ArduPlane SITL simulasion with MissionPlanner; Some questions

Hi there!
I am a new commer to the ArduPlane SITL simulation. I tried the latest V4.3.4beta2 AruduPlane code with the MissionPlanner, but I found some stranges.

  1. The aircraft flies from the begining at very slow speed of around 2m/sec. How I can stop this moving?
  2. After forced Arming, I set the Guided mode and tried to “Fly to Here”. The orange line directed to the point I set but the airplane flew straight and did not flew to there. Flight speed did not changed. Why?
  3. After about 10 minutes or so, the airspeed increased suddenly up to around 20m/sec and the Guided mode’s “Fly to Here” began to work. Why?

Could some one teach me correct ArduPlane SITL simulation procedure with the MissionPlanner ?