Podcast: Scared of Flying Boeing? Nature Might Be The Solution

In this episode, we explore how the mechanics of bird wings are inspiring new approaches to prevent airplanes from stalling and learn how bio-mimetic designs from nature are paving the way for innovations in aviation, enhancing stability and safety for future flights.

Episode Notes

(0:50) - Bird wings inspire new approach to flight safety

Become a founding reader of our newsletter: http://read.thenextbyte.com/

Transcript

What's up folks? On today's episode, we're talking about how a single bird feather might change airplanes forever. It's a team of Princeton engineers who studied special feathers on birds called coverts and how they affect the way that they fly super safe and super stable.

I'm Daniel, and I'm Farbod. And this is the NextByte Podcast. Every week, we explore interesting and impactful tech and engineering content from Wevolver.com and deliver it to you in bite sized episodes that are easy to understand, regardless of your background. 

Daniel: What's up homies? Like we said, today we're talking about flight safety, airplanes, the problem that is stalling that I didn't really know was a problem and how a team of engineers from Princeton are studying birds to try and fix it. Super interesting in my mind. I don't know what you Farbod, like I played a bunch of flight sim type games like Call of Duty, World War II era stuff with planes that were fun. And definitely like if you pulled the plane up too far and changed the approach angle to the wrong angle, you could, you would get a stall warning and then the plane starts to like fall out of the sky. That to me felt very far separated from something that people in actual contemporary aircraft today experience actually while flying. But we did some research coming into this podcast episode and we're like holy cow, man. So, stalling contributes to about 50% of total recordable accidents in general aviation. And you've got one related to the percentage of stalling and its incidents in terms of fatal accidents too, right?

Farbod: Yeah, so I got a stat from the FAA. They say more than 25% of general aviation fatal accidents occur in maneuvering phase of flight. Of those accidents, half involve a stall or a spin scenario, which is pretty frightening because I did not think that stalling was something you should be worried about in this day and age with airplanes, but apparently it is. I was kind of in the same boat as you where stalling was only a thing that I thought happened in video games. I loved pulling it in battlefield. I would get in the Russian plane, the Su-57, do a little stall, watch them go past me, shoot them down. But no, this is a real thing that can affect passenger flights.

Daniel: You were doing some stalling in the Russian plane.

Farbod: I know. I set you up real nice there, didn't I?

Daniel: Thanks, man. But yeah, it's crazy, right? The incidents in actual contemporary modern aircraft. Farbod, I want to escape the passing of the Boeing Reaper, but you had something related to Boeing as well, right?

Farbod: I did, yeah. I hope we don't make it on the naughty list for Boeing, but there was the whole scenario with the MCAT system that came out and remember it was my last year of college I was taking an aeronautics course. And the whole reason it happened to begin with was because Airbus their competitor came out with a much more efficient format of their regional jet and Boeing had to compete. And the way they decided to compete was instead of designing something new they just put on bigger engines. Now those bigger engines weren't really made for the height of that plane from 40 years ago and occasionally you could have an issue where in a certain angle of attack during takeoff, and that's the angle that the plane is, the nose is tilted up, you would have flow separation where the air that's sticky around the wing that's giving it lift would separate, cause it to stall a little bit. And then the MCAS software, it would point the nose down just enough for the float to come back. The problem as we know it now is that the nose was pointing down far too much and it wasn't auto correct. So, in recent history, a lot of the fears that people had about flying, I remember there was a period of time where people that even we knew would not get on a flight if it was a 737 MAX that had the MCAS system.

Daniel: I mean, dude, there was a time where I'm looking at two equivalent flights, right? Similar time, similar location, similar carrier, similar price. And if one of them was on a MAX 8 and one of them wasn't. I made the right decision.

Farbod: Yeah. And again, it's crazy to think that the underlying problem that was causing all this was like stalling. And you would think that that's not an issue anymore, but lo and behold, between the stat that you shared and I shared, it's prevalent.

Daniel: Well, and just for folks to understand, right, who didn't take an aeronautics class like you did, right, I'm trying to understand and explain stalling and the most simple of terms and I'm trying to use a shared human experience here. When you're driving, especially as a kid and like your parents rolled the window down and you'd stick your hand out of the window, like kind of like a wing. And if you tilted it up, you could feel like a little bit of lift, like pulling your hand up. That's exactly how airplane wings work, right? The wings are slightly tilted up so that the air on top of the wing has lower pressure and the air underneath the wing has higher pressure and it lifts the plane up. But imagine if you were to turn your hand too far sideways, right? So as opposed to being angled slightly upward, it were almost angled crossways versus the wind, that lift effect would stop and the air would actually just slam into the wing and pull your hand backward, slam into your hand and pull it backward. Similar effect happens on wings when the angle of approach and the wind speed end up being too funky for one another, the airplane actually can lose up to 100% of its lift and quite literally start to fall out of the sky. Similarly to the way that if you were to turn your hand too much, you would catch the wind the wrong way and your hand, instead of being lifted up gently into the air, get slammed back against the side of the car door. And that's my simplest way of explaining it as someone who's a little better educated than I did. I do it. Okay.

