9 ms·
The hidden engineering of runways
- noitpmeder 9mo agoVideo is great, came up in my youtube recommendation cycle last week. Honestly one of the better things youtube has pitched to me, the quality/relevance of the rest of its recommendations have been nose diving over the last year (or so it feels).
- shagie 9mo agoOne of the issues of YouTube is there is "discovery" vs "what I want to watch". https://www.youtube.com https://www.youtube.com is ok for discovery and pulls a lot of the "this is what I've subscribed to" in there too. Doing a subscribe to channels that give you consistent media that you want to watch and then going to https://www.youtube.com/feed/subscriptions https://www.youtube.com/feed/subscriptions as the "this is where I want to be when on YouTube" gives a completely different experience. (I'm also quite free with the "don't recommend this channel to me" option if something disappoints me)
- graypegg 9mo ago100% anecdata, but I think YouTube nudges your ad profile towards some averaged out cosign product of everyone’s ad profile at regular intervals. I’ll discover something new, then get pushed a ton of things related to it, which is really good! After a very long break of ~4 years, I started playing oldschool RuneScape again, and that interest weaved its way into my recommended feed perfectly for a month. Felt like I was picking up where I left off, new folks making OSRS video essays, folks I remembered from a long time ago that I had unsubscribed from, exactly what I want out of an algorithmic feed when I’m freshly into something. Then BAM, gaming content. Some sort of threshold gets hit and now I’m being pushed hyper popular gaming content regardless of RuneScape-y-ness. There’s still a nudge towards it, but I got placed in some “gaming” cohort and it totally crowds out my recommended feed. I don’t really do much gaming outside of this stupid old MMO! All that’s to say: it might have been a year since you last had one of these inflection points where YouTube will let your ad profile exist as an outlier for a bit.
- ashf023 9mo ago100%. I've always used youtube on desktop (connected to the TV usually), and it seems to me they're just making all versions of youtube into a mobile app optimized for shorts type content. Recommendations are hugely influenced by what you watched very recently. What used to be related videos in the side panel of the player is now just the home page again, but vertical. Even just generating a recommendation from "Whatever (part 2)" to "Whatever (part 3)" is hit or miss now. Some of the recommendations are actually quite good, but at least for the way I like to watch, it's only getting worse over time. The category labels on the home page are also pretty telling - horrible labels (e.g. I watch some cooking/recipe videos and the label will be "Baking sheets" or something like that), plus it emphasizes the recency bias when it shows 5 categories that are basically just the same content with different labels and forgets what I've always liked watching.
- kevin_thibedeau 9mo agoFor me my home page is now 95% videos I've already watched. The side bar is the only reliable source of new content. Until recently I had no subscriptions but that never used to matter. I had to subscribe to Patrick Boyle in solidarity when they demonetized his Epstein video.
- bityard 9mo ago> Recommendations are hugely influenced by what you watched very recently. Ah, well, I don't know that I fully agree. I watch channels that are people building things, repairing tools, or goofing around in an easy-going way without a lot of product placement or sponsored content. And yet, all of the recommendations I get are either sponsored unboxing videos with AI voiceovers or click-baity channels with ugly reaction faces in the video thumbnails. I guess those probably make more money for Google.
- unclad5968 9mo agoI suspect ad revenue isn't good for maker/hacker type videos. I watch a lot of woodworking and cnc projects, and I mostly get the kind of recommendations you're talking about
- spike021 9mo agoThe way Youtube (and I've started to notice in other platforms) does recommendations, for every 5+ that are nonsense, I'll get one I like. Youtube will then start showing me more of that video's channel content and similar channels for a week or so, and then it'll just stop showing any of it to me quite randomly. Sometimes it's when I click on that random recommendation out of 5 from a different topic. then the cycle starts again. sometimes youtube brings the content back and sometimes i really need to hunt for it. it's almost like they base interests into like a top 3 or so list and if the third favorite one cycles out a lot (however they deem it is being cycled out) they'll stop recommending or otherwise showing it to me.
- pbreit 9mo ago"Sign in to confirm your not a bot"...gone.
- jld 9mo agoI saw a talk a long time ago about the structural aspects of runway design. The most interested fact I remember was that the stresses on the runway generated by departures was higher than those of arrivals, as departures repeatedly stress the same part of the runway, while jets land on a much more distributed area of the runway. Plus jets weigh a lot less at arrival than at departure.
