View Full Version : B-25 Bomb Sight Releasing Too Early: Read This.

11-22-2004, 03:59 PM
Anyone that is having trouble with the B-25 bomb sight releasing the bombs early please note that the inputs have been changed to feet and miles per hour. This applies even if your speed bar is set to metric. It works fine if you put the data in as imperial.

11-22-2004, 04:24 PM
Ahh I heard on comms today a team mate complaining that he missed with 3 1000 lbers... hehe I'll go tell him why http://forums.ubi.com/images/smilies/16x16_smiley-tongue.gif

11-22-2004, 09:13 PM
did you adjust for the difference in ground speed VS air speed?

11-23-2004, 01:40 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by StellarRat:
Anyone that is having trouble with the B-25 bomb sight releasing the bombs early please note that the inputs have been changed to feet and miles per hour. This applies even if your speed bar is set to metric. It works fine if you put the data in as imperial. <HR></BLOCKQUOTE>

Here you go. enjoy hope this helps. We use this alot.
Download for our 380th BG AirSpeed Calculator. (http://www.310thvfs.com/Downloads/AirSpeed_Calculator.xls)
From the 380th Bomb Group. The Flying Circus. IL-2 FB's 1st USAAF Bomb Group.
www.310thVFS.com (http://www.310thVFS.com)

11-23-2004, 09:45 AM
First of all, Copperhead thank you for that airspeed conversion calculator, it will save me a lot of time.

In the previous post it was said the automatic bombsight in the B-25 was on target. However I have done some extensive testing and found when bombing a carrier from 10,000ft is slightly short by about the length of a carrier. Adjusting bombsight TAS by 10-20 mph helped but was not actual.

Has anyone else noticed this?


11-23-2004, 10:08 AM
Yes, I've noticed this as well. Thought it might be our calculator, but I tried in all three measurements (targets at sea level) and all bombsite ac...same consistant results...bombs falling short. http://forums.ubi.com/groupee_common/emoticons/icon_confused.gif

11-23-2004, 10:46 AM
After more testing last night I noticed the bombs are falling a bit short too. I'm wondering if you need to input the TAS as knots (knots per hour) instead of mph? That would certainly explain the problem and why your 20 mph adjustment helped. The speed bar can be set for knots (KIAS). 200 mph = 176 knots/hour. The factor is .88 from mph to knots/hour or 1.13 going from knots/hour to mph. I'm going to try this tonight and see if it fixes the problem. I bet one of the programmers at Oleg's place just got a bit confused on the units of measure since there are now effectively three different standards being used, metric, naval, English.

11-23-2004, 10:52 AM

Good info, I'll try it tonight.


11-23-2004, 11:41 AM
By the way, since we're talking about bombing. Does anyone know what the side slip adjustment on the sight is for and how/when to use it? I've never used it, but I'm assuming it has something to do with crosswinds or can the bombadier steer the plane left/right with it?

11-23-2004, 12:20 PM
Yes I've done some extensive testing and noticed the same things guys. The bombs are falling a bit short. You can see it in the sight as well - if you have the TAS set carefully the sight picture is not steady at the moment. Upping the TAS a bit seems to hold the target better and have more accurate results. I am betting you are right about it being messed up with Knots.

11-23-2004, 02:45 PM
I'll get with Some of our 380th BG CO's and we'll work over the probelm and see what we can come up with. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif http://forums.ubi.com/images/smilies/25.gif

11-24-2004, 12:32 AM
my observations:

when in the bomb site postion look to the airspeed guage on the left wall. it has 2 needles on it. i'm assuming that the higher reading needle is the ground speed and the lower reading needle is the airspeed. when skimming the water, both needles read the same. when higher up, there is seperation between the needles.

i found that the site is 1000ft off. if i set my site speed at what the faster needle reads(rounding down to the next 10) and add +1000 to my current altitude, it's a bullseye every time.

11-24-2004, 01:38 AM
I found that the amount of miss increases with altitude. To me that indicates that it is a problem with the speed input. xThurdx does your solution work from 20k and 25k feet? I will have to try that one. I was able to bomb accurately by using knots instead of mph when inputting the speed to the bomb sight. However, I only tried this from 15000 feet, so it could be a lucky coincidence.

11-24-2004, 03:36 AM
my previous post was more of a band aid. i came up with a newer method that is working better for me:

-set altitude as normal
-set the speed from the higher reading needle(just to start with)
-place cross hairs on the target

<then the tricky part>

-ride your airspeed inputs once you've started the automation to keep the hairs on the target.

11-24-2004, 03:01 PM
futher testing has told me that the site crosshairs are just not at the aiming point. site altitude is correct, site speed is correct(when you adjust it for TAS and not IAS)

the aiming point i use is 1 tick mark up from the center.

but there are no tick marks on the vetical hair, just some on the horizontial hair. the distance from the center mark to the next left or right tick mark is the distance up i use.

the testing continues....

11-24-2004, 03:32 PM
the site is FUBAR

i give up.......for the moment

11-24-2004, 06:30 PM
So.... how to turn the bombsight controls back to metric?

Now the speedbar and bombsight numbers do not agree.

11-24-2004, 08:05 PM
You can switch the speed bar to English. Check the toggle speed bar command in your quick reference sheet and setup a key. Or you can use the gauge on the left side of the bombadiers position. Use the needle that is showing a higher speed. Note: Even if you do this your bombs will fall short if you don not compensate somehow as the B-25 sight has a bug.

