All the answers here are wrong so far.
Flaps are used during landing to allow a slower airspeed without as much pitch. Flaps are not used in full during heavy wind gusts,
but flaps on landing are much greater degree (30-45) than flaps on takeoff (5-10).
The reason flaps are retracted is to follow the checklist. It seems redundant, but it would be a mistake to try and take off at flaps 45 because the previous crew didn't retract them.
(pilot here)
Originally Posted by
coplatsat
Once the plan is on the runway (front gear too), then there is no need for the flaps, and they are retracted to settle the airplane on to the runway. Since clean (no flaps), the speed required to fly is higher than when they are extended.
Wrong. Flaps are not retracted until the plane is well below flying speed. A pilot would
NEVER fully retract the flaps immediately upon landing because of the chance of a go-around (runway incursion, etc). Spoilers and speed brakes are used to slow the plane after touchdown, not the flaps.