Bomb ballistics, pipper depression and Z sleds

I want to create bombing sleds on my own to understand the theory and math behind it. I understand that those sleds are usually created by each squadron in real life and maybe even created per mission.

Also I want to figure out how good the ballistic model implemented in DCS is compared to real life.

Before I go into a totally wrong direction, I want to provide my progress here and get some input from experts on that matter.

I know that DCS is incorporating drag and wind in simulating the ballistics. I verified this by just calculating an expected bomb parabolic in vacuum with and compared this to actual bomb drops in DCS (with the help of TacView). The values were not close as expected.

In order to check how close the DCS ballistics model is to real life I did a lot of (about 250 so far) bomb runs with MK-82 on the center station with the A-10C at different release altitudes, dive angles and speeds. Again I used TacView to get the values.

(Side note: I noticed some deviations with TacView. When do a bomb run and record the metrics with TacView, then use DCS to watch the recorded track again and again capture the metrics during replay of that recording, TacView does show different values for the two different replays. The deviation is small, so I hope it can be neglected. I did this in standard atmosphere. bomb target was at sea level (I simply let the bomb hit the sea). Wind was zero everywhere.

The current results can be found here: https://docs.google.com/spreadsheets/d/1No9rlRnPx9m74BlGR8MJ7XCg5r8mxsbOhcztxz2R_uM/edit?usp=sharing

Bomb ballistics data for dive angles 45 and 60 is a bit tricky as it's quite hard to capture the exact airspeeds I need, but eventually I will have this data completed.

For real life I did only find ballistic tables for the Mk82 starting at KTAS 400. The data provided there for time of fall and bomb range more or less seem to match what I measured in DCS/TacView. The bomb ranges are off by about 100 ft and the TOF data by about 0.1 s. My airspeeds, release altitudes and dive angles where not exact which might even explain the deviation. As I do not have ballistic tables for airspeeds below 400 KTAS my captured data is still quite valuable - I hope.

With the measured data I then calculated the aim off distance and the aim off angle and depression from planned flight path. I hope the calculation is correct.

Now I need add the angle of attack to the depression. In order to do that, I need to calculate the AOA at the bomb release point. I understand that the AOA is based on drag index, gross weight, altitude, airspeed and dive angle. I hope to find some charts or tables for the A-10 which would help me. Maybe there are some formulas which can be used. So this is what I need to research next.

Furthermore I need to get the data for the altitude lost from bomb release until after executing the safe escape maneuver. This is of course dependent on the SEM itself. I intend to calculate/measure the data for CLM at first.

Also I will need to measure/calculate/get the data for the aircraft to start a dive at a specific angle, airspeed and altitude in order to arrive at a particular release speed and altitude.

I'm not sure if minimum time for fuzing is important in DCS. This needs to be clarified as well.

I have some formula to calculate Initial pipper placement, so this should be covered.

So much for the research. Again, any information you can provide would be highly appreciated.

I also heard that real life A-10 pilots train manual bombing quite often as they do not want to RTB when they have issues with there instruments while there a troops on the ground who need their help. I understand the concept with the pipper depression, but cannot understand how the pilot would measure the distance to the target when TGP and CDU are damaged and thus cannot provide this information. The distance would be quite important for the roll in point and to correct errors during the dive. Also, how can you get the dive angle correct without a HUD? Do you use the ADI or VVI for that?

"but cannot understand how the pilot would measure the distance to the target when TGP and CDU are damaged and thus cannot provide this information."

You cannot release the bomb if the CDU is damaged. And IRL an A10 pilot would never drop a bomb without precise instrument feedback with friendlies/civilians in the area. They would RTB or let wingman take over.

Losing HUD or CDU is a critical failure and I believe that prohibits the pilot from engaging without instruments.

I have never heard of "manual bombing" without instruments, and not sure how this would be done during training.

Ok, there might be different kinds of instruments/systems being damaged/malfunctioning. For instance if the IFFCC is out of service, you don't get a CCIP solution and have to do manual bombing. If the HUD is out of service, you can switch on the standby HUD and get that depressible pipper. If EAC/CDU is malfunctioning, you still get that pipper. If you do not have a pipper at all, bombing is just a gamble I agree. I assume that distances to targets can also be estimated by comparing them to the HUD symbology / pipper size or other reference objects (like those "antennas" sticking out left and right at head height from the seat).

But please don't let us get side-tracked by the question whether and when we would actually use manual bombing. I just want to do the calculations.

 

But please don't let us get side-tracked by the question whether and when we would actually use manual bombing. I just want to do the calculations.

I seriously doubt ED would give the hard data they have. But good luck on your project!

If you're looking for distance at which you need to initiate a turn or pull-up, use cockpit references to target - here you need to know MSL of your target so that you can compute desired MSL (ie. to get yourself into the correct AGL with respect to target). You fly to place the target in a particular place with respect to your cockpit refs (canopy bow, rail, whatever you have available) and initiate once it's in the right position.

How to get to the right position: Practice. Visual/contact flying is EVERYTHING in this case. Again, this will be target/landmarks + cockpit references after you get to your desired altitude.

Since you've already done a lot of math, you should be able to nail this one with just a little more work.

For the dive angle you can use the ADI, VVI as some sort of backup (you'll have to know the given data-point) but also visual/cockpit references - ie. what does it look like when the nose is 20/30/40 degrees below the horizon? Where does some part of the canopy bow or HUD or other cockpit thing intersect the horizon at this dive angle?

I understand the concept with the pipper depression, but cannot understand how the pilot would measure the distance to the target when TGP and CDU are damaged and thus cannot provide this information. The distance would be quite important for the roll in point and to correct errors during the dive. Also, how can you get the dive angle correct without a HUD? Do you use the ADI or VVI for that?

@GGTharos. Oh that's is very valuable input. Thanks! In order to look out for the cockpit reference points, it is necessary to have the same head position. Is there a procedure on how to align your position for the A10? Are there some objects I can align in order to get the correct position like in other aircraft? I fly in VR and need to change my position a bit more forward and up. Not sure if the is the correct position.

You're welcome!

As long as your position is consistent it's ok and you'll be in the ball-park. Obviously, you lose some bombing precision. I'm actually not sure what to advise here, though you could do things like line-up where the engines or wingtips (or any other part of the airframe) appears in your view. Also, things like sun-covers for the monitors, if they're there, can be of help since you can try to line those up as well to be 'perfectly flat' or 'a little down/up'. :)

For the dive angle you can use the ADI, VVI as some sort of backup (you'll have to know the given data-point) but also visual/cockpit references - ie. what does it look like when the nose is 20/30/40 degrees below the horizon? Where does some part of the canopy bow or HUD or other cockpit thing intersect the horizon at this dive angle?

I know that some pilots use markers to draw lines on the canopy glass, corresponding to different pitch angles, much like a HUD pitch ladder would. Or use their hands, placed in a specific way on the canopy, as known reference points. Would be cool to have the former and I think it's easily doable with some texture modding.

@GGTharos. Oh that's is very valuable input. Thanks! In order to look out for the cockpit reference points, it is necessary to have the same head position. Is there a procedure on how to align your position for the A10? Are there some objects I can align in order to get the correct position like in other aircraft? I fly in VR and need to change my position a bit more forward and up. Not sure if the is the correct position.

Here you go.

https://imgur.com/a/K8Ck914

+1 good resource.