Originally posted by thor
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Jeju Air737-800 Crash at MWX (Muan International Airport, South Korea)
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I’m sharing this only for grins- The MOVIE about Sully makes it seem that Sully USED COWBOY MONKEY IMPROVISATION TO START THE APU, GOING AGAINST THE PROCEDURES and that action significantly improved the outcome.
The APU certainly could have given a lot more information here, but it’s a whole other question if it would have changed the outcome.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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I am greatly enjoying the spoiler discussion. One thing I think we are missing is that they may have been a convenient way to manage the descent and speed and touch down closer to the approach end…
…use them glider-style. Before the touchdown.
Much quicker to turn on and off vs an s-turn.
I imagine they have some utility after touchdown but it’s probably a narrow set of circumstances where it makes a big difference.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Evan View Post
How?
Imagine Sully at a riverless airport, and he HAD hydraulics.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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This plane might have had hydraulics. The engines pumps can provide this if the engines are windmilling and they might have been still powered. But, unlike the A320, the 737 doesn't need hydraulics to fly (therefore, no RAT). The configuration (clean or minimal flaps, gear stowed) is ideal for gliding. And they turned around and reached the runway with a surplus of energy. If they had lowered the alternate gear extension on final and touched down near the threshold, I don't think this thread would exist. I don't see how the APU could have changed the outcome. It would have provided us flight data, but so would battery-backup flight recorders.
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3BS: “it’s a whole other question if the [APU] would have changed the outcome.”
Evan: “How so?”
3BS: [The plane was still powerless and somewhat likely to still “land” in a bad place]
Originally posted by Evan View Post***I don't see how the APU could have changed the outcome.***
So: “Yes.”
Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Gabriel View Post
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Originally posted by Evan View PostThere is no indication of the actual touchdown point, nor any detailed description of the landing. I take that to mean it was not out of the ordinary range in the TDZ. I've also studied the videos and the plane appears to touch down in the normal range and just at the beginning of the foamed area. Long story short, it was not a long landing.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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All in all, a nightmare. With total hydraulic failure but with electricity and the engines running, Boeing advises to make a long approach and have the airplane fully configured for landing well in advance, because the flaps will take a whole lot to extend. They also advise to keep the airplane in trim all the time to minimize the force needed on the control column, and to trim a bit nose up on final while pushing down to keep the desired speed and trajectory. That slight nose-up out-if-trim condition will help in the flare. I suppose that a very unlikely total hydraulic and electrical failure (except the essential bus) with the APU not available (MEL'd?) but with the engines running would still be manageable. You will absolutely need to put the plane on the ground in less than 30 minutes, else the battery that feeds the essential power will deplete and then not only you will lose every instrument up there (except perhaps the standby attitude indicator, airspeed indicator, altimeter and compass, which I think have their own battery, but it also last 30 minutes), but I don't know if the FADEC would keep working and if it doesn't, you lost the engines (or at the very least you lost control over the engines). But with 30 minutes and the engines running, you can set up yourself for a long final. There will be not much configuration to do, just extend the landing gear and keep the airplane manually trimmed. It will be a fast flapless landing but at least you have wheels, some steering and brakes.
But the most logical way that you would lose all hydraulics and electrical and hydraulic systems except the essential bus is a dual engine failure. And in those cases, most of the times the APU will be available and if it can be started, it will provide full electrical power and full hydraulics albeit at a slower flow rate (which will affect flaps extension times) and the plane can be flown, or glided, using the normal methods foe everything (normal gear, normal flaps/slats except slower, normal flight controls including roll spoilers, speedbrakes, ground spoilers, electric trim, all the instruments, everything, except thrust.
At high altitude, you may attempt a windmill restart immediately if you are going fast enough, or you can pitch down for airspeed to achieve the windmill start speed. And the APU may not be immediately available since there is an envelope of operation (a max altitude) at which it can be started.
But at low altitude? Unless you are almost on the flare already (or less than 1 minute from touching down, where the APU would not have time to start anyway), I don't see any reason why not to start the APU as the 1st action after a dual engine failure (or even after a single engine failure).
Evan mentioned that priority should be given to trying to restart an engine. With what? Will power? At below windmilling-start speed, no altitude to trade for speed, no engine to provide cross-pneumatic power, and no APU pneumatic power, I would not lose a microsecond even considering the idea of maybe attempting restart an engine.
