Sight accuracy on uneven terrain.

[Airhunter]

Is it just me or does the sight with radar ranging that is used for guns, rockets and bombs become pretty much useless when the target is on any kind of slope or uneven terrain?

[Harlikwin]

On the viggen?

[Airhunter]

On the viggen?

 

Yes. (Sorry, thought I posted it in the right sub-topic)

[corvinus]

Why would it be useless? Together with the depression angle (how much the target is below the horizon) you get the relative height of the target. This is enough info for computing a firing solution.

[Harlikwin]

Im not sure how the viggen is solving the bomb triangle in this case but it sounds pretty realistic if its using the radar alt to assume HOT and you are flying over uneven ground or a slope.

Edited March 5, 2019 by Harlikwin

[corvinus]

Actually, the Viggen does not use the radar altimeter for weapon deployment. It would lead to serious errors in uneven terrain as, I think, the OP was hinting at.

 

 

 

The Viggen does use radar ranging together with the depression (or pitch) angle. For this the main radar antenna is used (ground mapping is then disabled).

 

 

When radar ranging is disabled or the radar is used for ground mapping, it uses the QFE method. In the QFE method you set the barometric altimeter to the QFE of the target. The barometric altitude is then the altitude relative to the target.

 

From page 283 of the manual:

 

 

In ranging radar you have the range and pitch angle, so you can solve for the height. In the QFE method you have the height and pitch angle and you can solve for the range.

[Airhunter]

I mean, I get that it uses radar ranging and no, it is not disabled on my runs. Still, when using radar ranging the AKAN/ARAK attacks seem rather inaccurate on hilly terrain or when the targets are on somewhat of a slope.

[Harlikwin]

Is there a desination on the hud for exactly where the radar is ranging?

[corvinus]

It is "the dot":

Radar ranging is indicated by the “fin” appearing in the HUD above the sight dot.

 

The manual further mentions:

The radar will range to the spot that the sight reticule (dot) is aiming at. As the radar will determine more or less the exact distance to the aiming point, yielding far more accurate sight calculations (particularly against inclined ground) than triangulation based on QFE. Radar ranging is thereby preferable than triangulation due to this increased accuracy and greater flexibility with varying terrain elevation.

At least, according to the manual, radar ranging is accurate in case of sloped terrain.

[Airhunter]

 

At least, according to the manual, radar ranging is accurate in case of sloped terrain.

 

Yeah not in my experience. Guns either land short, overshoot or overshoot even more as you get closer.

[Harlikwin]

Yeah not in my experience. Guns either land short, overshoot or overshoot even more as you get closer.

 

Are you pointing the radar dot on the target or the CCIP piper? Generally you can't do both at the same time. The radar is meant to get you "close" as its continuously computing the slant range.

 

As an aside, I'm super glad they actually model it to this level of detail in the viggen.

[Fri13]

What the system should only care is that your INS is accurate, so the computer can calculate accurate pitch angle (dive angle) and then use radar to measure the range and the angle to the target, based to chosen weapon flight parameters.

 

It shouldn't care anything about the aircraft altitude below its position, nor the altitude below aircraft compared target altitude, only the range, angle and altitude difference between target and the aircraft.

 

INS gives the dive angle

Radar gives the range

Then the third value (altitude difference) is calculated from those two.

 

Question is, does the Viggen computer measure the barometric for air density as well? As it should matter are you firing cannon at target that is at 4000 meters altitude on mountain, or are you firing at it 4 meters at the beach, while diving at it 3 kilometer distance at 25 degree angle.

 

So maybe the aircraft altitude metering needs to be set to barometric, unless the computer can read it regardless it set to radar altitude ranging?

 

And I find it odd that you are given a CCIP, that you couldn't use as the radar would perform ranging from totally different location?

[corvinus]

The Viggen is measuring the barometric altitude, it probably uses the value in the calculations (to account for differences in air density and speed of sound etc.).

 

 

The altitude setting (barometric/radar altimeter) is only for HUD displaying. Afaik it does not affect the computations. In any case I cannot recall that it affected my aiming.

 

 

 

Note that in ARAK/AKAN deployment the Viggen does not provide a CCIP. You indicate the target position by putting the sight dot on the target and pulling trigger unsafe. You then keep the dot on the target (this main radar dish is also pointing at this position in order to measure the range) and wait for the firing cue. Only at the firing cue the sight dot corresponds to the impact point of the rounds.

[QuiGon]

The altitude setting (barometric/radar altimeter) is only for HUD displaying. Afaik it does not affect the computations. In any case I cannot recall that it affected my aiming.

Correct