A normal takeoff is one in which the airplane is headed
into the wind, or the wind is very light. Also, the takeoff surface is firm and of sufficient length to permit the
airplane to gradually accelerate to normal lift-off and
climb-out speed, and there are no obstructions along
the takeoff path.
There are two reasons for making a takeoff as nearly
into the wind as possible. First, the airplane's speed
while on the ground is much less than if the takeoff
were made downwind, thus reducing wear and stress
on the landing gear. Second, a shorter ground roll and
therefore much less runway length is required to
develop the minimum lift necessary for takeoff and
climb. Since the airplane depends on airspeed in order
to fly, a headwind provides some of that airspeed, even
with the airplane motionless, from the wind flowing
over the wings.