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anatolialevant
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 5:15 am

wjcandee wrote:
It's really more about identifying lower-likelihood events at this point than identifying the likely event. For example, this is not a dual-engine-failure flight profile, unless such a failure was not responded to as one would expect. There's no glide here. Etc.


Agree, my feeling that this isn't dual engine failure. In fact, the trend with spatial disorientation and/or CRM failure is usually not with major aircraft failure, such as dual engine failure, but rather with one engine failure like BMI Flight 92 or TransAsia 235. When things are too disastrous in a short period of time (dual engine failure, total hydraulic failure, etc.), pilots tend to be more attentive and aware of the dire situation and quickly take direct control (UA232, Gimli Glider/AC143, etc.). But with one engine failure or instruments mismatch, pilots tend to get distracted trying to solve secondary issue(s), while lose sight of basic flying parameters (Speed, Altitude, Attitude) which leads to irrecoverable error (like AF447or QZ8501).

Is my observation correct? Maybe experienced pilots can comment?
 
wjcandee
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 5:32 am

Spetsnaz55 wrote:
This video along with Peter lemme website description makes me think this is what happened on the 737. Except these pilots didn't recover like the topgun pilot did
https://www.youtube.com/watch?v=L2CsO-Vu7oc


Yeah. I posted it above for the same reason, but to illustrate that the thing can let go and you have to respond properly. Here you had Bear Smith in the left seat, former Blue Angel and then a McD test pilot, so they did. I knew that they were out that day because this airplane (which I think was the first test frame) was demonstrating unusual stall behavior and the engineers were trying to figure out why. Very interesting to hear from another post that it was ultimately to be determined to be inaccurate airspeed indication. Duh. Makes sense. In any event, Bear has the thing fully-cross-controlled when the lift vector gives way. Look at how much right aileron he has in before the incident.
 
SGN2021
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 6:29 am

Looking at the flight profile compared to previous flights it appears to be flown manually not on auto pilot , not that that is the cause just an observation.
Just before the final hard right dive the plane appears to veer to the left that would not be on coarse to destination but away from it ?
Then suddenly hard right and dive .
Fishermen said they heard two explosions one in the air and the other when it hit the water .
Now I know just about every crash someone says they saw an explosion in the air but it shouldn’t be totally discounted
Possibly a un contained engine explosion?
Pictures of recovered engine turbine appears to show it blackened but not sure if that is the way they would normally look ?
 
AntonioMartin
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 6:34 am

Flow2706 wrote:
wjcandee wrote:
jreeves96 wrote:

Crew is a very broad term. Myself and the mechanic on board when I fly are considered crew even though I’m asleep 95% of the flight. Goes the same for when we carry couriers. They’re also considered “crew.” Hell, I took two EOD handlers and their dogs from RMS to DOV and the dogs were listed on the gendec and as crew. Cant really call call them passengers as we don’t carry passengers on cargo flights, but in a passenger flight I would agree deadhead pilots or flight attendants aren’t crew. Believe it’s mostly done for customs issues.


Absolutely 100-percent true. I agree completely.

I think of "crew" as generally-encompassing everyone who actually is working, and maybe, maybe, people from that airline on the way to work for it. We are of like mind, because I actually thought "Would they have a ride-along mech on a short interisland flight?" before posting, but figured it was too remote to suggest. In retrospect, I'm glad you brought it up.

All that said, doesn't 12 seem like a lot to you on a 737-500? There could be a mixup in translation, like they really mean that to include all nonrevs, which would make the number more plausible. Family members, folks from other airlines and such.

I was based in Indonesia in 2012/2013 working for a different airline. Once in a while (but not frequently) we had a mechanic on board even on those short flights. This was mostly done as a precautionary measure in case any issue pops out in a destination without maintenance support. There are also certain MEL items that require a check/maintenance inspection prior to each flight (talking about A320, but I guess 737 is similar in this regard), that may be an other reason to have a mechanic on board. So it may be possible (although not very likely) that a mechanic was on board for this flight.


Don't they always have a mechanic??
 
spacecadet
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 9:50 am

anatolialevant wrote:
wjcandee wrote:
It's really more about identifying lower-likelihood events at this point than identifying the likely event. For example, this is not a dual-engine-failure flight profile, unless such a failure was not responded to as one would expect. There's no glide here. Etc.


Agree, my feeling that this isn't dual engine failure. In fact, the trend with spatial disorientation and/or CRM failure is usually not with major aircraft failure, such as dual engine failure, but rather with one engine failure like BMI Flight 92 or TransAsia 235. When things are too disastrous in a short period of time (dual engine failure, total hydraulic failure, etc.), pilots tend to be more attentive and aware of the dire situation and quickly take direct control (UA232, Gimli Glider/AC143, etc.). But with one engine failure or instruments mismatch, pilots tend to get distracted trying to solve secondary issue(s), while lose sight of basic flying parameters (Speed, Altitude, Attitude) which leads to irrecoverable error (like AF447or QZ8501).

Is my observation correct? Maybe experienced pilots can comment?


You're maybe incidentally correct, but not for the reasons you've given.

The real issue in these cases is basic technical and piloting skills, which are not evenly distributed among pilots even at the same certification level. A dual engine failure, while exceedingly rare to the point that you can almost rule it out in the absence of any other evidence, just turns the plane into a glider. It's fairly easy to control. You have a certain amount of potential energy that you can convert to kinetic energy by exchanging altitude. Even if you (as a pilot) don't know what those words mean, it's pretty intuitive. Take your hands off the controls and the plane is going to stay wings level and descend while maintaining or even gaining airspeed (you'd want to control that with pitch).