Farbod: I don't know about better educated. I'm pretty sure you did better than me in fluid mechanics, but yeah, as always you nailed it. And the only thing I wanted to add to that is at the end of the day, air is a fluid. Right? And the way that you get lift is by having that fluid stick to the wing. When it stops sticking, that's when you don't get lift and that's when stalling starts to happen. You and I, we're nerds, so we love sitting by the wing whenever we're flying. I always love looking at the wing when I'm taking off because occasionally you can actually see a slight flow separation before the flow restores itself. You know, because the angle of attack is really high, you're taking off. So that's always exciting to see. But, for folks that don't know that that's what's happening. I guess quick crash course on how wings operate. You hit it right on the head. Money is always.

Daniel: Wonderful. Thank you. But then I guess another shared human experience here is no matter how steep of flight a bird is in, no matter how gusty the wind a bird is in or in a complex flight pattern, I have, I don't think ever have yet to see a bird just fall out of the sky, in open air fall out of the sky. It's a little bit different.

Farbod: Unless they wanted to and they were hunting.

Daniel: Yeah, unless it's on purpose, right? And so, a team of engineers from Princeton are like, all right, let's study bird feathers. Let's understand what about the bird wings are, is it something in the structure? Is it something in the shape of the feathers? Is it a specific type of feather that is deployed during flight to help keep it steady? And they looked at a bunch of different feathers. And I think it was the covert feathers. Is that the right one?

Farbod: Yep.

Daniel: The covert feathers, they were like, oh, these are these are really, really interesting. And they found that covert feathers on bird wings are one of the ones that has the highest impact on their wing stability, on their lift and control and lack of stalling, even in critical flight angles. Which I don't know, crazy to me that you can find a specific feather in the bird wing that's super important, but needless to say, they take the inspiration here and are trying to take this into the aviation realm by updating the design of an airplane wing.

Farbod: I was going to say, as a non-expert on birds, when you Google covert feathers, it starts to make a lot of sense why they're able to operate the way they do, right? You have these bigger feathers that do the bulk of the flying and whatnot, and then you have these covert feathers that are actually like layered towards the back, like filling the gaps of the bigger feathers, and their textures are a little bit different, they're usually smaller in size. So, where the big feathers might lose the flow, these little ones are able to recapture it, right? So, like, whoever engineered birds compliments the chef. This is good stuff they got going on here. And what's more interesting is that the folks at Princeton aren't the first ones to notice this. Others in the field have taken recognition of this phenomenon and they've tried to integrate it into different aerospace applications, but a lot of them have just focused on the geometry and the location of it and missed a very critical component, which is that covert feathers can actually come in layers. And that's where the Princeton team really made their sauce happen. If it's like, I don't know, what's like a secret ingredient you would put in a delicious sauce, little cayenne pepper, little smidge of…

Daniel: I don't know. I'm not telling you my secret ingredient.

Farbod: Really, even after 200 episodes?

Daniel: I guess, yeah, this is an important point to mention. This is our 200th episode, everyone. I don't know, slight aside here. Kind of crazy, we've been doing this for so long, almost four years.

Farbod: Longer than we went to school together. We actually found that out right before we started shooting this episode.

Daniel: Yeah, we were reminiscing. And here's another bad joke. We have been potting, podcasting, longer than we had been nodding. Boom.

Farbod: Wow, you really, I mean, kudos, that was good.

Daniel: Thank you.

Farbod: Good for you. With that said. Let's get into what these folks at Princeton actually did by understanding that these covert feathers could have a lot of value being in rows instead of just what their geometry is. And they were like, we want to understand the underlying physics here. What's actually happening? So, they did some work and the work that they did was in a wind tunnel. So, wind tunnel in movies, that's where you always see the streams of air coming, looking all fancy, moving around a car, like, they're streamlining it. Well, they do it a lot for aerospace applications. They had an airfoil, like, I think a piece of a wing in there with the air stream moving, and you could clearly see where the flow is separating at a certain angle of attack. Then they started adding these covert-like feathers, these flaps, onto the wing and saw the impact of it. What the main takeaway was is that, on the leading edge, the front of the wing, as you start adding flaps, they, I'm trying to explain this to the best of my abilities, where the flow separation happens, keeps getting passed further and further and further down, which is beneficial because it means that the flow is sticking onto the actual wing for a longer or a more generous portion of its surface area, right?

