NeoHelios Posted March 22, 2018 Share Posted March 22, 2018 (edited) Hi, Community! Any math fans / Real Engineers want to check my work for fun? :) I'm trying to figure how the GBU-xx can be used as a 10nm stand-off weapon by the Harrier when released as a loft/toss projectile. Using the projectile formula from wikipedia (*coughsorrycough*) and a few basic assumptions about speed and release angle, I came up with a 10nm toss some altitude could put the GBU in a close enough vicinity that it could see the laser and maintain enough energy to follow it in. Assume buddy lase / TPOD / JTAC since you likely want to minimize ingress during a standoff attack. Some might argue, "Why not just use a maverick?" Well, I certainly agree that the Maverick would be ideal for standoff attacks, but the ability to fling a GBU over 10nm with a little math might be better for certain situations. Such as utilizing the 1000 lb payload of the GBU-16, or even lofting CBU-97/105 cluster munitions at tanks if someone wanted to mod the harrier to support such things (I digress). Let's just say for the sake of argument, you loaded up GBUs for the mission and, whoopsie daisy, there's an SA-8 in the middle of your target group... Formula here: https://en.wikipedia.org/wiki/Range_of_a_projectile Assumptions: Speed: 400 kts Release angle: 45 deg. distance = 10 nm friction/drag = sadly, unknown / unaccounted for height = solve. So I came up with 10,645 ft AGL at release. I would expect the bomb travel time to be around a minute and a half , give or take. I *think* I converted units correctly: knots to meters per second, and nautical miles to meters, etc... At any rate, I'd test this theory in DCS, but I'm at work right now between projects, so really just looking to start a conversation, I guess. I mean, does this concept of using GBU as standoff in harrier even sound PLAUSIBLE? Edited March 22, 2018 by NeoHelios VF-111 Sundowners [sIGPIC][/sIGPIC] F-16 Viper :: F-14 Tomcat :: F-18 Hornet :: A-10C Warthog :: AV-8B Harrier II :: AJS-37 Viggen :: Ka-50 Black Shark vCG-1 callsign: Cloudy Link to comment Share on other sites More sharing options...
TonyG Posted March 22, 2018 Share Posted March 22, 2018 I'm not an engineer....just curious, are you using corrected speed or IAS? I'm curious how this would work as well, it'd be great fun to try. Link to comment Share on other sites More sharing options...
mojomonkey Posted March 22, 2018 Share Posted March 22, 2018 So my current Harrier loadout in DCS mostly eschews mavericks in favour of GBU-12, because I can carry 4 mavs, or 14 guided bombs... I've been doing some trial and error of different drop profiles for the GBUs. I mostly drop as CCIP these days where possible, because the HUD does a good job of guiding me mostly to target zone, close enough for a lase. The CCRP/auto doesn't seem to give me the right drop zone at the moment, which is a bit of a challenge because I have to estimate drop heights from barometric, which frankly with my flying is more of an art than a science (read: luck). Link to comment Share on other sites More sharing options...
RShackleford Posted March 22, 2018 Share Posted March 22, 2018 Really need to have some drag numbers in there. 10nm from 10.6k' is an extremely long range for a gbu-12 Link to comment Share on other sites More sharing options...
NeoHelios Posted March 23, 2018 Author Share Posted March 23, 2018 SUCCESS! (with notes) Replies: * Used IAS (top left HUD) * Totally agree about the drag--ballistically (i.e. unguided) it would not have gone as far as I calculated Okay, so I drew up a quick mission (NO clouds!) and it worked! I started the run at 7500ft, 12nm out, and 500+kts. Climbed 45 deg angle on HUD pitch ladder as indicated by TVV, and CCIP released GBU-16 just as I flew through 10,000ft (still going 400+kts). Trim, lase, and orbit. Special notes are as follows: NO clouds; on first attempt I had clouds enabled, and LOS was blocked. JTAC would be better for this. Also, I struggled a bit with keeping the target lased as the TPOD would either lase a cloud or be masked from a wing as I was banked for my orbit. That GBU really does take a while to fly down, and I found that it really was a bit of a challenge for me to orbit the target area at 400+ kts and a slight bank towards target area. When I get home from work I'll try again with a JTAC, but for the purpose of this thread I'm saying that this is a plausible stand-off technique for people who can get a consistent lase and little cloud cover. Needs work, but very promising. If I can take 14 guided bombs instead of 4 mavs, there's certainly value in that! Here is the Tacview track. I'd provide the original track or youtube video, but the track playback in DCS never works for me (precision is a little off), and I don't video capture my gameplay. The tacview one is authentic, though, as will be noted when you open the file. At least you'll be able to see my telemetry :) Good luck with your experiments! https://drive.google.com/open?id=1LlWHdDdnPn0i7eD2Bt6o7-M-Hb9pytgo meh... posting original track anyways in case someone can get it to work. https://drive.google.com/open?id=1l6-3XMPgRfKdwVt75sbdH7ITDuLGeb6T Again, good luck! VF-111 Sundowners [sIGPIC][/sIGPIC] F-16 Viper :: F-14 Tomcat :: F-18 Hornet :: A-10C Warthog :: AV-8B Harrier II :: AJS-37 Viggen :: Ka-50 Black Shark vCG-1 callsign: Cloudy Link to comment Share on other sites More sharing options...
lemoen Posted March 23, 2018 Share Posted March 23, 2018 An observation: The GBUs can fly a bit further because of their fins -> more drag but also some lift. Maybe as a first approximation that cancels out drag. Link to comment Share on other sites More sharing options...
