Very Low Level Bombing

[Baumer]

I was reading on the AH boards that someone had a question about bomb arming and such. So I started experimenting with different aircraft and bomb loads. I was able to sink a cruiser today, in the MA, with an Ar 234 from 185 feet and 395 mph. It's important that you pull up ASAP after bomb release to clear the blast. The ack didn't start to fire until I was 2 or 3 seconds away from bomb release. I posted a few screen shots in the forum gallery if any ones interested. The next test will be a formation of 234's and I'll target the CV.

 

[Earthdog]

Great work Baumer.  I am really impressed with you methodical approach to the game.

FYI:  I did a little math:

The drop time of the bomb is found by:

Drop time =  SQRT((2 x Altitude) / G)  : G = 32ft/Second²

              = SQRT( (2 x 185) / 32 ) = 3.4 Seconds

And Horizontal Distance Traveled = Rate x Time = 395 x 3.4 = 1340 ft

Distance bomb traveled =  SQRT( Altitude² + HorizontalD²) = SQRT(185² + 1340²) = 1360 ft.
( The above is a simplifiation because it would not actually be a straight line, but close enough)

Anyway, it looks like you can get lower or slower, but not by much.  Of course if you did that you would probably blow yourself up.

[daddog]

Very nice guys.

Now if I could only get my system up and running so I could try this.

[Blutik]

Huh?

[Simaril]

Earth:

That is the kind of stuff I wish I could figure out, but the "how to" left my head shortly after my last math class in college! Does your calculation give only the linear horizontal distance, or is it allowing for the increased travel as the bomb drops on the angle? (That's the hypotenuse, right? See, this old dog still has something!)

Since you have a good handle on it, answer me this: Whats the lowest drop altitude giving 1000 feet bomb travel for a plane travelling 250mph?

I killed a carrier 2 nights ago in MW, but it took me 2 runs of Ju88s. I went NOE and pulled up to do a low alt drop at the last minute, which worked OK from a safety standpoint (well, KINDA ok...) But my seat of the pants estimated drop was off so the heavy bombs missed my first run.

[Baumer]

Simaril,
With my testing I've been drooping 1000lbs'er from a B-25C at 255 feet and 255 mph with good results. I'll do the actual calculation in a bit.

[Baumer]

I did the math and it's 1049.458 feet, so you can't get much slower or lower for them to arm. And you need to pull up at release to clear the blast.

As a note; you can copy the formula that Earthdog posted into excel and do your own calculations. This is just the hypotenuse calculation not the true ballistic trajectory. I'll see if I can dig up the formula for that and put it into an ***Excel spreadsheet of DOOM*** 

[Earthdog]

Simaril,

My calculation was for the distance of the hypotenuse.  This is an approximation, however, and probably only works for low altitudes.  The bomb would actually follow a parabolic path.  Also, this doesn't account for air resistance or any other aerodynamic effects HT might have modeled, but I doubt that matters much for a drop time on the order of seconds.  For your question: if I do a straight droptime x speed calculation ( no hypotenuse ) I get a minimum altitude of 256 for 250mph.  This is conservative since I'm ignoring the hypotenuse, so Baumer's numbers seem to be dead on.   I'll try to create a graph of min alt vs speed to get 1000ft, but I'm not sure how to post an image in the forum.  I should probably dig up the real trajectory equations for this and do it right, however.

[Baumer]

I found a freeware program for calculating the length of a parabola segment. If you don't count air resistance, ( or any other HT modeling issues) the lowest you could droop at 250 miles an hour is 239 feet. The bomb would arm 4.085 feet from impact.

[Simaril]

250 at 250 seems to be a pretty good rule of thumb then. Good news is that this is well under the DAR detection limit, so we could do bomb runs without showing up as dots. Interesting!

Of course, the real issue with Carrier runs is the darn 5" gunners. Some of those guys are downright scary, and drones simply refuse to fly under 150 ft AGL. I know that when I gun, I look for the drones because a true NOE primary is almost invisible -- especially when the sun is a bit dark. Makes me wonder how a single Lanc, running hard at wavetop height, would do attacking from the "weak" unengaged side of a CV group!

When I made those runs in Ju88, I found some real trouble from the ack when it was full up. I made the first run from about 4:30 on the clock face. When the ack started firing, it didnt do much because I was so low. I had to pull up to avoid hitting the trailing outside destroyer, and that's when the hits started telling. I lost an engine, some fuel, and maybe some critical parts from a drone...but was able to get the drop off. I did rush the drop, but enough of the 50kgs hit the tail of the carrier that it made a real difference on the second pass. And, since the group was just barely off our base, the 5" gunners were all busy trying to rack up kills on the furball swarm, and I didnt take a single hit from them.

Second pass was easier, with fewer guns around. I came in from the dead 6 figuring the 5" was already dead, and it worked ok. Actually got to land the lead plane, though the other two were hash after passing through the formation.

[Baumer]

Here's a graph of alt vs. airspeed for bomb arming. This is just for bomb arming, not necessarily a survivable pass that depends on ordinance and flight path after release.

[skernsk]

You guys are scaring me....... I don't enjoy math but it's part of my everyday life at work.  I am constantly doing coversions (some fools still use inchs and feet ) and caculating grades for storm/sanitary lines.

Once I leave work the math - stops.

Sadly, while I could not have come up with the right equation I understand what's going on.  I'm supposed to be skernsk the dumb canuck.  I feel shame.

[daddog]

This is a cool thread.

Of course, the real issue with Carrier runs is the darn 5" gunners. Some of those guys are downright scary, and drones simply refuse to fly under 150 ft AGL.

True, but they could not get us all. With practice we could sink any fleet we wanted if 10 or more of us were on.

[Baumer]

I sunk a carrier to day with a single B-24 in one pass! No defenders but, 4 x 2000lbs 230 MPH at 190 Feet and you need to pull up to 400 feet to clear blast.

Math is DANGEROUS and fun! 

After a little more testing it "appears" that bombs actually arm at 800 feet not 1000. I've revised the chart with the lower numbers but this is very near the edge so add a little alt for a cushion.