J-20 5th Gen Fighter Thread VI

[Inst]

@AFB: this is obviously sped up, but it's a nice shot of your vapor clouds. That said, including the time distortion, it looks like it's roughly 60 degrees / second, which is false because it's sped up. The question is, by what factor is it sped up? If it's a factor of 2, it's a 30 degree / second turn, if it's a factor of 3, 20, etc...

Of course, we don't have indications of afterburner, we don't know what speed this occurred at, and at what altitude (at 5000m, aircraft maneuverability degrades significantly to the extent than the F-16 is sporting 13-degrees / second turn rates).

 

[latenlazy]

@AFB: this is obviously sped up, but it's a nice shot of your vapor clouds. That said, including the time distortion, it looks like it's roughly 60 degrees / second, which is false because it's sped up. The question is, by what factor is it sped up? If it's a factor of 2, it's a 30 degree / second turn, if it's a factor of 3, 20, etc...

Of course, we don't have indications of afterburner, we don't know what speed this occurred at, and at what altitude (at 5000m, aircraft maneuverability degrades significantly to the extent than the F-16 is sporting 13-degrees / second turn rates).

You also don’t know anything about the atmospheric conditions to know at what pressure gradients vapor clouds will emerge.

 

[Deino]

May I ask a maybe stupid question: You guys are really discussing deducting/calculating the g-force and turn-radius und speed in that manoeuvre only from that grainy, blurred video clip without any reference??

Are you genius or am I plain dumb??

come on guys ... don't make a fool out of yourselves.

Deino

 

[latenlazy]

May I ask a maybe stupid question: You guys are really discussing deducting/calculating the g-force and turn-radius und speed in that manoeuvre only from that grainy, blurred video clip without any reference??

Are you genius or am I plain dumb??

come on guys ... don't make a fool out of yourselves.

Deino

I don’t think it’s a stupid question.

 

[Deino]

I don’t think it’s a stupid question.

Ok... so then I'll ask it: Is it really possible to calculate or estimate "anything" meaningless from that short blurred video??

It is a serious question and I'm not a technical guy, but from the maybe 5-7 seconds it seems more than eyeballing to make an educated guess.

And for me at least at seems as if a few are discussion as if their soul's future would depend on that outcome.

I simply don't understand that stuff ... but I'm willing to learn if one would explain.

Deino

 

[latenlazy]

Ok... so then I'll ask it: Is it really possible to calculate or estimate "anything" meaningless from that short blurred video??

It is a serious question and I'm not a technical guy, but from the maybe 5-7 seconds it seems more than eyeballing to make an educated guess.

And for me at least at seems as if a few are discussion as if their soul's future would depend on that outcome.

I simply don't understand that stuff ... but I'm willing to learn if one would explain.

Deino

Unless you have at least two angles of the same maneuver with properly scaled distances and some pretty tedious linear algebra you won’t glean anything objectively useful from these videos.

Edit: To be clear when I said “I don’t think it’s a stupid question” I meant you asking whether the last page or two was at all a useful exercise was not a stupid question, not trying to figure out the J-20’s performance parameters with grainy short gifs was not a stupid exercise.

 

[Deino]

Unless you have at least two angles of the same maneuver with properly scaled distances and some pretty tedious linear algebra you won’t glean anything objectively useful from these videos.

Edit: To be clear when I said “I don’t think it’s a stupid question” I meant you asking whether the last page or two was at all a useful exercise was not a stupid question, not trying to figure out the J-20’s performance parameters with grainy short gifs was not a stupid exercise.

Thanks so I got you correct.

... but in the end it will lead to such crazy results like a +210kN engine, Mach 3.5 capability and so on

 

[latenlazy]

Thanks so I got you correct.

... but in the end it will lead to such crazy results like a +210kN engine, Mach 3.5 capability and so on

¯\_(ツ)_/¯ I get why people are eager to know these things, but some people substitute overeagerness for sound thinking.

 

[Inst]

@latenlazy: not true. If you have a single picture and the right software, you can actually calculate the distance between the aircraft and the camera due to perspective distortion between the closest and furthest elements of the aircraft, when the size of these elements are known. Then you can determine the relative distance of the aircraft based on its movement relative to an object, etc etc etc. Your issue is more that I'm suggesting your pet plane isn't maneuverable.

@Deino: data-analysis of poor-quality is doable, but it does present issues regarding accuracy of data. Think about it another way, Say, you have a measuring tool that can give you the weight of a canteloupe within 1 kg, when a canteloupe usually weighs around 2 kg, +-1 kg. So, when you weigh the canteloupe, you'll get figures between 0 kg and 4 kg. The solution is to repeatedly weigh the canteloupe over and over again. As you get into really high numbers of measurements, the average of all your measurements begins to approach the average actual weight of the canteloupe. The same is possible with poor quality data; i.e, get the resulting figures out of poor quality data, then collate the vast sum of measurements together.

What latenlazy is saying is, don't bother. But if all you have is your wonky scale, and you desperately need to get the exact weight of the canteloupe, you're going to start collating bad data together to establish an estimate. This is what we're doing with these videos.

@AFB: here's the same video, slowed down 20x. You can definitely see the vapor clouds form in the video. I finally timed the video, and it is roughly a 60 degree/sec instantaneous turn if you ignore the fact that it's been sped up. So we get figures like 30 degrees, 20 degrees, 15 degrees, and 10 degrees depending on the degree to which it is sped up.

 

[latenlazy]

@latenlazy: not true. If you have a single picture and the right software, you can actually calculate the distance between the aircraft and the camera due to perspective distortion between the closest and furthest elements of the aircraft, when the size of these elements are known. Then you can determine the relative distance of the aircraft based on its movement relative to an object, etc etc etc. Your issue is more that I'm suggesting your pet plane isn't maneuverable.

1) You’d need to account for the specific lens and how it handles distortion relative to distance at different parts of the frame to be able to get anything useful through distortion effects, *especially* for small and distant objects in the camera frame.

2) Did you do *any* of those calculations? No. Don’t pretend to stand on a higher pedestal than you’re actually on.

If we’re going to engage in the disingenuous exercise of putting words in people’s mouths, your issue is that someone is calling you out for shoddy work and you seem to have a higher opinion of your intelligence than your peers do, so you imagine people believing and saying things that make you feel vindicated. What you’re doing here, Inst, is only a small grade better than what Mig-29 used to do when he was around.

What latenlazy is saying is, don't bother. But if all you have is your wonky scale, and you desperately need to get the exact weight of the canteloupe, you're going to start collating bad data together to establish an estimate. This is what we're doing with these videos.

If you have a wonky scale and still sell your cantaloupes by price for weight prepare to be sued for false advertisement. Do you know what happens to analysts, scientists, and engineers who present self assured claims on bad data? They get fired. That’s why no one who’s serious about accuracy and precision does what you do.