J-20 5th Gen Fighter Thread VI

[TerraN_EmpirE]

A 360 IRST can be used to get a HOBS lock

That's what EODAS is.

EODAS isn’t just useful for ground attack,

You are confusing what I said. EOTS is ground attack.
EODAS is air to air.
MAWS is a all around missile warning.
If your fighter has EODAS then it has full cover of HOBS shots. Even a fighter below you would be covered by EODAS.
EOTAS actually I should say EOTS. (Hooked on Phonix... failed)
EOTS Electro-Optical Targeting System is basically an integrated version of a ground attack pod mounted under the nose of a 4th gen. In the F35 it was mounted into the fighter to keep it stealthy.
J20 appears to have an EOTS and EODAS. But why mount both unless you intended ground attack? EODAS would cover below the fighter as well as above it's a 360/360 array.
You shouldn't need both on an Air superiority machine. Unless you don't have both in which case the EODAS isn't an EODAS but a MAWS and the EOTS is the IRST.

 

[latenlazy]

That's what EODAS is.

You are confusing what I said. EOTS is ground attack.
EODAS is air to air.
MAWS is a all around missile warning.
If your fighter has EODAS then it has full cover of HOBS shots. Even a fighter below you would be covered by EODAS.
EOTAS actually I should say EOTS. (Hooked on Phonix... failed)
EOTS Electro-Optical Targeting System is basically an integrated version of a ground attack pod mounted under the nose of a 4th gen. In the F35 it was mounted into the fighter to keep it stealthy.
J20 appears to have an EOTS and EODAS. But why mount both unless you intended ground attack? EODAS would cover below the fighter as well as above it's a 360/360 array.
You shouldn't need both on an Air superiority machine. Unless you don't have both in which case the EODAS isn't an EODAS but a MAWS and the EOTS is the IRST.

Oops. Forgot the DAS was short for Distributed Arperture System. Anyways, the point is the same. The EODAS and EOTS serve as complements. The EOTS is supposed to be part of the DAS, but as a bigger sensor it’s meant to provide better resolution and range in the forward angle, which is the fighter’s most important angle. It may not be necesssary to have both in a fighter but that doesn’t mean an EOTS doesn’t add more capabilities for air superiority beyond the EODAS.

 

[TerraN_EmpirE]

Except J20 already has a EODAS on the forward angle at the front of the cockpit. Same for F35.
EOTS may be larger but range isn't that big an issue vs the EODAS unless again the EODAS unit is inferior in some manor. The AN/AAQ37 is already said to be able to track ballistic missiles at 800miles.

 

[latenlazy]

Except J20 already has a EODAS on the forward angle at the front of the cockpit. Same for F35.
EOTS may be larger but range isn't that big an issue vs the EODAS unless again the EODAS unit is inferior in some manor. The AN/AAQ37 is already said to be able to track ballistic missiles at 800miles.

I think that arpeture at the front of the cockpit isn’t looking forward but up. It seems to me the dorsal angles for the DAS are handled by two windows, one in front of the cockpit and one behind.

Range is affected by sensor size. You can only make your distributed arpetures so big. Ballistic missiles are very hot and bright non-IR suppressed objects. Being able to track one at 800 miles doesn’t also mean you can see another fighter, especially in their cooler forward aspect, at long range and resolution.

 

[TerraN_EmpirE]

I think that arpeture at the front of the cockpit isn’t looking forward but up. It seems to me the dorsal angles for the DAS are handled by two windows, one in front of the cockpit and one behind.

it's in the forward position for forward scan.

Range is affected by sensor size. You can only make your distributed arpetures so big. Ballistic missiles are very hot and bright non-IR suppressed objects. Being able to track one at 800 miles doesn’t also mean you can see another fighter, especially in their cooler forward aspect, at long range and resolution.

the EOTS sensor on the F35 isn't just an single IR sensor it's a TV and rangefinder and laser designator that's part of why it's that big.
It's not one sensor but half a dozen.
Despite what it seems there are limits to what you can see with IR sensors even if that size. One of the biggest issues is that you start collecting information on planets and stars not potential aircraft. And remember the curvature of the earth is and light effects from the atmosphere come into play. Light defusion, Ambient temps of the aircraft and potential targets weather, altitude.
Sorry no IRST will ever match a Radar for long range.

 

[Jura The idiot]

now noticed the tweet

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Les pilotes et les personnels de la Base d'entraînement et d'essais en vol de l'armée de l'air chinoise, dont ceux du J-20, présentent leurs vœux du Nouvel An chinois.

