TID target VV (Aircraft Stabilized)

[Karon]

This is kind of embarassing, but I have an issue or two with the TID.

 

 

1. DL / AWG-9 Discrepancies

Sometimes the tracks don't match at all. I have found a number of issues for that. For instance the AWG-9 track is not updated (notch / ZDF). This is affects target seen in PD when the MLC is off.

Example:

 

Are there other reasons why DL and AWG-9 tracks do not match sometimes?

 

2. DL / AWG-9 Aircraft stabilized Velocity Vectors

I waste a week on this stuff. So, the VV module is: ΔV=VF14-Vtgt. If the target is faster, the module is negative, resulting in it "piercing" through the IFF symbol.

EG:

 

VF14=430kts; Vtgt=200kts. ΔV=430-200=230kts

 

VF14=200kts; Vtgt=400kts. ΔV=200-400=-200kts

 

Up to here, nice and easy. The problem is the heading of the velocity vector. I don't understand it.

 

So, this is my scenario:

ME: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission1.jpeg

DDD: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission1-ddd.jpeg

Ground Stab: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission1-tid.jpeg

Aircraft Stab: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission1-tid-aircraft-stab.jpeg

 

Then, I turned 30° to the right and the mess started.

This is a sketch that explains the situation:

 

This is the situation post turn. I wrote down MC and BRG of each target:

Interesting fact here, target II was notching (it's shown because I toggle the MLC off) and target V is missing due to ZDF (wasted speed during the turn, it later popped up as soon as ΔV > ZDF).

 

And this is where I lost it. How come that tgt II and V basically look the same (module excluded)? One is going SW, the other NW.

 

I then decide to make the test even more complex by adding a full circle of targets:

The only in common I see is that if the LS is decreasing, then the VV points towards the F-14. Or, actually, if the BH put us in a possible collision course then it points towards the F-14.

In other words, if 180<Δ(F14_HDG-TGT_HDG)<360 then the VV points towards the F-14. Does it make any sense?

 

EDIT: I've found another way to explain my theory: If hdg-wise (only hdg, no speed) we are on a collision course, then the VV points toward the F-14. Then will be norm of the vector to dictate if the collision can happen or not. Better?

Edited August 26, 2019 by Karon

[draconus]

1. I guess different radars from different places get different results, right?

 

2. http://www.heatblur.se/F-14Manual/general.html#tid-symbology

"In TID ground stabilized mode the vector direction represents track true heading and the vector length represents track ground speed.

 

In TID aircraft stabilized and attack modes the vector direction represents track relative heading (to own aircraft) and the vector length represents track speed relative to own aircraft."

So in the a/c stab think of it as where the track will be after a few seconds.

Edited August 27, 2019 by draconus

[Karon]

1. No, I don't think so. Often the two tracks overlap (you even see it in my pics). Moreover, locally compensating for the HDG Delta is quite easy and I'm definitely not smarter than Grunman engineers. I can imagine is a degradation caused by loss of tracking updates or something else. Almost like the TCN issues I asked about in this forum some weeks ago.

 

 

2. I don't follow you. Target V here: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission3-circle-test.jpeg

in a few seconds won't be hdg neither NE or SW.

 

 

I hold to my observation about the possible course yet independent from ΔV (which is bound to the norm of the vector).

[draconus]

2. I don't follow you. Target V here: https://karonshome.files.wordpress.com/2019/08/rio16-tid-vv-mission3-circle-test.jpeg

in a few seconds won't be hdg neither NE or SW.

Does the center of the radar cone on TID in this picture correspond to your own heading? If yes, then your drawing on the left is wrong and TID shows vectors correctly. Also vectors in this case don't show any aircraft heading - only position change on the radar picture.

[viper2097]

Yep, thats true.

 

While your drawing shows where the aircrafts are actual flying, your TID shows in which direction they are moving according to your own.

 

Change the TID to ground stabilize and you should get the picture you have drawn on the TID.

(The slower you fly, the more the VV will be like the true heading of the aircrafts. The faster you fly, the more they will point towards yourself)

[Karon]

I think I'm close, it's a matter of angles and vectors. It's getting much simpler by applying basic trigonometry.

[Chaogen]

Could it be magnetic variance setting of both donor A/C and receiving A/C? As Viper said the Radar Contact is relative to your A/C irrespective of what the INS thinks your heading and co-ordinates are. The Datalink contact is sending the co-ordinates and heading vector according to the Donor's INS systems. Presumably the Sentry has GPS built in, but the point being any discrepancy/drift would cause a Vector Difference. I assume a heading drift would be more noticeable than XYZ Co-Ordinate drift.

[Karon]

EDIT: scratch that, "unlucky" testing environment :S

 

 

EDIT2: sorted. I did an elementary-school level vector operation wrong and there's no way to prove a thesys with wrong hipotesis. Dumb *facepalm*

Edited August 28, 2019 by Karon