This particular plane seems to have been manufactured before backup batteries were required, so without main AC power the recorders would have stopped, standby power doesn't connect to the recorders.

[–] yardy_sardley@lemmy.ca 9 points 18 hours ago (1 children)

If both engines failed, that means they would have lost hydraulic power too, which is probably the reason they couldn't extend the landing gear or try to go around a second time.

One of the theories floating around is that a bird strike caused one engine to flame out and the pilots pulled the cutoff switch on the wrong engine. It wouldn't be the first time something like that happened.

[–] halcyoncmdr@lemmy.world 8 points 18 hours ago

IIRC the emergency landing gear deployment relies solely on gravity to drop and lock them into place, it's a passive system. Not 100% effective, but something that doesn't require a powered system of any kind for emergencies. Even if they didn't lock into place, they would at least deploy, which doesn't seem to have been the case here.

The cutoff to the wrong engine is sadly the most likely given the rest of the context like altitude and already aborting one attempt due to the strike. Lots of things to track that low to the ground, easy to forget you didn't deploy the landing gear the first time when your focus was trying to keep it in the air at that point and then going around and realigning for another attempt while also shutting down an engine.

[–] ryannathans@aussie.zone 2 points 19 hours ago (2 children)

How does one land a plane with no power at all

[–] halcyoncmdr@lemmy.world 8 points 19 hours ago (2 children)

Planes glide, fairly well. However, that requires having altitude and time to plan and maneuver since you cannot usually gain new altitude and any maneuver bleeds it off quickly. Control surfaces use hydraulics not electric motors, and standby power provides basic instrumentation, despite not powering the recorders.

And of course working landing gear (most landing gear drops and locks into position due to gravity, no power needed).

This particular case had basically none of those advantages, and possibly landing gear issues as well. There are a lot of questions in this crash, and many of the preliminary answers currently seem to be pointing towards things like poor maintenance, just bad luck, and the always possible pilot error.

This is why throat flight recorders are so useful. Hearing the pilot conversations in the cockpit helps with knowing what they were working through, and instrumentation logs help with what the plane was telling the pilots. Missing the last 4 minutes is the worst time for a gap, but the exact reason why battery backups are in newer planes. They should have been required to be installed in all previous ones as well.

[–] SirSamuel@lemmy.world 2 points 10 hours ago

Shouldn't the RAT automatically deploy with a power loss? Can the APU be turned on if there's a total power loss?

I imagine with four minutes and already at task saturation they may have just forgotten to deploy the gear. I also wonder if they had a single engine when they decided to go around, and then lost power and decided to loop back to runway 19. I also wonder if they decided to keep the gear stowed until final to improve performance, then lost power and forgot to deploy the gear.

I guess some of these things we might never know, especially without the CVR

[–] deadbeef79000@lemmy.nz 4 points 18 hours ago

They should have been required to be installed in all previous ones as well.

It's crazy that they weren't. Unusually so (at least the perception so) for the aviation industry.

The last few minutes is the most valuable data!

[–] yardy_sardley@lemmy.ca 2 points 19 hours ago

I don't know, but aiming for a short runway with a wall at the end doesn't seem to work.