Can be, but not always possible or advisable. Part of the type rating for any airliner is a gear-up landing. Normally you just skid along the engine nacelles.
Where this went wrong is they seem to have been going way too fast. And they also seem to have deployed the reversers, which you're not supposed to do. Although dragging on the runway could have just pulled the panels back. (Edit: after looking at the better quality version posted below, that's exactly what happened. #2 is open, but #1 is closed, so it likely just got dragged open).
In theory, if you're making a gear-up landing, you go in as slow as possible, and once you've made the runway, the fuel pumps get turned off just before touchdown to starve the engines and reduce the chances of a fire.
Not sure about the instrumentation failure theory mentioned below. In most airliners (737 included), the indication for the gear being down is three green lights. If any of those lights failed, you would think that something failed to deploy as no light = not down. It would be very strange for all three indicators to show a false positive.
My hot-take is they came in way too fast and touched down way too far. If executed properly, a gear-up landing doesn't result in an overrun and crashing into whatever lies beyond. It looks like the flaps are up, which is even more puzzling, but that would account for the excess speed.
Edit 2: As for the actual cause, it seems there was a bird-strike during a previous landing attempt that caused a go-around. The bird-strike could have caused damage to some of the hydraulics.
Edit 3: Muan International, on a normal approach, has about 8,000 feet of runway available. This should be more than enough to stop a 737 given that scraping the nacelles is a lot more draggy than landing on the wheels. That and the fact that they seem to have hit a berm tells me they were definitely coming in way to hot, and touched down way too late. There's 400ft of overrun protection on each end that's designed to collapse under the weight of an aircraft and slow it down. But it looks like that was just skipped right over. All things being equal, they should have done another go-around if they were high/fast enough that they floated that far down the runway before touchdown.
Edit 4: They were using Runway 19, which points south. The berm they hit was for the threshold lighting, and it 860 feet past the end of the runway, and 460 feet past the end of the overrun area. Yet another indication they were going too fast and touched down too late.
Protocol generally. Thrust reversers exist on most jet engines of various types, but they consist of one of two types, the rear of engine based scoop type, or the front of engine cowling type. The problem in this instance is that neither types could be deployed due to the engines being on the ground.
Jet engines do not have transmissions and only run in one direction - out the back. The blades and compressors can not work backwards, which is why "thrust reversers" only direct the thrust, not actually reverse the engine.
Exactly like Harrier jets and F35 thrust vectoring.
Landing gear failures will probably get a good looking into after this.
Foam would probably just make the runway more slippery, adding a thousand meters to the landing distance, and the design of the plane with the engines and cowlings as the low points on the wings make for very little contact surface friction even without foam. Looks like the two engines and the very end of the tail were the only areas touching the runway.
The biggest factor exacerbating this accident to me is the metal barrier at the end that not only stopped the plane but shredded the wings and fuel tanks, resulting in the explosion.
[ - ] localsal 1 point 4 monthsDec 29, 2024 07:02:57 ago (+3/-2)
Dumping all the fuel to empty the tanks is another good in theory idea, until a go-around is needed, then oops, no gas.
The amount of data pilots need to go through for a standard landing is immense, let alone for an emergency.
I need to look up more belly landing videos to see what the differences are - but my guess is that most aircraft and airline procedures for a belly landing are to just treat it like a normal landing to avoid flipping the plane over.
Past belly landings may have been on smaller engine planes or with engines not mounted to the wings, which gives the entire fuselage contact and lots of friction for slowing.
Also, learning which airports have metal barriers at the end would be very difficult for the number of active pilots and airports, etc.
Better concrete also could play a factor as it is stronger and as a result, has a lot less friction, making the skidding length dramatically longer. The under the wing engines also can't use the thrust reversers, so once on the ground everyone is just along for the terrible ride.
If the engines are in contact with the runway, there is little to no room for the thrust reversers to flare out.
I am not familiar with all models of thrust reversers, but some have elaborate mechanisms that essentially detach the back part of the engine covers and then join them together at the exhaust of the engine at an angle that blows back over the engine.
The best flow paths for the reversers is top and bottom of the engine - to keep the hot engine exhaust from hitting the plane itself - and I would assume most reversers are linked together. The bottom half of the reverser obviously can't deploy through the runway, and the linkage essentially locks the top half too.
At least that is my guess without having any knowledge of the 737 engine in use or design options.
Exactly. On the ground without wheels there isn't much the plane can do to stop itself.
If the plane had enough fuel to get to a longer runway, that would be my guess as to the proper procedure. Just have enough runway to stop due to friction.
I don't ever want to have to think about it too much, but those pilots do get all the bad news way before the passengers do (if ever) and dealing with those last seconds has to be torture.
