South Korea air crash recorders missing final four minutes
https://www.bbc.com/news/articles/cjr8dwd1rdno
Lots of discussion @ Airliners.net about how they could have lost both generators but still had enough thrust for a go around, best theory IMO so far involves tripping breakers:
The recorders will still cover the period from the initial (likely) birdstrike to whatever caused the second generator to go offline. That will tell us what went wrong at first, and likely indicate what caused the loss of each generator (excessive N2 variation, flameout, shutdown).
At the point when ADS-B cut out, they were ~500ft and didn't have nearly enough energy to overfly the runway and do a teardrop without further thrust, so at least one engine was producing at least partial thrust for a good chunk of that 4-minute period. You can't glide for four minutes from that, let alone accelerate to ~200kt. 1549 glided for about 10nm; this flight would have been about three-quarters that length it appears, scaling off some peoples' indicative tracks, plus with much more turn (which eats up energy).
The generators on the 737 do not automatically come on bus. Flight crew action is needed to reset them if they trip. I am wondering if the stalls caused changes in N2 RPM that were too fast for the constant speed drive to handle, so frequency excursion tripped the generator off bus.
I think this somewhat fits the 'shut down wrong engine' hypothesis. GEN 2 (probably) dropped offline during the initial birdstrike. GEN 1 dropped offline when the crew shut down engine 1, or possibly during a separate second birdstrike, but I feel this is unlikely.
Like in Transair 810, the failed engine continued providing not quite enough thrust to maintain level flight, forcing this flight to attempt a teardrop to land.
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