seem to gloss over the fact that in props out in, the more turbulent air on the outside edge at least has a clear path to the rear prop, whereas in props out that more turbulent air is directly next to the body of the quad, and I have to imagine that is going to _something_ to that turbulent air.

Very interesting and useful... I wait the pid tuning video! You are great man!

I too switched to props out a couple years ago. Nice to see a good theory breakdown on it.

This is a perfect summery of my own thoughts on the topic back when the in/out discussion started around 3 years ago and I flew all my quads props out ever since (not that it would make any difference on the skill level I am at).

Best explanation ever found I'm a new subscriber, keep up the good work.

Awesome analysis! I will definitely try props out!

I would be interested to hear your take on "pusher" whoops vs. traditional whoops. People like to say that pushers are aerodynamically superior because the frame does not block the air that exits the prop. However, with a "pusher", the frame does block the air that is flows into the prop. Isn't that just as bad? I have never observed a benefit in performance, but I have not done an apples-to-apples comparison, so it's hard to know for sure. For me, the main advantage of a pusher whoop is that it is easier to mount an HD camera near the front, where it won't see the guards. The main disadvantage is that you can only take off from a perfectly flat surface. If you try to take off from grass or dirt, you'll probably just make a mess of things. Anyway, the difference between clean air in vs clean air out could be an interesting thing to discuss in the future, if you're interested.

Wow very interesting. I always thought it was mostly a symmetric system when to end but when you couple a turn and realize you’re also going forward then it’s not at all symmetric. Very cool!! Thank you.

You are the MAN Chris and what you just explained makes good since brother so I'm switching to props out. Thanks good buddy.

I always run standard rotation but this video just made me decide to try “props out” as there is a clear scientific explanation about the benefits of it. 👍🏽

An Idol Chris, really blow my mind every single video of your!!! FPV BIBLE!!! THANK YOU 🙏🏻😊👏🏻👏🏻👏🏻👏🏻

After watching this, I had nothing much else to do so I figured I'd swap on my EMax Hawk Pro to props out (did put a new set on for complete fairness), and ran a few packs thru it, decided props out actually feels better. Amazing video, absolutely love the deep dive analysis on the individual subjects!

I have both and after watching this video all the facts make sense, and the glancing reaction to scraggly and what not makes it all worth while to go with pros out rotation

Thanks Chris. This is exactly what I have been testing and was hoping you would get to it. MrShutterbug (Nate Payne) opened my eyes to props out with his Beta75x washout tuning a couple years ago which dramatically reduced the insane yaw jerks on that model. I now run props out on the majority of my fleet. 🙏

Subbed! This is the first of your vids I’ve seen. This is great stuff!

I really enjoyed your scientific explanation :) I have been running props in all the time, cause its the default on betaflight, but after your video I am defenetly trying out props out now

Amazing job explaining this subject matter. Thanks 🙏

I've only ever run props out on indoor toothpicks to help bounce off when clipping objects. Most definitely going to explore props out on the other quads after watching this! I really like your copter physics videos. Thanks for sharing.

Thanks for the break down. Never thought about maximizing authority and aerodynamic efficiency. I have a quad that resonates going forward but not backwards. Just swapped motors a second time. Going to test lower kv then will try prop direction next.

Great video, actually made me change my prop direction to props out

I used to run props in back in the day. I switched initially because of camera fouling but quickly noticed the slightly better flight characteristics and bouncing of of branches instead of being sucked into them. Been running props out ever since. Thanks for showing the science behind it!

Another awesome one! Always liked out more, now I know why!! 😁

Nice So i been doing it right all the time :) Thanks for this great preparation and presentation as always :)

Iv never run props out. Will 100% give it a go! Thanks Chris!

Amazing content! Going to switch to props out and see if I notice. It would be cool to try to do two similar flights back to back props in versus props out and compare box logs.

I crashed my 5” quad and had to replace my esc. After doing that and making few other adjustments, (Lighter battery straps, less tpu mounting, no motor wire sleeving) The quad was actually 40 grams lighter. But It flies noticeably worse, the motors run hotter, and low ground passes were harder to pull off. I adjusted the pids and noticed I can’t push them as far. The only real variable that would make performance that much worse would be my prop direction. I got lazy and hate using bl32, so my motors are running inwards now. Never knew it made that big of a difference, I just ran props out because I used to crash my whoops often.

As usually really good content, nice to follow you

Amazing content. Thanks for the info dude!

O well at least I got half of my fleet with props out and my last build will change it to prop out. And check it out . Thank u for this video.

