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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

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).

krisoft 2y ago
> In the video it looked like the plane was only running on the rear landing gears, Are we talking about the same crash? In the video I have seen[1] the plane appears to be on its belly dragging on the runway. 1: https://www.youtube.com/watch?v=qJY7oaZpxDU https://www.youtube.com/watch?v=qJY7oaZpxDU
- formerly_proven 2y ago
  True! I misremembered, in the longer video it's hard to see that the nacelles are dragging on the ground all the way. Still doesn't seem to slow down much.
  - neom 2y ago
    It was in gound effect floating till very near the end, these two video show the story very well: https://x.com/vinfly4/status/1873285591900836307 https://x.com/vinfly4/status/1873285591900836307 https://www.reddit.com/r/aviation/comments/1hopl7d/longer_video_of_the_jeju_air_crash_including/ https://www.reddit.com/r/aviation/comments/1hopl7d/longer_vi... As you can see, it actually isn't touching the ground for quite some time, it looks like it because one of the engines is smoking and the plane is throwing up dust etc from the ground as it floats above. Pure guessing on my part as someone who isn't involved in aviation but spent a good 6 hours looking into this crash: Pilots tried to go around, put the plane in go around config, couldn't, didn't know what to do, and watched the berm come at them. Extremely sad. How both engines failed? We won't know til blackbox I guess, either pilot error or the bird strike was nuts and took out both engines, also some speculation the go around thrust caused a compressor stall. It looks to my uneducated eyes, from the first video, the left engine is not in great shape. Either way, very awful situation.
    - WalterBright 2y ago
      The reason he touched down halfway down the runway could have been because the gear was up. If the gear was down, he would have touched down much earlier. He may not have known the gear was up, or did not account for the gear being up in his approach.
      - neom 2y ago
        They executed a pretty difficult turn, apparently it's called the impossible tear drop and you're trained specifically NOT to ever do it. I looked at the flight tracking, I suspect the maneuver they pulled just put them at that point in the runway[1]. If you read my reply to the comment above you, it has some additional context you might find interesting. They pilots I watched all mentioned really, it doesn't make sense they cut off the approach, they should have taken the bird strike and continued the landing. The probable reasons given was: took evasive maneuvers to avoid the brids so came off glide slope, not enough engine power for a full go around, then started to get way behind the plane. [1]https://s.france24.com/media/display/579312a0-c8cb-11ef-81bd-005056a97e36/c6e5660a35c770c0b92aa9b666fd7c27fcb16d99.jpg https://s.france24.com/media/display/579312a0-c8cb-11ef-81bd...
        user_7832 2y ago
        > it's called the impossible tear drop Minor nit, I believe it’s called the teardrop go around for such cases. You also have the impossible turn which is meant typically for engine/power failure during takeoff, and it actually is possible to be safely done - as demonstrated by the former ALPA Air Safety Institute Senior VP Richard McSpadden in one of his YouTube videos. However, it can be deceptively difficult to have the right conditions to pull it off - as demonstrated by the ironically fatal crash that killed Commander (Ret) McSpadden (though iirc it was not clear if he was flying the craft at the time). (Edits made for clarity/content.)
        neom 2y ago
        Thank you for the clarification, I hoped I couched everything enough people knew I'm just reading internet and not at all an expert, I appreciate the reply!
dgfitz 2y ago
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.
- irjustin 2y ago
  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 https://www.youtube.com/watch?v=evLpE8Us-j0
- dredmorbius 2y ago
  True, though I don't have a breakdown of net effects. Commercial jet aircraft utilise thrust reversers, speed (or air) brakes (usually control surfaces which can extend out from the aircraft fuselage or wings), and landing gear brakes. The latter are not insignificant, but thrust reversers and speed brakes are major contributors, especially immediately after touchdown. There's also the effect of spoilers which increase the load over the gear and hence the braking capabilities of landing gear brakes. Jeju 2216 failed to utilise nearly all of these mechanisms. It landed without flaps, spoilers, or gear, and possibly w/o thrust reversers.
- 3ple_alpha 2y ago
  If one divides weight of the airplane by the number of wheels it has, one would find one wheel carries around 10 times more weight than that of a truck. You even get a slightly better deal on landing when you don't have as much fuel. That's a lot of weight but nothing crazy, so on a dry runway wheel brakes alone are more than enough to stop normally. They would also wear out a lot, overheat and occasionally ignite if used like that, so that's what thrust reversers are for.
  - mmooss 2y ago
    That mass has much more velocity than a truck.