Daniel: It basically meaning, just because of the geometry of the flaps here, right? Adding flaps in layers like covert feathers on a bird, you're essentially eliminating a portion of the original wing design where the flow would have separated and you would have lost lift completely. Now you're recovering a portion of that lift and making it so that the plane continues flying as opposed to falling.

Farbod: Correct, and they call it the shear layer interaction. Right?

Daniel: And that's at the front edge of the wing, right?

Farbod: Correct, yeah. And they tried a bunch of different combinations from no flaps to five flaps, from having only one in the front, only one in the back, to like two somewhere in the middle, to all of them populated. And I'm so frustrated because they didn't put this on the Wevolver article, but they did put it in their research paper. And it's so well done that just by glancing at these videos and these pictures, you can understand what's happening. So, you know, criticism of mine, why did you guys do this? You had all the material. It would have been a killer. Anyways, there was another thing that they wanted to study. So, this shear layer interaction, this is additive. So, the more of these flaps that you add, the better the performance becomes. Then there was the pressure dam, which is what happens if there's like a gap and the flow closes and opens back up again, do we see any kind of additive benefit there? And you really don't. In terms of everything that was discussed in this paper, that was the most insignificant one, in my opinion, whereas the shear layer interaction one added the most value. And that's pretty evident in terms of the results as well. They did this stuff in a wind tunnel. Eventually, they partnered up with another group at Princeton who does RC plane stuff. And they incorporated these five rows of flaps onto the RC plane and they noticed the exact same type of performance benefit they were seeing in the wind tunnel. 45% increase in lift, 30% reduction in drag, which is crazy because I thought it would add drag and enhance the wing stability. So, stalls and stuff like that were not as frequent.

Daniel: Well, and before everyone goes and complains about like, oh, you can't add this many parts to planes and you can't add this many moving parts to planes, right? Because there's a lot of complexity associated here.

Farbod: Right.

Daniel: I'm with you. My mind went to the exact same place. So, I ran sprinting to the study just now, like literally 30 seconds ago when Farbod said, they've got awesome videos on here of exactly what they're doing. We've got to just like the study at this point as well. Right.

Farbod: Yeah. We'll link both. Cause they're good.

Daniel: You got to check out the video. It's specifically the one that I'm talking about is movie S seven, which shows real time video footage of flap deployment on board the autonomous flight demonstrator. Check out movie S seven. Cause it shows you exactly what these things are. It looks like a row of sticky notes, five rows of sticky notes stuck to the top of the plane wing, right? It's not mechanically actuating. They have flaps there, just like these feathers, which aren't controlled necessarily or to an extreme extent by muscles, they're just attached there. And when the aerodynamics become correct around the geometry of the wing, because the attack angle is steep and the relative wind speed is low and the wing starts to stall, these flaps extend and help reduce the amount of stalling that experienced, it help reduce the amount of drag that's experienced and help increase the amount of lift that's experienced in one of these stalling scenarios. Definitely super interesting to check out helps me understand this and honestly helped get rid of one of my criticisms right off the bat, right? Which is like, hey, this isn't like an actively electronically controlled, mechanically actuated system. This is actually something that happens relatively passively. And when they say autonomous deployment of these flaps, they really should say that the aerodynamics of the wing make it so much that the flaps lift up all on their own and start to work.

Farbod: Yeah, and in terms of another, I think it might actually be in the same video that you were talking about. They have a curve of the pitch of the plane as it's starting to stall and the air speed and you can directly see the effect that these flaps have on the restoral of the performance of the plane. And that's so impressive to see. I was also concerned about the modifications needed to an airplane to make this happen. I still don't know how intensive that would be for like an actual commercial airliner, but it seems like a relatively easy lift. I can't put my finger on it, but there's these like little metal triangles that stick up from the wings of certain jets that help keep the air stream stuck to the wing. I don't know why I'm blanking on the name, but it reminded me of like something similar. It seems easy-ish to do if we see value in this. So yeah, I'm not too worried about it, but very impressive overall. It's nice to see that apparently there's a lot of folks that were looking at covert feathers. No one was thinking about them in the layers or they link two other studies out of the dozens that have looked into this that mention the multiple rows. So, it was awesome to see that these folks took a different perspective on the problem and are actually able to show a lot of value in their experiments. In addition to that, they also talk about how they focused on planes obviously, but the relationship between the flaps and the fluids around them means that you can kind of build off of this study and better understand how flaps could be used on cars. I was thinking on boats or submarines, there we go, on things like that, anything that moves through a fluid. Shout out James Cameron, I don't know if he's doing another Titanic, but I'm sure he could use something like this.