So would the APU have made a difference? Absolutely! I don't know if it would have changed the outcome, but compare having one pilot having to muscle the controls, having to trim manually, and having monitoring from the FO because he has no instruments to crosscheck, and having to do a lot of alternate-method thing that is just practiced in a sim session every once and then (actually just the gear, the rest would not work but they will at least think about that). Having the APU started would make the plane much more flyable, will let the pilots use familiar methods, will reduce the workload a lot, would allow for both pilots to be in the loop, and will give them tools not available otherwise. Oh the CVR and FDR would resume recording data.
Now, the elephant in the room... It seems that they did have hydraulics. The deployment of the #2 reverser is a hint. For me, the way they flare and keep the plane bleeding speed before touching down too (it would be hard to do by muscle force especially because it would be an unfamiliar feel). If they had hydraulics was because one engine was running, even if damaged. If an engine was damaged even if damaged. But then they would possibly have one generator too which most likely they did not, since the ADS-B, FDR and CVR all stopped at about the same time. So I don't understand.
Another thing to consider is that I can't imagine a world where they lost all thrust while on final int he 1st approach or shortly after starting the go around, and they still managed to fly a full circuit pattern from that altitude. The 737 clean is a pretty good glider (17:1), but starting from 1000 ft that means a track distance of17000ft or about 3 miles, and that in a straight line. Turning would reduce that. Just not enough to fly the downwind and make a 180-degrees turn. That also supports that they had at least some thrust available.
Blancolirio wondered whether a wrong engine shutdown could have been a factor.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostAll in all, a nightmare. With total hydraulic failure but with electricity and the engines running, Boeing advises to make a long approach and have the airplane fully configured for landing well in advance, because the flaps will take a whole lot to extend. They also advise to keep the airplane in trim all the time to minimize the force needed on the control column, and to trim a bit nose up on final while pushing down to keep the desired speed and trajectory. That slight nose-up out-if-trim condition will help in the flare. I suppose that a very unlikely total hydraulic and electrical failure (except the essential bus) with the APU not available (MEL'd?) but with the engines running would still be manageable. You will absolutely need to put the plane on the ground in less than 30 minutes, else the battery that feeds the essential power will deplete and then not only you will lose every instrument up there (except perhaps the standby attitude indicator, airspeed indicator, altimeter and compass, which I think have their own battery, but it also last 30 minutes), but I don't know if the FADEC would keep working and if it doesn't, you lost the engines (or at the very least you lost control over the engines). But with 30 minutes and the engines running, you can set up yourself for a long final. There will be not much configuration to do, just extend the landing gear and keep the airplane manually trimmed. It will be a fast flapless landing but at least you have wheels, some steering and brakes.
But the most logical way that you would lose all hydraulics and electrical and hydraulic systems except the essential bus is a dual engine failure. And in those cases, most of the times the APU will be available and if it can be started, it will provide full electrical power and full hydraulics albeit at a slower flow rate (which will affect flaps extension times) and the plane can be flown, or glided, using the normal methods foe everything (normal gear, normal flaps/slats except slower, normal flight controls including roll spoilers, speedbrakes, ground spoilers, electric trim, all the instruments, everything, except thrust.
At high altitude, you may attempt a windmill restart immediately if you are going fast enough, or you can pitch down for airspeed to achieve the windmill start speed. And the APU may not be immediately available since there is an envelope of operation (a max altitude) at which it can be started.
But at low altitude? Unless you are almost on the flare already (or less than 1 minute from touching down, where the APU would not have time to start anyway), I don't see any reason why not to start the APU as the 1st action after a dual engine failure (or even after a single engine failure).
Evan mentioned that priority should be given to trying to restart an engine. With what? Will power? At below windmilling-start speed, no altitude to trade for speed, no engine to provide cross-pneumatic power, and no APU pneumatic power, I would not lose a microsecond even considering the idea of maybe attempting restart an engine.
So would the APU have made a difference? Absolutely! I don't know if it would have changed the outcome, but compare having one pilot having to muscle the controls, having to trim manually…
Blancolirio wondered whether a wrong engine shutdown could have been a factor.
