22 ms·

I didn't know that was possible. Well sure, almost anything is possible but, this begs questions: how often does this happen, and is there a formal check at som

by ggm 2y ago

I didn't know that was possible. Well sure, almost anything is possible but, this begs questions: how often does this happen, and is there a formal check at some granularity outside of crash events, to check if a black box recorder is working? What's the failure rate? I'm not pushing conspiracy theory, I'm just a bit aghast the mechanism designed to log things for disaster analysis itself can have .. catastrophic failure before an event. 4 minutes is an eternity. This can't be down to buffer behaviour and the event itself surely? https://www.pprune.org/accidents-close-calls/663324-jeju-737-800-crash-muan-airport-south-korea-90.html#post11805112 https://www.pprune.org/accidents-close-calls/663324-jeju-737... has discussion. Yes, catastrophic loss of power takes them off-line. Some kind of UPS like capacity seems necessary.

phire 2y ago
Because "the event" was the bird strike, and 4 minutes before the crash is the right timeframe for that. At least one of the engines was hit, and they appear to have lost AC power. The crash on the second landing attempt is just a the conscience of the bird strike, not the actual event. Apparently this aircraft was just old enough that the black boxes weren't required to be hooked up to any of the redundant power buses.
- timewizard 2y ago
  > be hooked up to any of the redundant power buses. There are multiple busses, but you almost always have an option to tie the two busses together, so one generator can drive both sets of loads. You can also add a battery through an inverter to carry loads. You can also turn on the APU and use it's output to drive loads. They may have had a more severe failure.
  - phire 2y ago
    Tying buses together is a manual operation. All indications are that the pilots didn't have enough time to get that far in the checklist. It's also not that important to restore AC power. The standby bus automatically brings the standby instruments online in the event of a failure, and not that hard to restore the majority of instruments by connecting the main DC bus to batteries. The battery has enough power for 30min of flying, or a full hour if you have the dual-battery option. > They may have had a more severe failure. While we only have evidence of bird strikes on one engine, the actions of the pilots seem to suggest that they lost both engines. They were rushing to get back to a runway.
    - zmgsabst 2y ago
      The struck engine was still spinning — you can see the visual distortion from its thrust reverser being deployed while on the runway.
  - f1shy 2y ago
    You do not have time to start the APU. Moving any switch is a procedure with a checklist, at that hight, once you lost both engines… they had no chance.
    - timewizard 2y ago
      It's just a button press. US Airways 1549 had the captain starting the APU within seconds after their birdstrike. Your biggest concern after starting is likely exhaust temperature.
      - f1shy 2y ago
        Exactly! And he was called out because he did that without following the stablished procedures! Also is not instant, will take a minute or two. The APU is a turbine that takes time to start. Maybe they did turn in on, but 2 minutes too late. We don’t know. He was a super pilot, who had extreme good understanding of all systems in the plane, and many ours on that plane. You cannot expect that (and do both want that!) from an average pilot. It seems right now that this very accident may have been caused by not following the procedures.
        phire 2y ago
        Or they started the APU, but never got around to connecting its generator to the main bus. That's a second button press, after confirming it has successfully started.
        nctk21 2y ago
