Yurgon Posted April 6, 2021 Share Posted April 6, 2021 I was wondering about the min and max values of the two digits of the Huey's Mode 1 transponder. # The first digit can go from 0-3, and the second digit can go from 0-7; the above screenshot shows the maximum value of 37. However, in other modules (A-10C, F/A-18C) the value range for the first digit is 0-7 and for the second digit it's 0-3 - basically the digit ranges are swapped around in comparison to the Huey, with their max value being 73 (instead of 37 for the Huey). Is that just the way it is with the transponders in these different aircraft, or could it be that the Huey just has the min and max values the wrong way around on the panel? Link to comment Share on other sites More sharing options...
Kirk66 Posted April 6, 2021 Share Posted April 6, 2021 Every military Mode 1 I've seen/used has been 00 to 73. Newer ones can handle 0000 - 7777. My guess is the Huey is wrong. Vulture 1 Link to comment Share on other sites More sharing options...
Yurgon Posted April 6, 2021 Author Share Posted April 6, 2021 Great info, thanks! In the meantime I found this video that seems to support the mixing of the values in the Huey: Link to comment Share on other sites More sharing options...
Frederf Posted April 6, 2021 Share Posted April 6, 2021 (edited) These are all "octal" meaning 8 values, 0-7. APX-72 is 32 possible codes M1 (4x8, full octal times half an octal) while M3/M2 is 4096 8^4 (four octal). The Mark X standard apparently only had 32 codes while the modern stuff (Mark XII or newer?) has M1 64 codes. At some point they expanded the M1 codes in aircraft. Probably as the tech got better there was no savings in design or something. That's interesting. I wonder why they limited the M1 by a factor of 2 before. The idea was M1 encodes airplane-mission type and they didn't think there were more than 32 types of missions? Edited April 6, 2021 by Frederf 1 Link to comment Share on other sites More sharing options...
Yurgon Posted April 7, 2021 Author Share Posted April 7, 2021 I filed this as a bug report. Link to comment Share on other sites More sharing options...
Frederf Posted April 7, 2021 Share Posted April 7, 2021 I noticed the 3-7 vs. 7-3. It makes sense to a programmer counting in octal that it would be the first one not the second (zero to thirty-two in base 8). But video and other evidence shows as you say. Either designers of Mark X IFF system put least significant digit on left side or they are doing a weird sequence (1, 2, 3, 4, 9, 10, 11, 12, 17, 18, 19, 20, 25, 26, 27, 28). Link to comment Share on other sites More sharing options...
Yurgon Posted April 7, 2021 Author Share Posted April 7, 2021 7 minutes ago, Frederf said: But video and other evidence shows as you say. It's quite possible that the Huey has it the other way around IRL, though it wouldn't make much sense to me. The video I linked above was suggested to me by a former RL German Army UH-1D pilot, though he didn't say whether this was actually the way he remembers it or not. But I guess he wouldn't have given me the link if he remembered it the other way around. Link to comment Share on other sites More sharing options...
Frederf Posted April 7, 2021 Share Posted April 7, 2021 (edited) I searched google images for APX-72 and plenty of them had the 7/3 combo. Plus the DCS A-10C is 7/3. Edited April 7, 2021 by Frederf 1 Link to comment Share on other sites More sharing options...
Yurgon Posted April 7, 2021 Author Share Posted April 7, 2021 Yeah, the Hornet as well. The C-101EB allows 0-7 on both Mode 1 digits, but like Kirk66 said, newer devices can handle that, so that seems to be correctly modeled. But the 3/7 combo for the DCS Huey seems pretty unique. Link to comment Share on other sites More sharing options...
Akiazusa Posted May 15, 2021 Share Posted May 15, 2021 The IFF mode4 code control knob on the Huey also seems to be working oddly Kyoto Animation forever! Link to comment Share on other sites More sharing options...
Frederf Posted May 15, 2021 Share Posted May 15, 2021 (edited) The A B hold zeroize? That's a special kind of knob. For memory zeroize has to be lifted to access the erasing function and hold is spring loaded. The idea is that you really don't want to zeroize accidentally flipping AB. Normally the codes are auto erased on power off as they are secret. In order to save them the pilot holds the knob to hold during power off. Oh yeah, on mine the knob goes through the wrong rotation only between hold and zeroize. Edited May 15, 2021 by Frederf 1 1 Link to comment Share on other sites More sharing options...
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