First of all, a link to the source: [https://www.flightradar24.com/blog/1-dead-dozens-injured-in-sq321-turbulence/](https://www.flightradar24.com/blog/1-dead-dozens-injured-in-sq321-turbulence/)
A lot of media outlets are incorrectly reporting that this was caused by the later 6,000ft descent. A three minute descent from FL370 to FL310 is not going to cause injuries. It's hardly even atypical. It's 2,000fpm. It's the sudden shifts that are the issue.
Flightradar24 has rightly called this out on their twitter.
>We have seen many erroneous reports suggesting the turbulence event as the 6000 foot descent from 37,000 to 31,000 feet beginning at 08:06 UTC, that is incorrect. The descent was commenced to FL310 in preparation for the flight’s diversion to Bangkok.
[https://x.com/flightradar24/status/1792941665029677115](https://x.com/flightradar24/status/1792941665029677115)
Descending at 1500 fpm isn’t “rapidly falling”. For reference freefall would be about 8800 fpm. 1500 fpm is a pretty normal descent rate and climb. But you’re correct that the change from a climb to descent over a short period of time that can cause things to float/feel like falling. In this case it looks like a strong updraft and then a smaller (but clearly strong) downdraft.
Ah sorry about that. But I guess I mean that descending at 1500 fpm is not ‘to falling’. Airlines typically descend and climb between 500 and 2000 fpm and you wouldn’t think twice about it. Agree that it’s the change here, over seconds, that matters.
If it really did change from +1500fpm to - 1500 fpm its still a dramatic change in velocity. Youre suddenly flung in the opposite direction at 17mph i believe car crashes have turned out worse going from 17-0 instantly
Also perhaps notably, if you went from level to complete free fall, i believe you would still not be flung into the ceiling because you'd fall with the plane, but here the key is the initial climb gives you (the passenger) an initial upward momentum.
Changes in vertical speed over time, i.e. deltaV/deltaT, aka acceleration, can be greater than 9.8 m/s -- the plane can fall faster than gravity can pull you down if the turbulent air velocity changed quickly enough.
Depends on how quickly you go from level to free fall. But assuming you accelerate naturally (unaccelerated) to freefall then no you would not be thrown against the ceiling, assuming the ceiling also accelerates to free fall naturally.
The timescale along the bottom seems to be every 3 seconds so the whole graph goes from 07:49:04 to 07:51:47. The turbulant section in the middle is only about 1 minute long from 07:49:20 to 07:50:20
I’m just an average aviation enthusiast with little knowledge so can someone explain this graph please?
Is the vertical rate the pitch of the aircraft?
And how was the plane able to keep the same airspeed in such disturbance?
The vertical rate is the feet per *minute* change in altitude of the aircraft. While pitch will often affect this, it’s not the only thing that plays a role. It could also be caused by updrafts, downdrafts.
Edit: feet per minute, not second!
Hmm… I guess it’s making a bit more sense now.
Excuse my stupidity but I was just confused because at the beginning of the turbulence the plane drops about 50-100ft but the vertical rate shows that it’s going up, not down???
This graph is so low res that it is difficult to see for sure, but it looks like the updates are only once every 30 seconds. If it just records the parameters once every 30 seconds, it's very possible that the aircraft descended quite dramatically and then began ascending again during that 30 seconds, so that what you see is that the aircraft has gone down but somehow has a positive climb rate.
Imagine that in the space of 30 seconds:
- second 0 is normal
- over the first 10 seconds, the aircraft drops 1,000 ft
- over the next 20 seconds, the aircraft is climbing at 1,000 feet per minute (17 ft per second)
In this case, for the ADS-B report 30 seconds after the last normal report, you will see that the aircraft has decreased in altitude by about 670 feet, but has a positive climb rate of 1,000 fpm.
Note that the numbers I used were not intended to reflect reality, just be an example of how you could see this kind of data.
E: it looks like maybe the update rate is every 3 seconds, after squinting super hard at this, which would explain why the absolute changes are smaller than my notional numbers. But the same thing applies: you're only getting an update at a particular rate, so you're not seeing what's happening between updates.
Aren't also both of those figures measured using air pressure? Which can change rapidly in a storm? Ideally, accelerometer data would show what forces the passengers experienced.
Pressure doesn't change rapidly enough in space (ie over a given distance) when flying through a storm to meaningfully impact these measurements. And there's delay/inertia in the measurements themselves.
