Lethe
Captain
Also the RAT (Ram Air Turbine) deployed to provide electric power. This means that there either was complete loss of power from both engines or catastrophic loss of hydraulic pressure. Im leaning towards a dual engine failure.
Amidst all the theories that are emerging buttressed by often disputed evidence, I found this post from iamtom on interesting on the evidence for RAT deployment:
I've been seeing a lot of talk about the possibility of the RAT being deployed shortly after take off. Personally I think it's impossible to say from looking at the video, there does appear to be a dark line that is clearly not the gear, but it could just be a video artefact.
However, I come from an audio engineering background so I have been doing some experimentation with the audio from the video and comparing the frequencies of a known 787 RAT from a Boeing test video, where it is isolated without engine noise. I then compared it to a boeing test video of a 787-8 at take off thrust and another comparison to a JAL flight with both thrust and RAT.
From the 2 known and confirmed examples of the audio with RAT, the drone noise the RAT makes is strongest in the 350-700Hz frequency range. Taking the audio from the original higher quality AI171 fly-by video (according to the post), I can clearly identify RAT noise around the same 350-700Hz frequency range. It is very distinctive and when both confirmed RAT videos AND the AI171 audio is ran through a professional tuning app, they are all hovering around middle G (approx 391Hz) with an increasing pitch curve.
Lastly, I found a take off video of a 787 with the same Genx engines and extracted the audio to compare. There is clearly an absence of droning at the same frequency range, which was expected as there is clearly no RAT deployed.
My conclusion? I'd say with a high degree of certainty that the RAT sounding noise in the AI171 fly by video is a RAT and certainly not attributable to a passing car or motorcycle.
The only question is if the video's audio is real and undoctored. That I certainly can't answer.
Between the survivor's account of lights flickering on take-off, signs that the landing gear had indeed commenced retraction process, and evidence for RAT deployment, the theory that the pilots simply pulled the wrong lever (retracting flaps instead of landing gear) appears increasingly shaky.
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