ChthoniC Chao wrote on Jan 28^th, 2013 at 3:47am:

I got it Thanks :) Another questions: I saw the speed in MFD is not the true speed ?? :-?

Do you mean the ND (nav display) on the MFD?
TAS = true airspeed
GS = ground speed
The PFD shows IAS (indicated airspeed) on the speed tape. IAS is an accurate measurement of the dynamic pressure on the aircraft and so is useful for any speeds that involve aerodynamics such as stall speed or Vne (never exceed speed). However, IAS does not accurately measure the true speed of the aircraft through the air. This is due primarily to altitude and temperature.