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JDAM 31 distance reduced?

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    JDAM 31 distance reduced?

    Has the distance on the 31's been reduced. AT approx 37,000 feet I used to be able to get about 25 miles on them. Now it seems like 10 or so. Considering when you release the 31 at 37000 the initial speed of the 31 is 10 miles a minute, I think the new distance is bugged

    #2
    All JDAM flight profiles have been adjusted to behave more like actual bombs. Before they were performing glide-type profiles, which was extending their range.
    REAPER 51 | Tholozor

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      #3
      Thats what I am saying. I think the profile is way off. Like I said, the initial speed on the jdam is 500-600 kts. Thats 10 miles per minute. It would take only one minute for the bomb to reach 10 miles. Now of course the bomb is decelerating. Lets say on the lower end of things the bomb has an initial release of 300 kts or 6 miles per minute. Thats 2 minutes to reach 10 miles. We all know the bomb will stay airborne longer than 2 minutes. I think ED needs to revisit the profile and correct it. get a hold of an aeronautical engineer and they can probably give you a much better idea what the range will be and i'll bet it'll be a lot better than the current profile

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        #4
        As Tholozor said, a GBU-31 is not a glide bomb as it has no surfaces that generate lift unlike a JSOW for example. The strakes mounted on its body barely generate lift but help the overall stability. So the updated range is probably more accurate.

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          #5
          JDAM absolutely flies glide-type profile. It doesn't have wings but it does have a bomb body and the software will pitch the bomb to an AOA to maximize glide ratio. This should give JDAM a significant range increase relative to ballistic bombs. This should be similar to PIII giving up to ~12nm for a subsonic 30kft release.

          Supersonic above 30kft I don't know. 25nm sounds like a lot even releasing at 40,000' M1.6.

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            #6
            Just tested with GBU-38s, ~33,000ft just over M1.0 gave me an IN ZONE release cue at roughly 12.5nm, MAN release with no lofting from the aircraft, so pretty close to what Frederf described.

            With 31s, at ~30,000ft just under M1.0 gave me an IN ZONE release cue right around 9.3nm. Also noticed that 31s now correctly orient their roll to put the elevators on the horizontal plane and the rudder on the dorsal side.
            Last edited by Tholozor; 09-29-2020, 08:25 PM.
            REAPER 51 | Tholozor

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              #7
              Originally posted by Tholozor View Post
              Just tested with GBU-38s, ~33,000ft just over M1.0 gave me an IN ZONE release cue at roughly 12.5nm, MAN release with no lofting from the aircraft, so pretty close to what Frederf described.

              With 31s, at ~30,000ft just under M1.0 gave me an IN ZONE release cue right around 9.3nm. Also noticed that 31s now correctly orient their roll to put the elevators on the horizontal plane and the rudder on the dorsal side.
              That looks about right
              https://forums.eagle.ru/filedata/fetch?filedataid=259325&type=medium
              476th vFG Public Discord| 476th vFG Website

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                #8
                Originally posted by chief View Post
                ED needs to revisit the profile and correct it. get a hold of an aeronautical engineer and they can probably give you a much better idea what the range will be and i'll bet it'll be a lot better than the current profile
                Well ED already have at their disposal aeronautical engineers and some very good ones.

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                  #9
                  At 30000 ft the lift that a bomb can generate is very limited.
                  The LAR also changes with the angle of impact.

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                    #10
                    Originally posted by chief View Post
                    Thats what I am saying. I think the profile is way off. Like I said, the initial speed on the jdam is 500-600 kts. Thats 10 miles per minute. It would take only one minute for the bomb to reach 10 miles. Now of course the bomb is decelerating. Lets say on the lower end of things the bomb has an initial release of 300 kts or 6 miles per minute. Thats 2 minutes to reach 10 miles. We all know the bomb will stay airborne longer than 2 minutes. I think ED needs to revisit the profile and correct it. get a hold of an aeronautical engineer and they can probably give you a much better idea what the range will be and i'll bet it'll be a lot better than the current profile

                    Most public sources mention 31s range is being "up to 15 NM". How much would be realistic for you?

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                      #11
                      Originally posted by chief View Post
                      Thats what I am saying. I think the profile is way off. Like I said, the initial speed on the jdam is 500-600 kts. Thats 10 miles per minute. It would take only one minute for the bomb to reach 10 miles. Now of course the bomb is decelerating. Lets say on the lower end of things the bomb has an initial release of 300 kts or 6 miles per minute. Thats 2 minutes to reach 10 miles. We all know the bomb will stay airborne longer than 2 minutes. I think ED needs to revisit the profile and correct it. get a hold of an aeronautical engineer and they can probably give you a much better idea what the range will be and i'll bet it'll be a lot better than the current profile
                      It's decelerating and FALLING. A lot of that velocity is in the vertical vector.

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                        #12
                        I just had a little test with the latest stable version of DCS (2.5.6.52437 from 07-24-2020) so you can compare and see whether there had been changes.

                        2x GBU-31
                        ALT 34,400 ft
                        Speed mach 1.07 (IAS 351 kn, GS 628 kn)
                        Distance to target 17 nm
                        Time to impact 1:53min


                        did a drop of two Mk84 (similar weight as GBU-31) from exact same spot, same conditions:

                        Hit ground at a distance of 7.1 nm from spot of drop after a flight time of 52s.

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