Jump to content

[REPORTED] CCIP Incorrect Elevation Used


lukeXIII
 Share

Recommended Posts

In regards to: https://forums.eagle.ru/showthread.php?t=275176

 

After investigating this issue I noticed that dropping bombs in CCIP resulted in consistently impacting above the pipper when trying to hit a target on a mountain and consistently impacting below the pipper when trying to hit a target in a valley. This behaviour seemed very similar to how the radar altitude source mode should work and led me to believe that the elevation being used in the calculations was from the DTS elevation directly below the aircraft instead of using the SPI set on the target.

 

For reference, setting a manual steerpoint elevation resulted in bombs landing on target. Using a CCRP level drop also resulted in bombs landing on target indicating that the DTS elevation of the target is being used:

 

As the A10c generates a markpoint for every weapon impact, this can be used to determine the bomb trajectory and hence what elevation data is being used. The following test was performed for CCIP drops where the Height Over Ground was greater than the Height Over Target and vice versa. Bombs used were mk 82 LDGP.

 

• Create markpoint on target

• Set markpoint as SPI with DTS as source

• Drop bomb when pipper crosses target

• Change steerpoint to generated impact markpoint (MRK Z)

• Inspect MRK Z location compared to target location

 

Case 1: Target on a mountain. Height Over Ground > Height Over Target

 

Bomb impacted above the pipper, inspecting MRK Z showed that calculated impact point was inside the mountain and below the target. Figure 1 shows diagram of pipper and bomb trajectory. From this we can see that the elevation source being used was from the ground below the aircraft and not the target elevation.

 

Case 2: Target below a dam. Height Over Ground < Height Over Target

 

Bomb impacted below the pipper, inspecting MRK Z showed that calculated impact point was floating above and before the target. Figure 2 shows diagram of pipper and bomb trajectory. From this we can see that the elevation source being used was from the ground below the aircraft and not the target elevation.

 

To conclude, the CCIP solution is incorrectly using the DTS elevation directly below the aircraft instead of the SPI DTS elevation. DTS elevation is able to be used at the SPI as seen in level CCRP drops which means there must be a bug or oversight preventing the CCIP from obtaining this same data. If this issue gets fixed, the current behaviour should be similarly implemented into the Radar Altitude Source mode as this is accurate behaviour for that mode.

 

UPDATE: SPI not required for CCIP, however the results are still the same.

A10CCIP1.png.068623ecfb0b68b486b63d15234e4f51.png

A10CCIP2.png.5fe26995ff7c8683db3178191db95d37.png


Edited by lukeXIII
Adding update
Link to comment
Share on other sites

You’re not flying any Aim Off Distance (AOD) so yeah, bombs will fall short.

 

You don’t put your VV on the target.

 

Check the videos again, there is sufficient separation between the velocity vector and the pipper sight in both examples.

Link to comment
Share on other sites

To conclude, the CCIP solution is incorrectly using the DTS elevation directly below the aircraft instead of the SPI DTS elevation.

 

Target elevation directly below the airplane is certainly not the correct algorithm. I'm a little surprised that is the current state of affairs. But I'm not sure the correct behavior has anything to do with SPI which could be anywhere at any altitude without adversely affecting CCIP mechanization. E.g. you're bombing the Netherlands and your SPI is on the peak of Mount Everest. CCIP should still work fine even with your SPI at 29,000' 1000 mi away, right?

 

I think the target elevation should be derived by the intersection of the CCIP pipper LOS and DTSAS surface. Of course until there is an accurate pipper LOS it's impossible to calculate this intersection. But the intersection requires the pipper LOS to define it. The problem is circular but there are methods to solve it.

 

I have heard the real life solution is to start with a notional, temporary LOS to calculate an intersection. Take that elevation as input for a second attempt at a LOS and recalculate a new intersection for a new LOS and keep continuously updating the intersection. The solution should converge toward the actual solution quite fast.

Link to comment
Share on other sites

Indeed

Elevation should come from the CCIP pipper calculations or the HOT setting, SPI generator doesn't matter.

 

See screenshots below (taken with active pause on.)

Steerpoint is a WP on top of mount Elbrus (elev 18000+), SPI generator is STPT.

 

Target elevation is +/- 30 ft, so is the elevation below my aircraft.

In this example, because the elevation below my aircraft matches the elevation of the target, it is a direct hit.

If I would do the same in mountainous terrain, the bomb would go long/short depending on the elevation below my aircraft.

 

zmaG4r.jpg

 

iZ9Nzl.jpg

dUJOta.jpg

 

 

Windows 10 | i7 7700K @4800 | 32GB DDR3 | GTX 1070 | TM Warthog HOTAS | Saitek Combat Rudder Pedals | TM MFDs + Lilliput 8" | TIR5 Pro

Link to comment
Share on other sites

Target elevation directly below the airplane is certainly not the correct algorithm. I'm a little surprised that is the current state of affairs. But I'm not sure the correct behavior has anything to do with SPI which could be anywhere at any altitude without adversely affecting CCIP mechanization. E.g. you're bombing the Netherlands and your SPI is on the peak of Mount Everest. CCIP should still work fine even with your SPI at 29,000' 1000 mi away, right?

 

That makes sense, I'll update the main post to reflect that.

 

I think the target elevation should be derived by the intersection of the CCIP pipper LOS and DTSAS surface. Of course until there is an accurate pipper LOS it's impossible to calculate this intersection. But the intersection requires the pipper LOS to define it. The problem is circular but there are methods to solve it.

 

I have heard the real life solution is to start with a notional, temporary LOS to calculate an intersection. Take that elevation as input for a second attempt at a LOS and recalculate a new intersection for a new LOS and keep continuously updating the intersection. The solution should converge toward the actual solution quite fast.

 

If my understanding is correct you wouldn't need to use that method, as you already know the initial position of the aircraft (GPS/INS coordinates + barometric altitude), bomb trajectory and the DTS elevation map. You would just need to solve the bomb trajectory equation with the height map to get an impact location, and then use some trigonometry to determine the sight line angle (and hence the pipper location).

Link to comment
Share on other sites

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...