- WalterBright 9mo agoWhen I worked at Boeing, I talked about autoland systems with my lead engineer. He said the autoland was too perfect, as the airplanes would touch down at the same place every time. This caused that place in the runway to suffer severe fatigue damage.
- psunavy03 9mo agoIIRC, there was a similar problem on aircraft carrier flight decks, where they had to induce some randomized amount of dispersion to keep the tailhook from hitting the same spot over and over again.
- refibrillator 9mo agoHmm in distributed computer systems similar patterns exist, e.g. adding jitter to avoid thundering herd effects. This feels like an essential pattern of the universe or something…
- HPsquared 9mo ago"Spread spectrum" is used in EE to spread out the frequency ranges used and reduce interference. The extreme version being CDMA.
- username135 9mo agoIntriguing
- danpalmer 9mo agoWe had group coding projects at university, and the first one was always "sponsored" by the local airport. I think the ATC manager was friends with a lecturer. Every year the students built to the same spec in groups, being able to compare and contrast. It was great fun. The year before me was all about runway markings: take a bunch of industry specified XML describing the runway and produce accurate diagrams in a GUI browser. My year was runway "redeclaration", if a vehicle has broken down on the runway, you can still use the runway as a shorter strip, accounting for the onion layers of different zones radiating out from the tarmac itself, accounting for the height of the obstacle and angles of approach, accounting for all the necessary safety margins. It was my first real exposure to working in a team and to solving a real world problem with a good spec. Of course it was an absolute shitshow, but I look back on it fondly.
- r-johnv 9mo agoI absolutely love that Grady includes full transcripts of his videos. It's much faster to read the article than watch the video, even though that hurts him by 1 view. I just watched parts of the video after reading because I wanted to see his explanations. One of the few really good creators out there.
- dyauspitr 9mo agoReading the transcript doesn’t even give you 10% of the information actually conveyed in the video which is why it’s so much faster.
- cucumber3732842 9mo agoIf you already understand the concepts you're not gaining much by watching the video. If you don't then I'm sure it's better than nothing but idk if stock footage is where you should be developing your mental model of how a tire hydroplanes or how a paved transfers load into what's below it.
- dyauspitr 9mo agoSome of it is stock but Grady has a lot of custom animations and miniature scale replicas in his videos all the time.
- squigz 9mo agoWriting off Practical Engineering's videos as "stock footage" is utterly hilarious to me.
- cucumber3732842 9mo agoC'mon. I know everyone on HN just can't help but glaze anyone who deals with "real world things" rather than 1s and 0s but this is absolutely not one of his more original content videos. You can't simulate landing aircraft using a clear plastic box (one of his better props) like you can soil conditions so you get what you get.
- ggm 9mo agoSomething which still confuses me is the nature of the illuminations in the roadway. Because we can see edge elements, we see things on stalks. I don't see how that can work, for things the tires run over. But, the illuminations are there. They must be super-designed cats-eyes. Also, the approach lighting has very good engineering to keep you in the safe slot for approach angle. The lights must have fresnel lenses or shading or something to keep a very narrow angle of approach lit up "best" On take off if I have a window, I now look for the banding which I mentally model as "not yet.. " "almost .." "if you are doing <x> kph then YES" .. and "nope. don't wanna see this one" Gate approach, there are clues that pilots drive by following lines. So many lines! marked by aircraft type: if you are a <this> then follow <this track> type markers.
- tonyarkles 9mo agoYou’re on the right track! Some of them are embedded, some of them are on stalks, and some of them are highly directional: https://flightlight.com/airfield-products/ https://flightlight.com/airfield-products/
- deleted 9mo ago[deleted]
- Animats 9mo agoHere's the one-minute version from the FAA.[1] Runway overrun areas marked with diagonal stripes have an Engineered Materials Arresting System. There are several different materials used. One is pumice embedded in styrofoam, with a thin concrete layer on top. Large aircraft weigh enough to break through, and the pumice is crushed to powder, absorbing energy. This yields a surprisingly short stopping distance. The aircraft landing gear will be damaged, but the rest of the aircraft is usually intact. The overrun material comes in prebuilt blocks, and after an overrun, only the ones damaged need to be replaced. It gets a lot of use. The FAA has logged 25 overruns stopped by EMAS, out of 161 runway ends so equipped. That's surprisingly high. It's a simple, clever system. [1] https://www.youtube.com/watch?v=hVSvU06_NGE https://www.youtube.com/watch?v=hVSvU06_NGE
- hobofan 9mo agoThat's only a small portion of what the video is about.
