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That’s what I thought; I was confused by the “failed to restart” language, as if there might be something wrong with engine № 1.
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Feb 6, 2015 13:51
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Linedance posted:They're pretty much all engine parameters showing the effect of an engine flame out (blue line), and an engine shut down (green line), then attempted restart. I'm not as familiar with turboprops, but ITT is inter-turbine temperature (EGT, essentially), NP, NH and NL are prop, high press and low press compressor (I believe) speed in percentage of maximum. The rest are pretty self explanatory. poo poo, I wasn't fully awake when I was looking at the chart and didn't read the time stamps properly, woops. So the rising prop speed/compressor speed/oil pressure is actually just in the final quarter of a second and was probably just from increased airflow as it fell out of the sky.
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Feb 6, 2015 13:58
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Terrible Robot posted:poo poo, I wasn't fully awake when I was looking at the chart and didn't read the time stamps properly, woops. More likely the response of the engine to selecting the fuel back on 15-20 seconds prior to the end of the chart. Igniters would have already been firing due to the stall (I would have thought). e- The time stamp is hours:minutes:seconds UTC Finger Prince fucked around with this message at 14:11 on Feb 6, 2015 |
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Feb 6, 2015 14:06
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The "PLA" data on the chart is the power lever angle, which is basically how far forward the power levers (throttles) are. Since that just records the physical position of the levers, it's a decent indicator of what the crew was telling the engines to do. When you look at that line compared with the ITT or NP, it's pretty clear that the crew shut down the wrong engine for some reason. This is also a really good example of why the usual procedure for an engine failure on takeoff/initial climb is to just shove the power levers forward and fly the airplane, with the engine failure checklist typically not being done until the airplane is stabilized at a point where both crewmembers can verify which engine has failed and is being secured. On turboprops, the aerodynamics of the propeller feathering can initially cause a brief yaw in the wrong direction (towards the good engine) when the autofeather engages, so I have to wonder if whoever shut down the wrong engine did so in response to that phenomenon instead of just waiting a couple of seconds for things to stabilize going from there. azflyboy fucked around with this message at 21:00 on Feb 6, 2015 |
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Feb 6, 2015 20:37
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^^^We were simul-posting, you also bring up a good point. Most puzzling is the PLA (power lever angle)... almost immediately after the right engine fails, they make a slight throttle reduction on the good engine. About 25 seconds later, they commence a series of 3 more throttle reductions leading up to the shutdown of the good engine. Also, at the same time as the right engine quits and autofeathers, there's an increase in left engine "objective torque" (I assume meaning target torque that the computer wants the engine to have), as well as fuel flow, with no PLA increase. Is there a system that automatically increases power on the good engine when the other one fails? Anyone with ATR knowledge care to chime in? [Edit: an ATR pilot from another forum told me yes] I wonder if they just looked at the engine gauges and went to match the values... but matched the good to the bad instead of the other way around. If there is indeed such an automatic power-increase system, they could have seen the split in power, got into their brains that they were in a left-engine overtorque/overtemp situation, and under shocked tunnel vision failed to consider any other possibility, or for that matter SOPs. vessbot fucked around with this message at 23:05 on Feb 6, 2015 |
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Feb 6, 2015 21:13
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evil_bunnY posted:Also they thought pulling on the stick with no airspeed was how you gain altitude. Normally I decry the very same thing (a factor in every major recent crash) but in this case, it seems to have saved a bunch of lives the ground (intentionally or not) ... look at all the buildings they barely skirted over.
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Feb 6, 2015 22:58
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vessbot posted:^^^We were simul-posting, you also bring up a good point. I was thinking the stepped reduction in PLA might be a response to flame-out. You need to throttle back in order to perform a restart, both for fuel metering and spark, and for engine protection.