In a single engine failure, you're suddenly presented with a large amount of yaw. Different aircraft will respond to this while on autopilot/autothrottle in different ways. I am not 100% sure how the 737 responds; from what I understand the 737 autopilot is a 2-axis system with yaw damper, and it does not control rudder directly. In a single engine failure, you typically need a large amount of rudder to compensate or the airplane will roll. If this happens on takeoff, no amount of aileron alone will get it back - in fact, it will make things worse because you're in the low speed regime where the inboard and outboard ailerons are both working, as well as the spoilers. At 10,000 feet, this probably would not happen because they'd be at about 250 knots or even starting to accelerate beyond that, but you never know - maybe they were slower for some reason. They're also still ascending, so at climb power and with fairly good thrust in that low-altitude air. They'd still need to get that rudder in to keep from having an upset.

In other words, a single engine failure is harder to manage than a dual engine failure. A dual engine failure is going to result in you going into the ground, but it's probably going to be wings level and under control. But there have been many, many cases of single engine failure where airplanes have gone into the ground not under control. It shouldn't happen with modern training techniques, but it still does. (Don't misunderstand; I'm not saying the *outcome* is likely better in a dual engine failure. Just that the skills required to actually fly the plane are different, and in some ways easier than in a single engine failure. A single engine failure is more likely to result in a loss of control.)

To me the most likely cause of this is some kind of upset. Not necessarily from engine failure - that was just an example based on the post I was quoting above - but something that caused the pilots to lose control. It could be any number of things. It certainly would not be the first time; it's one of the most common causes of airline accidents, and it seems to fit the flight profile here.
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filipinoavgeek
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 10:32 am

One thing I find weird is that some news reports discussing previous crashes in Indonesia specify the 737 when it crashed, but not other airplane types when it happened to them. For example, the multiple (non-MAX) Lion Air 737 incidents have the 737 explicitly mentioned, but mentions of the AirAsia crash from a few years back don't say that it was an A320. Is there an anti-(non MAX) 737 bias in the media now or something?
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Starlionblue
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 11:24 am

filipinoavgeek wrote:
One thing I find weird is that some news reports discussing previous crashes in Indonesia specify the 737 when it crashed, but not other airplane types when it happened to them. For example, the multiple (non-MAX) Lion Air 737 incidents have the 737 explicitly mentioned, but mentions of the AirAsia crash from a few years back don't say that it was an A320. Is there an anti-(non MAX) 737 bias in the media now or something?


I don't think it is a conscious anti-737 bias. It is more likely the fact that the 737MAX debacle meant even the general public knew the aircraft by name. Hence, putting 737 in the article means readers can "relate".

Unlike in this forum, most people don't know an A320 from a Cessna 172.



Common questions I am asked:
"Do you fly the A380?"
"Do you guys have the 737MAX?"

Answer to both... "No."
"So what do you fly?"
"I fly the A330 and the A350."
Cue blank look.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
JayinKitsap
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 11:53 am

wjcandee wrote:
There are 50 things I could list that might have caused this from a mechanical-failure perspective, and I have with a broad-brush mentioned a few, like the physical departure of control surfaces from the airframe or loss of ability to manipulate the control surfaces, but I think beyond that, it's only going to be a lucky guess if somebody at this point brings up an old accident and says, "I think that's what happened here."


I'll bring up one of the 50 things, stabilizer jack screw or similar failure. Alaska 261 had two near vertical dives, one they recovered from before final failure, the second dive 10 seconds later when it failed. The Wiki page of the crash (yes I know) https://en.wikipedia.org/wiki/Alaska_Ai ... Flight_261

The investigators will sort it out, the recorders will probably tell the story quite well. Happened so fast no mayday.

Weather possible: lightning, turbulence, down draft.

Maintenance- upthread it was reported back from a heavy check late Dec. Wrong parts used, missed lube, overtorque / unbalanced bolt torque, missed bolt(s).

Worn parts - it is a 737 classic, late production though. Has it been in high cycle service, are the runways rougher, more weather buffeting etc.

Corrosion - I assume Indonesia is like Guam, makes Miami seem arid. Salt air and heavy dew daily. Air Conditioners that work well West Coast US died quickly there, rust breakouts in powder coated enclosures in just a few years, not decades. This just sets up for a failure of something though.

Pilots - a whole number of things could be here, in particular if the pilot was stressing about finances, or angry or up working a 2nd job.

---

One positive thing, it seems like the Indonesian equivalent of the NTSB handled the Lion Air crash professionally with a quality report produced. It is most likely this one will be solved.

A 2nd positive thing - the 735 is in its sunset days, anything plane related affects a relatively few planes now.
 
wjcandee
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 12:45 pm

JayinKitsap wrote:
A 2nd positive thing - the 735 is in its sunset days, anything plane related affects a relatively few planes now.


The 734 is the most-desirable Classic freighter. The only difference between it and the 735, as a practical matter, is a couple of fuselage sections. They're still converting 734s if they can find ones that are even remotely-serviceable. If this is something mechanical as an unrecoverable failure, that's still a big concern, because a falling aircraft can kill a lot of people on the ground. Very fortunate for those outside the aircraft that this happened over water and not over a populated area. Imagine if this was climbing out of LGA
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glideslope
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 2:04 pm

I noticed in the data at one point in the decent their airspeed was down to around 124kts, then the rapid increase to over 300kts prior to impact. Any thoughts on that? Just a glitch in the data?
I'm wondering if they got themselves into a flat spin trying to recover in IMC?
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Flow2706
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 2:38 pm

AntonioMartin wrote:
Flow2706 wrote:
wjcandee wrote:

Absolutely 100-percent true. I agree completely.

I think of "crew" as generally-encompassing everyone who actually is working, and maybe, maybe, people from that airline on the way to work for it. We are of like mind, because I actually thought "Would they have a ride-along mech on a short interisland flight?" before posting, but figured it was too remote to suggest. In retrospect, I'm glad you brought it up.