Been props out since I started flying fpv with an Eachine QX65 whoop. Project Mockingbird recommended props out to improve performance, went props out on all my builds since then. This video explains why. Thanks for sharing. 👍🤓

I can't wait until JB sees this. Will he finally change? It's great to finally see it all laid out so clearly, and finally someone that knows what they're talking about is getting some traction. I'd also not really considered the retreating blade effects. I believe the advantages it gives in cornering has been fairly well known in the whoop racing world for a while

Amazing explanation👍🏻

always props in for over 5 years :) Good video Chris.

Honestly, when I just started watching this video, I thought the final conclusion would be less definitive, with both configuratios having their advantages and disadvantages. I did not expect the 'props out' to be such a clear winnner... Personally, I started on the default 'props in' config, simply because this is how my first quads (Emax TH ii whoop and TH ii Freestyle) were set up by the manufacturer, but as soon as I learnt how to reverse the props I switched to 'props out'(I first reversed the motor direction by swapping wires, because I didn't know yet of BL Heli software 😶) and never went back to the 'props in' on any of my quads again - whether I build or buy kwads I always make sure they run in props out set up. It's reassuring to learn that there are other important reasons for running the props out, beyond just not wanting the kwad to look like a dirty lawnmower 🙄

Great explanation and detail! Thanks. Been flying props out for ages because it just ‘felt’ good. Now I know why.

Wow! Subbed! Thanks so much ! U made me switch to props out

Great video, I've always run props in because it's the betaflight default and I am lazy, but now I am definitely thinking of switching.

Thanks for the awesome video

Wow, super impressive explanation again. Thanks!

so interesting! even for a newbee! Thank you!

Thank you. Very informative.

I decide to use all my quad is props out , because i never using props in before. I just like it. And feels better, than my friends quad which they always using props in.

I subbed to ya, very informal and you do an amazing job, thats the least I could do. Thank you!

Cool! I will try props out. I've never tried it. I should be able to notice difference since I've been flying props in for close to 2 years now.

Great video thanks for the information!

Great video!

Thanks for another great and informative video Chris. I tested props in vs props out on low authority whoops to see if I could eliminate washout problems. With props in I would get uncommanded rolls during a washout, and with props out I would get uncommanded yaws. Washout would cease to be a problem if the quad had enough authority. Washout was also reduced by making sure I gave the quad extra throttle during a hard turn. On a quad with good authority, I had a hard time telling any difference between props in or props out, but I need to do a lot more testing on that as my flying skills have improved greatly since my initial experiments. Thanks again, I am grateful for all I have learned from you.

OK.. so this is just brilliant!! thank you for this.. thank you!

Thanks you for all the good work keep it up👍

started with the nazgul5. and it had props out, so ive just continued using props out on all my quads. happy to know it should be a little better :)

Good video again, I run all my quads pros in. Just because it is default. One time I experimented with reverse direction but when I got a broken prop and replaced it on autopilot with a new prop with the prop in direction the quad was almost eating my face at arming😝 so after that incident I never did it again. But your theories sounds interesting so I will give it a new try. Thx

Great explanation!

For the reasons you give, I generally run "props out". However, I am currently building a cinewhoop. With the ducts/prop guards cutting down on the crosswind, many of the advantages of "props out" don't matter any more. So I think I'll go with the Betaflight default of props in for my cinewhoop.

Great video. I wonder why props-in is/has been the default for most firmware given that props out has so many advantages. I think the biggest downside to props out is, you basically have to do it to all of your quads or none of your quads (to avoid confusion), and since props in is the default, I think most people just deal with it being a slight disadvantage purely out of connivence

Subscribed! I'll give it a go on my quads.

This raises the question, why is the default "props-in"?

Been running props out for over a year for the exact reasons you pointed out

Thanks, I may give it a go.

Great video mate 👍😎 I’ve been running props out for a long time for the reasons you mentioned but didn’t know about the potential aerodynamic benefits. Theres another benefit to props out if you run rx antenna backwards off the rear arms etc. they are less likely to be damaged by a prop strike, turtle mode aside. There’s two caveats I would say. Don’t land or take off on long grass, or disarm quickly when landing, or your stack will get covered in it. And best to have all your quads in OR out, a mixture can easily end in putting props on backwards which can suck big time 😂

I switch to props out on my 5 inch apex and I will not be going back to props in. I now have the ability to skim some pine needles or leaves on a tree and instead of getting throw into the tree I can now cut right threw them and continue in flight. nothing but positive response from my quad 👍👍 building a fresh quad today with pg-44a grease, really excited to go fly Ill post my maiden flight this evening ✌️ Chris you're awesome thank you for all u do ! epic flight video today ! I had a feeling you had some skills 🤘 👽

Thanks again Chris 👍 props out 👌👍

I would run props out on all my quads until 2019 I was building a 40mm propped tinywhoop carrying a naked gopro. For months it was unflyable until one day i went from props out to prop in as a last resort to try it out. It flew amazing. To this day I make all my whoops run props in but all my bigger quads run props out.

