Bogey altitude from DL cross-bar

So I know the cross-bar on HDD contacts denotes altitude but it seems fairly useless beyond a basic "target is very high or on the deck" assessment. Is there any way to read it into a useable number for radar relative altitude control input?

Sure. Don’t over think it. If bogy cross bar is anything like yours in width and range is BVR, then radar altitude difference is “0” (with default expected target range). Much wider, then “1” up. Much smaller, then “1” down.

Ah, so they're relative? I assumed they were absolute and I'd be trying to convert pixels of a bar length to an altitude. Or are they, and own bar length changes too?

I know you said don't overthink but in my experience with other planes getting the elevation right is really crucial to finding a target. Any approximations for when it's maybe +/-2 or 3? e.g. "if bar is twice the width of the V then elev is..."

VC said:

Ah, so they're relative? I assumed they were absolute and I'd be trying to convert pixels of a bar length to an altitude. Or are they, and own bar length changes too?

 

I know you said don't overthink but in my experience with other planes getting the elevation right is really crucial to finding a target. Any approximations for when it's maybe +/-2 or 3? e.g. "if bar is twice the width of the V then elev is..."

Yes, your cross bar changes, too. It's a simple and easy system to use. Speeds are relative as well. So, it's pretty easy to figure out who the most dangerous threats are.

You will almost never need to go to a 2 or 3 unless the range is extremely close. If that close, you might be best off selecting one of the CAC modes, anyway. But your HUD gives you a good indication of how high or low you have to go. This tutorial is something that I was working on and never finished. It has voicover but no arrows pointing to what I'm talking about. You might find it helpful, anyway:

https://youtu.be/J6nV6KFW3pk?t=789

What the display shows is not relative, it is absolute. A certain width or length could be translated into a certain altitude or speed.

But you can of course use the bandits line lengths in relation to the line length of your own plane to judge altitude/speed.

What the display shows is not relative, it is absolute. A certain width or length could be translated into a certain altitude or speed...

:) Show me.

What's my altitude? And my target's speed and altitude?

Actually I agree with you, in a sense. You know your own speed and altitude and, so, with experience you can judge the bogey's approximate speed and altitude. But his remains an approximation relative to the lengths depicted on the own-aircraft icon. There is no way for you to calculate it with absolutely.

Now go into a stall and you will see that the lengths of the lines of the target do not change. But yours do.

In other words:

If you would sit in the cockpit you could take a ruler and meassure the length of the lines, and from these lengths you would be able to calculate the target parameters (if you knew the factors that you woud have to multiply the lengths with).

But maybe we mean the same thing.

One could meassure at what altitude and speed the lines equal the length of the bottom left range scale (it never changes size). Then you can read the line length relative to the range scale for "absolute" numbers.

For very low altitudes it may be better to read the altitude in "widths" of the speed line, if you know what altitude the one width of the speed line equals to.

Now go into a stall and you will see that the lengths of the lines of the target do not change. But yours do.

 

In other words:

If you would sit in the cockpit you could take a ruler and meassure the length of the lines, and from these lengths you would be able to calculate the target parameters (if you knew the factors that you woud have to multiply the lengths with).

 

But maybe we mean the same thing.

 

 

One could meassure at what altitude and speed the lines equal the length of the bottom left range scale (it never changes size). Then you can read the line length relative to the range scale for "absolute" numbers.

 

For very low altitudes it may be better to read the altitude in "widths" of the speed line, if you know what altitude the one width of the speed line equals to.

:) You still haven't told me what my altitude is. Nor have you told me what my target's speed and altitude are.

We actually agree. It's just that we're referring to two different things when we say: relative. I'm saying that the parameters depicted by the bogey/target icon are determined relative to my own. There are no absolute numbers available for the other icons on the HDD. Yes, you can pull out a ruler but that just isn't practical in the cockpit, nor would you have absolute accuracy using that ruler, anyway. So the target's speed and altitude are judged relative to your own. It can be done quickly and with sufficient accuracy to make absolute numbers unnecessary. That's what I was trying to get across to the OP.