        If by "called out" you imply criticised, then that is not correct. Instead, the NTSB final accident report (https://www.ntsb.gov/investigations/accidentreports/reports/aar1003.pdf https://www.ntsb.gov/investigations/accidentreports/reports/..., p. section 2.3.1) praises the specific quick action: "Although the flight crew was only able to complete about one-third of the Engine Dual Failure checklist, immediately after the bird strike, the captain did accomplish one critical item that the flight crew did not reach in the checklist: starting the APU. Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode. This critical step would not have been completed if the flight crew had simply followed the order of the items in the checklist. The NTSB concludes that, despite being unable to complete the Engine Dual Failure checklist, the captain started the APU, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall." The final report also gave a new safety recommendation (A-10-66, p. 124) to develop more appropriate (shorter) checklist for dual-engine failure specifically for low-altitude incidents.
MadnessASAP 2y ago
With a complete loss of electrical power there isn't much for the FDR to record other then airspeed, altitude, and attitude from the standby instruments. However that's already available from radar, ADS-B, and in this case, video. CVR might have some value, but again in most cases you're just getting a bunch of yelling and swearing before the crash. As far as understanding what went wrong with Jeju 2216, the interesting bits are going to be right up until they lost both engines, after that it's fairly straightforward to put together the chain of events.
- timewizard 2y ago
  > there isn't much for the FDR to record other then airspeed, altitude, and attitude from the standby instruments. You forgot the _most_ important data. The position of the flight controls set by the crew. > but again in most cases you're just getting a bunch of yelling and swearing before the crash. That has not been my experience. You can hear the pilots trying to work the problem until the last minute and hearing how they made decisions is important. You can also hear the engines, the wind noise, cockpit warning horns, and possible sources of pilot interference.
  - MadnessASAP 2y ago
    > That has not been my experience. You can hear the pilots trying to work the problem until the last minute and hearing how they made decisions is important. You can also hear the engines, the wind noise, cockpit warning horns, and possible sources of pilot interference. Knowing the pilots were trying to prevent the inevitable crash right up until the end is a nice thing to know but now relevant for flight safety. The point of the investigation is to determine what went wrong before the crash became a certainty. Which for Jeju was the moment they lost both engines. > You forgot the _most_ important data. The position of the flight controls set by the crew. While manual flight controls are a thing, without hydraulic assistance they are really only useful if you're trying to maintain straight and level flight while you start backup power. W1ith compounding problems it gives you a little more control of which direction you will be crashing in. I won't deny that more data in an investigation is always useful, but the cost of ensuring that data is available has to be weighed against the potential value of that data. With this crash the data after the loss of both engines won't have much bearing on preventing the similar incidents in the future. To put it another way, should your commercial air liner lose both engines at 1000' in a descent the outcome will be crash, the objective is to prevent that scenario.
f1shy 2y ago
> 4 minutes is an eternity. private pilot here: 4 minutes is nothing while flying and coping with an emergency! NOTHING!
- ggm 2y ago
  Yes. My comment was to the amount of data loss. I'm not a pilot and I respect pilots. What a terrible situation to be in.
  - f1shy 2y ago
    Sorry. I misunderstood the context.