AG-51_Razor Posted March 23, 2018 Share Posted March 23, 2018 I was under the impression that when you are in the air to ground mode the figure in the top left of the HUD is True airspeed?? [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
lemoen Posted March 23, 2018 Share Posted March 23, 2018 To do the calculation correctly, the distance should be calculated referencing ground speed and the drag calculations should reference airspeed (IAS is probably close enough) Link to comment Share on other sites More sharing options...
NeoHelios Posted March 23, 2018 Author Share Posted March 23, 2018 (edited) I was under the impression that when you are in the air to ground mode the figure in the top left of the HUD is True airspeed?? Awesome catch! Didn't think of that. Will check the manual. ...(time passes)... EDIT: Here are some exerpts from A1-AV8BB-NFM-000 for comparison: section 23.16.2 :: HUD speed value in NAV master mode is "Calibrated airspeed" (CAS) section 23.17 :: top paragraph describes VSTOL master mode HUD symbology "The basic flight data of heading, airspeed, altitude ... are displayed and function the same as described in the navigation master mod" Now, if we take a look at figure 2-36 "BIT failure Indications" on page 2-124, we see that ADC.3 indicates "TAS not available on HUD when A/G is selected". This tells me that it is possbile to see True Air Speed (TAS)on the HUD with in A/G master mode. Within this pub, I don't really see any direct definitions for the HUD speed value specifically in the A/G master mode. There also seems to be alot of resources out there differentiating between GS, IAS, CAS, and TAS, so think might merit a larger discussion outside the scope of my initial question. For the sake of argument, however, I think we can imply some things based on above references. Not looking for super precision within 20-50 kts to pass the "is it feasible" test. That said, I absolutely do appreciate the thought experiment and challenge of diving in with this additional feature of the overall problem. So without better info, here is my best guess based on above: A/G airspeed in the HUD is True Air Speed. Rationale: why would they have an error code in the BIT test (fig 2-36) if it weren't normally as such. I suppose when I get home tonight, I could toggle between the master mode buttons a few times to verify this. Aside, interestingly (to me) while researching, I also found out that little "T" in the upper right corner of the HUD is to indicate that "true heading" is being used instead of magnetic (tmyk!) :: 23.17.5 Edited March 23, 2018 by NeoHelios VF-111 Sundowners [sIGPIC][/sIGPIC] F-16 Viper :: F-14 Tomcat :: F-18 Hornet :: A-10C Warthog :: AV-8B Harrier II :: AJS-37 Viggen :: Ka-50 Black Shark vCG-1 callsign: Cloudy Link to comment Share on other sites More sharing options...
NeoHelios Posted March 23, 2018 Author Share Posted March 23, 2018 An observation: The GBUs can fly a bit further because of their fins -> more drag but also some lift. Maybe as a first approximation that cancels out drag. This is a good point, but I was mainly focused on making the unguided trajectory as accurate as possible so that the sensor will align with the lased target. Kind of like throwing a football with a webcam on the front that has a narrow cone of vision. VF-111 Sundowners [sIGPIC][/sIGPIC] F-16 Viper :: F-14 Tomcat :: F-18 Hornet :: A-10C Warthog :: AV-8B Harrier II :: AJS-37 Viggen :: Ka-50 Black Shark vCG-1 callsign: Cloudy Link to comment Share on other sites More sharing options...
RentedAndDented Posted March 24, 2018 Share Posted March 24, 2018 Perhaps I am missing something, but can't you do that using the Auto mode pretty accurately? I've been practicing that using Mk.83s and if you line it up carefully it's actually reasonably accurate. Link to comment Share on other sites More sharing options...
Bullitthead Posted March 25, 2018 Share Posted March 25, 2018 (edited) After the Harrier was released I was trying to see how far I could toss a GBU12. If I remember correctly I was hitting targets out to around 15nm with a CCIP release from 20-25k feet AGL with a 25 degree climb and a release speed of around 400-450 knts I think. Haven't messed with it in awhile but, might have to try it out again! Edited March 25, 2018 by Bullitthead Link to comment Share on other sites More sharing options...
Eldur Posted March 26, 2018 Share Posted March 26, 2018 Perhaps I am missing something, but can't you do that using the Auto mode pretty accurately? I've been practicing that using Mk.83s and if you line it up carefully it's actually reasonably accurate. Yes, that works, of course. But the resulting CCRP calculation doesn't take into account the GBU's limted glide capability. That basically means you're able to drop one earlier and still get a good hit. I tried that yesterday, but I noticed something very weird. In case of long loft drops (between 10 - 12 nm at 18 - 24 kft and M .8 +, ~45° climb) I often saw the GBUs pick up the laser signal wrong causing them to drift away from the target, roughly into the direction I peeled off to. Eventually they'd even try to pull up successfully gaining altitide again once and then plummet into the ground or water afterwards. I made a track of this, but sadly it's broken. I'll try to catch this again in the next few days and put it here. Link to comment Share on other sites More sharing options...
NeoHelios Posted March 26, 2018 Author Share Posted March 26, 2018 ...I often saw the GBUs pick up the laser signal wrong causing them to drift away from the target, roughly into the direction I peeled off to. ... Isn't there some kind of bug/feature where you can't really turn too hard with the TPOD or else it will drift in some direction? I'm sure I've heard of it before, but I don't recall the source or context. Just that the TPOD will move if you turn too fast. Would love to know a safe turn speed. VF-111 Sundowners [sIGPIC][/sIGPIC] F-16 Viper :: F-14 Tomcat :: F-18 Hornet :: A-10C Warthog :: AV-8B Harrier II :: AJS-37 Viggen :: Ka-50 Black Shark vCG-1 callsign: Cloudy Link to comment Share on other sites More sharing options...
Eldur Posted March 27, 2018 Share Posted March 27, 2018 Then it must have pointed straight into the sky 'cos the bomb tried to climb Link to comment Share on other sites More sharing options...
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