Comment by n_ary
1 year ago
There is also a RAT at the back that can be deployed to generate some power(~5-10 minutes max) in case of severe emergency in Air. It is what you hear sometimes, when the aircraft is making a very shrill noise flying over your head.
However, if it is not a test flight, a RAT deployment should make you very uncomfortable and worried…
> RAT … It is what you hear sometimes, when the aircraft is making a very shrill noise flying over your head.
I’ve been around a lot of airplanes and I can’t say I’ve seen or heard a ram air turbine deployed in flight. There was a recent incident involving a Frontier Airlines flight in which the RAT was deployed when the aircraft was put in emergency electrical configuration. The deployment of the RAT would be quite rare.
https://en.wikipedia.org/wiki/Ram_air_turbine
I find it hard to believe that anyone reading this was within earshot of a plane in a severe emergency and heard this particular sound and since turbine engines are already quite shrill I am basically just sorta confused who your audience is for this suggestion.
The RAT makes an extremely distinctive sound. You'd recognize it nearly instantly. However the RAT will not power everything.
https://www.youtube.com/watch?v=KzejbxNj1hY
That's cute, it sounds like a little Cessna
Usually, when the RAT is really deployed because of an emergency, the jet engines will be a lot more silent (because they're not producing any power). Although I'm not really sure how loud a windmilling jet engine really is, and I somehow doubt there is a YouTube video of a plane landing with both engines disabled - but you never know...
Indeed unlikely to hear RAT deployed due to emergency. But they do deploy it sometimes on test flights after maintenance.
Would you hear it from inside the plane? Even if it’s not as loud as the main engine, if it’s audible at all a lot of people would notice a change in pitch/tone. At least, I notice when the sounds the plane is making change even though I don’t know anything about the reason.
It's apparently quite loud
> After starting the descent, the flight crew made an announcement to the passengers; however, unbeknownst to the flight crew, the noise generated by the RAT (because of its high rotation speed) prevented the passengers and the cabin crew from hearing the announcement.
https://asn.flightsafety.org/wikibase/187755
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I feel like it's not the RAT you'll notice from inside the plane, it will be the silence from the engines. That combined with at least a momentary flicker of the lighting (I'm not sure if a RAT on a 787 will run cabin lighting but I doubt it), and you'll know.
Username does not check out.
Jokes aside... I'm certainly part of the intended audience: point me at an interesting rabbit hole, and there I gooo.
Haha I didn’t parse it that way but I can see how you thought that upon rereading. I just want to understand why we would hear the RAT when there wasn’t an emergency overhead. I supposed planes regularly test them?
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The chances of you being on multiple commercial flights where the Ram Air Turbine are deployed is infinitesimal, no?
Also, RAT can power limited systems indefinitely on most models, not all or limited systems for a limited amount of time.
Why would the Ran Air Turbine be time restricted? As long as the plane is moving there’s power.
> Why would the Ran Air Turbine be time restricted?
Gravity?
But the turbine generates power to keep the plane flying. Why would it only work for 10 minutes? Certainly the flight time is a product of fuel level and altitude. Even if both engines fail the flight time would be a function of altitude. I don’t see how deployment of the RAT informs flight time.
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By definition, when you are using the RAT, you don't have any electrical power and you probably don't have thrust.
You are constrained by battery, airspeed, and altitude.
Well you aren’t constrained by battery if the RAT is deployed, that’s the point of the RAT.
“Probably” is doing a lot of work here, there could be a power failure without engine failure.
If the RAT could keep the plane flying indefinitely we would just be using RAT instead of fuel I suppose.
/s? A generator or alternator powered directly by the engines is more efficient than towing a wind vane (still indirectly powered by the engines and/or the potential energy of the airplane) every single time.
This discussion has nothing to do with engine out failure modes.
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Huh? It’s a generator. It generates minimum power to keep the flight controls and instruments working. It’s not propulsion.
The RAT is a generator, not a device that can provide thrust. If anything it will minutely slow the plane down.