All that said, doesn't 12 seem like a lot to you on a 737-500? There could be a mixup in translation, like they really mean that to include all nonrevs, which would make the number more plausible. Family members, folks from other airlines and such.

I was based in Indonesia in 2012/2013 working for a different airline. Once in a while (but not frequently) we had a mechanic on board even on those short flights. This was mostly done as a precautionary measure in case any issue pops out in a destination without maintenance support. There are also certain MEL items that require a check/maintenance inspection prior to each flight (talking about A320, but I guess 737 is similar in this regard), that may be an other reason to have a mechanic on board. So it may be possible (although not very likely) that a mechanic was on board for this flight.


Don't they always have a mechanic??

It's unusual to have an engineer on board. Outside of "major" (C/D) Checks the only scheduled maintenance required on the aircraft are daily and weekly checks (obviously plus unscheduled maintenance due to technical faults, ADs/Service Bulletins). Airlines usually have contracted maintenance at outstations that can be called if they are needed due to a reported fault on the previous flight, but unless there is a requirement for maintenance to be there to rectify a fault they usually don't show up on turnarounds. Depending on the legislation in the operators country pilots may be allowed to put minor faults on the HIL under MEL provisions after consulting with the companies maintenance department without having an engineer in place. Therefore there is usually no requirement to have an engineer on board, except on flights to small airports that don't have a maintenance provider in place that is allowed to work on the specific aircraft type.
Last edited by Flow2706 on Mon Jan 11, 2021 2:38 pm, edited 1 time in total.
 
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flyingturtle
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 2:38 pm

glideslope wrote:
I noticed in the data at one point in the decent their airspeed was down to around 124kts, then the rapid increase to over 300kts prior to impact. Any thoughts on that? Just a glitch in the data?
I'm wondering if they got themselves into a flat spin trying to recover in IMC?


I noticed that too, but haven't given it lots of thought yet. Remember that the speeds reported by ADS-B is ground speed, not air speed.

Question to the more knowledgeable people here: If I was in a fighter jet, and I would zoom upwards or downwards (zero lateral speed, just a ludicrous vertical speed) - would Flightradar24 show my ground speed as 0 knots?
Reading accident reports is what calms me down
 
o0OOO0oChris
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 2:46 pm

I don't think this is an engine out issue. Those are trained so often in the sim, should not be a problem.

The hard rudder issue should have been corrected, but would not apply to this phase of flight, as the hard rudder issue was caused by very cold hydraulic fluid due to cruising a long time entering the valve. Hydraulic fluid should have been warm enough here.

I also wouldn't guess something like flight controls breakup, as the groundspeed increased again to the end, which looks like a recovery attempt like on the air asia A320.

For me, this looks really a lot like the flight profile of West Air Sweden Flight 294, which was a deep dive due to instrument failure.

Something similar happend on a 737 too:
https://en.wikipedia.org/wiki/Copa_Airlines_Flight_201
 
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zeke
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:18 pm

AntonioMartin wrote:
Don't they always have a mechanic??


Don’t think so.

flyingturtle wrote:
Question to the more knowledgeable people here: If I was in a fighter jet, and I would zoom upwards or downwards (zero lateral speed, just a ludicrous vertical speed) - would Flightradar24 show my ground speed as 0 knots?


Correct, ground speed would be zero. I’ll have a look at the FR24 data and calculate the speeds and post them later.
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slvrblt
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:19 pm

What I don't understand is this: It's broad daylight, not night time. Can't a jetliner be flown by the 'seat of the pants?' Lets say your instruments are all haywire for some reason, but the airplane is otherwise fine (engines good, flaps/gear work) can't the pilots hand fly the plane back to base? I hear pilots say all the time, ''disconnect the auto-functions and fly the damn plane.'' Forgive me if this is a stupid question, I'm not a pilot but it seems to me one should be able to get back to base with your mechanicals still working as designed.
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awthompson
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:34 pm

Once FDR and CVR are studied, I feel the cause may be largely a repeat of other similar crashes.
From ground track, the climb out from take off to end of recording appears to be flown manually with no autopilot engaged, one can speculate as to why the crew may have chosen to do that in IMC conditions. Airport cam of actual pushback on ground shows low cloud and rain so aircraft was in IMC from moments after take-off.
Manual climb in those circumstances would require a high level of concentration.
It would not be the first time a crew assumed autopilot was engaged when it wasn't.
Do I need to continue?
From the altitude / speed graph (already posted earlier and widely available online) I can see a speed build up throughout the climb to around 290 knots. Then a quick drop off to around 110 knots. Plane will have stalled at that point, before entering the dive where speed rapidly builds up to 350+ knots before impact.
How many times have we seen the above scenario, or similar, in many different types of aircraft without any engine failure, explosion, collision, mechanical failure, in flight break up or other factor necessary to explain what happened?
 
awthompson
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:37 pm

Re the above, I am aware those speeds may be ground speed and not air speed, but still gives the general idea.
 
mxaxai
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:41 pm

slvrblt wrote:
What I don't understand is this: It's broad daylight, not night time. Can't a jetliner be flown by the 'seat of the pants?' Lets say your instruments are all haywire for some reason, but the airplane is otherwise fine (engines good, flaps/gear work) can't the pilots hand fly the plane back to base?

If they can see outside, then yes, they should be able to. In clouds (or even just between clouds, if the horizon or ground features aren't visible) the lack of references makes it impossible to 'fly by the seat of the pants'. Humans are exceptionally bad at guessing attitude, altitude or velocity without visual cues. That's why the artificial horizon is so critical.

When they say "Disconnect the auto-function", they don't mean "Disregard all instruments & assistants" but rather "Turn off everything that can interfere with the control surfaces".
 