I have sent a bug report to Oleg about this problem (bomb sight does not work correctly.)

11-25-2004, 03:57 PM
OK, more testing completed. If you convert your TAS to knots the bomb sight is accurate. So, if you TAS is 250 enter 220. If it's 290 enter 260. Basically, reduce your TAS mph by about 13%. Once you have start bomb sight automation make sure to adjust the altitude as you approach the bomb point as the plane will tend to lose altitude with the level autopilot on. You may also need to adjust your airspeed slightly.

11-26-2004, 11:51 PM
i think the site issues were not addressed in the 3.02b patch

11-27-2004, 02:12 AM
maybe cause we're bombing with used 1938 bomb site from a worn out he-111 & not the Nordan bomb sight. Nordan put them on the dot every time. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

12-06-2004, 12:23 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by xTHRUDx:
i think the site issues were not addressed in the 3.02b patch <HR></BLOCKQUOTE>Yeah, I tested it today with the 3.02b patch and it's still dropping short. I've just been taking 10% off the TAS and aiming a just a little short to make up for the other 3%, seems to be OK then. I sent Oleg some tracks and written description of the problem. Hopefully it will be fixed in the next patch??

12-06-2004, 06:05 AM
bombsite..bombsite??BAH!!! back in my day we didnt have bombsites..
i had to have externals on for my b-17, go up to 9~10K.. keeps switching angles/views keep her strait, then cycling thru different gunsite views/angles for proper tracking..all mine was "guestimation"

and ya know what... i was very proffecient at it http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

to bad nobody allows externals/ and 17 on servers anymore (specially the "real" ones). or id still be bombin by "hand" at 9 k http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

ok ..rant , over.. i miss my b-17..

ill see what my bomber cohorts can think of ... hopefully a true fix comes soon. in the meantime, im sure well get somethin worked out

12-06-2004, 08:35 AM
<span class="ev_code_PINK">B-25 Bomb Sight Releasing Too Early</span> I had a problem of similar kind when I was young....girls related it was http://forums.ubi.com/images/smilies/16x16_smiley-sad.gif

12-06-2004, 10:07 AM
****.. I have a complete and precise excel spreadsheet so I can convert IAS/TAS and now they change the units again http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

12-06-2004, 10:08 AM
Ooops, I'm not allowed to say D@mn

12-06-2004, 04:14 PM
I feel ya Gau-8! I want that B-17 too. I know people have brought up issues with it being a human flown plane but heck its in the game and there are a million other planes for the fighter boys. I just want that Fortress! http://forums.ubi.com/images/smilies/784.gif

I dont want to take away from the topic. But yes, I've exerienced the bombs coming short. Old news but yes. Its there.

12-06-2004, 10:05 PM
thanks guys for making your spread sheets and all, but there is a handy little guage in the bombsite postion that shows you the GS as well as the AS. it says AIRSPEED and has 2 needles on it. the faster reading needle is the GS.

12-06-2004, 11:37 PM
TAS Calculations (FAQ) posted at: http://www.scenery.org/faq_aviation.htm
================================================== ======
True Airspeeds

1) True Airspeed Calculation--Divide your indicated altitude by 1000, multiply this figure by 5, and add this number to your indicated airspeed. Ex: 30000/1000= 30*5= 150+280= 430 is your TAS. [assuming IAS is 280 knots]

2) True Airspeed (TAS)--To find True Airspeed increase your indicated airspeed [IAS] by 2% per thousand feet of altitude. Ex. If your indicated airspeed at 8000ft is 120kts, add 16% (2*8=16%) to your indicated airspeed. Your True Airspeed is 139kts

================================================== ======

The second example results in the equation:
TAS[knots] == IAS[knots] + IAS[knots]*(0.02*Altitude[feet]/1000[feet])

This second example equation closely approximates the method used in IL-2/FB for calculating/simulating TAS|IAS. Conversely, the first example provides a quick, but less accurate rule of thumb which may provide a "good enough" nautical units TAS solution in most instances.

The metric conversion of the second example yields:
TAS[kph] == IAS[kph] + IAS[kph]*(0.066*Altitude[meters]/1000[meters])

I do not recall if there is a metric analog to the first TAS rule of thumb calculation example that I mentioned above.

Summarizing, the metric units TAS equation adds 6.6% more kph per 1000 meters altitude to IAS. The English/nautical units TAS example adds 2% more knots per 1000 feet altitude to IAS.

IMO, I am not sure why anyone would want to convert aeronautical navigation distances into statute miles in a flightsim, anyway.

12-15-2004, 08:24 AM
Just been pointed to this thread as I'm learning the B25 sight at the mo. I seem to have some working numbers for manual bomb release but would be interested to hear if anyone ever received an official line on whether the sight is taking input in metric or imperial!

Cheers, Spinner

12-15-2004, 10:34 AM
You want to use imperial, but make sure to reduce your TAS by about 10%.

12-16-2004, 01:14 AM
Im used to using AI B 17 and such, so for level bombing I use Mk I eyeball in external view....remarkably accurate, once you get used to doing it that way

Mostly though, with the Mitchell, I dive bomb...incredibly accurate

B 25s did dive bomb IRL, too...North American even made a dedicated dive bomber from a Mitchell, with reinforced wing spars and large spinners...but during testing it shed its wings and the project abandoned