Man I really love how you "build the house" in getting to the conclusion. Both in this video and in the ducts video are great examples. Although this begs the question why is props in so prevelant or is this one of those things where it just so happened that way (like clockwise clocks).

Thanks for the info

I absolutely can with out a doubt can tell a HUGE difference when I clip a tree or even a post. I probably bounce off at least 50% of the time, depending on how hard I clip something. Sometimes it’s amazing how well it works. That is the main reason I ONLY fly props out. I don’t know why it isn’t the standard configuration. I have definitely noticed other advantages, but now see more through the turbulence diagrams. I always FELT that it flew smoother, and just makes more sense to me.

When i switched to props out after the first few months of flying, I never went back until recently with iNav. It started mostly with wash out on whoops when coming out of a dive, etc.

Complimenti Crhis...domani provo a invertire, e mi iscrivo subito al tuo canale,finalmente qualcuno che parla di questo argomento interessante.Grazie👍

I never thought of trying props out. Until I bought a Iflight xl5 BNF. That came props out. I did notice slight differences compared my built iflight Xl5

@snakefpv used to do blind tests all the time...i miss those. This needs a blind test.

I'm certainly loving all of your videos and the information you provide based on science... but I gotta say you're probably going to make an enemy of Joshua "FPV Know-It-All" Bardwell LOL. The other day I listened to one of his podcasts and he made some snide comments about your frame greasing recommendation, and now you're recommending Props-Out configuration while he has recommended Props-In for basically forever. You should make your motto "And today you're going to learn something... based on science!"

I fly props out from the beginning.Tnx Chris

Would be interesting to see a blackbox log. Fly the "exact" same path with the same quad in the two different configurations and everything else equal, and discuss the difference=) I'll switch to props out to check this out! I've always ran props out on my 3", but the 5" is props in.

Wow this is really interesting and helpful. All of my drones came on the props in set up. My tiny hawk freestyle 2 would greatly benefit from props out because I fly around lots of vegetation! I wonder if props out would reduce the shudder I get with my 75 mm tiny whoops when I am descending... thanks for this great video!

Thank you for the vid. To be honest I never really noticed anything different Performance wise with either prop direction. Lol whichever direction the props spin from start of a build and the convenience of which arm I just so happen to be working on usually influences the prop direction of my builds lol. If one should fly Fpv and rely on the quality of the image then props out.

I use to only run props in and switched this year and it is way better

The back motors work harder anyway because we fly pitched forward which means there is a bit more drag pushing the rear down and the motors work harder to maintain that angle. So by running props out we basically relieve the rear motors. Credits: JB

Thanks, had not thought about switch prop in vs out direction, just used the default betaflight. After your video I gave it a try and men I just got an extra 3 to 4 minutes flight out of my quad, from nearly 9 to 10 min to over 13 minutes. Not to mention banking turns are much smoother plus better turn control in general. Same quad, battery, blades and that in heavy winds... flying a light weight 5" which is setup for long-range. just around the 250grams

These videos are so good and informative but so hard to get through, not that it's boring just to long and there's only so much time in a day.

Barely hitting a twig in a tree and getting sucked into the tree, causing camera wires to be cut by props made me go to props out. That's never happened to me again.

I run props in because I prefer to take 5 seconds once in a while to clean my camera than risking to short something on my FC or ESCs because of wet grass projections (and spending much more time cleaning electronics). But statements about authority and aerodynamic are very interesting and make me hesitate to switch... ;) Thanks for the video !

The only caveat to the camera issues is if you use Turtle mode in areas that have gravel and loose aggregate. If you run props out, they'll be throwing rocks and gravel at the lens of your camera. I have a runcam hybrid betnow has a textured lens do to sand getting thrown at it while in Turtle mode. The issue is soft pretty easily though, it's as simple as not using Turtle mode when gravel is present

Luckily the difference is so pronounced to feel its really not a difficult switch. I honestly think steel is the only guy who runs props in just for its yaw feel specifically. Rest of us peasants already run props out.

My first quad build was prop in. At the moment, my most recent build I'm running props out for the first time. I feel like I have better control on the roll axis with props out. Props in feels like I have better control on the pitch axis. I also feel that acceleration is a bit different in forward flight and during punch outs or last minute throttle recoveries. I feel that I get less thrust with props out but it might be the tune. Both my quads are generally identical in frame and components. I've only been flying quads for over a year so it's just an observation. It would be interesting to see if there's a difference in frame resonance with props in versus props out.