Ok, got you!

Just for fun:

Your and the targets altitude is about 1750m (width of the speed line equals about 500m, your altitude line looks slightly less than 4 times as long, hard to tell as it looks like it is a photo taken from the screen. May as well be 2000m because the 500m/width is just a rough approximation)

The length of the line on the bottom left of the display equals the length for the speed of the plane at 1500 km/h. But it is a little harder to judge the speed because you have to rotate the line in your head and also ignore the IFF mark.

Looks like around 1000 km/h for the target.

That escalated quickly :D Most of what you've said is just confirming or slightly expanding on stuff I more or less already knew. It's the estimating hard numbers from the line sizes that is really the core of what I'm asking.

So what I got from the last bit... cross-bar about as wide as the triangle on the target is ~2000m. So double would be ~4000 etc. But I can always use my own plane as a basis for the estimate.

While we're here, why does boxing a target in TWS not give you their speed and altitude?!

Ok, got you!

 

Just for fun:

 

Your and the targets altitude is about 1750m (width of the speed line equals about 500m, your altitude line looks slightly less than 4 times as long, hard to tell as it looks like it is a photo taken from the screen. May as well be 2000m because the 500m/width is just a rough approximation)

 

The length of the line on the bottom left of the display equals the length for the speed of the plane at 1500 km/h. But it is a little harder to judge the speed because you have to rotate the line in your head and also ignore the IFF mark.

Looks like around 1000 km/h for the target.

Close enough for horse shoes and throwing missiles. :)

That escalated quickly :D Most of what you've said is just confirming or slightly expanding on stuff I more or less already knew. It's the estimating hard numbers from the line sizes that is really the core of what I'm asking.

Not sure why so many people place such an emphasis on generating hard numbers. They give you the illusion of knowledge when, in practice in a situation such as this, they're of little help. For altitude, all you really need to know is low-medium-high. For speed, is our rate of closure high-medium-low? I've never tried to use hard numbers because, even though hard numbers generate the image, it's obvious the display is not meant to be give them back. It's more a case of, relative to me, what's he doing.

So what I got from the last bit... cross-bar about as wide as the triangle on the target is ~2000m. So double would be ~4000 etc. But I can always use my own plane as a basis for the estimate.

 

While we're here, why does boxing a target in TWS not give you their speed and altitude?!

You already have their speed and altitude before you even enter TWS. Boxing in TWS gives you accurate range information in addition to the traget track TWS itslef builds.

I think the targets from the "TWS" are not accurate enough. At least that is said in some MiG-29 document. There it is said that the coordiantes from TWS/SNP are not accurate enough to guide a weapon (via radio correction/datalink).

You already have their speed and altitude before you even enter TWS. Boxing in TWS gives you accurate range information in addition to the traget track TWS itslef builds.

I wonder if the targets that we see in regular scan modes on the HDD are realistic, or if it will only show them when the scan is done in TWS/SNP in the real Flanker?

Not certain of an answer for either of your observations/questions. It may very well be that a sufficiently detailed target track isn’t built until a potential target is designated and, then, only for that one. As far as your last question is concerned, my impression is that it is reasonably accurate. But I don’t recall the specifics from the RW manual that make me think that and it might just be an assumption on my part. I’d have to look into it. But now we’re veering off topic.

Not sure why so many people place such an emphasis on generating hard numbers. They give you the illusion of knowledge when, in practice in a situation such as this, they're of little help. For altitude, all you really need to know is low-medium-high. For speed, is our rate of closure high-medium-low? I've never tried to use hard numbers because, even though hard numbers generate the image, it's obvious the display is not meant to be give them back. It's more a case of, relative to me, what's he doing.

 

You already have their speed and altitude before you even enter TWS. Boxing in TWS gives you accurate range information in addition to the traget track TWS itslef builds.