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Feb 6, 2015 23:06
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vessbot posted:Normally I decry the very same thing (a factor in every major recent crash) but in this case, it seems to have saved a bunch of lives the ground (intentionally or not) ... look at all the buildings they barely skirted over. Except if they didn't spin it they'd have cleared the highway. Also their good engine was actually on at that point.
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Feb 6, 2015 23:13
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Linedance posted:I was thinking the stepped reduction in PLA might be a response to flame-out. You need to throttle back in order to perform a restart, both for fuel metering and spark, and for engine protection. Do you?
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Feb 6, 2015 23:23
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vessbot posted:^^^We were simul-posting, you also bring up a good point. I know the ATR 72-600 uses FADEC of some kind, so an engine overtorque/overtemp would be very unlikely, and the checklist for those situations would probably call for reducing power on the affected engine to try and solve the issue, with a shutdown being called for only if the torque or temperature continued to increase (or failed to decrease) at a lower power setting. From looking through the manual for an ATR 72-500, the power increase on the good engine is automatic if an engine fails on takeoff or climbout, which would mean the crew had to do nothing except keep control of the airplane and eventually secure the failed engine when it was safe to do so. azflyboy fucked around with this message at 01:44 on Feb 7, 2015 |
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Feb 6, 2015 23:39
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hobbesmaster posted:Except if they didn't spin it they'd have cleared the highway. Not necessarily so. If they were losing speed+altitude and were pulling back to trade speed for altitude (while losing both at the same time) then any cease in the elevator pull would have meant an even steeper dive, and therefore a crash into the bridge. When you get on the back side of the power curve in a glide, you can stretch the glide only as long as you keep decreasing the airspeed (pulling back). This only works if you run out of altitude before you run out of airspeed. These guys ran out of airspeed first. quote:Also their good engine was actually on at that point. Also not apparently so. I don't know the details of the ATR start cycle, but the prop is fully feathered to the end and the rest of the parameters are in the process of increasing. vessbot fucked around with this message at 00:08 on Feb 7, 2015 |
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Feb 6, 2015 23:41
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Bob A Feet posted:Do you? Depending on how the engine controller is set up, it might require certain power and condition lever positions to get the system to allow an airstart, but the fuel scheduling and hot start protections should be largely automatic once the start sequence begins. azflyboy fucked around with this message at 01:25 on Feb 7, 2015 |
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Feb 7, 2015 00:03
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Bob A Feet posted:Do you? Good question! I believe you do, at least there are N2 speed limits, generally, for restart, but I will answer that more definitively tomorrow (including if I didn't get my facts straight). Turboprops might be different though, as they generally use some form of centrifugal compressor.
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Feb 7, 2015 00:49
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Linedance posted:Good question! I believe you do, at least there are N2 speed limits, generally, for restart, but I will answer that more definitively tomorrow (including if I didn't get my facts straight). I found a copy of the operating manual for an ATR 72-500 online, and the dual engine failure checklist calls for both power levers to be at flight idle and the condition levers to be at shutoff before restarts are attempted. The section dealing with airstarting an engine also calls for the condition lever to be in shutoff before the restart is attempted, but the airstart envelope only depicts airspeed and altitude, so there don't seem to be any N2 or other engine limitations for restarting an engine. Another thing to keep in mind is that the start and unfeather sequence for a turboprop can take a while, so the TransAsia crew likely weren't going to get an engine restarted before they ran out of altitude. On the Q400 (which uses a more powerful variant of the engine on the ATR 72), the start sequence typically takes about 15 seconds to get the engine running, and unfeathering the propeller can be another 10-15 seconds after the condition lever is moved out of start/feather. I'd assume the start process might be shortened somewhat if the engine were already windmilling, but since the FDR data doesn't show the restart beginning until the airplane was about 700ft off the ground, there's no way the engine was going to restart and unfeather before impact.