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glideslope
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:49 pm

flyingturtle wrote:
glideslope wrote:
I noticed in the data at one point in the decent their airspeed was down to around 124kts, then the rapid increase to over 300kts prior to impact. Any thoughts on that? Just a glitch in the data?
I'm wondering if they got themselves into a flat spin trying to recover in IMC?


I noticed that too, but haven't given it lots of thought yet. Remember that the speeds reported by ADS-B is ground speed, not air speed.

Question to the more knowledgeable people here: If I was in a fighter jet, and I would zoom upwards or downwards (zero lateral speed, just a ludicrous vertical speed) - would Flightradar24 show my ground speed as 0 knots?


Right, ADS-B is ground speed, and yes your ground speed would be 0 in a vertical climb. I’m just trying to rectify the difference with the kts at impact if they were indeed vertical all the way down as reported. I suppose they may have been able to bring the nose up enough prior to impact to register the 300+ kts ground speed.
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Revelation
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:54 pm

slvrblt wrote:
What I don't understand is this: It's broad daylight, not night time. Can't a jetliner be flown by the 'seat of the pants?' Lets say your instruments are all haywire for some reason, but the airplane is otherwise fine (engines good, flaps/gear work) can't the pilots hand fly the plane back to base? I hear pilots say all the time, ''disconnect the auto-functions and fly the damn plane.'' Forgive me if this is a stupid question, I'm not a pilot but it seems to me one should be able to get back to base with your mechanicals still working as designed.

Sure, in the ideal world, that is how it should go.

Yet in the real word it is monsoon season in Indonesia so the plane was almost certainly in cloud and the pilots almost certainly lacked a ground reference. One needs to exercise flying on instruments often or one gets rusty at it. The body sends the brain signals about balance (or lack thereof) that contradict the instruments. The pilots need to trust the instruments more so than what their brain is telling them. If you don't, you tend to over bank the plane and tend to end up in a spiral and crash. This is for instance how JFK Jr. crashed a perfectly good airplane. Airlines prefer pilots fly with the automation on because it's more efficient that way so the pilots don't get a lot of opportunities to fly by hand. They become overly dependent on automation. I'm not saying this is what is happening in the crash we are discussing. I'm just giving you one reason why the "fly the damn plane" thing sometimes does not work out. We've seen plenty of cases where pilots have crashed due to over reliance on automation. It seems strange to think that is the case in 737-500 which is a very basic aircraft by today's standards and in Indonesia where you would think pilots grew up flying through monsoons so should be very skilled at instrument flying. These two pilots had many hours so again it seems unlikely this is what happened. We need to wait to learn more.
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snowzilla
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 3:59 pm

I just have to say any commercial pilot flying a jet can hand fly an airplane in IMC just as well as if it were VMC. Hand flying a 737 in a climb is about as easy as it gets. If you have to turn the autopilot on at 1000’ you should look for a different job.
Now an unreliable airspeed situation would be different for sure, or just flying by the standby horizon in a 737-500 would definitely be a stressful situation in any conditions (except maybe smooth air in broad daylight).
 
morrisond
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 5:36 pm

snowzilla wrote:
I just have to say any commercial pilot flying a jet can hand fly an airplane in IMC just as well as if it were VMC. Hand flying a 737 in a climb is about as easy as it gets. If you have to turn the autopilot on at 1000’ you should look for a different job.
Now an unreliable airspeed situation would be different for sure, or just flying by the standby horizon in a 737-500 would definitely be a stressful situation in any conditions (except maybe smooth air in broad daylight).


Your optimism about "Any Commercial" pilots abilities does not seem to be reality when you look back at most of the fatal crashes of the last twenty years and what there rout or contributing causes were.

A lot of airlines are advocating turning on the Autopilot at 1000'.

The evidence would suggest that almost all commercial pilots should fly a lot more without the nannies especially in CVU conditions (where if they screw up they still have outside visual reference to save them) so that when needed they haven't lost the sharpness that is required.

This crash/flightpath I think is still best explained by a Bomb or mechanical failure causing an explosion or suicide. You would think if it was just loss of control there would have been some kind of transmission or more variance in the Flight path. Look at ET 409 they were all over the place before finally losing it.
 
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zeke
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 6:03 pm

glideslope wrote:
Right, ADS-B is ground speed, and yes your ground speed would be 0 in a vertical climb. I’m just trying to rectify the difference with the kts at impact if they were indeed vertical all the way down as reported. I suppose they may have been able to bring the nose up enough prior to impact to register the 300+ kts ground speed.


I downloaded the granular FR24 data from https://www.flightradar24.com/blog/wp-c ... elease.csv

From the timestamp position at 2021-01-09 07:40:09Z.844 to 2021-01-09 07:40:27Z.752 the aircraft moved form position -5.97542 106.56785 to -5.96395 106.57453 which is a great circle distance of just 45.07 meters in 17.91 seconds, hence the near zero ground speed. The vertical change was 10400 ft (10,650 ft to 250 ft) or 3169.92 meters.

The 3D distance is SQRT(45.07^2+3169.92^2) or 3170.24 meters. That means the speed over those 17.91 seconds was 177.03 m/s or 344 knots. Vmo on the 737 classic is 340 kts. It was in a near vertical vector over that period with a rate of descent of around 35,000 ft/min (34,844)
.
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kalvado
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 6:55 pm

zeke wrote:
glideslope wrote:
Right, ADS-B is ground speed, and yes your ground speed would be 0 in a vertical climb. I’m just trying to rectify the difference with the kts at impact if they were indeed vertical all the way down as reported. I suppose they may have been able to bring the nose up enough prior to impact to register the 300+ kts ground speed.


I downloaded the granular FR24 data from https://www.flightradar24.com/blog/wp-c ... elease.csv

From the timestamp position at 2021-01-09 07:40:09Z.844 to 2021-01-09 07:40:27Z.752 the aircraft moved form position -5.97542 106.56785 to -5.96395 106.57453 which is a great circle distance of just 45.07 meters in 17.91 seconds, hence the near zero ground speed. The vertical change was 10400 ft (10,650 ft to 250 ft) or 3169.92 meters.

