Ramsay Posted February 24, 2020 Share Posted February 24, 2020 (edited) I'm not certain this is a bug as I don't wholly understand how the MAD is modelled but it seems likely. I've noted that the F-14B's HSI compass and HUD are effect by compass errors due to effects from Magnetic Azimuth Detector. This is excellent and to be commended. Unfortunately the compass error also appears to effect the TACAN radial, which AFAIK it shouldn't as the radial information is encoded in the signal not calculated/measured by the aircraft. F-14B HUD tape looks correct (if -2° error is due to MAD or similar) However the TACAN thinks we're on the 117°M radial, despite being on the 119°M radial Although tested in DCS 2.5.6.43931, AFAIK the bug has been present for a while. Edited February 24, 2020 by Ramsay Delete Carrier TACAN info/speculation as unable to reproduce i.e. it seems good with little error. i9 9900K @4.8GHz, 64GB DDR4, RTX4070 12GB, 1+2TB NVMe, 6+4TB HD, 4+1TB SSD, Winwing Orion 2 F-15EX Throttle + F-16EX Stick, TPR Pedals, TIR5, Win 10 Pro x64, 1920X1080 Link to comment Share on other sites More sharing options...
RustBelt Posted February 24, 2020 Share Posted February 24, 2020 Are you on the TACAN or the ILS? Because the tacan station isn’t along the runway centerline. Link to comment Share on other sites More sharing options...
Ramsay Posted February 24, 2020 Author Share Posted February 24, 2020 (edited) Are you on the TACAN or the ILS? Because the tacan station isn’t along the runway centerline. At 10.8 Nm the 390 ft difference between the TACAN and runway center line isn't significant at 0.34°. 390 ft / 10.8 Nm = 390 ft / (10.8 * 6076) ft = 0.00594323 Arcsin (0.00594323) = 0.34° A larger problem is that DCS tends to round numbers down, so 119°M may actually be 119.1°M or 119.9°M i.e. there may be upto 1° of error, rather than +/- 0.5° However, I am comparing the F-14B's TACAN behaviour to other modules such as the A-10C, F-5, AV-8B, etc. which may or may not be appropriate. I wouldn't normally be worried by a 1-2° error but I've seen regular heading errors of near 10° flying TACAN approaches to intercept the carrier FB / ICLS. As this is nearly 2x the stated 4° ships magnetic effect, I wondered if this was the cause. In this picture from 17th April 2019, the carrier's BRC is 270°T and FB is 254-255°M but due to compass error the HUD tape reads 248°M i.e. -6°; this close in the HUD is using ICLS so I don't recall what the TACAN was doing. Unfortunately a airspawn off the carrier's FB @ 10 Nm doesn't have the same effect, so it likely requires some manoeuvring to build up the compass/heading error I usually see flying east to west. Hopefully HB will have the tools to see if MAD error, etc. is effecting the displayed TACAN radial (i.e. by injecting a large MAD error) or if I'm incorrect. Edited February 24, 2020 by Ramsay i9 9900K @4.8GHz, 64GB DDR4, RTX4070 12GB, 1+2TB NVMe, 6+4TB HD, 4+1TB SSD, Winwing Orion 2 F-15EX Throttle + F-16EX Stick, TPR Pedals, TIR5, Win 10 Pro x64, 1920X1080 Link to comment Share on other sites More sharing options...
draconus Posted February 24, 2020 Share Posted February 24, 2020 Btw: TACAN radial is given as from station. In this case 117 is bearing. Win10 i7-10700KF 32GB RTX3060 Rift S T16000M TWCS TFRP FC3 F-14A/B F-15E CA SC NTTR PG Syria Link to comment Share on other sites More sharing options...
RustBelt Posted February 25, 2020 Share Posted February 25, 2020 This sounds like this problem. https://forums.eagle.ru/showthread.php?t=238390 Link to comment Share on other sites More sharing options...
draconus Posted February 25, 2020 Share Posted February 25, 2020 This part: If your directional gyro/synchro is shifted, it may result in erroneous interpretation of the TACAN direction on all instruments. You might have the carrier straight in front of your nose, but the BDHI will show the TACAN a few degrees to your left or right. However, the radial (bearing) reading would be correct; it would be just your magnetic heading wrong. Win10 i7-10700KF 32GB RTX3060 Rift S T16000M TWCS TFRP FC3 F-14A/B F-15E CA SC NTTR PG Syria Link to comment Share on other sites More sharing options...