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Feb 7, 2015 01:42
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Tsuru posted:There were reports from within the airline that the no.1 engine was written up the day before due to excessive vibration, and that the captain had demanded a thorough inspection of it before he would take the airplane that day. Confirmation bias at work. So the plane's saying "engine 2 is busted" but the flight crew is hearing "engine 1 is busted" because they were having so much trouble with it earlier? poo poo, I've done stuff like that before where I hear what I expect to hear and not what's really being said - but I'm sure as poo poo glad it was never in a life or death situation.
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Feb 7, 2015 10:36
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The NTSB released the probably cause findings for Asiana 214, the Boeing 777 that http://tinyurl.com/ofs2wgy quote:The National Transportation Safety Board determines the probable cause(s) of this accident as follows: Full report here: http://www.ntsb.gov/investigations/AccidentReports/Pages/AAR1401.aspx The Ferret King fucked around with this message at 18:03 on Feb 7, 2015 |
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Feb 7, 2015 17:57
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quote:Contributing to the accident were (1) the complexities of the autothrottle and autopilot flight director systems that were inadequately described in Boeing's documentation and Asiana's pilot training, which increased the likelihood of mode error; I don't necessarily disagree that this is a contributing factor, but to put it at #1 seems kind of silly. As soon as the pilots realized there was a problem, they should have turned off the auto-throttle and flown the airplane. Also I've not found the autothrottle all that complicated.
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Feb 7, 2015 18:13
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How many hours do you have in the 777?
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Feb 7, 2015 18:23
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Colonial Air Force posted:I don't necessarily disagree that this is a contributing factor, but to put it at #1 seems kind of silly. As soon as the pilots realized there was a problem, they should have turned off the auto-throttle and flown the airplane. They did. But it was too little, too late.
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Feb 7, 2015 19:04
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sellouts posted:How many hours do you have in the 777? You know what I meant. It's not a complex system. vessbot posted:They did. But it was too little, too late. Which should be #1.
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Feb 7, 2015 19:10
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Linedance posted:Good question! I believe you do, at least there are N2 speed limits, generally, for restart, but I will answer that more definitively tomorrow (including if I didn't get my facts straight). So, interestingly enough, Airbus has you select throttles to idle for a flameout and restart, 767 has you select max continuous thrust. 777 and 787 the only thing I see is a recommendation to select idle in volcanic ash to avoid getting a flameout. So the answer is.... Maybe?
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Feb 7, 2015 20:08
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Colonial Air Force posted:You know what I meant. It's not a complex system. Uhh, it's a hugely complicated system, with all kinds of interplay between the autothrottle and the autopilot, and many different modes that can have all kinds of effects, both intended and unintended, on how the entire autoflight system behaves.
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Feb 7, 2015 20:17
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We have a 787 pilot here. Proprietary system so I imagine he can explain it. Every auto throttle I've ever used is a speed selector and a push button. The complicated part of using it is when to use it (approach? Climb out? Enroute?) And the CRM involved.
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Feb 7, 2015 20:21
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Bob A Feet posted:We have a 787 pilot here. Proprietary system so I imagine he can explain it. Every auto throttle I've ever used is a speed selector and a push button. The complicated part of using it is when to use it (approach? Climb out? Enroute?) And the CRM involved. What the pilot sees is very simple. What goes on behind the scenes is very not.
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Feb 7, 2015 20:28
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Linedance posted:777 and 787 the only thing I see is a recommendation to select idle in volcanic ash to avoid getting a flameout. Is this a standard section of the flight manual, or did they add it after ejafallajokul or w/e it's called
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Feb 8, 2015 00:30
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Sagebrush posted:Is this a standard section of the flight manual, or did they add it after ejafallajokul or w/e it's called Makes me think of British Airways flight 009 that flew into a volcanic plume and had all its engine flame out. http://en.wikipedia.org/wiki/British_Airways_Flight_9
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Feb 8, 2015 00:36
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Jesus Christ, the captain on that flight...quote:Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.