The 3D distance is SQRT(45.07^2+3169.92^2) or 3170.24 meters. That means the speed over those 17.91 seconds was 177.03 m/s or 344 knots. Vmo on the 737 classic is 340 kts. It was in a near vertical vector over that period with a rate of descent of around 35,000 ft/min (34,844)
.

I would look at an interval of 2021-01-09 07:40:12Z.214 to 14Z022. Plane looses 750 feet = 230 meters in 2 seconds starting from level flight. That is 10g of acceleration, if you take those numbers at face value.
If you choose 17Z.146 as an end point, it is 770 meters in less than 5 seconds, that is "just" 5g sustained acceleration.
If those are aerodynamic forces provided by the wing.... Wing is desingned to 2g *1.5 safety margin = 3g of upward load at MTOW if I understand correctly. Plane wasn't at MTOW, but safety margin taken for wear and imperfection probably have reduced at 25+ years of service.
I don't think engines have enough power to acceleate plane at such a rate as well.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 7:19 pm

kalvado wrote:
I would look at an interval of 2021-01-09 07:40:12Z.214 to 14Z022. Plane looses 750 feet = 230 meters in 2 seconds starting from level flight. That is 10g of acceleration, if you take those numbers at face value.


Need to understand what the ADSB data is displaying, I removed all the data points that have no position information. The aircraft was doing around 280-290 ground speed then kts then, or 470-490 ft/s, it is easy to get that rate of change in altitude by changing the vector from horizontal to vertical at the same speed.
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kalvado
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 8:09 pm

zeke wrote:
kalvado wrote:
I would look at an interval of 2021-01-09 07:40:12Z.214 to 14Z022. Plane looses 750 feet = 230 meters in 2 seconds starting from level flight. That is 10g of acceleration, if you take those numbers at face value.


Need to understand what the ADSB data is displaying, I removed all the data points that have no position information. The aircraft was doing around 280-290 ground speed then kts then, or 470-490 ft/s, it is easy to get that rate of change in altitude by changing the vector from horizontal to vertical at the same speed.

If you choose two points with coordinate, those are 2021-01-09 07:40:09Z.844 and 2021-01-09 07:40:14Z.202, and that is still at least 2.5g sustained.
It may be easy to convert energy of horizontal motion to vertical motion, but something still must provide that centripetal force for conversion; "something" being either wing, engines, or external factor.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 8:44 pm

My guess: Dispondent flight crew member disposed of other (read shot) then took care of the rest to the water. Simple, and a reason no attempt to recover from dive. Seemingly rational explanation as any IMO.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 9:15 pm

I will speculate the upset start with a roll to the left. Height/speed from ADSB data initially dont show this, only the heading change to the left show this. After a few second as roll angle passes 90 degrees the nose drops significantly, height loss/ROD still very small. Left roll continues, pilots scramble, dont understand what happens, starts to pull hard. The aircraft nears inverted while pilots are pulling hard, this causes a huge negative G (as seen from the outside, pilots of course firmly pressed into their seats while beeing inverted) and the ROD now really picks up. Left turn (as seen from above) have now stopped due to the aircraft beeing fully inverted, still large negative G. The left roll continues, aircraft passes inverted while the pilots pulls hard, ROD increases phenomenally. Right turn (as seen from above) starts. The aircraft passes 90 degrees right bank, toward wings level, still pilots pulling, right heading change with very high rate (as seen from above). The aircraft is now close the sea surface, wings near level at moment of impact, huge positive G, dive angle gets more shallow during the last few seconds.

This is my completely uneducated speculation to how the aircraft lost 11.000 feet in less than 30 sec. As to the reason for the initial roll to the left I have no suggestion, whether it was aileron or the rudder, whether it was something mechanical, electric or hydraulic, or something else.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 9:35 pm

zeke wrote:
glideslope wrote:
Right, ADS-B is ground speed, and yes your ground speed would be 0 in a vertical climb. I’m just trying to rectify the difference with the kts at impact if they were indeed vertical all the way down as reported. I suppose they may have been able to bring the nose up enough prior to impact to register the 300+ kts ground speed.


I downloaded the granular FR24 data from https://www.flightradar24.com/blog/wp-c ... elease.csv

From the timestamp position at 2021-01-09 07:40:09Z.844 to 2021-01-09 07:40:27Z.752 the aircraft moved form position -5.97542 106.56785 to -5.96395 106.57453 which is a great circle distance of just 45.07 meters in 17.91 seconds, hence the near zero ground speed. The vertical change was 10400 ft (10,650 ft to 250 ft) or 3169.92 meters.

The 3D distance is SQRT(45.07^2+3169.92^2) or 3170.24 meters. That means the speed over those 17.91 seconds was 177.03 m/s or 344 knots. Vmo on the 737 classic is 340 kts. It was in a near vertical vector over that period with a rate of descent of around 35,000 ft/min (34,844)
.


Thanks, I think I understand the scenario now.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 9:45 pm

awthompson wrote:
Once FDR and CVR are studied, I feel the cause may be largely a repeat of other similar crashes.
From ground track, the climb out from take off to end of recording appears to be flown manually with no autopilot engaged, one can speculate as to why the crew may have chosen to do that in IMC conditions. Airport cam of actual pushback on ground shows low cloud and rain so aircraft was in IMC from moments after take-off.
Manual climb in those circumstances would require a high level of concentration.
It would not be the first time a crew assumed autopilot was engaged when it wasn't.
Do I need to continue?
From the altitude / speed graph (already posted earlier and widely available online) I can see a speed build up throughout the climb to around 290 knots. Then a quick drop off to around 110 knots. Plane will have stalled at that point, before entering the dive where speed rapidly builds up to 350+ knots before impact.
How many times have we seen the above scenario, or similar, in many different types of aircraft without any engine failure, explosion, collision, mechanical failure, in flight break up or other factor necessary to explain what happened?