You don't use reversers in a gear-up landing anyway. Ever. You wait until just before touchdown (past the point where you'd call for a go-around) and you kill the fuel pumps.
Also, the 737 uses the sliding type cold-stream reversers (whereas an A320 will use pivoting doors). Cold-stream reversers just shunt the bypass air forward, but the core section continues providing some thrust (but that only accounts for like 20% of total thrust tops on modern high-bypass engines). If you look at the video, #1 is stowed but #2 is open, so the cover probably got dragged back. The system you're describing is the "bucket" type reverser. Those were on earlier 737's with the JT8D engines, but done away with once they started using the larger CFM engines. Almost no aircraft use bucket type reversers anymore.
To answer @bobdole9 - most aircraft with reversers also have a switch in the landing gear that prevents the reversers from being unlocked unless there's weight on the wheels. One of the few exceptions is the C-17, which can unlock the reversers in flight for combat approaches, allowing for a much steeper descent.
As for fuel dumping, not all aircraft are capable of it. The 737 is one that isn't.
I wouldn't rule anything out. Things don't usually happen as single failures, and it isn't hard to take one unexpected event and turn it into a series of unfortunate events.
There is a lot more to uncover in this accident - such as why the landing gear didn't extend at all, and how the pilots handled the landing itself, and what the actual procedure for a belly landing is.
I obviously haven't been to most airports, but from what I have read, the runways are typically built along the most common wind directions to allow for easier takeoff and landing.
Because the runways are bi-directional, they could have equipment on either or both ends, and due to the security there is most likely a fence around the entire airport - and since the runway is the largest part of the airport, the buffer zone from the runway to the fence is probably just enough to allow for worst case landings.
Watching some of the takeoff and landing videos on youtube it is easy to get an idea of how close some of the runways are to the fences, although there could be some perspective shift due to the cameras, etc.
I would definitely expect some equipment at one end - like the beacons and weather stations, but no idea how much metal is actually close to the runway.
No matter what, all runways have to end, and I would guess they end to some form of earth covering, like grass or just dirt - and if the engines are oriented in such a way as to dig in, the entire plane will then flip back to front.
This is why water landings (Sulley's aside) are so dangerous with underwing engines. Those engines will grab the water and want to stop immediately, flipping the plane. Water landings with any size wave is way worse - example:
Fucking amateur pilots. Dump fuel until you hit bingo, then dump more, then dump air speed until you almost stall. Or why not a water landing if the airport wasn't landlocked? There's miles and miles of water to land on.
[ + ] Deplorablepoetry
[ - ] Deplorablepoetry 9 points 4 monthsDec 29, 2024 07:54:14 ago (+9/-0)
[ + ] MuricaPersonified
[ - ] MuricaPersonified 9 points 4 monthsDec 29, 2024 08:53:54 ago (+9/-0)
[ + ] goatfugee12
[ - ] goatfugee12 5 points 4 monthsDec 29, 2024 10:37:40 ago (+5/-0)
[ + ] uvulectomy
[ - ] uvulectomy 1 point 4 monthsDec 29, 2024 13:12:44 ago (+1/-0)
[ + ] Deleted
[ - ] deleted 6 points 4 monthsDec 29, 2024 05:19:11 ago (+6/-0)
[ + ] bobdole9
[ - ] bobdole9 4 points 4 monthsDec 29, 2024 07:37:57 ago (+4/-0)
Too noob to rip the video myself.
https://x.com/Breaking911/status/1873175983995666619
[ + ] localsal
[ - ] localsal 3 points 4 monthsDec 29, 2024 09:06:27 ago (+3/-0)
Starting at the relevant time
https://www.youtube.com/watch?v=QMmA--l0HKE&t=900s
[ + ] Deleted
[ - ] deleted 4 points 4 monthsDec 29, 2024 09:10:27 ago (+4/-0)
[ + ] duke_cannon
[ - ] duke_cannon 3 points 4 monthsDec 29, 2024 07:00:16 ago (+3/-0)
[ + ] Deleted
[ - ] deleted 3 points 4 monthsDec 29, 2024 07:52:41 ago (+3/-0)
[ + ] bobdole9
[ - ] bobdole9 2 points 4 monthsDec 29, 2024 09:38:17 ago (+2/-0)
[ + ] uvulectomy
[ - ] uvulectomy 2 points 4 monthsDec 29, 2024 13:19:10 ago (+2/-0)*
Where this went wrong is they seem to have been going way too fast. And they also seem to have deployed the reversers, which you're not supposed to do. Although dragging on the runway could have just pulled the panels back. (Edit: after looking at the better quality version posted below, that's exactly what happened. #2 is open, but #1 is closed, so it likely just got dragged open).
