Shenyang FC-31 / J-31 Fighter Demonstrator

shen · Jul 15, 2015

Bltizo said:
What I'd like to know is why their F-22 detection range is lower than B-2's... are these ranges for when both are subsonic? Because if it was for F-22 supercruising or on afterburner the detection range should be far larger for even a four engined subsonic flying wing.

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anyway the company is called jiangsu a-star it seems
they have a website, but it seems like these products (or any products) are put up...

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They say their IR sensors are tuned for long wave IR. Long wave IR are mostly generated by the friction of the airframe traveling through air, so I guess a large aircraft like the B-2 is going to generate a stronger signature than a F-22.

plawolf · Jul 16, 2015

shen said:
They say their IR sensors are tuned for long wave IR. Long wave IR are mostly generated by the friction of the airframe traveling through air, so I guess a large aircraft like the B-2 is going to generate a stronger signature than a F-22.

If that is the case, maybe the Americans will have to reconsider their Batman Black paint schemes for their B2s...

On a more serious note, being able to register the heat generated by moving airframes as opposed to just looking for exhaust heat is an interesting development that could have huge implications for core 5th gen characteristics like supercruise or operating height.

The F22 typically likes to operate at very high altitude, whereas the B2 usually flow lower, where the air is denser, so the F22 should hit fewer air particles, and thus could potentially generate less air friction than the larger, lower flying B2 even if the B2 is flying slower.

Anyone have any figures for what kind of air friction heat your typical aircraft generates while flying at high subsonic and supersonic speeds?

I would have thought it would not be that high, so if the system is sensitive enough to be able to pick that up, surely they would be able to detect even cooled exhaust like those from the F22 and B2 easier?

latenlazy · Jul 16, 2015

plawolf said:
If that is the case, maybe the Americans will have to reconsider their Batman Black paint schemes for their B2s...

On a more serious note, being able to register the heat generated by moving airframes as opposed to just looking for exhaust heat is an interesting development that could have huge implications for core 5th gen characteristics like supercruise or operating height.

The F22 typically likes to operate at very high altitude, whereas the B2 usually flow lower, where the air is denser, so the F22 should hit fewer air particles, and thus could potentially generate less air friction than the larger, lower flying B2 even if the B2 is flying slower.

Anyone have any figures for what kind of air friction heat your typical aircraft generates while flying at high subsonic and supersonic speeds?

I would have thought it would not be that high, so if the system is sensitive enough to be able to pick that up, surely they would be able to detect even cooled exhaust like those from the F22 and B2 easier?

As I understand it, any gain in heat reduction for supersonic aircraft flying at high altitude is negated by the speed at which it's flying, and then some.

siegecrossbow · Jul 16, 2015

plawolf said:
If that is the case, maybe the Americans will have to reconsider their Batman Black paint schemes for their B2s...

On a more serious note, being able to register the heat generated by moving airframes as opposed to just looking for exhaust heat is an interesting development that could have huge implications for core 5th gen characteristics like supercruise or operating height.

The F22 typically likes to operate at very high altitude, whereas the B2 usually flow lower, where the air is denser, so the F22 should hit fewer air particles, and thus could potentially generate less air friction than the larger, lower flying B2 even if the B2 is flying slower.

Anyone have any figures for what kind of air friction heat your typical aircraft generates while flying at high subsonic and supersonic speeds?

I would have thought it would not be that high, so if the system is sensitive enough to be able to pick that up, surely they would be able to detect even cooled exhaust like those from the F22 and B2 easier?

Also keep in mind that if the air is thinner, it is also harder to lose heat via convection.

thunderchief · Jul 16, 2015

shen said:
They say their IR sensors are tuned for long wave IR. Long wave IR are mostly generated by the friction of the airframe traveling through air, so I guess a large aircraft like the B-2 is going to generate a stronger signature than a F-22.

IR wavelength depends on temperature . Greater the temperature higher the frequency, i.e. shorter the wavelength .

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Now, IR sensors are usually optimized to detect heat coming from engines, not the heat generated by friction with air . Therefore, bombers like B-2 should be somewhat more stealthy in IR spectrum then fighter like F-22 with "hot" engines . B-2 uses four F-118 engines, which are non-afterburning version of F-110 used on F-14 and some F-15 and F-16 .

shen · Jul 17, 2015

thunderchief said:
IR wavelength depends on temperature . Greater the temperature higher the frequency, i.e. shorter the wavelength .

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Now, IR sensors are usually optimized to detect heat coming from engines, not the heat generated by friction with air . Therefore, bombers like B-2 should be somewhat more stealthy in IR spectrum then fighter like F-22 with "hot" engines . B-2 uses four F-118 engines, which are non-afterburning version of F-110 used on F-14 and some F-15 and F-16 .

You are right of course that wavelength is ultimately determined by temperature. Early IR missile such as the AIM-9B with PbS based detector sensitive to around 1 micron band can only track very hot objects such as the tailpipe of a jet. Later, "all-asepct" AIM-9L tuned for around 4 micron band can detect the plume of the exhaust. The latest IR sensors are sensitive into the true long wave IR band of 8-12 micron. That means even very small temperature difference can be detected. For example, all object moving through air compresses the air in front of it, compression cause the air to heat up, greater speed increase compression and thus heat. A F-22 supercruising at high altitude is the ideal target for long wave IRST. Eurofighter's PIRATE IRST claims capable of detect subsonic fighters from 90 km from front and 145 km from rear, and 10% great against supercruising fighter.

broadsword · Jul 17, 2015

Is there any anti-aircraft missile capable of consistently distinguishing flares from the exhaust of aircraft?

siegecrossbow · Jul 17, 2015

t2contra said:
Is there any anti-aircraft missile capable of consistently distinguishing flares from the exhaust of aircraft?

Sophisticated air-to-air missiles supposedly use thermal imaging to match the heat signature profile (as in a picture!) with that of an aircraft. Even before that, missile seekers are designed to filter out certain bands of heat signatures.

Air Force Brat · Jul 18, 2015

shen said:
You are right of course that wavelength is ultimately determined by temperature. Early IR missile such as the AIM-9B with PbS based detector sensitive to around 1 micron band can only track very hot objects such as the tailpipe of a jet. Later, "all-asepct" AIM-9L tuned for around 4 micron band can detect the plume of the exhaust. The latest IR sensors are sensitive into the true long wave IR band of 8-12 micron. That means even very small temperature difference can be detected. For example, all object moving through air compresses the air in front of it, compression cause the air to heat up, greater speed increase compression and thus heat. A F-22 supercruising at high altitude is the ideal target for long wave IRST. Eurofighter's PIRATE IRST claims capable of detect subsonic fighters from 90 km from front and 145 km from rear, and 10% great against supercruising fighter.

That is a very challenging manner in which to detect a high flying, high speed aircraft, and I view that with a great deal of skepticism when it comes to achieving a firing, or tracking solution? The engines on the other hand provide a very distinct heat source for tracking, but heat from air friction while distinct, does dissipate very rapidly?

I would remind all that while the SR-71 was very hot all over as result of very high speed, over 4,000 missles were fired at that aircraft as "hail Mary" shots and O connected!

siegecrossbow · Jul 18, 2015

Here is a closeup image of the 3D printed support struss similar to the one used on J-31. I don't think that this particular image has been posted.

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Shenyang FC-31 / J-31 Fighter Demonstrator

shen

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plawolf

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latenlazy

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siegecrossbow

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thunderchief

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shen

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broadsword

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siegecrossbow

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Air Force Brat

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siegecrossbow

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