radar target distance confusion

[snomhf]

I'm very new to lomac so please forgive me if my questions are stupid.

 

I'm learning the radar system on the F-15. I'm very confused about "target distances." There seems to be a lot of contradiction in what I see. Last night, I was using the F-15 "Quick Flight" mode to experiment with trying to lock up targets by going to the "Theater View (F10)" and querying a target's alt, bearing and then using the "distance measuring button" to show the distance between my plane and the target. I would then return to the cockpit and try to find that target on the VSD and lock it up. For starters, the distance in the Theater View would show say 34NM to a target way across the map which did not seem right to me at all. Sure enough, when I would finally find it on the VSD, it would lock on the 160 page of the VSD and show a distance of 86NM or some such thing in the lower right corner of the VSD. Strange! I thought at first that there was some sort of "metric-imperial" problem but after investigating that pretty well, I'm satisfied that that's not it.

 

Then, I noticed that when I go into STT mode, the position of the PDT icon does not even agree with the range in the lower right corner. I wish I had thought to turn on aircraft labels so I could see what range that reported. I'm going to try that next.

 

From reading the lomac 1.1 manual (apparently the most recent thing we have), I see the same disagreement in distance. [Assuming of course, that I'm reading this right] On page 86, you see a PDT in STT mode in the 40NM range. In the lower right corner, it reports the target at 24NM. However, looking at the position of the icon, it appears to be at about 32NM. Maybe, that is some sort of radar "estimation error" or something but as I recall from my lock in the 160 range, the difference between the icon and what was shown in the lower right corner was a lot more than just a few miles. [side note: the "824>" on the right side of the VSD is labeled "Current range" which should actually be "Closure rate" (measured in knots - 824 KTAS). That really threw me off for a while too. That's just a typo in the manual. No big deal there.] Also, the "Theater View" for a similar situation as that on page 86 would probably show the target to be about 9NM which is really crazy.

 

So, I'm just complely confused. I must be looking at this wrong but I certainly don't know how.

 

Thanks for thowing me a bone here.

-mark

[S77th-konkussion]

Hmm nope- it looks right to me. Think of the bottom of the VSD as the nose of your aircraft. With 40 NM range slected- the top of each set of blocks is 10 NM. Thus the SU17 in the example- shown slightly above the 2nd set of blocks is at about 24 NM.

 

I mostly agree with you about the typo regarding VC. The ">" is a range of sorts.. for the effective range of the selected weapon.. the 824 should be the VC..

 

 

I'm not sure about the map screen measurement issue- The only time I've ever used the MAP screen at all is in the mission editor and the briefing.

[Flocke.LE]

Side note: the "824>" on the right side of the VSD is labeled "Current range" which should actually be "Closure rate" (measured in knots - 824 KTAS). That really threw me off for a while too. That's just a typo in the manual.

 

Hi snomhf,

 

The ">" is the range-indicator, the number "824" is the closure-rate. The ">" is moving with the PDT on the (vertical) Y-Axis from the VSD. The 5 horizontal lines of the VSD are a kind of range-scale, which depends on the selected range of the radar. On page 86 the radar is set to 40 miles so the distance for every horizontal line is (fromt down to top):

 

1st line (bottom): 0 NM

2nd: 10 NM

3dr: 20 NM

4th: 30 NM

5th (top): 40 NM

 

On page 86 the ">" and the target symbol are slightly above the 3rd horizontal line, which means that the range to the PDT is about 24 NM. Hope that helps.

 

P.S.: Sorry for my bad english, I'm german :)

[snomhf]

Thanks guys for straightening out my faulty thinking on this.

 

I have always seen the scope range as a continuation of the previous range where the "nose of the airplane" only appears at the "10 range." Pretty dumb. Duh!

 

So, the range settings are sort of like a zoom but a zoom that always keeps the nose of the airplane at the bottom of the view. Right? That would mean if I were to enter an unkown airspace and wanted to radar sweep it, I would set the range to 160 and sample various elevations being confident that if a target were to appear in the 8NM range (or anywhere within that 160NM space), it would appear on the 160 screen (assuming it was bracketed within my elevation setting) and I would "zoom" into it for a "closer" view (or I would simply see it visually). I've always been hesitant to go to the upper range settings because I was afraid I was "losing" the shorter range sweep. I've been misunderstanding this concept for an embarrassingly long time.

 

As for the "824>", I didn't realize that those were meant as two separate pieces of information: closure-rate (824) and range ">". That makes a lot of sense now that I see it that way. Thanks Flocke for explaining that.

 

Now, does that mean that if I'm in unknown airspace that I should always keep my scope at 160?

 

Thanks

-mark

[S77th-konkussion]

As I understand it- it wouldn't be terribly hard for a smaller, manuevering contact to avoid detection due to fewer or less than complete sweeps.. not really explaining this well, I know...

 

ok here..

 

The shorter ranges allow for the area where the contact is to be scanned more often, thus minimizing the chances of him hiding from you by notching/ beaming the reflection.

[GGTharos]

Nope, it's just for operator's convenience ... doesn't change radar parameters at all. So I hear.

[S77th-GOYA]

Now, does that mean that if I'm in unknown airspace that I should always keep my scope at 160?

 

You'll never pick up a fighter at ranges longer than ~60nm. An 80nm scan range is the maximum useful setting. The advantage of lowering the range setting as a bandit moves closer is that it enables more precise control of the TDC and displays more seperation of bandits in formation, making TWS multi-designation easier.

