Originally posted by Evan
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Jeju Air737-800 Crash at MWX (Muan International Airport, South Korea)
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Originally posted by BoeingBobby View Post
Not enough to compensate for the amount of drag. Again as I asked Gabe, do you ou think the deployment of spoilers would have made a significant difference?
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Originally posted by Evan View Post
I will defer to Gabe on that one. I think spoilers would make a significant difference (significantly greater weight pressing down, greater friction, greater drag--think of the plane as a brake pad and the runway as a brake disk and your spoiler lever as a brake lever) but I think when you land at that speed halfway down that runway and proceed to slide down the remaining half, you're essentially doomed to hit, rather destructively, whatever lies beyond it.
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Originally posted by thor View Post
its strange, never heard of that happened before, that the cvr and fdr would stop itself right before a big crash.
The battery-operated standby essential electric bus doesn't feed the CVR and FDR, but even if it did you would still lose a lot of information because a lot of sensors, instruments and computers would go offline so they would stop providing data.
In several of the past cases, the CVR and FDR came back online shortly afterwards (between several seconds and a couple of minutes later) when the APU was started and its generator came online.
Towards the beginning of the thread I predicted that the FDR and CVR might have stopped recording on the 1st approach at 900ft, when the ASD-B data stopped being broadcasted. The most likely cause for that was the transponder stopping working, and a good candidate cause for that would be the loss of both main electrical systems (the transponder is not on the battery-operated essential bus either).
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--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Evan View Post
The obvious complication here is that the lever is going to remain armed unless you have the presence of mind to move it manually. And I don't expect that to happen.
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--- Defend what you say with arguments, not by imposing your credentials ---
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BB, please READ, not like the last time, because I am going to re-state things already said, even things you quoted me saying.[QUOTE=BoeingBobby;n1206177]
When it be slidin down da runway on her belly, ain't much lift being produced at dat point.
I ALSO SAID that ZERO is NOT the minimum lift. The extension of spoilers can (and many times does) make the lift NEGATIVE, drastically increasing the weight-on-wheels (or weight-on-nacelles-and-belly). How do you think F1 cars can achieve 7G in high-speed curves? They would not have enough weight-on-wheels to provide such traction if they depended only on weight.
Airplane spoilers can make lift negative in an airplane rolling on a runway even with take-off flaps/slats. Without flaps, it would make the lift even more negative
(except that full ground spoilers would not have been available, only max flight spoilers)
If you think that spoiler extension would have saved their ass, I ain't gettin in no flying machine wit you been doing da flying!
2) I specifically said that spoilers would have helped slow down, but that it is hard to tell if that would have helped survive. Not like a crash against a wall at 100 kts and subsequent explosion is much more survivable than the same thing at 150 kts.
I need to change my signature. It is too sophisticated for this audience.
I need to make it "Read what is said before judging what is said".
--- 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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FWIW, I checked the final report on the LOT 767 that pulled off a successful gear-up landing. There was no ground (or flight detent) spoiler activation. The plane touched down near the threshold and stopped after using a bit less than 2/3's of the 3690m (foamed) runway. However, the crew had both engines, plenty of time for the approach and the touchdown speed was 127kts.
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[QUOTE=Gabriel;n1206194]BB, please READ, not like the last time, because I am going to re-state things already said, even things you quoted me saying.Originally posted by BoeingBobby View Post
I said that the wing would n not be producing much drag at that small AoA and with no flaps.
I ALSO SAID that ZERO is NOT the minimum lift. The extension of spoilers can (and many times does) make the lift NEGATIVE, drastically increasing the weight-on-wheels (or weight-on-nacelles-and-belly). How do you think F1 cars can achieve 7G in high-speed curves? They would not have enough weight-on-wheels to provide such traction if they depended only on weight.
Airplane spoilers can make lift negative in an airplane rolling on a runway even with take-off flaps/slats. Without flaps, it would make the lift even more negative
(except that full ground spoilers would not have been available, only max flight spoilers)
1) The chances of you flying in a plane with me at the controls are from remote to zero, regardless of what I think about the spoilers.
2) I specifically said that spoilers would have helped slow down, but that it is hard to tell if that would have helped survive. Not like a crash against a wall at 100 kts and subsequent explosion is much more survivable than the same thing at 150 kts.
I need to change my signature. It is too sophisticated for this audience.
I need to make it "Read what is said before judging what is said".
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Originally posted by Evan View PostFWIW, I checked the final report on the LOT 767 that pulled off a successful gear-up landing. There was no ground (or flight detent) spoiler activation. The plane touched down near the threshold and stopped after using a bit less than 2/3's of the 3690m (foamed) runway. However, the crew had both engines, plenty of time for the approach and the touchdown speed was 127kts.
Report says that it stopped 42m past the intersection with RWY 29. That would make a grand total of 2100m (57%) of runway used.
Lacking a better number, I am going to assume that the plane touched down 500m down the runway (which is the touchdown zone markers were located) so the skidding distance was 1600m
The plane touched down with a ground speed of 127 knots, or 65m/s. Unfortunately I could not find a continuous video from touchdown to stop to time how long it took and be able to calculate the average acceleration. If the deceleration was constant then it would have been about 1.3m/sē (about 0.13g or 2.6 kts/s) to go from 65m/s to 0 in 1600, and it would have taken some 50 seconds.
The Jeju 737 landed quite faster (speed yet to be determined), but at the same time the runway was dry instead of treated with wet and slippery firefighting foam, so it should have been able to decelerate at a faster rate, but starting from a higher speed.
--- 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 BoeingBobby View PostYeah you are absolutely right. If those giant spoiler panels had come out. Landing at what looked to me about 150 - 160 knots. And touching down about half way down the runaway, they would certainly have slowed down enough to make a tremendous difference. Why I even bother at this point?
What was your reason to bother and stir the dulce de leche?
--- 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 Post
Where did you get that the plane touched down near the threshold?
Report says that it stopped 42m past the intersection with RWY 29. That would make a grand total of 2100m (57%) of runway used.
Lacking a better number, I am going to assume that the plane touched down 500m down the runway (which is the touchdown zone markers were located) so the skidding distance was 1600m
The plane touched down with a ground speed of 127 knots, or 65m/s. Unfortunately I could not find a continuous video from touchdown to stop to time how long it took and be able to calculate the average acceleration. If the deceleration was constant then it would have been about 1.3m/sē (about 0.13g or 2.6 kts/s) to go from 65m/s to 0 in 1600, and it would have taken some 50 seconds.
The Jeju 737 landed quite faster (speed yet to be determined), but at the same time the runway was dry instead of treated with wet and slippery firefighting foam, so it should have been able to decelerate at a faster rate, but starting from a higher speed.
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Originally posted by Evan View Postone of the graphics [of the report] shows a line beginning at the threshold.
Page 26.
--- 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 thor View Postwhy the pilots didn't start the APU at once after they lost both engines? which could have provided power to continue recording.
A better question to ask is: why didn’t the recorders have internal battery power in the year 2024 on a $50M commercial aircraft? Why is that not a certification requirement?
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Originally posted by Evan View Post
Time compression. Tunneling. Four minutes from total power loss to landing. Manual gliding. Navigation. Probably focused on recovering the engines. And what I suspect was a collapse of CRM and situational awareness.
A better question to ask is: why didn’t the recorders have internal battery power in the year 2024 on a $50M commercial aircraft? Why is that not a certification requirement?
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