IFF LOS - How is it suppose to work exactly?

[GrEaSeLiTeNiN]

Hi, the manuals say...

ED:

• Scan - Press TMS Left short (1 second or less) to interrogate all contacts in the radar scan volume.
• Line of Sight (LOS) - Press TMS Left long (more than 1 second) to interrogate the locked target or immediate area around the radar cursor.

Chuck's:

• SCAN interrogates a locked target or immediate area around the radar cursor.
• LOS (Line of Sight) interrogates all contacts in the radar scan volume.

6. With Radar Cursor/Enable Switch, slew the Acquisition Cursor over the contact you want to interrogate
7. If desired, you can bug the target by using TMS UP, but this step is not necessary
8. Press TMS LEFT LONG (more than 1 second) to interrogate the locked target or immediate area around the radar cursor

So it's a bit confusing but in doing some tests (latest OB), I find IFF LOS simply interrogates whatever is in the current FCR scan azimuth. So locking a target or having the radar cursor near a contact (let alone a contact under the cursor) is kind of pointless? because it does not interrogate only the locked target or the contact(s) 'near' the cursor (whatever distance that means is not clear). As such, IFF LOS with a scan azimuth of 60deg would also yield the same results as IFF SCAN (interrogates all contacts regardless of radar scan azimuth).   

Did I miss something? Is this WIP or should IFF LOS be more correctly defined as "interrogates only contacts in current radar scan volume".

TIA

Edited August 19, 2022 by GrEaSeLiTeNiN

[RuskyV]

ED’s statement is correct, chuck’s guide has it flipped.
 

When using IFF it will tell you what mode is being used in the bottom left of the FCR, as for LOS also scanning entire radar volume I’d have to check as i nearly never use it.

[Frederf]

The IFF beam is not nearly as precise as the radar. LOS correlates the IFF beam (fan, much taller than it is wide) to the same direction as FCR cursor. IFF is as narrow as it can be. This is usually narrower than the radar scan area but bigger than the cursor. You can get returns other than bugged target, especially above, below. The IFF return symbol won't be exactly on radar symbology and radar makes no attempt at correlation.

Scan sweeps the IFF fan through its range. I'd have to check if it limits to the radar azimuth or not.

[Charly_Owl]

The ED manual is correct in that regard, I don't know why I have them flipped since the tutorials themselves have the procedures correct. I'll get my version updated tonight to fix that mistake.

[GrEaSeLiTeNiN]

Old thread revisited.

ED Manual says:  "...This is done by transmitting a coded signal aimed at a specific radar contact or volume of space within the selected radar azimuth and elevation. Transponders in friendly aircraft receive this signal and reply with the correct coded response... The IFF system is not radar dependent so interrogation of contacts is still possible with the radar off.

• Scan. Press TMS Left short (1 second or less) to interrogate all contacts in the radar scan volume.
• Line of Sight (LOS). Press TMS Left long (more than 1 second) to interrogate the locked target or immediate area around the radar cursor."

Some questions - I found the following after testing latest OB as of today (track attached):

1. IFF SCAN
Seems to interrogate whatever is in shown in the radar MFD display including contacts outside the Scan Azimuth setting. Is this not scanning outside the "Radar Scan Volume" which is contrary to what the ED manual says? Or have I misunderstood what "Radar Scan Volume" is?

2. IFF LOS
a)  What exactly is the "immediate area around the radar cursor" that is to be interrogated? It seems some contacts that are quite 'far' from the cursor are also interrogated. Has this got to do with the way contacts are represented in the FCR where contacts in the radar cone are spread out into the square of the display.
b)  In fact the radar cursor can be at the bottom of the display and it will interrogate contacts at the top of the display (eg, 40nm) that are in its LOS. This is not the "immediate area around the radar cursor" as the manual describes. Should the manual not add "contacts in the LOS of the cursor" as the name implies?
c)  Contacts outside the Radar Azimuth gates are also interrogated if they are 'near' enough. Does this mean IFF LOS does not depend on Radar Azimuth settings? 

3. Not sure how Radar Azimuth and Scan Volume are involved if IFF does not require radar. 

Appreciate your feedback. Thanks.  

UPDATE: Based on Bogey Dope's tutorial, IFF LOS is an "in line" of sight interrogation as opposed to "immediate area around the radar cursor". But it works both ways in the sim including interrogating out of LOS but near cursor contacts. IFF SCAN on the other hand "scans the entire view of the radar" which I suppose means the same as "radar scan volume" because contacts outside the azimuth gates would have dropped off in the display if I had waited longer (see track). So the azimuth setting acts more like a filter in the declutter sense. Although radar is not required for IFF to work, you need it to see the contacts and their response in the radar display.  

DCS F16 IFF SCAN LOS TEST 4Feb2023 Latest OB.trk

Edited March 18, 2023 by GrEaSeLiTeNiN

[falconzx]

I think they just forgot to add the word: - possible- before "radar scan volume" .

So the equivalent of that is the 60+- elev and 60+- azimuth, so the MFD display.
In RL the only limitation here should be the range.

The fact it's not correlated with the radar, the radar can also be turned off, It make sense the IFF continues to work regardless to radar state and settings.