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That’s interesting. It’s a little unclear from the reporting whether the engines rolled back to idle (in which case electrical power would still have been avail

by foldr 1y ago

That’s interesting. It’s a little unclear from the reporting whether the engines rolled back to idle (in which case electrical power would still have been available, I assume) or shut down completely. A software bug rolling both engines back to idle seems kind of conceivable. But shutting them both down completely, simultaneously, while in flight? It seems so unlikely that I’m inclined to be skeptical of the RAT claims. But obviously, no-one really knows anything at this point. Edit: I see that the WSJ now claim to have a source inside the accident investigation for deployment of the RAT: https://www.wsj.com/business/airlines/boeing-787s-emergency-power-system-likely-active-before-air-india-crash-148b7e02 https://www.wsj.com/business/airlines/boeing-787s-emergency-...

tim333 1y ago
There seems clear evidence the RAT was deployed from the sound on videos - you can analyse the frequencies and the like. For whatever reason in the ANA flight the engines both shut down completely https://www.aerosociety.com/news/ana-787-engine-shutdown/ https://www.aerosociety.com/news/ana-787-engine-shutdown/ not sure why you'd want to do that rather than idle them. It's reminding be a bit of the 737MAXs crashing due to a faulty sensor triggering some badly designed system. If you watch the takeoff video the plane climbs normally for about 10 seconds and then suddenly starts descending without any change of direction or rudder suggesting both engines went simultaneously which probably wouldn't be the case with fuel or birds - they found no birds when they looked. Some info on that system design https://www.pprune.org/rumours-news/617426-ana-787-engines-shutdown-during-landing.html#post10366128 https://www.pprune.org/rumours-news/617426-ana-787-engines-s... It's designed to trigger if an engine is at high thrust while the throttle is in the idle position and the plane is on the ground. Maybe there was a low probability combination of sensor failures which could explain why it only happened after much successful flying and maybe why it was when they raised the gear if that effected the on the ground sensor?

by foldr 1y ago

tim333 1y ago

There seems clear evidence the RAT was deployed from the sound on videos - you can analyse the frequencies and the like. For whatever reason in the ANA flight the engines both shut down completely https://www.aerosociety.com/news/ana-787-engine-shutdown/ https://www.aerosociety.com/news/ana-787-engine-shutdown/ not sure why you'd want to do that rather than idle them. It's reminding be a bit of the 737MAXs crashing due to a faulty sensor triggering some badly designed system. If you watch the takeoff video the plane climbs normally for about 10 seconds and then suddenly starts descending without any change of direction or rudder suggesting both engines went simultaneously which probably wouldn't be the case with fuel or birds - they found no birds when they looked. Some info on that system design https://www.pprune.org/rumours-news/617426-ana-787-engines-shutdown-during-landing.html#post10366128 https://www.pprune.org/rumours-news/617426-ana-787-engines-s... It's designed to trigger if an engine is at high thrust while the throttle is in the idle position and the plane is on the ground. Maybe there was a low probability combination of sensor failures which could explain why it only happened after much successful flying and maybe why it was when they raised the gear if that effected the on the ground sensor?