Ramsay Posted February 25, 2020 Author Share Posted February 25, 2020 (edited) This part: I am aware of this ... If your directional gyro/synchro is shifted, it may result in erroneous interpretation of the TACAN direction on all instruments. You might have the carrier straight in front of your nose, but the BDHI will show the TACAN a few degrees to your left or right. However, the radial (bearing) reading would be correct; it would be just your magnetic heading wrong. the error I suspect is in this ... However, the radial (bearing) reading would be correct; With compass error, when on the correct radial the course deviation bar should be centered, even when the course select pointer isn't pointing towards the TACAN station i.e. due to compass error. I suspect I've seen the deviation bar centered while not on the correct radial - but I need to test further (i.e. induce a significant compass error) before I can confirm or refute my suspicion. Edited February 25, 2020 by Ramsay i9 9900K @4.8GHz, 64GB DDR4, RTX4070 12GB, 1+2TB NVMe, 6+4TB HD, 4+1TB SSD, Winwing Orion 2 F-15EX Throttle + F-16EX Stick, TPR Pedals, TIR5, Win 10 Pro x64, 1920X1080 Link to comment Share on other sites More sharing options...
mattag08 Posted February 26, 2020 Share Posted February 26, 2020 He's correct. The TACAN should not use instrumentation other than the TACAN radio itself for radial determination. This is quite clear if you actually know how a VOR or TACAN radio determines the radial. Flying the DCS: F-14B from Heatblur Simulations with Carrier Strike Group 2 and the VF-154 Black Knights! I also own: Ka-50 2, A-10C, P-51D, UH-1H, Mi-8MTV2, FC3, F-86F, CA, Mig-15bis, Mig-21bis, F/A-18C, L-39, F-5E, AV-8B, AJS-37, F-16C, Mig-19P, JF-17, C-101, and CEII Link to comment Share on other sites More sharing options...
Super Grover Posted February 26, 2020 Share Posted February 26, 2020 Hey Ramsay! Actually, you weren't precisely on the radial 117° (297°) but probably around 118-119. The deflection needle isn't accurately aligned, and the direction to the TACAN station (that little arrowhead) is slightly shifted to the right from your heading. You are right that the sensed magnetic north direction and the declination shouldn't affect TACAN radial readings. However, we the TACAN itself has some limited accuracy, and according to the specification for the AN/ARN-84(V) the error can be as large as between 0.5° and 2.0° for the digital bearing and between 1.0° and 2.5° for the analogue bearing. The error depends on the strength of the signal received. We measure the signal reception, and we model the errors, so it is possible that in your case that's the reason for the difference you observe. BTW these TACAN bearing measurement errors are the main reason why TACAN fixes for the INS may introduce INS errors even more significant than before the fix. Krzysztof Sobczak Heatblur Simulations https://www.facebook.com/heatblur/ Link to comment Share on other sites More sharing options...
Ramsay Posted February 26, 2020 Author Share Posted February 26, 2020 (edited) Actually, you weren't precisely on the radial 117° (297°) but probably around 118-119. The deflection needle isn't accurately aligned, and the direction to the TACAN station (that little arrowhead) is slightly shifted to the right from your heading. As I understand it, the little arrowhead points to the currently detected radial (118-119°) and was shifted right (with the compass scale) due to the ~2° compass error. ... the TACAN itself has some limited accuracy, and according to the specification for the AN/ARN-84(V) the error can be as large as between 0.5° and 2.0° for the digital bearing and between 1.0° and 2.5° for the analogue bearing. The error depends on the strength of the signal received. We measure the signal reception, and we model the errors, so it is possible that in your case that's the reason for the difference you observe. 6° compass + 2° TACAN error = 8° which IIRC is close to the error I've seen flying inbound on the FB radial @ ~15 Nm. Thanks for checking. Edited February 26, 2020 by Ramsay i9 9900K @4.8GHz, 64GB DDR4, RTX4070 12GB, 1+2TB NVMe, 6+4TB HD, 4+1TB SSD, Winwing Orion 2 F-15EX Throttle + F-16EX Stick, TPR Pedals, TIR5, Win 10 Pro x64, 1920X1080 Link to comment Share on other sites More sharing options...
Satarosa Posted February 26, 2020 Share Posted February 26, 2020 Learn here (fr) Real War, Youtube Channel: https://www.youtube.com/channel/UCCs1uki5QsyuHUdvtmWJTOg?view_as=subscriber Real War, Voice Chat: https://discord.gg/UGa3KMe [sIGPIC][/sIGPIC] Link to comment Share on other sites More sharing options...
RustBelt Posted February 27, 2020 Share Posted February 27, 2020 (edited) Nope. the Arrow head has nothing to do with compass error. It just is conveniently put on the compass for ease of use. You want the 117 Inbound BEARING TO you dial the course to 117. The Magnetic HEADING you see when you keep the CDI centered won't necessarily be 117 for a TON of reasons most of which you won't notice because the big reason is of course WIND, but your COURSE indicator has to be on the actual course you want. You fly to keep the needle centered, not to a magnetic heading when flying a Course. Edited February 27, 2020 by RustBelt Link to comment Share on other sites More sharing options...
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