BN-2 Vertical Speed Autopilot

Hello! An issue I’m consistently running across with the BB BN-2 is the autopilot’s ability to hold a negative vertical speed.

As shown in my screenshot, I have descent set at -400fpm, while the autopilot has dropped us down to over -1000fpm, where it fluctuates. This is pretty consistent. And I can also see it’s not moving the trim wheel much to compensate. This only happens on descent, while ascents work fine.

Is this behavior normal for this plane? Thanks for any info

You weren’t at idle power were you? The Islander likes a bit of power and you might notice this most on an ILS approach.

not idle but lower power. it seems the AP wasn’t even attempting to correct though as the trim wheel hardly spun. i wonder if this is how the real thing works, it won’t do a low-power descent

has anyone else experience autopilot issues as well?

I can’t get the Islander’s autopilot to work either - it seems as though it sometimes just stops working when in climbs or descents. It could just be me, but I don’t have this kind of autopilot problem with any other aircraft.


exactly! there are basic AP functions in many 3rd party addons and I don’t have any issues with this, the BN-2 autopilot has consistent issues with descent/approach. I’m glad you chimed in as I wanted to make sure it wasn’t an issue on my end.

I wonder if we can somehow officially submit the bug and get the devs to take a look. It’s an otherwise amazing plane!

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I find the AP problematic as well.

It seems incapable of holding pitch as soon as the airspeed drops to the region of 100kts.
(It feels like the AP control surfaces lack the authority to keep the nose)

Which makes and kind of AP approach somewhat… tricky

(I believe I’m seeing the same thing in the Aerosoft Twin Otter so this may be a problem with default KAP140 AP ?)


Hey gang! I am running into this as well. I didn’t know if it was a lack of knowledge on my part, something broken with the default KAP-140, or what.

Replied to this because of that, plus I want to keep the thread alive. I’m chasing down some other information to see if there have been any (current) mods / fixes for that specific AP.

Just FYI if you’re running across this thread & info for the first time - the Honeycomb Bravo AP controls do not play well with the KAP-140. I’ve got the Logitech G Multipanel (basically a physical KAP-140), but while there’s some interaction with the sim, “something” isn’t working right. Gonna try and figure that out.

(edit) I found this project over on GitHub. If I’ve interpreted the page correctly, it looks like the last time it was updated was 10 months ago.

Still looking for more info.

Although non standard, I tend to keep full flap for the approach, the increased drag making sure that I need a fistful of power for the approach and thus, the aircraft remains more controllable on the glideslope. Non standard, but it does work for me. However, you do need to watch it.

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To expand on my last post, it seems that the problem with the Islander is slowing it down once you have intercepted the glideslope at stage one flap, hence the previous suggestion. Maybe a touch more drag from stage one would be an improvement as far as the sim goes, although I couldn’t be sure how this would compare with real World operation. Cut the power and it drops like a brick which doesn’t lose you any speed in a coupled approach and you are then caught porpoising your way to an uncertain arrival on either the runway or a farmers field.

There is a marked symbiosis (of course!) Between AP and power, but it is a very marked one in the BN 2. Of course, trim will control this in a visual approach more effectively. Yesterday, I purchased the Orbx Bristol EGGD package because I was bored and then set up the most miserable Weather I could find, with very low cloud, heavy rain and crosswind and set up to go flying. Of course, Bristol is also on something of a hilltop. The Islander can be a handful on approach as we know, but using the above method and watching the glideslope like a Hawk, had the most spectacular approach I have ever seen in this or any other simulator, the approach lights vaguely coming into view at around a quarter of a mile. I can’t wait to set this one up again. I really don’t think I would have made this with stage one flap but around 70 to 75 knots with stage two and it worked beautifully.

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The default AP ( which is what is involved here ) has all sorts of issues - I have had trouble with it holding a GS too, but as I generally hand fly this a/c it’s not generally an issue either. It has trouble in other a/c too - and AP behaviour is causing issues even with a/c with custom AP still.

To the above poster - the full flap speed is 80ish kts and stall speed is about 40kts, so you’re very fast for an Islander landing! if you hold altitude until you can go full flaps the thing will slow down extremely fast, as you might imagine. During the last big UK storm I was flying it around London, and managed a landing at LCY with about 8kts ground speed.


Yup, the key is getting it down to 80 before approach proper and although you should never “drive” against drag, it does succeed as a workaround.

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From reading flight tests approach speeds are somewhere in the mid 50s usually, which shouldn’t need much power to mantain. If you did that at Bristol I’d imagine there’d be a lot of swearing from everyone queueing behind you though!

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For anyone that doesn’t have a BN-2 POH / Checklists, I’ve got them here. (Neither is a payware thing.)

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JayDee’s BN-2 Checklist is also available on


Greetings sim nerds!! Haha

Ive been having an issue where I can not select the ATL using my Siatek AP pannel. If i try the ATL just returns back to zero. The only way im able too use AP to get to any altitude is VS. And once i get to desired ALT the AP does not lever off, I have to physically go into ATL hold mode. Any one else with this issue?

Im using the Cargo VS and im using real sim gear GNS530… of the matters.

What has worked for me is to set the ALT (I think you mean that and not Atlanta) :wink: - if I set the ALT before I take off, then once airborne it’ll work. If i wait until I’m in the air I have seen the behavior you’re talking about, but I can’t explain it and I can’t really seem to duplicate it on command. (Oops - sorry, with the Logitech AP panel and also a RSG GTN 750)