Authorities investigating the disaster plan to look into what caused the black boxes to stop recording, South Korea's transport ministry says.

Summary

A Jeju Air Boeing 737-800 crashed at Muan International Airport, South Korea, killing 179 people, with only two crew members surviving. The black boxes stopped recording four minutes before the crash.

Authorities are investigating the cause of the malfunctioning black box. They suspect a bird strike, as feathers were found in one engine, and video footage confirmed a bird impact. However, the exact cause of the crash remains elusive.

Investigators are probing why the landing gear wasn’t deployed, the role of power failure in missing black box data, and the construction of the airfield wall the plane hit.

  • tal@lemmy.todayEnglish
    161·
    2 days ago

    Now it looks like some electrical systems, including power to the data recorders, died right at the start of the incident, which would require not just double engine failure but failure of the APU and backup battery systems. That just seems incredibly unlikely.

    Electrical failure doesn’t absolutely require that the engines fail. Supposing you short the electrical system?

    Like, United Air Flight 232 had an uncontained engine failure that then severed all three hydraulic systems. The real problem that the pilots faced wasn’t “we’ve lost one of our three engines”, but rather the secondary damage to other aircraft systems resulting from that failure.

    I assume that there’s some level of electrical system redundancy, but then, the same was true of the hydraulic systems on UA232 – it just required a really unlucky failure, with the engine shrapnel hitting multiple things, to cause the redundancy to also be wiped out.

    looks for WP page

    https://en.wikipedia.org/wiki/Jeju_Air_Flight_2216

    Authorities said that a bird strike may have caused a malfunction that affected the hydraulic system controlling the landing gear and that there was insufficient time for the pilots to manually deploy the landing gear.

    I don’t see how a hydraulic system failure alone would have caused the flight recorder to go offline.

    But it does kinda sound to me like maybe they’re talking about a bird strike causing some kind of secondary problems. Supposing a bird strike caused an uncontained engine failure – which has happened before – and that then caused secondary problems as bits of engine severed other things in the aircraft. What if those secondary problems were electrical in nature, rather than hydraulic?

    EDIT: The landing was also apparently done without use of flaps. Looking online, it sounds like the lack of landing gear and flaps suggests that hydraulics weren’t available. But I’d guess that a loss of electrical power to the hydraulic system, rather than the hydraulics themselves failing, could also explain such a situation.

    EDIT2: If there’s power loss, some aircraft have a ram air turbine that drops down to get a small amount of electrical power. I was thinking that that might have been usable as an indicator that electrical power was gone. In the video, I don’t see that, but it sounds like a 737-800 doesn’t have one. According to this, that aircraft is also apparently capable of being controlled to a limited degree even without electrical power due to mechanical connections:

    https://aviation.stackexchange.com/questions/42565/does-a-boeing-737-800-have-a-ram-air-turbine-rat

    • If all fuel is gone and the batteries are depleted, the aircraft can be flown by hand, directly overcoming the aeroforces by pulling hard! This is called manual reversion.

    • In manual reversion, the aileron trim tabs now function as geared tabs, assisting in overcoming the aeroforces. Elevators will have high aeroforces, high friction forces, and freeplay around centre point. Stabiliser trim wheels provide additional pitch control. The rudder has no manual reversion.

    That’d permit for them being able to bring the plane down the way they did, assuming that they didn’t have electrical power.

    • Thrashy@lemmy.worldEnglish
      13·
      2 days ago

      Hydraulics and electric system are independent in commercial aircraft – hydraulic pumps are directly driven from the engines, as are electrical generators. Redundancy is provided via independent loops/buses from each engine. A bird strike on its own is unlikely to be energetic enough to sever one of those independent systems, let alone all four. Losing both engines could do it, – but again, they had enough thrust to attempt a go-around, so they weren’t a glider immediately after the bird strike. The 737 is an old-school design, too, so most critical components have full manual reversion – as long as you have airspeed and altitude enough to get to the runway, you can fly and land the plane just with cable controls and manual releases in the event of total electric and hydraulic failure.

      I did a bit of reading from other sources and this particular aircraft predates the requirement for battery backup of the FDR and CVR, and the APU does not start up automatically on a power failure, so the failure chain for that part of the incident isn’t as long as I initially thought. Still, lots of questions, and I think the simplest explanation so far is the aircrew panicking and making a survivable situation into a bloodbath.

      • tal@lemmy.todayEnglish
        5·
        2 days ago

        Hmm. Fair enough.

        Looking at a couple other sources, it also sounds like ADS-B data stopped being transmitted prior to the landing. So that does seem like another data point besides the data recorder maybe cutting out arguing for some measure of electrical issues (which doesn’t necessarily mean that the electrical system is damaged, but for power not to be going to part of the plane’s systems).

        https://www.flightradar24.com/blog/jeju-air-2216-muan/

        The last ADS-B message received from the aircraft occurred at 23:58:50 UTC with the aircraft located at 34.95966, 126.38426 at an altitude of 500 feet approaching Runway 1 at Muan.

        Based on visual evidence (see video below, viewer discretion advised) and the altitude and vertical rate data received by Flightradar24, we believe that the final ADS-B messages received represent preparation for a possible flypast of the airport. A flypast is often performed to visually confirm that the landing gear is either down or not prior to making a decision on next steps. The chart below shows the altitude and reported vertical rate of the aircraft from 2000 feet to the last signal received at 500 feet.

        Post-ADS-B data

        It appears that ADS-B data was either no longer sent by the aircraft or the aircraft was outside our coverage area after 23:58:50 UTC. Based on coverage of previous flights and of other aircraft on the ground at Muan before and after the accident flight, we believe the former explanation is more likely. There are multiple possible explanations for why an aircraft would stop sending ADS-B messages, including loss of electrical power to the transponder, a wider electrical failure, or pilot action on the flight deck.

        EDIT: I did also see a pilot talking about the video and pointing out that while the crew didn’t get flaps or gear, they managed to deploy at least one thrust reverser. I’m not sure what drives that (Do you need hydraulics? Electricity?), but it might say something about what was available to them.

      • Enoril@jlai.luEnglish
        1·
        1 day ago

        I wonder if they had an electrical fire under the cockpit while flying.

        The loose of systems normally segregated with multiple backup, the strange 2nd approach too fast without using the gears or flap…

        Total chaos and panic… or system damaged because of the impact with birds… or a drone? Damaged battery can produce a lot of heat and fire…