Hiya,how does an aircraft know how fast the winds are around it? You see on the PFD the wind direction and velocity, is this a pilot entered perameter or is it an aircraft detected value? Does the pilot have to enter all the winds data in the FMC? cheersrici

rici,The aircraft knows, or more correctly, can calculate the winds if it "knows" its True Airspeed, groundspeed, heading and drift. The true airspeed info comes from an air data computer usually and the other information is provided by some type of RNAV equipment (IRS, GPS, etc). If you have this info then it is simple math (trigonometry) to calculate the wind vector.Pilots do enter the forecast wind data in the FMC/FMS so that the enroute time/fuel predictions are more accurate. Enroute the FMS will use a blend of the actual winds (measured as per above) and the forecast winds to make accurate predictions of time/fuel.Kevin in CYOW

Ok, thanks for the help!