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Why was there a wall near runway at S Korea plane crash airport?

bbc.com

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Re: Why was there a wall near runway at S Korea plane crash airport?

#131

Post by davisp »

thekevan wrote: post #64
gazchop wrote: post #58

Earlier quoted context omitted.

There is a whole chain of causality. They were killed by multiple successive problems compounding. See Swiss cheese model.

I'm really not sure the chain of bird strike, belly landing, mid runway landing and fiery explosion are equal parts of that chain. One seems to weigh heavier than the rest.

Absolutely correct! Had the bird strike not occurred, there wouldn’t have been a crash. Had things with the go around been handled properly, there would have been no crash.

Etc etc. The fact that a wall was 50m out of compliance or whatever it ends up being will be a footnote at best in the review of this crash.

Re: Why was there a wall near runway at S Korea plane crash airport?

#132

Post by dgfitz »

formerly_proven wrote: post #90
mmooss wrote: post #89

Earlier quoted context omitted.

> it took them ~1.7 sec from leaving the tarmac until they hit the construction. If you measure the distance on Google earth you come up with ~140m. That means they hit the construction with roughly 296km/h or 160 knots. (Assuming the math is correct:) That's the average speed over that distance. The plane would have been slowing down the whole time.

I'm not a pilot. In the video it looked like the plane was only running on the rear landing gears, I assume with no brakes applied, since that would've caused it to violently pitch down I assume. Only in the last bit did it pitch down and started scraping along the runway. It certainly doesn't look like it was efficiently shedding speed (but looks can be deceiving).

I have been under the distinct impression for a long time that a plane slowing on the runway has very little to do with landing gear brakes.

Re: Why was there a wall near runway at S Korea plane crash airport?

#133

Post by aaron695 »

inoffensivename wrote: post #92

Lots of airports have obstacles not far from the end of the runway. Burbank, Midway, Orange County are a few that come to mind. Why did they need to land when they did? Why did they need to land so soon after the mayday call? (only 8 minutes from mayday to crash, as I understand it) Why couldn't they land on a longer runway? Why did they land so far down the runway? What forced them to land in a clean configuration?…

[dead]

Re: Why was there a wall near runway at S Korea plane crash airport?

#134

Post by dmurray »

pfannkuchen wrote: post #113
inoffensivename wrote: post #92

Lots of airports have obstacles not far from the end of the runway. Burbank, Midway, Orange County are a few that come to mind. Why did they need to land when they did? Why did they need to land so soon after the mayday call? (only 8 minutes from mayday to crash, as I understand it) Why couldn't they land on a longer runway? Why did they land so far down the runway? What forced them to land in a clean configuration?…

Were those obstacles installed by the airport though? I thought it was like stuff on land outside of the airport for those other examples.

Does it matter? Either it's safe to have obstacles within 300m of the end of the runway, and this was a reasonable location for the Korean airport to put their localizer in, or it's not, and the likes of Burbank should shorten their runway to ensure there's sufficient buffer space at the end of it.

Re: Why was there a wall near runway at S Korea plane crash airport?

#135

Post by snypher »

foxglacier wrote: post #95
Mistletoe wrote: post #18

Earlier quoted context omitted.

He’s going extremely fast, a few hundred meters would do nothing. I think the estimates I saw were over 150 knots. That’s about 77 meters per second. I found this comment helpful from a Reddit thread. >The embankment is there to protect the road from the jetblast of departing aircraft in oposite runway direction. Thats why it is allowed directly in the safety area.

> a few hundred meters would do nothing. I think the estimates I saw were over 150 knots Show you working. Not feelings because people don't have intuition for such unusual motion. You could equally have said "a few hundred meters would be enough."

150 knots is like 77 meters a second, a 747 can do like 2m/s^2 braking giving 35 seconds to stop, 1500 meters required.

Stopping time: t=v/a, t=77/2. Stopping distance: d=v^2/2a, d=77^2/2*2

Re: Why was there a wall near runway at S Korea plane crash airport?