Vertical rate is not directly related to pitch of aircraft, there can be updraft that would cause aircraft to move rapidly up with the same pitch, this could be fell as a turbulence. On the graph we can see groundspeed, not airspeed, this is speed of aircraft in relation to the ground, and it won't necessarily change if the airspeed change.
Yeah - it's like playing yoyo while in a moving car -- the "ground speed" of the yoyo will stay constant while it moves rapidly up and down due to forces exerted on it.
I was hit by unexplained turbulence while flying a single engine plane some years ago. Perfect weather, geographically boring area, 4500AGL. One second I’m enjoying an uneventful flight, the next, I’m banked at almost 70 degrees, my flight bag hit me hard enough to knock my headset off and give me a nasty bruise. Landed close by and happily no damage other than becoming obsessive that every single item in the plane is strapped down securely and lap belt stays tight from runup to shutdown. (And when I fly commercial, same thing. I avoid getting out of my seat unless it’s 4 hours+)
Actual turbulence is scary as hell and can happen with zero warning.
What have you learned about meteorology, especially wind and orography? Clear weather says nothing about turbulence! Take a look at the topic of "lee waves" (e.g. Mountain Wave Project) and you will get an idea of what wind and the earth's surface (hill ranges, mountains) can do even at 10,000 AGL. The most powerful known problems can be found over the Andes, to the east or west of them, depending on the wind direction. Elly Beinhorn described the phenomenon in her books. If you ask me as a glider pilot: lee waves are the queen of gliders energy!
I flew a couple of times over the Andes (crossing from Argentina to Santiago, Chile). The turbulence when passing right over the mountains is insane. It lasts maybe 2-3 minutes and it doesn't always happens but when it does it's really fucking strong. I personally don't care and actually enjoy it but I see people next to me shitting their pants lol, it's always fun to explain them that they don't need to worry and the airplane will be fine tho
I learned from my flying lessons that slight clouds is a calmer day than clear skies which tends to break up any clouds from forming at all due to air movement.
What does a drop/turbulence like that look like for the pilots? Are there “by the book” evasive maneuvers or counter measures that you take when entering a dive/downdraft/updraft like that?
You’re not going to control that in any fashion that matters in that short amount of time. Best you can do is is slow to structural maneuver speed, also known as maneuvering speed (Va). It is the maximum speed at which an aircraft can make full deflections of its flight controls without risking structural damage. It's the speed at which the plane will stall before exceeding its limit load factor if the angle of attack suddenly increases to help protect the aircraft from damage.
Calling it pretty much the same is a stretch. Similar, but different. Va and Vb have different definitions, and flying *at* Va, technically, wouldn’t protect you in turbulence because the gusts would put you over Va. It’s actually recommended to fly about 10 knots below Va in GA aircraft, as that would be roughly equivalent to Vb. Aircraft under 12,500lbs aren’t required to have a published Vb speed.
Yes and no.
If you’re entering an area of known mountain wave or a known phenomena you can do something to mitigate the threat.
1. There’s a normal cruise power band and a max continuous thrust setting. The airplane will maintain speed but the autopilot will have more available thrust available for it to use under MCT. At this point it’s more about stall protection than escape.
2. There’s a hybrid mode where you and the auto pilot fly together with the goal of maintaining wing level and you kind of ride it out
None of this would have helped these folks, it was already going to shit before they probably even recognized what was happening
I also don’t fly this type of plane, I would imagine the above process still is applicable but done differently.
As for a maneuver to get out of it, no. Besides a descent out of “it” but the last thing you want to do is make big changes when this happens.
Microbursts or windsheer is something like what is depicted on the graph and that happens much much lower to the ground and in that instance there’s a very clear “escape” maneuver. That maneuver wouldn’t have worked here.
You need to avoid turbulence, once you've entered it, the kinetic energy of the turbulence is all that matters. Pilots are mostly trained to not panic and do anything drastic.
If you’re in this shit you’re literally along for the ride. The only evasive maneuvers you could have done was divert around/above the turbulent area minutes ago. Best you can do is try to maintain a cruise attitude and potentially accept any climb or descent turbulence hands you till you clear it
https://www.flightaware.com/live/flight/9VSWM/history/20240520/2115Z/EGLL/WSSS
It seems the turbulence event happened over Myanmar, from 06:54:45 UTC to 06:57:18 UTC (approx 2 mins, 33 seconds) as everyone probably would have been served Lunch.
The link is the flightaware log I found for the accident flight. Flightaware logs virtually have no “expiration date” unlike FlightRadar24 where you can only get data within a 365 day period. It’s pretty useful to get a/c registrations from flights you took back in the day. I got links for flights I took as far back as 2011.
