reported Harm in POS - PB will not aim the designated waypoint without line of sight to the waypoint

[Topper81]

I observed that the Harm in POS - PB mode will not aim the designated waypoint if the there is no line of sight to the designated waypoint.

Istead the missile seems to aim the point where the line of sight intersects the terrain.

I expect that the harm will climb for lofting because it knows the distance to the selected waypoint as I understood.

Note in the track file that the first both harms will not climb and instead they'll aim the a point before the waypoint and crash into the ground.

After the waypoint is not masked by terrain anymore, the 3rd and 4th harm will climb and aim the waypoint as expected.

This behaviour is reproducable for the Hornet as well.

If it's no bug, please explain me how the harm knows if the target waypoint is masked by terrain or not, and why it's commanded to crash into the ground in this case.

Sketch for explainaition:

First Case: Harm always crashes near the intersection point

Second Case: Harm is lofting as expected (because it knows the corect distance?)

 

Thank you

harm crash3.trk

Edited March 15, 2022 by Topper81

[BIGNEWY]

Hi,

you are trying launch harm with an azimuth to target of more than 5 degrees. If you want do this you need to use other submodes.
Also if use a waypoint which is not at the ground level there is no guarantee that harm will attack SAM. 

hope that helps. 

thanks

[Topper81]

Hello BIGNEWY,

the azimuth is not more that 5° on the launch of the second harm or what do you mean?

I tried it in all other PB modes: It's not possible to launch the missile correct when the target is masked by terrain.

If target is not masked and I have an RWR Icon, it always worked fine for me.

[Edit]

harm crash3.trk is another trackfile. Here I fired 4 Harms, on the first two, the waypoint is mask by terrain, they crash into ground without climbing. On the shoot of the 3rd and 4th harm, the wp is not masked, they will climb and hit.

I also changed the waypoint to be at 30 feet above the ground, so this seems not to be the reason.

From my point of view this is definitely a bug.

I never get the Harm on target in PB mode when the waypoint is masked, so I maybe belive that it's no bug when somebody shows me a scenario where the harm hits in PB mode and the designated waypoint is masked by terrain when launching the harm.

 

Edited March 14, 2022 by Topper81
Further investigation

[Chain_1]

Definitely unexpected behavior.  Even when lofting the aircraft, the missile seems to fly itself downward in a direct path to the target steerpoint if there's no line of sight from the aircraft to the target steerpoint, regardless of if the emitter is on the rwr.  However, when line of sight is established, the missile lofts normally.    harmLOStest.trk

 

Edit: Just tried it with the Hornet and the same thing happened.  I can make a separate topic in the Hornet forum if you want @BIGNEWY, but it looks like this is a general AGM-88 issue.

Edited March 12, 2022 by Chain_1
Additional text

[BIGNEWY]

Hi,

HAS or POS RUK mode - the HARM will not loft.

if POS PB or POS EOM the HARM should loft.

What I can see in the above track is a long shot taken but not using the optimal release parameters. You have the minimum and maximum lines in the HUD but the two chevrons give you the optimal for launch, try again using the optimal launch and you should see a difference. 

thanks

[Topper81]

harm crash 5.trk

@BIGNEWY Here it's another track file.

You are right the missile will loft, but it's hits the montain anyway.

I guess it aims the intersection point between the line of sight on lanch and the terrain which is between the missile and the waypoint at launch.

See, on the first two missile launches, the is terrain between missile at launch and the waypoint, so the missile aims the inteseciton point of the terrain.

On the third launch, the runway where the waypoint is positionized is in sight and the missle impacts exact on the runway.

Edited March 15, 2022 by Topper81

[BIGNEWY]

I have asked the team to take a look. 

 

Thanks

[Chain_1]

If it helps the team, here's a track from a higher altitude.  With line of sight already established the missiles loft normally in both EOM and PB modes, even with a non-optimal aircraft loft angle.

harmLOStesthighalt.trk

[Topper81]

25 minutes ago, Chain_1 said:

If it helps the team, here's a track from a higher altitude.  With line of sight already established the missiles loft normally in both EOM and PB modes, even with a non-optimal aircraft loft angle.

harmLOStesthighalt.trk 134.17 kB · 1 download

As told before, I guess I a can explain the behaviour much better know: That the missile will not loft is just a result of a wrong calculted distance to the designated waypoint because the missile amis not the waypoint but instead the intersection point of the line of sight on launch and the terrain (The point where the line of sight intersects the terrain for the 'first time'). I have updated the description.

Edited March 15, 2022 by Topper81

[Topper81]

On 3/15/2022 at 1:02 PM, BIGNEWY said:

I have asked the team to take a look. 

 

Thanks

@BIGNEWY, and could the team take a look on it and confirm it as a bug?

[BIGNEWY]

27 minutes ago, Topper81 said:

@BIGNEWY, and could the team take a look on it and confirm it as a bug?

It is already reported and fixed internally. Fix should be in the next patch