BFL Pourcentage for Dive bomb / Pop Up

Hi guys,
I try to find a good solution to compute the BFL % for a DB / Pop up profile. It seems link to be the “Teta i” (Depression) setting in the 34.
I have found that: Teta i = tan1 (Roll out alt / Horizontal Range)  Dive angle.
But it seems I need the IPP too (Initial Pipper Placement). For the IPP I need some data I cannot find.They’re is the data I have:
Ingress Speed
Roll Out Alt
Roll Out distance
Dive Angle
AOD
Release AltSomebody have any idea?

Let me check, i’ll get back to you.

Hi
Well i looked into it but i couldn’t find the formula but, in case anyone can complete me, here is what i figured would be necessary to do to calculate it :
We know our tracking time, we also know our distance from the target when we are going to drop the bomb, and we also know our descent angle.
We also know that usually the piper down of the BFL is touching the ground when we roll wings level on target.
If we draw a triangle and we keep all proportions is it then possible to figure out at what % the target will be on the BFL ?
I am almost certain that it depends on our descent angle and distance from the target , but my biggest question what is the scale of the BFL and what is the size of the BFL? what is the rule of thumb for knowing how much distance does the BFL represent at X distance from tgt ?
If anyone with more knowledge on the subject could give his input it would be greatly appreciated.
Spooky

Is this for computed or fixed reticle bombing? I’m no fighter pilot but I’m enough of a mathematician to do the geometry.
I assume “teta i” is thetai or Θi if we use the Greek character. If it’s the difference between the position angle of the aircraft and the dive angle then it describes how far over the target your path takes you. It’s also the angular difference between the target at roll out and the AOP.
%BFL is going depend on the position of the target and the position of the bottom of the BFL. For CCIP the pipper is a good bottom. For CCRP that might be the bottom of the HUD display area? CCRP doesn’t really have a BFL, just an ASL. For fixed reticle bombing the fixed pipper is the obvious choice. Target position in the HUD is Θi+AOA from the ZSL or simply Θi from the FPM.
In the CCIP case the bottom of the BFL or rather the pipper location is nontrivial. It’s going to be a genuine bombing solution at the instantaneous values the aircraft is experiencing at that time which are impossible to predict with basic geometry unless the CCIP pipper is clamped with the delay cue.
In the clamped case the pipper is “approximately 14 degrees from the boresight cross” so an example would be:
Θi 3 degrees
AOA 2 degrees
Target is at the 3 degrees down of a 142 length BFL which is 3/12 so 25%. 
Could you put your findings in an example please ?

Thanks for the feedback. It’s not easy to understand even in french, so excuse me in advance if the follow sentence is not easy to understand, I’ll try to do my best ;).
% BFL is use for any DB / HADB / HARB / Pop up final parameter. It’s only for CCIP. It permit to the pilot to know where the target will be after the roll out, in the begin of the tracking point. So the % BFL is the theoric position of the target between the FPM and the Pipper ot this exact moment. 100% BFL mean that the target is exacly on the pipper after the roll out. 50% mean the target is on the middle position between the FPM and the target. When %BFL compute is above 100%, the pilot know that I’ll need to push the stick to intercept the target, and so I can’t follow exactly the pre plan dive angle.
It’s easy to know that the % BFL will be link to the pipper position (and then, to the bomb range, the speed and the dive angle). But it’s also link to the ZSL AoA (Zero Sightline AoA  call “Alpha i”).
If you have the GR1F16CJ3411, look the page number 3428. As you can see, you have the dive angle (flightpath).
Under this angle, you have the sightline, witch is the exact angle between the target and the position of the aircraft at rollout. I can compute this angle with the SDFP and the bomb range (I extrapolate the bomb range with the AOD give by the Weapon Delivery Planner).
With this angle, you know what will be the angle of the target when you dive.
But to know the % BFL, you need the pipper position. And this will be give by the IPP angle (Initial Pipper Placement). The problem, I don’t undertand how to find this value.
The formula for IPP is: IPP = Depression (D)  ZSL AoA (alpha i)  Target depression at rollout (teta i)
Finally I found how to compute the Depression and the Target Depression at rollout (D and teta i).
But I’m still unable to compute the ZSL AoA.Hope my sentence still clear to understand. Thanks a lot.

I understand %BFL (is it called BFL? PBIL?) as a aid to expectations as to FPMtargetpipper picture on rollout.
But to know the % BFL, you need the pipper position. And this will be give by the IPP angle (Initial Pipper Placement). The problem, I don’t undertand how to find this value.
Pipper position is a complex math solution based on the current instantaneous bombing solution. Ideally you feed your expected flight parameters into FCC at rollout position and record the result. Next is to use a paper bombing table. Lastly there might be some very approximate rule of thumb for this that I don’t know. I think real squadrons have access to theoretical bombing solutions so they can predict CCIP pipper placement in all cases. I think this would be in 34111 for the table or a computer program for the numerical simulation.
Then again %BFL can be very approximate and still useful. Supreme accuracy isn’t necessary. If we find a good rule of thumb experimentally of pipper location at various common rollout parameters then this can be a reference to solve for %BFL.

Okay guys, I got it!!!
Well, all my computed is only for a 500kts TAS and 4G turn, but this is pretty standard.
I’ve been able to compute the BFL% when I compute before the Depression , Target Depression, and IPP. To find the lost value (ZSL AoA), I made multiple pass with various angle and with always 500kts TAS, and the AoA is between 1.4 and 2.3 AoA. So I choose 2°.
I’m happy :drink: 
Okay guys, I got it!!!
Well, all my computed is only for a 500kts TAS and 4G turn, but this is pretty standard.
I’ve been able to compute the BFL% when I compute before the Depression , Target Depression, and IPP. To find the lost value (ZSL AoA), I made multiple pass with various angle and with always 500kts TAS, and the AoA is between 1.4 and 2.3 AoA. So I choose 2°.
I’m happy :drink:Congrats on that, mate.
How about some calculations spread sheet sharing? 
Okay guys, I got it!!!
Well, all my computed is only for a 500kts TAS and 4G turn, but this is pretty standard.
I’ve been able to compute the BFL% when I compute before the Depression , Target Depression, and IPP. To find the lost value (ZSL AoA), I made multiple pass with various angle and with always 500kts TAS, and the AoA is between 1.4 and 2.3 AoA. So I choose 2°.
I’m happy :drink:How about using the AOA value described in HAFF16Supplement.pdf p30?
It looks that the AOA is dependent on GW, altitude, Mach.
When i roughly measured the AOA with the given value 500KTAS(0.75M), assuming altitude 0 and GW 30k lbs, it might show 2degs AOA.