by ggm 2y ago

phire 2y ago

Because "the event" was the bird strike, and 4 minutes before the crash is the right timeframe for that. At least one of the engines was hit, and they appear to have lost AC power. The crash on the second landing attempt is just a the conscience of the bird strike, not the actual event. Apparently this aircraft was just old enough that the black boxes weren't required to be hooked up to any of the redundant power buses.

timewizard 2y ago
> be hooked up to any of the redundant power buses. There are multiple busses, but you almost always have an option to tie the two busses together, so one generator can drive both sets of loads. You can also add a battery through an inverter to carry loads. You can also turn on the APU and use it's output to drive loads. They may have had a more severe failure.
- phire 2y ago
  Tying buses together is a manual operation. All indications are that the pilots didn't have enough time to get that far in the checklist. It's also not that important to restore AC power. The standby bus automatically brings the standby instruments online in the event of a failure, and not that hard to restore the majority of instruments by connecting the main DC bus to batteries. The battery has enough power for 30min of flying, or a full hour if you have the dual-battery option. > They may have had a more severe failure. While we only have evidence of bird strikes on one engine, the actions of the pilots seem to suggest that they lost both engines. They were rushing to get back to a runway.
  - zmgsabst 2y ago
    The struck engine was still spinning — you can see the visual distortion from its thrust reverser being deployed while on the runway.
- f1shy 2y ago
  You do not have time to start the APU. Moving any switch is a procedure with a checklist, at that hight, once you lost both engines… they had no chance.
  - timewizard 2y ago
    It's just a button press. US Airways 1549 had the captain starting the APU within seconds after their birdstrike. Your biggest concern after starting is likely exhaust temperature.
    - f1shy 2y ago
      Exactly! And he was called out because he did that without following the stablished procedures! Also is not instant, will take a minute or two. The APU is a turbine that takes time to start. Maybe they did turn in on, but 2 minutes too late. We don’t know. He was a super pilot, who had extreme good understanding of all systems in the plane, and many ours on that plane. You cannot expect that (and do both want that!) from an average pilot. It seems right now that this very accident may have been caused by not following the procedures.
      - phire 2y ago
        Or they started the APU, but never got around to connecting its generator to the main bus. That's a second button press, after confirming it has successfully started.
      - nctk21 2y ago
        If by "called out" you imply criticised, then that is not correct. Instead, the NTSB final accident report (https://www.ntsb.gov/investigations/accidentreports/reports/aar1003.pdf https://www.ntsb.gov/investigations/accidentreports/reports/..., p. section 2.3.1) praises the specific quick action: "Although the flight crew was only able to complete about one-third of the Engine Dual Failure checklist, immediately after the bird strike, the captain did accomplish one critical item that the flight crew did not reach in the checklist: starting the APU. Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode. This critical step would not have been completed if the flight crew had simply followed the order of the items in the checklist. The NTSB concludes that, despite being unable to complete the Engine Dual Failure checklist, the captain started the APU, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall." The final report also gave a new safety recommendation (A-10-66, p. 124) to develop more appropriate (shorter) checklist for dual-engine failure specifically for low-altitude incidents.

MadnessASAP 2y ago

With a complete loss of electrical power there isn't much for the FDR to record other then airspeed, altitude, and attitude from the standby instruments. However that's already available from radar, ADS-B, and in this case, video. CVR might have some value, but again in most cases you're just getting a bunch of yelling and swearing before the crash. As far as understanding what went wrong with Jeju 2216, the interesting bits are going to be right up until they lost both engines, after that it's fairly straightforward to put together the chain of events.

timewizard 2y ago
> there isn't much for the FDR to record other then airspeed, altitude, and attitude from the standby instruments. You forgot the _most_ important data. The position of the flight controls set by the crew. > but again in most cases you're just getting a bunch of yelling and swearing before the crash. That has not been my experience. You can hear the pilots trying to work the problem until the last minute and hearing how they made decisions is important. You can also hear the engines, the wind noise, cockpit warning horns, and possible sources of pilot interference.
- MadnessASAP 2y ago
  > That has not been my experience. You can hear the pilots trying to work the problem until the last minute and hearing how they made decisions is important. You can also hear the engines, the wind noise, cockpit warning horns, and possible sources of pilot interference. Knowing the pilots were trying to prevent the inevitable crash right up until the end is a nice thing to know but now relevant for flight safety. The point of the investigation is to determine what went wrong before the crash became a certainty. Which for Jeju was the moment they lost both engines. > You forgot the _most_ important data. The position of the flight controls set by the crew. While manual flight controls are a thing, without hydraulic assistance they are really only useful if you're trying to maintain straight and level flight while you start backup power. W1ith compounding problems it gives you a little more control of which direction you will be crashing in. I won't deny that more data in an investigation is always useful, but the cost of ensuring that data is available has to be weighed against the potential value of that data. With this crash the data after the loss of both engines won't have much bearing on preventing the similar incidents in the future. To put it another way, should your commercial air liner lose both engines at 1000' in a descent the outcome will be crash, the objective is to prevent that scenario.

f1shy 2y ago

> 4 minutes is an eternity. private pilot here: 4 minutes is nothing while flying and coping with an emergency! NOTHING!

ggm 2y ago
Yes. My comment was to the amount of data loss. I'm not a pilot and I respect pilots. What a terrible situation to be in.
- f1shy 2y ago
  Sorry. I misunderstood the context.