In theory, if you're making a gear-up landing, you go in as slow as possible, and once you've made the runway, the fuel pumps get turned off just before touchdown to starve the engines and reduce the chances of a fire.
Not sure about the instrumentation failure theory mentioned below. In most airliners (737 included), the indication for the gear being down is three green lights. If any of those lights failed, you would think that something failed to deploy as no light = not down. It would be very strange for all three indicators to show a false positive.
My hot-take is they came in way too fast and touched down way too far. If executed properly, a gear-up landing doesn't result in an overrun and crashing into whatever lies beyond. It looks like the flaps are up, which is even more puzzling, but that would account for the excess speed.
Edit 2: As for the actual cause, it seems there was a bird-strike during a previous landing attempt that caused a go-around. The bird-strike could have caused damage to some of the hydraulics.
Edit 3: Muan International, on a normal approach, has about 8,000 feet of runway available. This should be more than enough to stop a 737 given that scraping the nacelles is a lot more draggy than landing on the wheels. That and the fact that they seem to have hit a berm tells me they were definitely coming in way to hot, and touched down way too late. There's 400ft of overrun protection on each end that's designed to collapse under the weight of an aircraft and slow it down. But it looks like that was just skipped right over. All things being equal, they should have done another go-around if they were high/fast enough that they floated that far down the runway before touchdown.
Edit 4: They were using Runway 19, which points south. The berm they hit was for the threshold lighting, and it 860 feet past the end of the runway, and 460 feet past the end of the overrun area. Yet another indication they were going too fast and touched down too late.
[ + ] Deleted
[ - ] deleted 2 points 4 monthsDec 29, 2024 05:16:12 ago (+3/-1)
[ + ] bobdole9
[ - ] bobdole9 3 points 4 monthsDec 29, 2024 07:40:02 ago (+3/-0)
Is there a way to tell from the video clip? Amazing there was no real way to slow it down at all.
[ + ] SundayMatinee
[ - ] SundayMatinee 3 points 4 monthsDec 29, 2024 09:04:55 ago (+3/-0)
[ + ] bobdole9
[ - ] bobdole9 2 points 4 monthsDec 29, 2024 09:31:00 ago (+2/-0)
[ + ] localsal
[ - ] localsal 2 points 4 monthsDec 29, 2024 07:56:46 ago (+3/-1)
Jet engines do not have transmissions and only run in one direction - out the back. The blades and compressors can not work backwards, which is why "thrust reversers" only direct the thrust, not actually reverse the engine.
Exactly like Harrier jets and F35 thrust vectoring.
[ + ] localsal
[ - ] localsal 0 points 4 monthsDec 29, 2024 05:32:58 ago (+3/-3)
Foam would probably just make the runway more slippery, adding a thousand meters to the landing distance, and the design of the plane with the engines and cowlings as the low points on the wings make for very little contact surface friction even without foam. Looks like the two engines and the very end of the tail were the only areas touching the runway.
The biggest factor exacerbating this accident to me is the metal barrier at the end that not only stopped the plane but shredded the wings and fuel tanks, resulting in the explosion.
[ + ] PeckerwoodPerry
[ - ] PeckerwoodPerry 3 points 4 monthsDec 29, 2024 06:37:41 ago (+3/-0)
[ + ] localsal
[ - ] localsal 1 point 4 monthsDec 29, 2024 07:02:57 ago (+3/-2)
The amount of data pilots need to go through for a standard landing is immense, let alone for an emergency.
I need to look up more belly landing videos to see what the differences are - but my guess is that most aircraft and airline procedures for a belly landing are to just treat it like a normal landing to avoid flipping the plane over.
Past belly landings may have been on smaller engine planes or with engines not mounted to the wings, which gives the entire fuselage contact and lots of friction for slowing.
Also, learning which airports have metal barriers at the end would be very difficult for the number of active pilots and airports, etc.
Better concrete also could play a factor as it is stronger and as a result, has a lot less friction, making the skidding length dramatically longer. The under the wing engines also can't use the thrust reversers, so once on the ground everyone is just along for the terrible ride.
[ + ] bobdole9
[ - ] bobdole9 3 points 4 monthsDec 29, 2024 07:43:39 ago (+3/-0)
Why not? Explain like I'm retarded...
[ + ] localsal
[ - ] localsal 4 points 4 monthsDec 29, 2024 07:52:19 ago (+4/-0)
I am not familiar with all models of thrust reversers, but some have elaborate mechanisms that essentially detach the back part of the engine covers and then join them together at the exhaust of the engine at an angle that blows back over the engine.
The best flow paths for the reversers is top and bottom of the engine - to keep the hot engine exhaust from hitting the plane itself - and I would assume most reversers are linked together. The bottom half of the reverser obviously can't deploy through the runway, and the linkage essentially locks the top half too.