There is no way to find out from the ADS-B/FR24 data whether the autopilot was engaged or not. Manual flight will not result in any large deviations from the SID, if you are unable to follow a simple procedure like a SID accurately you won't be able to pass the sim check. On the other hand, autopilots/FMGCs are also not always 100% perfect, especially in older aircraft.
Wrongly assuming that the autopilot was engaged won't result in this flight profile. It's a design requirement of all civil aircraft that they are aerodynamically stable, i.e. without any control input the aircraft will roughly maintain it's previous orientation or possibly deviate slightly, but it won't enter a rapid dive without any input. Neither will it rapidly enter a stall condition.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 10:06 pm

sprxUSA wrote:
My guess: Dispondent flight crew member disposed of other (read shot) then took care of the rest to the water. Simple, and a reason no attempt to recover from dive. Seemingly rational explanation as any IMO.


I have no problem with reasonable speculation but that is one wild theory.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 11:04 pm

zeke wrote:
it is easy to get that rate of change in altitude by changing the vector from horizontal to vertical at the same speed.


Just in terms of physics, or in terms of input to the controls by the pilot too?
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 11:47 pm

I wont speculate on this crash and I'm so sorry for all that perished and the families involved, but as we saw not that long ago with Atlas 3590, it is 100% possible to achieve an almost unthinkable flight profile like this from nothing more than a pilot trying to fly the aircraft. I'm not saying this is what happened, but just that at this point anything is possible.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Mon Jan 11, 2021 11:49 pm

SteinarN wrote:
I will speculate the upset start with a roll to the left. Height/speed from ADSB data initially dont show this, only the heading change to the left show this. After a few second as roll angle passes 90 degrees the nose drops significantly, height loss/ROD still very small. Left roll continues, pilots scramble, dont understand what happens, starts to pull hard. The aircraft nears inverted while pilots are pulling hard, this causes a huge negative G (as seen from the outside, pilots of course firmly pressed into their seats while beeing inverted) and the ROD now really picks up. Left turn (as seen from above) have now stopped due to the aircraft beeing fully inverted, still large negative G. The left roll continues, aircraft passes inverted while the pilots pulls hard, ROD increases phenomenally. Right turn (as seen from above) starts. The aircraft passes 90 degrees right bank, toward wings level, still pilots pulling, right heading change with very high rate (as seen from above). The aircraft is now close the sea surface, wings near level at moment of impact, huge positive G, dive angle gets more shallow during the last few seconds.

This is my completely uneducated speculation to how the aircraft lost 11.000 feet in less than 30 sec. As to the reason for the initial roll to the left I have no suggestion, whether it was aileron or the rudder, whether it was something mechanical, electric or hydraulic, or something else.

I agree with this, I’m thinking of the similarities with Flash Airlines flight 604, I think the pilots overreacted to a bank and either tried to overcorrect or simply did the wrong action. I know it’s premature to blame pilot error but we’ve seen similar before in that Adam Air 737-400 that also crashed into the sea.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 12:54 am

sprxUSA wrote:
My guess: Dispondent flight crew member disposed of other (read shot) then took care of the rest to the water. Simple, and a reason no attempt to recover from dive. Seemingly rational explanation as any IMO.


Agreed..A despondent flight crew or some other severe mental issues not caught. Such as Captain of the Air Egypt 767, or the FO that flew the A 320 into the side of a mountain in the Alps (Germanwings??)

to me it look way to similar.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 1:07 am

Tan Flyr wrote:
sprxUSA wrote:
My guess: Dispondent flight crew member disposed of other (read shot) then took care of the rest to the water. Simple, and a reason no attempt to recover from dive. Seemingly rational explanation as any IMO.


Agreed..A despondent flight crew or some other severe mental issues not caught. Such as Captain of the Air Egypt 767, or the FO that flew the A 320 into the side of a mountain in the Alps (Germanwings??)

to me it look way to similar.

Jeez bit of an irrational jump they haven’t even analysed the tapes yet.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 1:56 am

Deliberate actions by the pilot(s) shouldn't be ruled out, but at this point we don't know enough to say it is the mostly likely cause.
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wjcandee
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:01 am

Moose135 wrote:
Deliberate actions by the pilot(s) shouldn't be ruled out, but at this point we don't know enough to say it is the mostly likely cause.


Is there a pattern as to the phase of flight in which suicidal/mass-murdering ATP pilots typically do this?
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:06 am

slvrblt wrote:
What I don't understand is this: It's broad daylight, not night time. Can't a jetliner be flown by the 'seat of the pants?' Lets say your instruments are all haywire for some reason, but the airplane is otherwise fine (engines good, flaps/gear work) can't the pilots hand fly the plane back to base? I hear pilots say all the time, ''disconnect the auto-functions and fly the damn plane.'' Forgive me if this is a stupid question, I'm not a pilot but it seems to me one should be able to get back to base with your mechanicals still working as designed.


Without any instruments at all it would be very difficult. It is very hard to deduce what an airliner is doing by the seat of your pants. Humans are pretty useless at judging altitude, attitude, and airspeed by sight and feel.

Say you lose all instrumentation. The first thing you need is "God's Attitude Indicator" (the horizon). At 10000 feet you need a pretty clear day to have a really clearly defined horizon but it could work. So you can hold an attitude, more or less. But this being Indonesia in the daytime, there was probably cloud.

Your next problem is speed. If you know your attitude, more or less, you can set a known thrust, and with that combination get a known airspeed. If you don't have engine instruments this becomes rather tricky, if not impossible.

