J-20 5th Generation Fighter VII

siegecrossbow said:

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It is quite obvious. Three spurts in the opening 10 seconds.

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Oh I see, I've never actually watched the video before, so that's interesting.

Seems like it was quite periodic and brief, and visible in the initial part of the display (though the quality of the video might obscure others). given how period it was, and given how we haven't really seen much of it among the aircraft it's in service with in other occasions, I wonder what the cause is..

Bltizo said:

Oh I see, I've never actually watched the video before, so that's interesting.

Seems like it was quite periodic and brief, and visible in the initial part of the display (though the quality of the video might obscure others). given how period it was, and given how we haven't really seen much of it among the aircraft it's in service with in other occasions, I wonder what the cause is..

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There really isn’t too much to it. In an Airshow setting the fighter is running at military power where the fuel supply to the engine is the greatest. Some of it is not fully burned and show up as smoke. In videos we have of WS-10 equipped aircraft we rarely see them operating in similar conditions.

siegecrossbow said:

There really isn’t too much to it. In an Airshow setting the fighter is running at military power where the fuel supply to the engine is the greatest. Some of it is not fully burned and show up as smoke. In videos we have of WS-10 equipped aircraft we rarely see them operating in similar conditions.

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There are only finite causes for a bit of smoke from jet engines, that isn't much of a question.
I was more wondering why would the videos and pictures we have of aircraft operating normally in service to not also run at military power?
In fact, wouldn't it make more sense that the aircraft during the airshows are running their engines below military power?

In that video, the smoke also seems more pronounced at the moment the aircraft banks and turns. I think a sudden shift in perspective might account for this. The exhaust trail is less visible when viewed from its side at a more oblique to perpendicular angle, but when the aircraft turns, you're suddenly staring down the central axis of the trail, which now becomes more visible because it's literally 'thicker' when viewed in that perspective.

Bltizo said:

There are only finite causes for a bit of smoke from jet engines, that isn't much of a question.
I was more wondering why would the videos and pictures we have of aircraft operating normally in service to not also run at military power?
In fact, wouldn't it make more sense that the aircraft during the airshows are running their engines below military power?

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First, there might not be anything unusual if the pictures themselves are a biased sample (more pictures are taken when the plane starts to execute a manoeuvre, which is when airflow to the engine changes). The video by78 posted doesn't show any unusual smoking, just the spurts accompanying thrust changes.

I guess we don't see that in "normal" videos of planes because we're not seeing them transitioning into afterburner or going into a manoeuvre, we usually see them in level flight at constant speed. If I were to guess a cause for these smoke spurts, it might be a timing thing between the airflow into the engine and the fuel injectors.

by78 said:

I think a sudden shift in perspective might account for this.

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Could be but it doesn't seem like it. It looks like the smoke starts as the plane turns. I would guess its because the fuel injection is going by "old" airflow for a couple of ticks, while turning might marginally reduce the airflow to the engine - this means it runs fuel rich for a short period of time.

One more video.

by78 said:

One more video.

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I got motion sickness watching that.

We'd had so few images of WS-10C until now. The floodgate is open, and it feels like Christmas.

by78 said:

We'd had so few images of WS-10C until now. The floodgate is open, and it feels like Christmas.

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Why does the WS-10C use no moving outer petal for the afterburner? does the design uses space between the inner and outer petals to create a "cylinder" of colder air enveloping the hot exhaust, therefore reducing IR signature?

I thought it wouldn't matter but it actually does make a difference in terms of looks

The fact that the WS-10C looks shorter makes the plane seem more proportional