Escape From Frame

COMPASS COURSE:

The compass course is the angle as measured CLOCKWISE between the COMPASS NORTH and the course

DRIFT:

This means that that airplane’s TRUE ROUTE does not coincide with the set course, due to the influence of the wind.

Positive drift:

The drift is positive if the airplane is pushed away to the "RIGHT" by the wind.

DRIFT (negative):

The drift is negative if the airplane is pushed away to the "LEFT" by the wind. 

AIR & GROUNDSPEED:

Airspeed: ( T.A.S. = True  Air - Speed )

The airspeed is the speed of an aircraft with relation to the air.

Groundspeed: ( G.S. =  Ground - Speed )

The groundspeed is the airplane’s speed relative to the earth.

Relative wind:

The relative wind is the wind that one putting his hand outside the cockpit feels.  The relative wind corresponds the airspeed, but in the opposite direction.

TRUE WIND DIRECTION:

The true wind direction is the angle between the true north and the direction from which the wind blows.

The true wind direction is always given by the meteorological services.

MAGNETIC WIND DIRECTION:

The magnetic wind direction is the angle between the magnetic north and the direction from which the wind blows.

The TOWER informs the pilot of the airplane that is taking off or landing about the magnetic wind direction.  Consequently, the pilot does not need to take the VARIATION into account, since the direction of the runway is also expressed magnetically.