BTW, Evan does not prioritize engine relight over starting the APU. The QRH procedures do. I think this is because the procedures are written for high-altitude failure where there is ample time to pull up the QRH and run procedure. Dual engine failure at this height has to be an instant recall procedure, and IMO APU start should be one of the first actions if not the first action.
But I was looking more closely at the reported timing of events here. Whatever happened to the electrical power happened before the go-around. If electrics were lost due to both engines being crippled from multiple bird strikes, at least one must have still been providing useable thrust and sufficient hydraulics to retract the gear.
Three possibilities come to mind:
The engine-driven generators automatically went offline due to low rpm (some do on the NG, depending on the installed equipment). They may need to be manually recovered.
The pilots mistakenly switched off both drives. (A theory posted on AV Herald speculated that cabin smoke following a bird strike might have caused the crew to switch off both engine bleeds but they used the electrical panel by mistake due to low visibility and confusion. The switches are similar.)
They lost the #2 engine to a bird strike and accidentally shut down #1. And then distraction and chaos. That has always been a strong possibility.
This is why the CVR is so critical and hopefully, if one thing comes from this investigation, it will be an expedited mandate to retrofit all major fleets with RIPS flight recorders.
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AvHerald: https://avherald.com/h?article=52225189&opt=0
On Jan 13th 2025 South Korea's Ministry of Transport further detailed, that the CVR stopped recording at 08:58:49L before the crew declared emergency at 08:59L.
Timeline becomes more clear and interesting. We can guess now that the total electrical failure (and hence the damage to both engines) happened before or as they were starting the go around. It's not like the started the go around when one engine was impacted and some time later, when they were already in the go around and gaining altitude, the second engine was impacted.
The call for bird strike and going around sounded quite desperate in the audio. I first thought that was a normal startle reaction. But if you have a total electrical failure and 1/2 of the cockpit goes blind and the AP and AT disconnect and you get a plethora of master cautions, master warnings, and blinking lights (remember no ECAM/EICAS), that would increase the stress / panic level a few levels.
This also kind of confirms that they did not lose all thrust. On one hand they cold have never make it from there to landing on the other runway with zero thrust. On the other hand they still had hydro power to retract the gear and flaps and no Evan, I am not buying the windmill theory at 150ish knots. Even if there was some windmill and some EDP action, and even if that helped boost the cable-muscle controls, retracting gear and flaps is another kind of beast that consume a lot of hydro flow and power. I feel quite confident at this point that they had at least one EDP functioning normally or almost normally as to retract the gear and flaps, use the controls in a normal way (except the stabilizer trim), and deploy the reverser upon landing (the reverser in the 737 doesn't need weight on wheels to deploy but a radalt < 50 ft). If that is confirmed, not lowering the landing gear even in the final moments before touchdown looks more like an overlook than a decision or an impossibility, unless it was a strategy to extend the glide and they turned final already over the runway and too close to touchdown as to attempt the gear extension, something that now we will never know.
I hope that there is raw primary radar data available to see what was the trajectory and speeds (probably not altitude) during the circuit pattern.
The ministry further reported that structures endangering flight safety like concrete mounds for ILS antenna will be replaced or removed. Three more airports in South Korea with such structures have been identified.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostAvHerald: https://avherald.com/h?article=52225189&opt=0
...not lowering the landing gear even in the final moments before touchdown looks more like an overlook than a decision or an impossibility
Curious if they find out at what position the flaps/slats were. As mentioned before, clean config isn't a GA setting.
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Originally posted by Evan View PostThe pilots mistakenly switched off both drives. (A theory posted on AV Herald speculated that cabin smoke following a bird strike might have caused the crew to switch off both engine bleeds but they used the electrical panel by mistake due to low visibility and confusion. The switches are similar.)
(Don't know if this works with the 737 PA without generator power)
With a total electrical failure and an (at least assumed) double engine failure, smoke removal is the very last thing to consider and this procedure takes a loooong time.
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Originally posted by bstolle View PostTo release the landing gear on the 737, the Copi needs to move his seat to the aftmost position, open the hatch and pull three handles. I don't think that this was an option, that close to the runway, at that low altitude and low speed.
Again guys, PLESE READ what I say before objecting to what I say.
I know that I tend to write too long and I would not blame you if you don't want to rad it. But PLEASE in that case don't object to what you don't know what it is that you are objecting.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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