#136

Post by irjustin »

dgfitz wrote: post #132
formerly_proven wrote: post #90

Earlier quoted context omitted.

I'm not a pilot. In the video it looked like the plane was only running on the rear landing gears, I assume with no brakes applied, since that would've caused it to violently pitch down I assume. Only in the last bit did it pitch down and started scraping along the runway. It certainly doesn't look like it was efficiently shedding speed (but looks can be deceiving).

I have been under the distinct impression for a long time that a plane slowing on the runway has very little to do with landing gear brakes.

That's under normal operation. All planes are certified to stop without any air reverse thrust[0] given they land at the right sized runway, right conditions, right position, etc etc.

But it's definitely part of the program.

They must also sit on the tarmac post heavy braking and the brakes must not burst into flames.

[0] https://www.youtube.com/watch?v=evLpE8Us-j0

Re: Why was there a wall near runway at S Korea plane crash airport?

#137

Post by hu3 »

blueflow wrote: post #77

I'll recite an avherald comment: If you look at "Video of aircraft after touchdown sliding along the runway and impacting the fence:", you will find out that it took them ~1.7 sec from leaving the tarmac until they hit the construction. If you measure the distance on Google earth you come up with ~140m. That means they hit the construction with roughly 296km/h or 160 knots. If it wasn't the construction it would have…

160 knots?

Google tells me: "Modern jets land between 120–150 kt. This depends on weight, weather conditions and several other factors."

So even after scratching asphalt for 2/3 of the runway it was still faster than the normal landing speed.

My uneducated gut feeling says pilot was trying to abort the landing.

Re: Why was there a wall near runway at S Korea plane crash airport?

#138

Post by DoctorOetker »

sio8ohPi wrote: post #127
DoctorOetker wrote: post #115

Earlier quoted context omitted.

> 1.3 Pilot shall use extreme caution during carrying out final approach into RWY 01 or missed approach or departure for RWY 19 due to obstacle located east of extended RWY at approximately 2.1 NM from threshold of RWY 01. it seems this is the same structure: https://en.wikipedia.org/wiki/Jeju_Air_Flight_2216#Non-stand...

No. The ILS localizer was 260 meters from the threshold, not 2.1 NM (3800m).

Why would there be a warning for an "obstacle" 4km away from the end of the runway?

3800 - 2800 = 1km.

Did the plane skid for 1km before crashing into the obstacle?

Re: Why was there a wall near runway at S Korea plane crash airport?

#139

Post by sio8ohPi »

DoctorOetker wrote: post #138
sio8ohPi wrote: post #127

Earlier quoted context omitted.

No. The ILS localizer was 260 meters from the threshold, not 2.1 NM (3800m).

Why would there be a warning for an "obstacle" 4km away from the end of the runway? 3800 - 2800 = 1km. Did the plane skid for 1km before crashing into the obstacle?

Because the system is bureaucratic and stupid. Notices warning pilots about irrelevant obstacles are, literally, a meme. Example: https://www.reddit.com/r/flying/comments/wzsvru/the_notam_sy...

Re: Why was there a wall near runway at S Korea plane crash airport?

#140

Post by sio8ohPi »

hu3 wrote: post #137
blueflow wrote: post #77

I'll recite an avherald comment: If you look at "Video of aircraft after touchdown sliding along the runway and impacting the fence:", you will find out that it took them ~1.7 sec from leaving the tarmac until they hit the construction. If you measure the distance on Google earth you come up with ~140m. That means they hit the construction with roughly 296km/h or 160 knots. If it wasn't the construction it would have…

160 knots? Google tells me: "Modern jets land between 120–150 kt. This depends on weight, weather conditions and several other factors." So even after scratching asphalt for 2/3 of the runway it was still faster than the normal landing speed. My uneducated gut feeling says pilot was trying to abort the landing.

Normally they land with flaps down, which reduces landing speed.
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