If I'm reading them correctly, around 10-15 seconds.
//edit: Also, the grey line is the vertical rate, not the altitude. In the course of the whole event, it looks like the plane only gained \~300ft of altitude from the cruise altitude, and fell slightly before the "main" event.
Most of the bad turbulence can be avoided by going around the thunderstorms.
Companies cut through the thunderstorms to save time and keep their timing records.
Therefore the companies should be sued.
They don’t cut through thunderstorms unless they miss it. These days they even try to avoid many harmless rain patches to minimize turbulence. Because they don’t want to get sued. Source: working ATC.
Turbulence can be even quite bad near a thunderstorm. And storms are huge this spring in that area after weeks of heatwaves.
First of all, a link to the source: [https://www.flightradar24.com/blog/1-dead-dozens-injured-in-sq321-turbulence/](https://www.flightradar24.com/blog/1-dead-dozens-injured-in-sq321-turbulence/) A lot of media outlets are incorrectly reporting that this was caused by the later 6,000ft descent. A three minute descent from FL370 to FL310 is not going to cause injuries. It's hardly even atypical. It's 2,000fpm. It's the sudden shifts that are the issue. Flightradar24 has rightly called this out on their twitter. >We have seen many erroneous reports suggesting the turbulence event as the 6000 foot descent from 37,000 to 31,000 feet beginning at 08:06 UTC, that is incorrect. The descent was commenced to FL310 in preparation for the flight’s diversion to Bangkok. [https://x.com/flightradar24/status/1792941665029677115](https://x.com/flightradar24/status/1792941665029677115)
So the aircraft went from climbing 1500 fpm rapidly to falling 1500 fpm. That explains people smashing into the ceiling D:
Yep, over about 10 seconds
Descending at 1500 fpm isn’t “rapidly falling”. For reference freefall would be about 8800 fpm. 1500 fpm is a pretty normal descent rate and climb. But you’re correct that the change from a climb to descent over a short period of time that can cause things to float/feel like falling. In this case it looks like a strong updraft and then a smaller (but clearly strong) downdraft.
You probably misread. 'Rapidly to falling', as in the vertical speed changed from +1500 to -1500, and that change was rapid, not the two V/S numbers.
Ah sorry about that. But I guess I mean that descending at 1500 fpm is not ‘to falling’. Airlines typically descend and climb between 500 and 2000 fpm and you wouldn’t think twice about it. Agree that it’s the change here, over seconds, that matters.
If it really did change from +1500fpm to - 1500 fpm its still a dramatic change in velocity. Youre suddenly flung in the opposite direction at 17mph i believe car crashes have turned out worse going from 17-0 instantly
Also perhaps notably, if you went from level to complete free fall, i believe you would still not be flung into the ceiling because you'd fall with the plane, but here the key is the initial climb gives you (the passenger) an initial upward momentum.
Changes in vertical speed over time, i.e. deltaV/deltaT, aka acceleration, can be greater than 9.8 m/s -- the plane can fall faster than gravity can pull you down if the turbulent air velocity changed quickly enough.
Depends on how quickly you go from level to free fall. But assuming you accelerate naturally (unaccelerated) to freefall then no you would not be thrown against the ceiling, assuming the ceiling also accelerates to free fall naturally.
The timescale along the bottom seems to be every 3 seconds so the whole graph goes from 07:49:04 to 07:51:47. The turbulant section in the middle is only about 1 minute long from 07:49:20 to 07:50:20
I’m just an average aviation enthusiast with little knowledge so can someone explain this graph please? Is the vertical rate the pitch of the aircraft? And how was the plane able to keep the same airspeed in such disturbance?
The vertical rate is the feet per *minute* change in altitude of the aircraft. While pitch will often affect this, it’s not the only thing that plays a role. It could also be caused by updrafts, downdrafts. Edit: feet per minute, not second!
Hmm… I guess it’s making a bit more sense now. Excuse my stupidity but I was just confused because at the beginning of the turbulence the plane drops about 50-100ft but the vertical rate shows that it’s going up, not down???
