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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 sever
by Animats 9mo ago
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 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.
- mrexroad 9mo agoThat’s pretty cool. I’d assumed there would be something similar to the run-away truck ramps you see on steep grades — basically a deep gravel pit. However, actually thinking about it, something along the lines of a gravel pit would likely cause significant damage to engines (not to mention risks created by engine damage) but also seriously impede emergency services.
- marcosdumay 9mo agoGravel flies. You can't have it anywhere near an airport runway. (Some planes have no problem with it, though. You can make even the entire runway of gravel if you only fly those.)
- andkenneth 9mo agothe distinction here is mainly jets vs props.
- stackghost 9mo agoGravel will happily fuck up a prop just as much as a turbine; it's more about ground clearance. The engines on modern airliners are quite low to the ground, which is why they tend to ingest gravel kicked up by the nose gear.
- CGMthrowaway 9mo agoWhat's the ground clearance of a flying piece of gravel! (in a gust of wind for example)
- stackghost 9mo ago>What's the ground clearance of a flying piece of gravel! (in a gust of wind for example) I'm not sure I understand the question you're asking. "Ground clearance" refers to the space between the thing and the ground. Airliners are low-wing monoplanes with the engines slung underneath the wings, and aft of the nose landing gear. The tires at the nose can kick up gravel which not only dings up the underside of the fuselage but can also get sucked into the jet intakes. There's only about 2 feet of clearance between the engine cowling and the ground. Compare this to a C-130 Hercules which is a high-wing monoplane with turboprops, which is designed to handle some degree of unprepared surfaces. The prop tips are never less than about 5 feet from the ground. Or, compare to a Piper Cub which has much less prop ground clearance but has the prop mounted forward of the nose landing gear so it's much less likely to encounter gravel. "What is the ground clearance of a flying piece of gravel" is... not really a question that makes sense to me.
- kmarc 9mo agoHah, I guess this is the same then as in formula 1 (and possibly other motorsports). After the end of a straight (speeding) section, just before the curve they have 150/100/50 (m?) distance indicators. Sans the concrete block at the top. That would obviously shave the driver's head off. When a driver hits these, they evaporate as dust.
- bonzog 9mo agoIt's not quite the same thing - the EMAS is the overrun surface itself, rather than the signs warning of it. However you are quite close to the money on another aspect of airfield design. Lots of obstructions near the runway - signs, lights, aerial masts, meteorological equipment, fences - are supposed to be "frangible" [1]. They must break into pieces less likely to cause damage to an aircraft in a high-energy collision. There's a heck of a lot of GFRP used in lieu of metal around an airfield. 1. ICAO Doc 9157, particularly part 6.
- Night_Thastus 9mo agoEMAS is going to save a LOT of lives in the long run. It's consistently effective at its job. I'm very excited to see it more widespread.