Even a minimal number of instruments improves the situation immensely. And if you have all the instruments but no autoflight, the situation isn't an emergency. Just handfly.

In reality, if you lose all instrumentation, the aircraft probably has so many separate issues that you're toast anyway. We don't train for loss of all instrumentation because it is pretty much impossible.


kalvado wrote:
zeke wrote:
glideslope wrote:
Right, ADS-B is ground speed, and yes your ground speed would be 0 in a vertical climb. I’m just trying to rectify the difference with the kts at impact if they were indeed vertical all the way down as reported. I suppose they may have been able to bring the nose up enough prior to impact to register the 300+ kts ground speed.


I downloaded the granular FR24 data from https://www.flightradar24.com/blog/wp-c ... elease.csv

From the timestamp position at 2021-01-09 07:40:09Z.844 to 2021-01-09 07:40:27Z.752 the aircraft moved form position -5.97542 106.56785 to -5.96395 106.57453 which is a great circle distance of just 45.07 meters in 17.91 seconds, hence the near zero ground speed. The vertical change was 10400 ft (10,650 ft to 250 ft) or 3169.92 meters.

The 3D distance is SQRT(45.07^2+3169.92^2) or 3170.24 meters. That means the speed over those 17.91 seconds was 177.03 m/s or 344 knots. Vmo on the 737 classic is 340 kts. It was in a near vertical vector over that period with a rate of descent of around 35,000 ft/min (34,844)
.

I would look at an interval of 2021-01-09 07:40:12Z.214 to 14Z022. Plane looses 750 feet = 230 meters in 2 seconds starting from level flight. That is 10g of acceleration, if you take those numbers at face value.
If you choose 17Z.146 as an end point, it is 770 meters in less than 5 seconds, that is "just" 5g sustained acceleration.
If those are aerodynamic forces provided by the wing.... Wing is desingned to 2g *1.5 safety margin = 3g of upward load at MTOW if I understand correctly. Plane wasn't at MTOW, but safety margin taken for wear and imperfection probably have reduced at 25+ years of service.
I don't think engines have enough power to acceleate plane at such a rate as well.


Correction on the load limits. For transport category aircraft it is +2.5G/-1G when clean. (+2G/0G dirty.)

The ultimate limit is 50% higher, +3.75G/-1.5G. Between the load limit and the ultimate limit you may have permanent deformation but not failure.

I don't think safety margin should decrease too much with wear and imperfection. Wing spars and such would be regularly inspected. But I could be wrong.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:19 am

wjcandee wrote:
Moose135 wrote:
Deliberate actions by the pilot(s) shouldn't be ruled out, but at this point we don't know enough to say it is the mostly likely cause.


Is there a pattern as to the phase of flight in which suicidal/mass-murdering ATP pilots typically do this?


Not this soon after take off. I mean why? It wasn’t that short of a flight. To speculate deliberate action is compel th absurd.
 
FlyingViking
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:31 am

Severe turbulence, maybe with wing or control surface deforming? Lightning strike with loss of electrical power like NFD flight 108, February 1988? Rudder hard over like USAir in 1994 and United in 1991? Hopefully the recorders will give more answers than questions. Just my 2 cents.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:50 am

kalvado wrote:
I would look at an interval of 2021-01-09 07:40:12Z.214 to 14Z022. Plane looses 750 feet = 230 meters in 2 seconds starting from level flight. That is 10g of acceleration, if you take those numbers at face value.
If you choose 17Z.146 as an end point, it is 770 meters in less than 5 seconds, that is "just" 5g sustained acceleration.
If those are aerodynamic forces provided by the wing.... Wing is desingned to 2g *1.5 safety margin = 3g of upward load at MTOW if I understand correctly. Plane wasn't at MTOW, but safety margin taken for wear and imperfection probably have reduced at 25+ years of service.
I don't think engines have enough power to acceleate plane at such a rate as well.

Thanks kalvado, very interesting calculations.

With the limited info so far it is of course premature to come up with much speculation. I can, however, not get Partnair Flight 394 out of my mind. This SJ-182 could be a carbon copy. (Could be because Partnair 394 is the closest air disaster to my home ever in history - only120 miles away).

https://en.wikipedia.org/wiki/Partnair_Flight_394

Partnair 394: A 36 years old plane, tail controls worn out and partially repaired with counterfeit parts, tail vibrates, maybe flutter, and disintergrates in flight, rest of the plane enter a high negative G dive, wing breaks. Debris scattered over roughly a mile of seabed.

I cannot get it out of my head. If I was an SJ-182 investigator, then I would be looking carefully at the location of all extreme corners of the plane on the seabed. In order to prove or disprove any inflight structural breakup.
Last edited by prebennorholm on Tue Jan 12, 2021 2:58 am, edited 1 time in total.
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 2:54 am

kalvado wrote:
If you choose two points with coordinate, those are 2021-01-09 07:40:09Z.844 and 2021-01-09 07:40:14Z.202, and that is still at least 2.5g sustained.
It may be easy to convert energy of horizontal motion to vertical motion, but something still must provide that centripetal force for conversion; "something" being either wing, engines, or external factor.


The data at 2021-01-09 07:40:09Z.754 and 2021-01-09 07:40:09Z.844 are the same, so its the same packet picked up by two different receivers. The 2021-01-09 07:40:09Z.844 data needs to be filtered out as well.

I did some further analysis, the aircraft at the bottom had a flight path angle of 87 degrees.

From 2021-01-09 07:40:05Z.652 at 10900 ft to 2021-01-09 07:40:14Z.202 at 9525 ft the flight path angle change from zero to 84 degrees over 8.55 seconds. The speed didn't change much however the direction did, at a average rate of 9.85 degrees per second, that is about 3 times higher the normal rate we would rotate an aircraft on takeoff.