[Cobra360]

displays more seperation of bandits in formation, making TWS multi-designation easier.

 

While we all wait for TWS RAID mode if and when the F-15 gets re-modeled.

[snomhf]

How about this analogy?

 

If the radar signal is like a flashlight beam that is capable of shining out ahead of the plane (reliably no more than 160NM) forming a cone with an azimuth of +/- 60 degrees (but tunable to 30 degrees) and an altitude equal to how ever many bars of sweep it does (I've heard 2-bar or 4-bar with lomac). From what I remember reading, the sweep delay is a function of the azimuth setting and the altitude setting (1-bar, 2-bar, 3-bar, or 4-bar). It seems I recall that a 4-bar radar takes eight seconds to complete a sweep. So, based on what GGT is saying, it sounds like the VSD simply adjusts the "view" of that beam. That would mean that unless more than one target blip shows up close together and you can't reliably select one of them, then there would be no "real" reason to tune down from the 160 range other than convenience. Does that sound right?

 

Wow, an azimuth of 120 degrees at 160NM, that's a huge path! I'm too lazy to do the math on that but we're talking about at least a couple hundred mile wide beam.

 

Sorry, I'm not trying to complicate this or sound like I know what I'm talking about but I'd like to at least come to a journeyman's understanding so I can use it more effectively.

 

Thanks

 

Just noticed Goya's comment that slipped under mine. Sounds like the effective range is 80, not 160. That's good to know.

[GGTharos]

Actually, if you're hunting big game, you can pick'em up at 130nm. However I haven't been bale to pick up a fighter beyond 70 ... 70 is the farthest I can recall.

 

You're correct about how the radar works.

 

LOMAC specifics:

 

4-bar scan only at 2.5 deg/bar

Selectable 120 or 60 deg azimuth

Antenna steerable in altitude and azimuth.

[snomhf]

I'm going to need some practice, that's for sure.

 

After all I learned yesterday, I fired up a Quick Flight in the F-15 and headed south a ways and turned back so that all the aircraft are well within my radar cone. At 160, I barely pick up anything at all. When I went to TWS, I couldn't do much of anything. I sure wish lomac had "freeze mode" like Falcon4. That would make the learning process much easier (those pesky targets keep moving around!). Oh well.

 

I'll keep practicing and will finally catch on to this.

 

BTW, it appears that when a target dips below 2,000 ft you lose the lock. Is that true? What other reasons do you lose a lock?

 

Thanks for all the advice and help.

[GGTharos]

He probably exited your scan zone ... you need to move that antenna up and down!

[snomhf]

Sorry to keep this thread going, but I need more help understanding this radar.

 

I understood that the TDC moves along the horizontal plane. This is clearly not the whole story. I see that when I move the TDC, the antenna moves up and down with it [sometimes]. In fact, about half the time, I can't move the antenna at all until I finally find that "magic" place to put the TDC. This is maddening. It's sort of like the TDC is following the slope of the cone but then about half the time, I can move the antenna as well. This just makes no sense to me. After a while, I find myself just cranking the TDC and the antenna elevation around randomly until I see targets pop up. That is very unsatisifying!

 

I don't mean to be so mentally retarded about this but if you can explain this to me, I'd be grateful.

-mark

[GGTharos]

The TDC doesn't move the antenna at all. The display you see for the antenna merely shows you the upper/lower limits of the scan zone at the distance you've placed the TDC at.

 

To move the antenna use shift and /.,; ... you'll be particularely interested in shift-; and shift-. as they move the antenna up and down

[Jason76]

hey there snomhf...

 

As GGTharos stated, the TDC does not tilt the radar up or down at all. The upper and lower altitude readings (on the left of the radar dispplay)expand when you try to search for a target further away because the radar beam must cover a broader area as it searches further away (since it spreads out). For example, let's say that the cursor is in the middle of the display and the radar is set to 20 nm. If you get a reading of 20 over 7 altitude, it means that at 10 miles, the radar is scanning the altitudes of 7,000 to 20,000 feet. Now you will notice that when you move the cursr towards the top of the radar, the altitude coverage will expand. If you move the cursor to the top quarter of the scope lets say, and you see the numbers 30 over 0 altitude, it means that at 15miles, the radar is scanning the altitudes of 0 to 30,000 ft.

 

You can tilit the radar up and down independent of the radar cursor, however, as GG stated. Just use the shift : and the shift . keys. Hope this clears things up!

[ROE_Wedge]

Understanding radar theory can go a long way too. I work on radars on larger aircraft. I already had a head start when it came to radars in LOMAC. That made my time learning the F-15's radar a lot easier. So just read the overall theory of how they work and it could help you :). It is very accurate!

[snomhf]

Thank you all for the good explanations. I have a much better understanding now.

 

I still am confused a bit as to why the antenna seems to get "stuck" and won't move at all based on the position of the TDC. I spent half a day yesterday reinstalling Falcon 4 (and SP4.2) because I didn't remember having "stuck antenna" issues with it. Sure enough, it always moves regardless of the position of the TDC, unlike lomac. It's not a big deal really though as I am able to sample all the altitudes with a combination of TDC movement and antenna movement. I just wish I understood what was going on a little better.

 

BTW, I have examined the distances reported in the Theater view (F10) and I have to retract my earlier claim. The distances look right. I don't know what I was thinking on that as all seems well.