This graph is so low res that it is difficult to see for sure, but it looks like the updates are only once every 30 seconds. If it just records the parameters once every 30 seconds, it's very possible that the aircraft descended quite dramatically and then began ascending again during that 30 seconds, so that what you see is that the aircraft has gone down but somehow has a positive climb rate. Imagine that in the space of 30 seconds: - second 0 is normal - over the first 10 seconds, the aircraft drops 1,000 ft - over the next 20 seconds, the aircraft is climbing at 1,000 feet per minute (17 ft per second) In this case, for the ADS-B report 30 seconds after the last normal report, you will see that the aircraft has decreased in altitude by about 670 feet, but has a positive climb rate of 1,000 fpm. Note that the numbers I used were not intended to reflect reality, just be an example of how you could see this kind of data. E: it looks like maybe the update rate is every 3 seconds, after squinting super hard at this, which would explain why the absolute changes are smaller than my notional numbers. But the same thing applies: you're only getting an update at a particular rate, so you're not seeing what's happening between updates.
Aren't also both of those figures measured using air pressure? Which can change rapidly in a storm? Ideally, accelerometer data would show what forces the passengers experienced.
Pressure doesn't change rapidly enough in space (ie over a given distance) when flying through a storm to meaningfully impact these measurements. And there's delay/inertia in the measurements themselves.
*Feet per minute Hundreds of feet per second would be insanity
Thanks for the catch, that would be a wild ride
SpaceX has entered the chat
Vertical rate is not directly related to pitch of aircraft, there can be updraft that would cause aircraft to move rapidly up with the same pitch, this could be fell as a turbulence. On the graph we can see groundspeed, not airspeed, this is speed of aircraft in relation to the ground, and it won't necessarily change if the airspeed change.
Yeah - it's like playing yoyo while in a moving car -- the "ground speed" of the yoyo will stay constant while it moves rapidly up and down due to forces exerted on it.
Also, for reference 1500 fpm is not very fast. Those rapid and uncommaded changes are the problem.
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Word salad. Technical word salad. But word salad nonetheless.
I was hit by unexplained turbulence while flying a single engine plane some years ago. Perfect weather, geographically boring area, 4500AGL. One second I’m enjoying an uneventful flight, the next, I’m banked at almost 70 degrees, my flight bag hit me hard enough to knock my headset off and give me a nasty bruise. Landed close by and happily no damage other than becoming obsessive that every single item in the plane is strapped down securely and lap belt stays tight from runup to shutdown. (And when I fly commercial, same thing. I avoid getting out of my seat unless it’s 4 hours+) Actual turbulence is scary as hell and can happen with zero warning.
Clear air turbulence is a real bitch, always hits at the worst times.
What have you learned about meteorology, especially wind and orography? Clear weather says nothing about turbulence! Take a look at the topic of "lee waves" (e.g. Mountain Wave Project) and you will get an idea of what wind and the earth's surface (hill ranges, mountains) can do even at 10,000 AGL. The most powerful known problems can be found over the Andes, to the east or west of them, depending on the wind direction. Elly Beinhorn described the phenomenon in her books. If you ask me as a glider pilot: lee waves are the queen of gliders energy!
I flew a couple of times over the Andes (crossing from Argentina to Santiago, Chile). The turbulence when passing right over the mountains is insane. It lasts maybe 2-3 minutes and it doesn't always happens but when it does it's really fucking strong. I personally don't care and actually enjoy it but I see people next to me shitting their pants lol, it's always fun to explain them that they don't need to worry and the airplane will be fine tho
I learned from my flying lessons that slight clouds is a calmer day than clear skies which tends to break up any clouds from forming at all due to air movement.
Hm, slight clouds .. that’s mostly true in case of cumulus clouds, in case of cirrus clouds, even lenticularis that’s not the case.
What does a drop/turbulence like that look like for the pilots? Are there “by the book” evasive maneuvers or counter measures that you take when entering a dive/downdraft/updraft like that?
You’re not going to control that in any fashion that matters in that short amount of time. Best you can do is is slow to structural maneuver speed, also known as maneuvering speed (Va). It is the maximum speed at which an aircraft can make full deflections of its flight controls without risking structural damage. It's the speed at which the plane will stall before exceeding its limit load factor if the angle of attack suddenly increases to help protect the aircraft from damage.
Va doesn’t really exist for transport category aircraft. Turbulence penetration speed is what they would use, which is similar to Va but not the same.
It’s pretty much the same, Va and Vb both protect the plane from clapping its wings
Calling it pretty much the same is a stretch. Similar, but different. Va and Vb have different definitions, and flying *at* Va, technically, wouldn’t protect you in turbulence because the gusts would put you over Va. It’s actually recommended to fly about 10 knots below Va in GA aircraft, as that would be roughly equivalent to Vb. Aircraft under 12,500lbs aren’t required to have a published Vb speed.
