Best Answer: First segment is defined as the segment from liftoff to the point where the gear is fully retracted with flaps in the takeoff setting. It's flown at V2 speed. Second segment is from the gear up point to 400' AGL also flown with takeoff flaps and at V2 speed. Third segment is the distance required to go from the end of the second segment climb at V2 to the final climb speed with the flaps retracted. It's flown level while accelerating. Final segment is from the end of the third segment till 1500' AGL. It's flown at final climb speed with flaps retracted.