Comment by octaane

You're 100% right, and that's exactly what I'm getting at - they hit V1 and were aware they had a serious problem, but couldn't abort.

As far as the rest of my comment - watch the videos that I linked.

> Do runways have some sort of barrier between them and the next "important" thing. It seems like that would be prudent both for cases like this

Ha, Jeju Air Flight 2216 smashed into a barrier on the second landing attempt in Muan last year [0], and people commented "How could there be a barrier at the end of the runway, so obviously stupid, irresponsible", etc.

Now a plane does not smash into a barrier at the end of the runway and people suggest putting barriers at the end of the runway.

Don't mean to attack parent post, but may I suggest that

a) hordes of experts have thought long and hard about these issues, and it is unlikely that you can encounter this for the first time as a lay person and come up with a solution that has eluded the best engineers for decades ("why don't they attach a parachute to the plane?"), and

b) we are very close to an optimum in commercial aviation, and there are few if any unambiguous ("Pareto") improvements, but rather just tradeoffs. For example: You leave cockpit doors open, terrorists come in and commandeer the plane to turn it into a weapon. You lock the cockpit doors closed, and suicidal pilots lock out the rest of the crew and commandeer the plane to turn it into a weapon of mass-murder-suicide.

There are no easy answers.

[0] https://en.wikipedia.org/wiki/Jeju_Air_Flight_2216

ETA: In 2007 an A320 overran a runway in Brazil and crashed into a gas station, killing 187 pax & crew + 12 on the ground. https://en.wikipedia.org/wiki/TAM_Airlines_Flight_3054

> Do runways have some sort of barrier between them and the next "important" thing.

Some do. Here is what it looks like when an overshooting plane utilizes such a barrier: https://www.youtube.com/watch?v=zW71FrX8t_g

179 dead.

Consider the possibility that gigantic flying aluminum tubes filled with tons of flammable fuel hurtling around at hundreds of kilometers per hour comprise a dilemma that has no trivial answers. Even defining what "important thing" means at any given instant is not straightforward.

Unless you have a berm several dozen meters high with a 100 meter base, you ain't stopping something like this from a physics standpoint unfortunately.

Many airports have this problem. The recent korean air disaster which echos this is another example. BTW, this is why most airports, if possible, point out to sea...

Some runways have been extended with ‘engineered materials’ surfaces, often a form of porous concrete into which an airliner’s wheels will sink, absorbing a lot of energy and arresting the airplane without causing it to break up. It is very effective for landing overruns, but I don’t know about last-seconds aborted takeoffs.

Security/debris fencing yes, but that's like, orders of magnitude short of what would stop the amount of energy we're talking about here.

You also don't particularly want it to be catastrophically effective as there are real world cases where planes have clipped the fence and then NOT gone on to crash, or at least to crash in a fairly controlled manner with the majority onboard surviving. Hitting a brick wall at 180mph is going to have a 0% survival rate.

Airports are usually built (originally) out in the boonies away from the major metro area. As time goes by and that land gets more valuable developers grease palms of politicians in land use commissions to allow developments closer and closer to the airports.

Airports also grow themselves. Some municipal airports sited for small aircraft extend their runways to handle larger planes.

It depends on whether or not, at the point in which you realize you have an engine on fire, you have room on the runway left to stop.

As I understand it, there is a low speed regime, under 80 knots, where are you stop for basically anything.

Then there is a high speed regime, where you only stop for serious issues, because you now have so much kinetic energy that stopping the plane, while still possible, will involve risk. (i.e. fire from overheated brakes.)

At a certain point, called V1, there’s no longer enough room to stop, no matter what your problem is. You’re either getting airborne or you’re crashing into whatever is ant the end of the runway. In general, getting airborne is the safer option, while obviously still not risk free.

However, this calculation also assumes that the engine fails in an isolated fashion, and its failure did not affect the other engines. If the failure of the left engine threw off debris that damaged the middle engine then we are now talking about a double engine failure. I’m sure the pilots knew there was a problem with the engine when they made the decision to continue, but it’s possible that problems with the middle engine weren’t apparent yet and that it only started to fail once they were committed.

Obviously, this is just speculation, and we will have to wait for the preliminary report at least.

RIP

V1 is the speed at which you can still stop the plane before the end of the runway. (It is computed for each takeoff based on runway length, aircraft mass, takeoff engine power setting, flaps, wind, runway condition, etc.)

When the plane reaches V1, pilots take the hand off the throttle: they're committed to takeoff, even if an engine fails. It is better to take off and fix the problem or land again, than to smash into whatever is beyond the end of the runway.

It was at a point where they were going to fast to stop or land safely. At that point you're just trying to pick the best place to crash.

To avoid mass casualties at the end of the runway - on the road, or the buildings that the runway points to. Check the layout on google maps.

More specifically, V1 is the max speed at which you're about to take off, but you can still abort from. They hit that max speed and realized there was a major problem that hypothetically, they could have slowed down from, but realistically was not possible. They had no choice.