krisoft 2y ago

> In the video it looked like the plane was only running on the rear landing gears, Are we talking about the same crash? In the video I have seen[1] the plane appears to be on its belly dragging on the runway. 1: https://www.youtube.com/watch?v=qJY7oaZpxDU https://www.youtube.com/watch?v=qJY7oaZpxDU

formerly_proven 2y ago
True! I misremembered, in the longer video it's hard to see that the nacelles are dragging on the ground all the way. Still doesn't seem to slow down much.
- neom 2y ago
  It was in gound effect floating till very near the end, these two video show the story very well: https://x.com/vinfly4/status/1873285591900836307 https://x.com/vinfly4/status/1873285591900836307 https://www.reddit.com/r/aviation/comments/1hopl7d/longer_video_of_the_jeju_air_crash_including/ https://www.reddit.com/r/aviation/comments/1hopl7d/longer_vi... As you can see, it actually isn't touching the ground for quite some time, it looks like it because one of the engines is smoking and the plane is throwing up dust etc from the ground as it floats above. Pure guessing on my part as someone who isn't involved in aviation but spent a good 6 hours looking into this crash: Pilots tried to go around, put the plane in go around config, couldn't, didn't know what to do, and watched the berm come at them. Extremely sad. How both engines failed? We won't know til blackbox I guess, either pilot error or the bird strike was nuts and took out both engines, also some speculation the go around thrust caused a compressor stall. It looks to my uneducated eyes, from the first video, the left engine is not in great shape. Either way, very awful situation.
  - WalterBright 2y ago
    The reason he touched down halfway down the runway could have been because the gear was up. If the gear was down, he would have touched down much earlier. He may not have known the gear was up, or did not account for the gear being up in his approach.
    - neom 2y ago
      They executed a pretty difficult turn, apparently it's called the impossible tear drop and you're trained specifically NOT to ever do it. I looked at the flight tracking, I suspect the maneuver they pulled just put them at that point in the runway[1]. If you read my reply to the comment above you, it has some additional context you might find interesting. They pilots I watched all mentioned really, it doesn't make sense they cut off the approach, they should have taken the bird strike and continued the landing. The probable reasons given was: took evasive maneuvers to avoid the brids so came off glide slope, not enough engine power for a full go around, then started to get way behind the plane. [1]https://s.france24.com/media/display/579312a0-c8cb-11ef-81bd-005056a97e36/c6e5660a35c770c0b92aa9b666fd7c27fcb16d99.jpg https://s.france24.com/media/display/579312a0-c8cb-11ef-81bd...
      - user_7832 2y ago
        > it's called the impossible tear drop Minor nit, I believe it’s called the teardrop go around for such cases. You also have the impossible turn which is meant typically for engine/power failure during takeoff, and it actually is possible to be safely done - as demonstrated by the former ALPA Air Safety Institute Senior VP Richard McSpadden in one of his YouTube videos. However, it can be deceptively difficult to have the right conditions to pull it off - as demonstrated by the ironically fatal crash that killed Commander (Ret) McSpadden (though iirc it was not clear if he was flying the craft at the time). (Edits made for clarity/content.)
        neom 2y ago
        Thank you for the clarification, I hoped I couched everything enough people knew I'm just reading internet and not at all an expert, I appreciate the reply!

dgfitz 2y ago

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.

irjustin 2y ago
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 https://www.youtube.com/watch?v=evLpE8Us-j0
dredmorbius 2y ago
True, though I don't have a breakdown of net effects. Commercial jet aircraft utilise thrust reversers, speed (or air) brakes (usually control surfaces which can extend out from the aircraft fuselage or wings), and landing gear brakes. The latter are not insignificant, but thrust reversers and speed brakes are major contributors, especially immediately after touchdown. There's also the effect of spoilers which increase the load over the gear and hence the braking capabilities of landing gear brakes. Jeju 2216 failed to utilise nearly all of these mechanisms. It landed without flaps, spoilers, or gear, and possibly w/o thrust reversers.
3ple_alpha 2y ago
If one divides weight of the airplane by the number of wheels it has, one would find one wheel carries around 10 times more weight than that of a truck. You even get a slightly better deal on landing when you don't have as much fuel. That's a lot of weight but nothing crazy, so on a dry runway wheel brakes alone are more than enough to stop normally. They would also wear out a lot, overheat and occasionally ignite if used like that, so that's what thrust reversers are for.
- mmooss 2y ago
  That mass has much more velocity than a truck.