Daniel: Yeah, I mean, you're right. So, the fundamentals here are just fluid dynamics. It's not limited to aviation, right? Anywhere where fluid dynamics come into play, aerodynamics, hydrodynamics. There's an interesting way for these covert feather imitation flaps, let's say, which are completely passive, super low cost and can help prevent stalling in both small and large aircraft, helping improve safety. I had also wondered if there was a potential application here for windmills.

Farbod: Oh yeah.

Daniel: Unsure, right. But I'm sure if the angle of the wind is inappropriate, right. As compared to the angle of the blade on a windmill, it's not generating as much thrust as it possibly could. I'm wondering if by adding a bunch of adhesive rows of these flaps to the top side of a windmill blade could have any benefit to energy output. Maybe.

Farbod: That's a really good point. Yeah, I didn't even think about that.

Daniel: I don't know. Just something to chew on.

Farbod: That's the benefit of something like this study that just takes a new novel look at what seems to be a problem that's already solved. That's another reason why I love bio-inspired topics as well.

Daniel: Yeah, me too.

Farbod: Because once you crack the first code, there's just domino effect on the things you could apply it to.

Daniel: Well, and it's just like, comparatively, we've got incredible aerospace technology. But don't misconstrue me as a pessimist in this space, because I think it's incredible. I think it's super interesting. I love following every single development that there is. And I'm generally an aerospace optimist, let's say. But if you compare that to like just looking at the window and watching a bird fly around, you're like, there's no freaking way. Any passenger plane could do that. Or when it does, when you see like the blue angels do a really, really cool flight trick, like it blows your mind that this is with manmade technology and nature does that all the time. So, I'm with you. There's something awesome about like just looking at the geometry of a bird's wing, finding that these layers of feathers help stabilize it in some way and then just mimicking that on the best of the best of our manmade technology and finding that it does a 45% increase in lift and a 30% reduction in drag. Those are huge numbers. Like aerospace manufacturers are fighting over a tenth of percent of drag reduction. And we found 30 right here just by looking at a bird's wings. It's awesome.

Farbod: Dude, it's sick. It's sick. What do you say we start wrapping up the episode?

Daniel: Yes, sir. I'll do a quick recap here.

Farbod: Please do.

Daniel: I think this single bird feather will change airplanes forever and here's how. Birds have special feathers called coverts. These small feathers kind of pop up on their wings to help them stay steady when they've got strong winds or tight turns and a bunch of Princeton engineers studied this and tried to create similar flaps but for airplane wings and just like the way that these feathers are layered and they pop up on their own during flight the flaps do the same thing there's multiple layers of them they pop up on their own when the wind changes during flight and they help keep planes stable and prevent stalling without any extra power or any extra controls. I think that these flaps are really awesome and I love that they're nature inspired so I think it's awesome that this bird inspired tech can make flying even safer than ever and save a bunch of fuel and that's why I think a single bird feather might just help change airplanes forever.

Farbod: Boom. Love it.

Daniel: Thanks, Doug.

Farbod: Unrelated, but have you heard that Billy Eilish song, Birds of a Feather?

Daniel: Yes.

Farbod: Dude, I love it. It's so good.

Daniel: Is this our theme song for this episode?

Farbod: Do we get copyright strikes if we do?

Daniel: Probably.

Farbod: What if we sing it?

Daniel: I don't know the words.

Farbod/Daniel: We should stick together. There we go. *singing*

Daniel: Wonderful.

Farbod: That's the 200th special.

Daniel: Yeah, well, and I will say, right, it's our 200th episode. We're super grateful for everyone who's been rocking with us for all 200. I think that's a very small minority of you, but we're appreciative of anyone who's listened to any episode along the way. And to celebrate our 200th episode of doing this together. Farbod and I are gonna finally bite the bullet and do something that we've been wanting to do for a long time, which is update our intro and outro music. So, hopefully starting next episode, you will hear something that sounds much better and makes us happier and more proud of the product we're putting out every single week because the intro music we have now was made almost four years ago and it's definitely time for a refresh.

Farbod: We haven't been happy about it for at least 100 episodes. So, let's see what this next 100 brings us.

Daniel: Some of us haven't been happy for almost 200 episodes.

Farbod: All right, all right, that's it. Folks, thank you so much for listening. As always, we'll catch you in the next one.

Daniel: Peace.

As always, you can find these and other interesting & impactful engineering articles on Wevolver.com.

To learn more about this show, please visit our shows page. By following the page, you will get automatic updates by email when a new show is published. Be sure to give us a follow and review on Apple podcasts, Spotify, and most of your favorite podcast platforms!

--

The Next Byte: We're two engineers on a mission to simplify complex science & technology, making it easy to understand. In each episode of our show, we dive into world-changing tech (such as AI, robotics, 3D printing, IoT, & much more), all while keeping it entertaining & engaging along the way.