Hi guys, I have asked this question before, however I am still having problems.

When I am landing, I am on full AP, and I am about 10nm from touchdown, I hit the Approach switch, however it does not switch off my alltitude switch.

My question is, how far from the runway should you hit approach switch, and do you have to be near perfect online, and at a minimum hieght before you hit the approach switch?

I have the correct ils frequency set, and set to Nav.
Thanks again....Tomcat61

When you press the APR switch ALT HLD will stay engaged until you intercept the glideslope. This is why you must be below the glideslope when you line up, usually 2000-2300ft above ground at 8-10nm from runway. Get close to lined up, hit APR, autopilot should begin to line you up with the localizer while maintaining the current altitude. When the glideslope comes down to center the ALT hold will disengage.
The autopilot cannot and will not capture the glideslope from above. This is true in alot of real airplanes as well.