The data does suggest a very sharp change in direction from level to near vertical, without much of a change in speed.

Timestamp,time,delta_t,lat,long,delta_dist,alt_ft,alt_m,delta_alt_m,3D_dist,FPA
2021-01-09 07:40:02Z.716,1262.716,0.438,-5.98389,106.56585,3.525756338,10900,3322.32,0,3.525756338,0
2021-01-09 07:40:02Z.782,1262.782,0.066,-5.98438,106.56558,3.525756338,10900,3322.32,0,3.525756338,0
2021-01-09 07:40:02Z.824,1262.824,0.042,-5.98331,106.56615,7.644150238,10900,3322.32,0,7.644150238,0
2021-01-09 07:40:04Z.372,1264.372,1.548,-5.98196,106.56672,9.267714028,10900,3322.32,0,9.267714028,0
2021-01-09 07:40:04Z.528,1264.528,0.156,-5.98096,106.56705,6.675282535,10900,3322.32,0,6.675282535,0
2021-01-09 07:40:05Z.652,1265.652,1.124,-5.97954,106.56743,9.330970847,10900,3322.32,0,9.330970847,0
2021-01-09 07:40:08Z.084,1268.084,2.432,-5.97688,106.5678,17.08385359,10775,3284.22,38.1,41.75485664,65.84876927
2021-01-09 07:40:08Z.264,1268.264,0.18,-5.97605,106.56781,5.284715387,10725,3268.98,15.24,16.1302764,70.87518785
2021-01-09 07:40:09Z.754,1269.754,1.49,-5.97542,106.56785,4.018362983,10650,3246.12,22.86,23.21048989,80.03031927
2021-01-09 07:40:14Z.202,1274.202,4.448,-5.97009,106.56686,34.46120558,9525,2903.22,342.9,344.6273127,84.26108445
2021-01-09 07:40:14Z.262,1274.262,0.06,-5.96906,106.56654,6.838076531,9125,2781.3,121.92,122.1116116,86.78983861
2021-01-09 07:40:14Z.586,1274.586,0.324,-5.96869,106.56641,2.483706941,8950,2727.96,53.34,53.39779396,87.33402305
2021-01-09 07:40:16Z.726,1276.726,2.14,-5.9673,106.56601,9.174962117,8125,2476.5,251.46,251.6273267,87.91038927
2021-01-09 07:40:17Z.202,1277.202,0.476,-5.9666,106.56577,4.687337298,7650,2331.72,144.78,144.8558578,88.14566329
2021-01-09 07:40:20Z.992,1280.992,3.79,-5.96452,106.56599,13.30943179,5400,1645.92,685.8,685.929137,88.88819109
2021-01-09 07:40:24Z.390,1284.39,3.398,-5.96367,106.56857,16.50911322,2850,868.68,777.24,777.4153127,88.78318113
2021-01-09 07:40:27Z.752,1287.752,3.362,-5.96395,106.57453,36.07080515,250,76.2,792.48,793.3004811,87.39390338


Flow2706 wrote:
There is no way to find out from the ADS-B/FR24 data whether the autopilot was engaged or not.


ADSB data does include the the status of the autopilot, FCU setting, and FMC waypoint. FR24 just doesn't record it, the ATC recording of the ADSB data should have that on it.
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tigerzhong13
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 3:26 am

Can the reason possibly be the STAB TRIM cable broke apart? This can create MCAS-like effects.

Given long-term storage complications in humid weather, this can be a reason.
 
wjcandee
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 3:40 am

zeke wrote:

ADSB data does include.... FR24 just doesn't record it.


Would ADSBExchange be more helpful, then? It makes my brain hurt to use it, but it does give you FMS Heading, FMS Altitude, the broadcast of the plane's IAS by the plane, etc.
 
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 3:49 am

zeke wrote:
The data does suggest a very sharp change in direction from level to near vertical, without much of a change in speed.


That seems to be a VERY significant data point. So play out that scenario if the ADS-B data is correct. What in your expert opinion could cause that?
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zeke
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Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 4:43 am

SuseJ772 wrote:

That seems to be a VERY significant data point. So play out that scenario if the ADS-B data is correct. What in your expert opinion could cause that?


The data is only useful in describing the flight path, it provides no visibility to the how and why it occurred.
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jabarei
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Joined: Tue Apr 23, 2019 1:54 pm

Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 5:27 am

KNKT (Indonesian Transportation Safety Committee) in their initial analysis of the damage to the wreckage (fan blades and turbine) says that the engines, most probably, were operating up to the impact. That is conclusive to the wreckage site estimated to 100 x 300/400m.

Source (in Indonesian): https://www.merdeka.com/peristiwa/krono ... j-182.html
 
BEG2IAH
Posts: 1018
Joined: Thu Apr 22, 2004 3:42 pm

Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 6:06 am

zeke wrote:
I did some further analysis, the aircraft at the bottom had a flight path angle of 87 degrees.


zeke, thanks for this analysis. A quick and totally uneducated question: is the 87-degree angle nose up or nose down? It would make more sense that it was nose down considering the speed at which the aircraft fell out of the sky. I hope the PAX lost consciousness when it all started. May they RIP.

Thanks.
Flying at the cruising altitude is (mostly) boring. I wish all flights were nothing but endless take offs and landings every 10 minutes or so.
 
User avatar
zeke
Posts: 16138
Joined: Thu Dec 14, 2006 1:42 pm

Re: Sriwijaya Air 737-500 (SJ182 CGK-PNK) crashes shortly after takeoff

Tue Jan 12, 2021 6:18 am

BEG2IAH wrote:
A quick and totally uneducated question: is the 87-degree angle nose up or nose down?


The flight path angle would be the velocity vector relative to the ground plane, I suspect it was achieved with a combination of high bank angle of around 60 degrees and nose low attitude of around 50 degrees.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
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