- horsawlarway 9mo agoHonestly - the video barely touches on this at all, despite making it the "hook". I was pretty disappointed that he doesn't discuss the EMAS mechanics, structure, actual stopping distance, or impact to the plane in nearly any real way. He does show a LOT of animation of layered runways, which are mostly not that informative. There is some decent discussion around maintenance and material choice, and some very basic discussion of infrastructure requirements outside of the runways themselves that's... ok. Overall... I thought this was a solid C+ video. It shows planes plowing into an EMAS, then does jack all to discuss that, while bringing up a lot of less interesting discussion of runway building (which despite the claims in the video, do actually correspond very highly to how we build highways, just with different weight/maintenance requirements.)
- ash_091 9mo agoI don’t think anything you said is wrong, but I do think you’re misreading the intent of the channel. Practical Engineering is very deliberately framed as edutainment. The animations, pacing, and level of depth are conscious choices meant to keep non-specialists engaged rather than to maximize technical rigor. In that sense, it belongs alongside other popular "science-y" channels like Kurzgesagt, Vsauce, and Technology Connections: content that prioritizes narrative and engagement over completeness or instruction. The target audience is the broad middle of the technical bell curve. Animations of runway layers may make the video less appealing to you, but more accessible to a much larger, less technical audience. Different goals imply different success criteria. If the goal is reach rather than comprehensive education, a million views in seven days looks like success.
- lenerdenator 9mo agoHe does such great videos and content. Might have to watch this one with my dad; he used to joke that his Eagle Scout project was putting in the north-south runway at MCI.
- hybrid_study 9mo agoI can never watch just a minute of these guy’s video — it’s always the whole thing, always so interesting.
- deleted 9mo ago[deleted]
- darkspine 9mo agoI absolutely love this channel. It provides a reasonably no nonsense view into parts of engineering I'm not super familiar with. It's made cooler by the fact that I occasionally interact with the systems being described. (Though hopefully not this one). Does anyone have recommendations for similar high quality engineering adjacent content?
- abenga 9mo agoThere's Farmcraft101 if you are interested in DIY builds and repairs. There was a series of videos repairing an excavator from scrap to finish, and he is currently doing a series of videos adding hydro generation to a pond. Interesting metal fabrication, hydraulics, power, etc content.
- r-johnv 8mo agoVeritasium (https://www.youtube.com/veritasium https://www.youtube.com/veritasium) has well researched content, but they are broad in terms of their topic selection. Real Engineering (https://www.youtube.com/@RealEngineering/videos https://www.youtube.com/@RealEngineering/videos) is focused on engineering, but more on specific vehicles or products than individual concepts.
- isolli 9mo agoEvery time I fly, I marvel at how much engineering and know-how went into making the airport that I'm using. From the oddly shaped trucks with various functions, to mundane elements (elevators, escalators, ...) to advanced technology (radio communication, radars...) to the sheer organizational feat (thousands of people coming in every day to execute their carefully planned tasks). This text will give me one more thing to think about :)
- matwood 9mo agoGlad I'm not the only who is fascinated with airports and the technology/engineering that makes them function at scale.
- eschulz 9mo agoSame, and I also just marvel at the airplanes. This video made me think of the several grass runways that are in my area. They're literally just maintained by some guy mowing them, and yet people land on them in tiny planes as well as two-engine aircraft.
- inaccuratebee 9mo ago> The FAA says that for each percent of downhill slope, landing distance is increased by 10%. This is accurate as to their recommendation, but it was surprising. I know it’s inaccurate, because at a perpendicular angle there would be no way to land. I know they don’t allow an angle that steep, but that means this is “gut feel” inexact math that seems unsafe.
- InitialLastName 9mo agoThe force required to stop on an inclined plane is proportional to the sine of the angle. At angles less than 10 degrees (~17% slope, far steeper than the FAA would allow for an airport), the small angle approximation of sine is within 0.5% of linear.
- dsvf 9mo agoI don't know if their math is incorrect, but your intuition of the limit case is - downhill slope is the ratio of height change per length. A perpendicular angle thus has "infinite percent" slope (since the denominator, length, is zero), which intuitively matches an infinite landing distance.