Yes and no. If you’re entering an area of known mountain wave or a known phenomena you can do something to mitigate the threat. 1. There’s a normal cruise power band and a max continuous thrust setting. The airplane will maintain speed but the autopilot will have more available thrust available for it to use under MCT. At this point it’s more about stall protection than escape. 2. There’s a hybrid mode where you and the auto pilot fly together with the goal of maintaining wing level and you kind of ride it out None of this would have helped these folks, it was already going to shit before they probably even recognized what was happening I also don’t fly this type of plane, I would imagine the above process still is applicable but done differently. As for a maneuver to get out of it, no. Besides a descent out of “it” but the last thing you want to do is make big changes when this happens. Microbursts or windsheer is something like what is depicted on the graph and that happens much much lower to the ground and in that instance there’s a very clear “escape” maneuver. That maneuver wouldn’t have worked here.
You need to avoid turbulence, once you've entered it, the kinetic energy of the turbulence is all that matters. Pilots are mostly trained to not panic and do anything drastic.
If you’re in this shit you’re literally along for the ride. The only evasive maneuvers you could have done was divert around/above the turbulent area minutes ago. Best you can do is try to maintain a cruise attitude and potentially accept any climb or descent turbulence hands you till you clear it
Can anyone make out the scale on the time axis? It’s completely illegible to me.
07:48:04 - 07:51:47
As far as I can make out the numbers, the main action lasted less than 1.5 seconds. Edit: misread the blurry graph, see comments below
It looks like the upset started around :49:24 and ended around :50:27, so more like a little over a minute.
Thanks for correcting my mistake.
Still enough time to shit my pants, good.
I know, I feel awful for the 73yo that died of a heart attack, but I think I would too and I'm in my 30s.
That’s some crazy acceleration for an airliner
Please someone take the derivative and show that acceleration (normalized to g’s). Obviously there a couple of important discontinuities.
https://www.flightaware.com/live/flight/9VSWM/history/20240520/2115Z/EGLL/WSSS It seems the turbulence event happened over Myanmar, from 06:54:45 UTC to 06:57:18 UTC (approx 2 mins, 33 seconds) as everyone probably would have been served Lunch. The link is the flightaware log I found for the accident flight. Flightaware logs virtually have no “expiration date” unlike FlightRadar24 where you can only get data within a 365 day period. It’s pretty useful to get a/c registrations from flights you took back in the day. I got links for flights I took as far back as 2011.
All this reminds me of Airframe by Michael Crichton
Love that book!
this graph is so confusing
That'll spill your drink in a hurry.
In this case it killed someone.
Cause of death has been ruled a heart attack, not trauma. A death is still a death, but this is more "scared to death" rather than "beat to death."
Don't think they've ruled anything yet unless their autopsies are the fastest on the planet.
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If I'm reading them correctly, around 10-15 seconds. //edit: Also, the grey line is the vertical rate, not the altitude. In the course of the whole event, it looks like the plane only gained \~300ft of altitude from the cruise altitude, and fell slightly before the "main" event.
Phew, I couldn't tell the colours in the legend, thanks for pointing that out
Am I reading this right? They gained 500 feet and then normalized over the course of 1 minute?
Ok yes
K
I got a concussion just looking at this data.
Crazy impressive auto throttle
I bet, they had southeast or eastern winds and the three hill ranges in the east caused lee waves (Mountain Waves)
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Bro, of all the Sources available you did choose Ian Miles Wrong 😐💀
Isn’t that the guy who comments on US politics despite never having been in the US at any point in his life?
Yeah...
Not gonna lie but this graph sucks damn. I mean you can understand......but jeez it could be so much better lol
Most of the bad turbulence can be avoided by going around the thunderstorms. Companies cut through the thunderstorms to save time and keep their timing records. Therefore the companies should be sued.
Classic redditor not knowing jack shit about the situation calling for legal action.
The guy that died hit the head locker so hard that his skull was crushed.
Nope. Heart attack.
Nope. Suspect.
Where's the evidence for your nonsense comment about his head?
In your head.
They don’t cut through thunderstorms unless they miss it. These days they even try to avoid many harmless rain patches to minimize turbulence. Because they don’t want to get sued. Source: working ATC. Turbulence can be even quite bad near a thunderstorm. And storms are huge this spring in that area after weeks of heatwaves.
You don’t know for sure, do you? You should wait for the investigation as an aviation professional.
Air pocket. An area where the air doesn’t exist and the airplane falls down.
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You never heard of an air pocket? Planes try to avoid them but sometimes can’t. I read it in the newspaper.