I see what you mean, I had a couple of successful Flanker sorties and I was able to make use of the bars to get above targets and find them with the radar. I guess the reason I was chasing hard numbers is because the relative altitude control is a hard number and I felt I needed to know what to aim for in conjunction with the expected target range. In the F-18 for example a 2-bar scan is quite narrow, so I use the hard altitude numbers it gives you to make sure I'm scanning in the right place. The Flanker pattern seems wide enough that a more approximate approach works. The "no numbers" system is somewhat elegant in its simplicity, guess I should have trusted the Soviet designers instead of chasing western style explicit display.

I see what you mean, I had a couple of successful Flanker sorties and I was able to make use of the bars to get above targets and find them with the radar. I guess the reason I was chasing hard numbers is because the relative altitude control is a hard number and I felt I needed to know what to aim for in conjunction with the expected target range. In the F-18 for example a 2-bar scan is quite narrow, so I use the hard altitude numbers it gives you to make sure I'm scanning in the right place. The Flanker pattern seems wide enough that a more approximate approach works. The "no numbers" system is somewhat elegant in its simplicity, guess I should have trusted the Soviet designers instead of chasing western style explicit display.

:) It's often best to use the equipment the way it was designed to be used instead of trying to force it into a different usage. In many ways, it's very elegant, while in some ways it's very lacking. Thank god the HDD has data link capability. Without it, situational awareness would be next to zero just as it is in the MiG-29's pit.

I wonder if the targets that we see in regular scan modes on the HDD are realistic, or if it will only show them when the scan is done in TWS/SNP in the real Flanker?

If you consider the F-15's TWS for a moment, just because it gives you a more informative display for 'science purposes', the issues with it (and with the Su-27, because it's really the same code):

Antenna scans too fast (irrelevant for this discussion right now)

Target tracks are created instantaneously, but in reality they require anywhere between 2-4 hits, depending on the radar. All the eagle docs I have say 4 hits to build a track (but you can easily get one or even a couple hits for 'free' if you come into STT from RWS).

Likewise, direction accuracy is accumulated from hit history, so it may not be very accurate.

Altitude is determined by the bar that 'hit' the contact, so if your contact somehow manages to be hit by two bars, you might get a 'jumping altitude' or perhaps two contacts at different altitudes. The fun part is that at longer ranges, the track's altitude may have a 1km to 2km error.

All of this applies to all TWS. The longer the frame (full volume scan at selected settings) takes to complete, the less accurate your TWS information. Altitude accuracy, logically, is better closer in and worse further away.

Consider the F-14's TWS as a reasonable example, though I suspect the more modern radars wouldn't dump tracks as easily.

:) It's often best to use the equipment the way it was designed to be used instead of trying to force it into a different usage. In many ways, it's very elegant, while in some ways it's very lacking. Thank god the HDD has data link capability. Without it, situational awareness would be next to zero just as it is in the MiG-29's pit.

This is a nice summary. People gets upset because there's no altitude information on the TDC about which sector of space you are scanning so you can't know where to look for and you have to start guessing around. Which is fair but it's also looking at the scan volume problem from a western PoV and not trying to understand how the Su-27 weapon system actually works. It is supposed to be heavily linked to the GCI, so in theory you do know the target's altitude and distance, which then you can input into the system and it will take care of setting the antenna to scan for that volume of space perfectly. I haven't touched the datalink part of the RW manual yet but by the looks of it, the display is not meant to give you a perfectly numeric assesment of the situation, but rather a good general view of it. And I think it works nicely, thanks to the lines you can see which target is more dangerous at a glance, without needing to be looking at numbers. I think we are also lacking some information that should appear on the display, but that's another story

:) It's often best to use the equipment the way it was designed to be used instead of trying to force it into a different usage. In many ways, it's very elegant, while in some ways it's very lacking. Thank god the HDD has data link capability. Without it, situational awareness would be next to zero just as it is in the MiG-29's pit.

