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Preliminary report is out:
Not much new (if anything).
Not much new (if anything).
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I think we know by now as much as we ever will know. Maybe forensics can determine the state of either engine at impact. Nevertheless, some important things be learned from it, and possibly done about it.Originally posted by Gabriel View PostPreliminary report is out:
Not much new (if anything).Comment
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Disconcur.Originally posted by Evan View PostLes règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.Comment
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Aha! The emergency exit light behind the forward door was lit? And that would indicate a loss of all AC power? Sort of the RAT telltale of the 737. Not that we didn't already strongly suspect this to be the case, but it does back that speculation up. Not addressed in the video: how did they retract the gear and flaps after the bird strike if this resulted in a loss of engine pumps and generators?Originally posted by Gabriel View PostComment
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He did mention it, some things were very explicit and others more subtle because he doesn't want to draw conclusions.Originally posted by Evan View Post
Engines don't just either work or don't, and neither do hydraulic pumps. Generators on the other hand do because they trip (shut themselves down) when certain conditions are not met.
Thrust, hydro and power do not need to have failed simultaneously, instantly and catastrophically at once at the moment of the bird strike.
The crippled engine(s) may have continue to provide at least some level of thrust and hydro power after the generators shut down.
In fact, they had to. Otherwise they could have not retracted the flaps and gear and, more importantly, they would have not made it to circle around and land on the runway.
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--- Defend what you say with arguments, not by imposing your credentials ---Comment
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Yes, obviously they had enough hydraulics to do these things. Mentour pilot shows us a scenario of total loss of hydraulic power and s p e c u l a t e s that purely human-powered flight control might explain the s-turns we see in the video. The hydraulics may have further degraded after the gear came up. The engine pumps are always running if the engine is turning at all. I'm just saying that he doesn't address this at all in his 45 minutes of detailed explanation, and it sort of is a central part of this mystery.Originally posted by Gabriel View PostComment
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You said he doesn't mention it.
I said he does.
You said again he doesn't.
Watch 20 seconds here
16 seconds here
And 34 seconds here
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---Comment
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Where does he mention it? He talks about the APU, pointing out that the lack of gear and flaps would be consistent with NOT starting it. He mentions that they must have been able to climb, eith with the energy they had or with some remaining thrust. I don't see where he addresses the mystery of how the gear was retracted after losing both generators to dual engine failure. In one of your posted links, the plane is seen going around with gear extended and then landing with gear retracted and there is no mention of how this might have happened. It would have been interesting if he could explain what level of N1 might be required to power gear retraction, yet be insufficient to keep the generator online.Originally posted by Gabriel View PostYou said he doesn't mention it.
I said he does.
You said again he doesn't.
Watch 20 seconds here
16 seconds here
And 34 seconds here
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Sorry, the link of the 3rd video is wrong. Use this one.
The engines must have continue to run, even if crippled, after the generators stopped, to allow the plane to climb and accelerate and retract the flaps and gear.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---Comment
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The links must not be taking me to the right place because there is no mention of how the gear might have been retracted. He does say “the gear was never extended” which I take to mean never extended a second time. And again, I concur with you that one or both engines must have remained operational enough to explain both the gear retraction and the successful turn back to the opposite runway. I would just like some technical detail on what the required N1 would be and why it wouldn’t allow flap extension as well. I will s p e c u l a t e that the engine progressively degraded and perhaps the accumulated pressure was depleted with the gear retraction and thus not available to assist flap extension.Originally posted by Gabriel View PostSorry, the link of the 3rd video is wrong. Use this one.
The engines must have continue to run, even if crippled, after the generators stopped, to allow the plane to climb and accelerate and retract the flaps and gear.
All of this is important because I think procedures need to be written, trained and memorized for this scenario (engine failure 1+2 on approach) that stipulate that the plane must continue the approach and not retract gear or flaps (perhaps retracting flaps one notch to reduce drag) unless continuing would clearly increase the danger. And the first memory action after the left seat takes control and stabilizes the aircraft should be the APU start. Would you disagree?Comment
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