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Feb 8, 2015 02:14
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Godholio posted:Jesus Christ, the captain on that flight... So hey guys, all our engines are dead and we're falling like a brick. Be chill, though - we're trying to make it work. We hope we can pull that off, haha!
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Feb 8, 2015 02:29
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Sagebrush posted:Is this a standard section of the flight manual, or did they add it after ejafallajokul or w/e it's called It's a standard section under "abnormals" - likely been there since that BA flight Okan170 mentioned Another thing I found interesting was the preface to the 'engine problems on takeoff' section, stating categorically to continue takeoff and establish stable flight before attempting to address the problem, and then doing so in a deliberate and controlled fashion, because "incidents have turned into accidents when crew have inadvertently shut down the incorrect engine" (or words to that effect).
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Feb 8, 2015 02:34
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Godholio posted:Jesus Christ, the captain on that flight... Old school BA, wot wot 
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Feb 8, 2015 02:35
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In doing some research on early Soviet jet aircraft, I've thought of something that bugs me. Why are the Chinese so bad at producing jet engines, even copies of existing ones? I know this sounds odd, but bear with me-much of the early Soviet jet engine production was based on reverse-engineered versions of existing German or British designs (the Jumo 004 as the RD-10, the BMW 003 as the RD-20, the Rolls-Royce Nene as the RD-45/VK-1, and the Rolls-Royce Derwent as the RD-500), and even with the lovely metallurgy that went with the German designs, and picking up metallurgical tips for the British ones by stealing shards of metal in their socks (really), they still managed to eventually start making jet engines that worked well. The Chinese have been building jet engines of one design of another for at least that long, yet they still seem to keep hitting a brick wall in terms of performance, and I'm not sure why. Obviously, there have been significant factors impeding progress in just about anything in aviation in-country (they received documentation to produce the Antonov An-12 in the early 1960s, and did not successfully put the Shaanxi Y-8 into service until 1981), but they've still been able to produce aircraft that may not be original, but are at least reasonably good at their intended role. I've also noticed that Wikipedia articles on Chinese aircraft always seem to refer to the "General Designer" in a weirdly reverential way, even for what are essentially copies of Russian designs.
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Feb 8, 2015 02:48
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Short answer: metallurgy, insane tolerances, and quality control, all of which are difficult to replicate without a long time of trial and error. Basically China started down this path decades after everyone else, and just stealing blueprints doesn't give you the full leg up to make up that gap.
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Feb 8, 2015 03:48
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Colonial Air Force posted:You know what I meant. It's not a complex system. What are you basing that evaluation on? Can you expand?
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Feb 8, 2015 03:55
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Godholio posted:Short answer: metallurgy, insane tolerances, and quality control, all of which are difficult to replicate without a long time of trial and error. Basically China started down this path decades after everyone else, and just stealing blueprints doesn't give you the full leg up to make up that gap. Pretty much this. Hell even Russia lags behind the West as well.
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Feb 8, 2015 04:02
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It seems like a good metric to look at would be each country's space program -- success in that field requires the same sort of expertise as building jet engines. China's space program is at about the same point that the USA and Russia were in the 1960s and 70s.
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Feb 8, 2015 04:08
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Here's another angle on the ATR72 crash: http://youtu.be/RUQWJai59lo
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Feb 8, 2015 07:30
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vessbot posted:What are you basing that evaluation on? Can you expand? He bought an 80 dollar add on to Microsoft flight simulator x
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Feb 8, 2015 09:00
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http://edition.cnn.com/2014/03/08/us/plane-skydiver-collision/ Whoa
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Feb 8, 2015 14:19
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vessbot posted:What are you basing that evaluation on? Can you expand? I mean from the pilot's perspective, the only complicated thing about it in this situation was that it was still on. sellouts posted:He bought an 80 dollar add on to Microsoft flight simulator x Which came with a manual! 
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Feb 8, 2015 14:25
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Those stills are pretty intense but I'd like to watch his go-pro footage.
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Feb 8, 2015 17:24
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