IRST elevation indicator on HUD problem?

[PeaceSells]

You know on the right part of the HUD there's the elevation indicator for the IRST (and for the radar antenna) and also an indicator of HUD vertical position. When these two are aligned side by side, it means that the IRST is searching the HUD area (AFAIK). When you lower the IRST elevation, it's indicator goes below the HUD indicator and you know it's scanning now an area below the HUD. Since the IRST sensor is mounted above the fuselage, its down view in level flight is blocked by the nose of the plane, so you you can't scan an area much below the horizon in level flight, and this limit is shown by the IRST indicator not being able to get more than a few degrees below the horizon (AFAIK).

 

But when you take a dive, the IRST should now see more below the horizon. And this is what I think is the bug: the indicator of HUD position goes below the horizon, but the IRST indicator is still limited exactly as if the aircraft was still in level flight. You can't align the two indicators when diving. I suspect this is a bug, because AFAIK, these two indicators are there so you have an idea of where the IRST is scanning, is it scanning the HUD area, below, or above it?

 

Please take a look at the video I recorded to better illustrate. You can see I take a dive at 00:10s, the HUD indicator goes down, but the IRST indicator can't align with the HUD anymore, no matter how much I use the knob to lower it. You can't see me moving the knob, but you can see the -14 indication, showing I've lowered it to maximum.

 

[amazingme]

I noticed that too.. Thanks for posting the bug.

[Frostie]

I think it is down to the elevation limits of the sensor, with it being stabilised on the horizon its max negative elevation will always remain at -2 even though as you say there is scope to look.

 

I think of it like the MiG21 radar, it is limited in the look down for a reason.

Edited April 6, 2018 by Frostie

[PeaceSells]

I think it is down to the elevation limits of the sensor, with it being stabilised on the horizon its max negative elevation will always remain at -2 even though as you say there is scope to look.

 

I think of it like the MiG21 radar, it is limited in the look down for a reason.

 

So I did some testing, went on a dive after another aircraft below me and, as you say, I couldn't seem to get the IRST sensor to see him in any of the times I tested. It seemed like the sensor was limited on the horizontal plane as you said. But, if this was true, you wouldn't be able to lock enemies in dogfight modes when diving after them, would you? And it turns out you can...

 

I repeated the same test, now using the radar instead of the IRST. Went on a dive after the other plane, my radar searched and found him. I then locked him and "transferred" the lock to the IRST - turned IRST on and radar off, while maintaining the lock. The IRST kept the lock while looking down, so it's definitely not limited on the look-down (which we already knew from doing dogfights).

 

The only explation I can seem to think for this is that it's limited on the look-down only when in search mode, but free to look down in dogfight modes or when it already has a lock. The other explanation is that it's a bug...

 

Do you have the MiG-21? Does the radar behave like this? Does it have dogfight mode? Does it "look-down" in dogfight mode? Does it keep the lock when enemy is lower than you?

[Ironhand]

...

 

The only explation I can seem to think for this is that it's limited on the look-down only when in search mode, but free to look down in dogfight modes or when it already has a lock...

That's correct. In Long Range Scan Mode, the IRST is horizon stabilized. In any of the CAC modes, it is not. It is simply limited from -3° to 60° below and above your nose--I think those are the ° involved. I just got through chasing another Su-27 around the sky in Vertical Scan mode and those parameters seem to be correct.

[PeaceSells]

That's correct.

 

Crap. That explains why in multiplayer I can never find anyone with IRST when I'm flying higher then them, even though I know they're there. Have to stick with radar or go low...

 

I wonder, is it intentionally not allowed to look down in search mode because ground heat would prevent it to find those targets anyway, similar to old generation radars that can't detect contacts below?

[Ironhand]

Crap. That explains why in multiplayer I can never find anyone with IRST when I'm flying higher then them, even though I know they're there. Have to stick with radar or go low...

 

I wonder, is it intentionally not allowed to look down in search mode because ground heat would prevent it to find those targets anyway, similar to old generation radars that can't detect contacts below?

Actually, the radar works in exactly the same way. It's just that the radar is able to move in ways that the IRST cannot so that you don't have the same severe restriction in looking "down". As a result, most people don't notice it when RLPK is the primary channel.

[PeaceSells]

Actually, the radar works in exactly the same way. It's just that the radar is able to move in ways that the IRST cannot so that you don't have the same severe restriction in looking "down". As a result, most people don't notice it when RLPK is the primary channel.

 

Not sure I understand you. Both the radar and the IRST are vertically stabilized, we always knew that. That doesn't prevent looking down, it just means looking down is controlled by pilot, and not by aircraft movement. Additionally, the down view of the IRST is blocked by the aircraft's nose, but the down view of the radar isn't, we also already knew that. What we're discussing here is an additional limitation of the IRST, which seems to propositally prevent it from looking down, even when the nose is not blocking it (when on a dive). The radar also doesn't have that.

[Ironhand]

Not sure I understand you. Both the radar and the IRST are vertically stabilized, we always knew that. That doesn't prevent looking down, it just means looking down is controlled by pilot, and not by aircraft movement. Additionally, the down view of the IRST is blocked by the aircraft's nose, but the down view of the radar isn't, we also already knew that. What we're discussing here is an additional limitation of the IRST, which seems to propositally prevent it from looking down, even when the nose is not blocking it (when on a dive). The radar also doesn't have that.

There is also a limit as to how far down the radar can look. Pointing the nose down in RLPK long-range scan mode does not allow you to look any lower. It's just that the radar's downward limit is sufficient that you are seldom in a position to notice it.

[PeaceSells]

There is also a limit as to how far down the radar can look. Pointing the nose down in RLPK long-range scan mode does not allow you to look any lower. It's just that the radar's downward limit is sufficient that you are seldom in a position to notice it.

 

You're right. Never noticed that before, but it does have a limit that doesn't change no matter how much you dive.

[Dino Might]

I always wondered about vertically stabilized, mechanically scanned arrays. If you are physically bottoming out the array, but your nose is pointed above the horizon, then pointing the nose lower should lower the scan zone, correct? Is this the way it works in DCS?

 

This is how I imagine it working (and this may be way wrong):

Set at 0, array attempts to point at the horizon? When pitch changes, array tilts to maintain look angle pointed at horizon. But at some point, if you nose up too much, the array will physically bottom out and will now start looking above the horizon. But, if you bring the nose back down, it will regain alignment with the horizon. Similarly if you set the array angle to the max downward angle, it will try to maintain that angle relative to the horizon. If you pitch up from horizontal, the array will remain physically bottomed out, and the look angle will rise closer to the horizon. But if you nose over again, the look angle will come back down. Now, with nose level and array physically bottomed out, if you nose down, the look angle of the radar should not change, but the array will physically no longer be bottomed out.

 

So, there is a max look-down angle, but it's relative to the horizon, not to your aircraft?

[PeaceSells]

^^I believe so. All that you described is how I think it works, but I'm not sure.