"The embankment isn't to protect anything, it's to raise the localizer array, to compensate for the runway slope." Thanks (+1) but then why make it sturdy?

@FranckDernoncourt: Piling up some earth was presumably cheaper and easier long-term. (e.g. for maintenance access you just walk up it). What would they do instead? A specially designed structure of wood or metal that was just strong enough to not fall down on its own even in strong winds, but which a plane could knock over in an emergency? Or a giant sand dune to act as a brake on runway overshoots? Or a longer more gently-sloped piece of earthworks so a plane could go up it instead of hitting a wall? All of these are cost tradeoffs, and presumably they gambled on cheap+easy, and lost?

@FranckDernoncourt: But yes, as your answer points out, apparently some people think extra expense should have been spent to make it less of a solid wall somehow, exactly because of accidents like this where a plane probably wouldn't have gone all the way to the water even with no barrier, and a barrier resulted in serious impact causing loss of life and more damage to the plane. Oh, and it was concrete? Not just a pile of earth that might give some under impact. That's pretty far from ideal.

@PeterCordes I think you may have hit the proverbial nail on the head: They gambled on cheap+easy, and lost. I don't think it would have taken a genius or much money to implement a better design that would have saved lives. But at least on the surface, based on the design they implemented, cheap and easy seem to be the priorities and values they chose. So sad. Will a lesson be learnt?

@FranckDernoncourt: Your are tunneled by this latest accident, and see another solution would have been better, this is true. But when engineers have to select a solution they do a compromise on the best solutions for many possible cases, feasibility and cost. If they have thought this type of runway excursion had to be prevented, they would have built an EMAS.

@mins Thanks, I'm surprised that airport designs aren't more standardized. I agree that hindsight is 20/20.

@FranckDernoncourt: Airport design is standardized in ICAO Annex 14 and associated documents. However there is no single solution to problems. What the pilot says in your own answer is what the reporter wanted to hear, not a serious statement, many airports he lands at have hangars, concrete obstacles or water 260 m after the end of the runway.

@FranckDernoncourt: Unfortunately sitting an ILS is done on a case by case basis due to the specificity of reflections in the local environment. Multipath interferences must be accounted for to prevent false guidance. A solution which works at a place may not work at another place, see this interesting case at Eindhoven.

@FranckDernoncourt airport design is influenced greatly by geography, local law (noise abatement etc.), as well as security considerations. Hence why airports in some countries have just a ditch around them, in other places it's a fence, in others again it's a high concrete wall with machine gun posts and barbed wire. And local culture and economy also plays a part.

@jwenting I guess that that Muan was built DMZ style then :) But I think we're back to my original question: Why build a sturdy embankment at the end of a runway if there isn't much to protect beyond it? So far sounds like it's because it was cheaper.

@FranckDernoncourt they had to raise the ILS antennae, had some dirt at hand from digging a ditch somewhere, and used it. Quicker (and yes, cheaper, but that's often not a major consideration) than ordering sturdy concrete and steel posts. Posts which would also turn an airliner into grated cheese btw. ILS antennae need to be very firmly placed AND are pretty heavy. I'm not familiar with South Korean airport perimeter security, but I'd not be surprised if it's more secure than a simple fence.

@FranckDernoncourt: "sounds like it's because it was cheaper", cost is a driving factor in aviation, you can't just ignore this and ask to have solutions for extremely rare accident cases, whatever the cost. Airlines will just land at another airport, else passengers will just use another operator. In the end that's the passenger who decides for the prevention of extremely rare accident cases (not only this one, but any other rare case, there is a lot of them), it's you who decides.

@mins Not at all meant to be a criticism, I understand that indeed. I thought, as a non-expert, that there could be other reasons too, and that being something less sturdy could be cheaper.

The specific circumstances of this crash might be rare, but the general type of incident isn't: Aviation Herald has about 300 hits for "overrun".

@Mark: Based on 2015 IATA worldwide figures, Inadequate overrun area, trench, ditch, proximity of structures, contributed to 2% of a total of 68 accidents (it's at the bottom of the linked list, the least contributing factor. IATA members = commercial aviation). That is it contributed to 1 or 2 accidents. I don't know if any was related to a localizer sitting.

YouTube Pilot blancolirio uses the first two minute of his [31 Dec 2024 post] (youtu.be/BzmptA6s-1g?si=CDJyGwiCEPRS-nFt) to excoriate the decision makers who saw to the erection of the berm. However, he bases much of his certainty of a misreading of the map in which he measures the distance to the berm from the post-runway ramp, not the published runway terminus. He's not alone, however. Many highly visible experts are rushing to make seemingly definitive claims.