Dear expert colleagues,I've been trying out the "roll" knob on the JS41 autopilot console on final approach, to try to see if it helps with runway alignment in light crosswind or offset ILS ... but I'm not sure if that's its real purpose nor whether it's actually been modelled in our PMDG version.Could someone very kindly educate me on this! I've read the PMDG JS41 tech manual, but I didn't detect any lateral nav disengaging when I turned the knob nor any roll!Any advice and enlightenment would be much appreciated.Thanks and best wishes,David

I have a feeling you're talking about the aileron trim wheel. It has little/nothing to do with the actual command of the autopilot.

Hi, Kyle. Thanks for the thought. No, it's not the aileron trim wheel, but the so-called TURN Knob referred to in the AOM page 8.11.60 at the bottom of the page (numbered "4" but really "6"). Sorry, I should have used the correct terminology from the beginning :(. It's situated on the same console as the electronic trim but on the right-hand side. There's an illustration on AOM 8.11.65 in the middle of the page.So, to my earlier question, does the TURN Knob work on our PMDG model - and what's it's RW function? My guess is that it's designed to correct course when the other AP functions ought not to be disengaged - such as a coupled ILS, when TURN can help maintain runway alignment in strong cross winds (along with rudder??). Again, any insight would be gratefully received. I've tried TURN but can't detect it's functioning ...Thanks. Best wishes,David

Interesting question. I do not know the answer, but I am pretty sure it is not for adjusting AP behaviour. There is a clear instruction that it must be in detent before AP can be engaged and that its use cancels any lateral mode.

It should turn the AP into a wing-leveler, with the ability to make standard rate turns. Most would prefer using the HDG mode if a manual adjustment of heading is desired. This might work when tracking a VOR radial but the ILS requires much more precision than this method will provide.

It should turn the AP into a wing-leveler, with the ability to make standard rate turns. Most would prefer using the HDG mode if a manual adjustment of heading is desired. This might work when tracking a VOR radial but the ILS requires much more precision than this method will provide.

Thanks as always, Dan. If I may :So, to check my understanding, you mean that the TURN option is less precise, right? Much easier to offset crosswind with a precise into-wind HDG adjustment? Is this use of HDG legitimate for coupled approach in the RW? Guess you would then have to sacrifice fully-coupled ILS APP and end up with NAV only for the ILS approach?Also, is the TURN feature actually enabled on our PMDG JS41? I haven't seen its effect when playing around with it on mine!Best wishes,David

The approach should either be hand flown or with NAV/APP as appropriate for the approach type. There's no point at all in trying to sit there and mess with a heading knob to keep yourself centered. The NAV/APP will adjust for the wind, as appropriate to maintain centered on the radial/LOC. Why make it more difficult than it really is? If you used HDG, you wouldn't be NAV-only, as HDG cannot work in conjunction with NAV. It would be a HDG "approach" with V/S or IAS for "glideslope. Again, more complicated than it needs to be, so use NAV/APP or handfly.Same goes for the turn knob - it's not for anything other than that. It is meant to turn the aircraft at various degrees of bank.

The approach should either be hand flown or with NAV/APP as appropriate for the approach type. There's no point at all in trying to sit there and mess with a heading knob to keep yourself centered. The NAV/APP will adjust for the wind, as appropriate to maintain centered on the radial/LOC. Why make it more difficult than it really is? If you used HDG, you wouldn't be NAV-only, as HDG cannot work in conjunction with NAV. It would be a HDG "approach" with V/S or IAS for "glideslope. Again, more complicated than it needs to be, so use NAV/APP or handfly.Same goes for the turn knob - it's not for anything other than that. It is meant to turn the aircraft at various degrees of bank.

Again thanks, Kyle. You're quite right that HDG knocks out NAV - of course it does :( . Best wishes,David

The only exception is when you're too far from the AP's NAV capture range in HDG mode. Meaning, when you're on a heading to intercept the LOC or VOR radial, you can have HDG active, with NAV on CAP mode. As soon as the AP can capture the radial, it kicks HDG off and autoselects NAV.

The only exception is when you're too far from the AP's NAV capture range in HDG mode. Meaning, when you're on a heading to intercept the LOC or VOR radial, you can have HDG active, with NAV on CAP mode. As soon as the AP can capture the radial, it kicks HDG off and autoselects NAV.

Thanks, Kyle. Absolutely.Best wishes,David