I 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.
When 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.
IIRC, 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.
Planes all start their take off from basically the same position and stress the whole runway, slowly lowering as lift increases, but at their highest weight.
It's the same principle as walking on snow in normal shoes vs. snow shoes. Taking off is normal shoes, a lot of pressure concentrated at the very first part of the runway. Landing is snow shoes because it's distributed across more of the physical surface, and the plane weighs a lot less when it lands anyway.
Yeah, the higher departure stress due to greater fuel weight at takeoff was mentioned in this video.
I'm now curious about the engineering of the displaced threshold. This is a portion of the runway that aircraft can taxi onto and use for takeoff but not for landing. I thought (assumed) that the landing was harder on the runway surface than takeoffs, hence the displaced threshold wasn't designed for that force.
The displaced threshold could also be used to ensure obstacle and terrain clearance on landing - simply disallow that portion from being used in order to create an offset from the obstacle. But I don't know whether this is a very common reason for displaced threshold usage.
--
Video also mentions https://skybrary.aero/ which I'd not heard of previously. Looks neat. I'll have to check it out.
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.
Video 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).
100% 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.
100%. 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.
> 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.
For 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.
One of the issues of YouTube is there is "discovery" vs "what I want to watch". 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 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)
The 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.
He 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.
We 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.
Something 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.
I can never watch just a minute of these guy’s video — it’s always the whole thing, always so interesting.
I 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.
When 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.
IIRC, 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.
Isn't it the opposite? Landing stress a sub-section of the runway while departures stress a larger portion?
I'd be surprised that a heavier plane on takeoff exerts more force on the runway than a lighter plane landing.
And as the departing plane goes faster, doesn't the lift take stress off the runway?
Planes all start their take off from basically the same position and stress the whole runway, slowly lowering as lift increases, but at their highest weight.
It's the same principle as walking on snow in normal shoes vs. snow shoes. Taking off is normal shoes, a lot of pressure concentrated at the very first part of the runway. Landing is snow shoes because it's distributed across more of the physical surface, and the plane weighs a lot less when it lands anyway.
Yeah, the higher departure stress due to greater fuel weight at takeoff was mentioned in this video.
I'm now curious about the engineering of the displaced threshold. This is a portion of the runway that aircraft can taxi onto and use for takeoff but not for landing. I thought (assumed) that the landing was harder on the runway surface than takeoffs, hence the displaced threshold wasn't designed for that force.
The displaced threshold could also be used to ensure obstacle and terrain clearance on landing - simply disallow that portion from being used in order to create an offset from the obstacle. But I don't know whether this is a very common reason for displaced threshold usage.
-- Video also mentions https://skybrary.aero/ which I'd not heard of previously. Looks neat. I'll have to check it out.
I 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.
Here'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
That's only a small portion of what the video is about.
Video 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).
100% 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.
100%. 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.
> 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.
For 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.
One of the issues of YouTube is there is "discovery" vs "what I want to watch". 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 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)
"Sign in to confirm your not a bot"...gone.
The 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.
He 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.
We 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.
Something 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.