In real world, I can hear the autopilot disconnect warning from the cockpit shortly before landing, maybe at 300 feet.
In IF, I feel I have to disconnect it a bit earlier, when about 3 nm out, because after disconnecting, the aircraft violently rushes up or down, and I need some time to stabilize the approach again.
When do you take control? Is there any way I can keep the same attitude and vertical speed when disconnecting the autopilot, so that I didn’t have to do violent corrections?
Calibrate your device. Once you disconnect the autopilot, keep your device still and then slowly start moving around. I typically disconnect the autopilot around 1,500 feet. Just remember to keep your device still. And calibrate your device, it helps ;)
How do you trim the plane before disconnecting? I wouldn’t know the correct trim value.
If I calibrate before autopilot off, it still doesn’t help because the autopilot is pulling up a bit to maintain the right vertical speed, but when I switch it off, I’m holding the plane at neutral setting (not pulling up), which means the plane dives down.
What I do is I disconnect weit all and horizontal AP when I am lined up square with the runway, based on the ILS come. If I am feeling adventurous, I will hand fly it as soon as I have the runway in sight, but, if you are still having trouble flying in general I do not recommend this. I use auto throttle most of the way down, and if the weather is bad, sometimes all the way down.
Also, the ILS cone and the glidescope will help you immensely in this situation.
Usually disconnect around 800ft. I only do it lower if I can not see the runway. I have been in 100 metre visibility in a 737 where I just have to use autopilot and I disengage at 60 ft. Extremely dangerous if it is not calibrates correctly.
I lock the heading, and at 150 feet, I unlock the altitude autopilot only. This gives me a nice centerline landing and I only have to worry about my rate of descent, makes it a whole lot easier. And allows for a nice flare (just not in the 717. No one can land it).
For me, sometimes I turn off auto pilot at about 4-5 nm. But almost all the time I like to fly the whole approach manually, which would be at about 10 nm out.