At least that is my guess without having any knowledge of the 737 engine in use or design options.
[ + ] bobdole9
[ - ] bobdole9 2 points 4 monthsDec 29, 2024 08:39:12 ago (+2/-0)
As in, "fuck, landing gear is shit" then do all you can to scrub speed before contacting the ground?
Driving a car is far less difficult.
[ + ] localsal
[ - ] localsal 3 points 4 monthsDec 29, 2024 08:45:44 ago (+3/-0)
If the plane had enough fuel to get to a longer runway, that would be my guess as to the proper procedure. Just have enough runway to stop due to friction.
[ + ] bobdole9
[ - ] bobdole9 2 points 4 monthsDec 29, 2024 08:56:01 ago (+2/-0)
Pilots staring at the inevitable for those seconds must've felt like years.
[ + ] localsal
[ - ] localsal 2 points 4 monthsDec 29, 2024 09:15:49 ago (+2/-0)
[ + ] JudyStroyer
[ - ] JudyStroyer 2 points 4 monthsDec 29, 2024 09:22:45 ago (+2/-0)
[ + ] uvulectomy
[ - ] uvulectomy 0 points 4 monthsDec 29, 2024 13:48:21 ago (+0/-0)
Also, the 737 uses the sliding type cold-stream reversers (whereas an A320 will use pivoting doors). Cold-stream reversers just shunt the bypass air forward, but the core section continues providing some thrust (but that only accounts for like 20% of total thrust tops on modern high-bypass engines). If you look at the video, #1 is stowed but #2 is open, so the cover probably got dragged back. The system you're describing is the "bucket" type reverser. Those were on earlier 737's with the JT8D engines, but done away with once they started using the larger CFM engines. Almost no aircraft use bucket type reversers anymore.
To answer @bobdole9 - most aircraft with reversers also have a switch in the landing gear that prevents the reversers from being unlocked unless there's weight on the wheels. One of the few exceptions is the C-17, which can unlock the reversers in flight for combat approaches, allowing for a much steeper descent.
As for fuel dumping, not all aircraft are capable of it. The 737 is one that isn't.
[ + ] Deleted
[ - ] deleted 2 points 4 monthsDec 29, 2024 08:28:10 ago (+2/-0)
[ + ] localsal
[ - ] localsal 3 points 4 monthsDec 29, 2024 08:42:02 ago (+3/-0)
There is a lot more to uncover in this accident - such as why the landing gear didn't extend at all, and how the pilots handled the landing itself, and what the actual procedure for a belly landing is.
[ + ] bobdole9
[ - ] bobdole9 1 point 4 monthsDec 29, 2024 09:35:58 ago (+1/-0)
Do airports have sandtraps after the runway stops, or is it more common to see "a couple hundred yards of dirt" and the wall?
I get there might not be actual room for emergency mitigation techniques...
[ + ] localsal
[ - ] localsal 2 points 4 monthsDec 29, 2024 09:45:39 ago (+3/-1)
Because the runways are bi-directional, they could have equipment on either or both ends, and due to the security there is most likely a fence around the entire airport - and since the runway is the largest part of the airport, the buffer zone from the runway to the fence is probably just enough to allow for worst case landings.
Watching some of the takeoff and landing videos on youtube it is easy to get an idea of how close some of the runways are to the fences, although there could be some perspective shift due to the cameras, etc.
I would definitely expect some equipment at one end - like the beacons and weather stations, but no idea how much metal is actually close to the runway.
No matter what, all runways have to end, and I would guess they end to some form of earth covering, like grass or just dirt - and if the engines are oriented in such a way as to dig in, the entire plane will then flip back to front.
This is why water landings (Sulley's aside) are so dangerous with underwing engines. Those engines will grab the water and want to stop immediately, flipping the plane. Water landings with any size wave is way worse - example:
https://www.youtube.com/watch?v=uby1a9SIlP4
[ + ] Sal_180
[ - ] Sal_180 -3 points 4 monthsDec 29, 2024 06:41:47 ago (+1/-4)
[ + ] RevengeOfNeri
[ - ] RevengeOfNeri 0 points 4 monthsDec 29, 2024 16:15:32 ago (+0/-0)
[ + ] TheNoticing
[ - ] TheNoticing 0 points 4 monthsDec 29, 2024 11:31:04 ago (+1/-1)
[ + ] Ragnar
[ - ] Ragnar 0 points 4 monthsDec 29, 2024 10:34:15 ago (+1/-1)
[ + ] PostWallHelena
[ - ] PostWallHelena -3 points 4 monthsDec 29, 2024 09:04:19 ago (+0/-3)