Duke LNAV has mind of its own
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I'm not really sure why this is happening but I'm having multiple issues with the AP and FD in both variants of the Duke.
Most notably, without any GPS equipped and everything set up correctly (including HSI source switches), it will not follow a VOR radial at all. I don't know why this is, but it either goes into NAV and does orbits, or doesn't intercept at all, despite what the HSI is saying. Same goes for the ILS (tested at EMA East Midlands and HUY Humberside).
With the KLN-90B, I've picked up a fair amount of zig-zagging too and LNAV inaccuracies (image attached - OLNEY 2B at LTN).
Using the latest version. Any help would be appreciated!
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I have been flying the with the KLN-90B in the turbine duke for many trips and it works beautifully. A fantastic freeware addition.
It will slightly overshoot turns but that is perfectly realistic. ~0.3 NM as the biggest deviation in a sharp turn here. There is a beta version of the KLN-90B out with more turn anticipation. Only issue is that it is probably turning better than the real life unit.
Remember that the 90B is an old unit and only technically RNAV2 capable.Once on track it does not zig zag.
Have also been flying with no GPS, and only real "issue" I have seen there is that it simulates signal degradation unlike most planes. Perhaps it is a bit too noisy when at long ranges from powerful VOR stations, but I don't have real life experience to compare with.
With no GPS installed you can also use the KNS-81 as your nav source. If you accidentally have use that it will be super confusing what the plane is doing.Engaging APP while at full deflection will mess up trying to follow the ILS, and it can be a bit finicky to get it to intercept the GS so I have had to fly some approaches raw data.
Could be something like rouge keybindings causing all your issues. If fx you have something unintentionally giving rudder input I'm sure it will mess with the autopilot in all modes.
If you post some proper screenshots of what is happening in the sim it will be much easier to figure out what is going on. Can't really tell anything from a wonky flightpath on vatsim.
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Checking the OLNEY 2B it includes intercepting radials. The KLN-90B can only fly fix to fix automatically.
For radials you have to use OBS mode and set course (in this case you can also use the VOR in the traditional way).6-25 and 6-26 in the 90B pilots guide has examples of how SID/STARS have to be flown on this unit. Remember it is not a modern unit so it has some fun quirks.
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The current version of the KLN assumes an instant bank of 25° in its calculation, which is physically impossible and thus overshoots turn. I checked with the KLN-89 trainer by Bendix/King and I think they do also add some time before the turn to account for the change of bank angle. I added this in my calculations in the latest betas, you can try it out here:
https://github.com/falcon71/kln90b/releases -
@Avionic My apologies, I explained that poorly. The thing regarding radials and ILS etc is when using the nav radios, I get a perfect signal on the VOR or ILS yet the AP just either does not intercept the radial with the source in VLOC and the CDI moving across the HSI showing I've gone straight through it (tested at EMA, HUY and LGW with various intercept angles, usually around 45 degrees, and also different arming times - I.e. arming APP with 2nm or so to intercept), or will turn in the completely wrong direction despite what the HSI is showing. Thanks for letting me know about the KLN though, as I didn't know it functioned this way.
Also, @falcon71 thank you for providing us with such an awesome GPS unit :)
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Do you perhaps have any pics/vids of your panel when trying to intercept radials - would make it easier to detect anything wrong. Sounds like you are doing things correctly.
I just know, that for me it has been working fine for me intercepting VOR radials. So there is likely not anything fundamentally wrong with the Duke.