I agree about using equipment, though I wouldn't go quite that far in terms of SA. The SPo-15 can be surprisingly helpful in terms of estimating distance to emitting threats though you need to transpose between displayed signal strength & estimated distance in your head based on anticipated threat type.

Like most things in the Su-27, it can be surprisingly capable but isn't in any way 'new pilot' friendly and places additional work load on the pilot.

...[The Su-27 weapon system] is supposed to be heavily linked to the GCI, so in theory you do know the target's altitude and distance, which then you can input into the system and it will take care of setting the antenna to scan for that volume of space perfectly.

Yes, that's the main reason for the "Expected" Target Range at the bottom of the HUD in Long-Range Aerial Combat mode. You're flying under direction of ground controller, given the heading and altitude and airspeed to fly. Your radar is in standby. You are then given the target range and elevation to enter. Given the order to switch radar to emit and your target will appear on the HUD's vertical centerline at the expected range. The target is then automatically or manually locked which you report back to the ground controller. And he knows that the target he wanted targeted has been targeted.

I haven't touched the datalink part of the RW manual yet but by the looks of it, the display is not meant to give you a perfectly numeric assesment of the situation, but rather a good general view of it. And I think it works nicely, thanks to the lines you can see which target is more dangerous at a glance, without needing to be looking at numbers. I think we are also lacking some information that should appear on the display, but that's another story

It never provides numerical readouts, so, you're right. Much is as we see in the sim, though a bit of information may be missing on the HDD screen such as fuel reserve but even that isn't numerical. Also not sure if that last appears on everyone's screen or just certain screens.

I agree about using equipment, though I wouldn't go quite that far in terms of SA. The SPo-15 can be surprisingly helpful in terms of estimating distance to emitting threats though you need to transpose between displayed signal strength & estimated distance in your head based on anticipated threat type.

 

Like most things in the Su-27, it can be surprisingly capable but isn't in any way 'new pilot' friendly and places additional work load on the pilot.

True as long as you know which threat you're facing in that instant. Otherwise all you know is that, by the time the signal strength reaches 3/4 of the way around the dial, you'd better be paying rapt attention. And, if there's a Phoenix-toting F-14 around, you won't even get to 1/2 signal strength before you might be in trouble. As for the rest, just using a signal strength of 3 lights (for instance), that F-14 will be 90 km away, an F-15C or Su-27 185, an F-5E 43, a Mig-29S 117, and a MiG-21bis 22. So it's only useful for even rudimentary ranging information, if you know exactly what you're facing.

If we ever get a fully modeled Su-27, it had better come with adequate GCI control. Otherwise, if all the systems are modeled accurately, this aircraft will feel like it's been kneecapped compared to what it is now. As an FC3 aircraft the radar never provides false returns, etc, always works flawlessly and instantly, etc. Nor will that SPO designate targets as clearly as it does now. For instance, there is no one light for A2A threats. Rather those lights reference general radar types with ground and aerial radars intermixed.

Also not sure if that last appears on everyone's screen or just certain screens.

What I've seen is that an flight lead would get some extra information that the wingman wouldn't get.

If we ever get a fully modeled Su-27, it had better come with adequate GCI control. Otherwise, if all the systems are modeled accurately, this aircraft will feel like it's been kneecapped compared to what it is now. As an FC3 aircraft the radar never provides false returns, etc, always works flawlessly and instantly, etc. Nor will that SPO designate targets as clearly as it does now. For instance, there is no one light for A2A threats. Rather those lights reference general radar types with ground and aerial radars intermixed

I'm looking forwards that "advanced" Beryoza implementation, that'd be useful in some situations and could help when going against unknown targets. Also, I heard Razbam was planning to do the Lazur interception system for the MiG-23MLA, or at least were considering doing it. I really would like to know how they are pulling that off, and if it would be using ED technology or they would be writing everything themselves. It's pretty much what the Su-27 would need too in terms of simulation mechanics, the current AWACS/GCI system would work poorly for them.

:) We’ll just have to wait and see what transpires.