Translated from French by

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The pilots and personnel of the Chinese Air Force training and flight test Base, including those of the J-20, present their Chinese New Year wishes.

 

[Inst]

Actually, when it comes to sensor range, it's a combination of aperture (lens) and sensor size. A large sensor with a relatively small aperture will have the same performance as a small sensor with a relatively large aperture. The need for a large sensor primarily comes out to resolution; once pixels drop below a certain size for an aperture, hazing starts to kick in due to quantum effects. In either case, the equation still remains, the larger the sensor-lens combination, the better. That was why I was disappointed that the camera aperture for the J-20 wasn't significantly larger than on the F-35.

 

[latenlazy]

it's in the forward position for forward scan.

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Forward area looks *really* small here. Pretty sure that camera has an upward tilt. Also worth noting that with the only other upward looking camera is behind the cockpit. If that arpeture on the top of the nose isn’t looking up there is no sensor handling the dorsal view in front of the cockpit.

the EOTS sensor on the F35 isn't just an single IR sensor it's a TV and rangefinder and laser designator that's part of why it's that big. It’s not one sensor but a half dozen.

Sure, but that doesn’t mean the IR sensor in the EOTS is the same size as the ones used in the EODAS. Also not like the F-35’s EOTS isn’t used for A2A engagements. Worth remembering as well that we don’t actually know what’s inside the housing for the J-20’s nose pod. Maybe it’s identical to the F-35 or maybe it’s a different suite.

Despite what it seems there are limits to what you can see with IR sensors even if that size. One of the biggest issues is that you start collecting information on planets and stars not potential aircraft. And remember the curvature of the earth is and light effects from the atmosphere come into play. Light defusion, Ambient temps of the aircraft and potential targets weather, altitude.

IRSTs have been getting more powerful because of more sensitive higher resolution sensors, better and more sophisticated filtering, and more powerful signal processing. As your resolution and sensitivity go up your signal processing can better distinguish between different objects and conditions and figure out if they’re worth including in the final image feed, especially as signal processing can become more intensive due to better compute power. This is how the AN/AAQ37 can distinguish between a ballistic missile and stars at a distance of 800 miles. There’s a soft limit to how capable a larger sensor is but that limit is being pushed forward all the time by improvements in the technology. Within those soft limits a bigger sensor is still much more powerful than a smaller one.

Sorry no IRST will ever match a Radar for long range.

Did I say that?

 

[Blitzo]

Correct.
This by the way is part of my reasoning for feeling J20 is multi role.

As J20 has both those array and the EOTAS like array.
If the system on J20 is an EODAS then as a pure air superiority mission machine it shouldn't need EOTAS. As the functions of a IRST would be taken by the EODAS. The spherical coverage of the IR cameras being you IRST.
Unless the J20 system is somehow limited like the older system on the Raptor and just a all around MAWS. In which case the EOTAS like sensor is the IRST but only works in the forward arc.

But as F22s AN/AAR-56 MAWS has been said to be upgradable so, to should that on J20.
The two sensors AN/AAQ-37 EODAS and AN/AAR-56 MAWS
have similar image resolution, frame rate and operate in the same spectrums. Presumably the system on J20 is analogous and with the J20 not yet in full rate. One would assume that they could upgrade when ready, making the large optic on the underside of the nose redundant unless it was intended for ground attack.

As latenlazy has written, the benefits of an EODAS like system has many applications including for air superiority fighters. Rapidly being able to ID airborne, ground and ground to air (SAM) targets as well as the overall benefit in situational awareness is something that is as useful for air superiority as any other combat aircraft role.

The EOTS like system on J-20 is really an EOIRST, and many fighter aircraft have such systems mounted and have air to air as their primary mission.

In fact looking at the geometry of J-20's EOIRST housing we can see it is opaque in the rear panels meaning it likely is not designed for 360 degree coverage (which you'd expect if it had strike as an important role) but optimized for forward aspect coverage which is consistent with an A2A role.

 

[latenlazy]

In fact looking at the geometry of J-20's EOIRST housing we can see it is opaque in the rear panels meaning it likely is not designed for 360 degree coverage (which you'd expect if it had strike as an important role) but optimized for forward aspect coverage which is consistent with an A2A role.

Also, the very small surface area of the bottom facet for the J-20’s nose pod suggests that an orthogonal downward looking aspect is not nearly as important.