Planes use flaps to land and to take off. So why do they retract them while they are on the ground, ie why not just leave them deployed?
In: Engineering
People keep mentioning the possibility of damage to extended flaps (which I’m sure is a secondary reason), but the main reason is to keep the plane on the ground. Flaps are designed to create significantly more lift at low speeds at the expense of increasing drag. They deploy them on takeoff and landing so the plane can transition to and from flight at lower ground speeds, which reduces stress on the airframe and landing gear and is just easier for the pilot to manage.
If you leave flaps deployed on the ground you risk gusts of wind lifting one or both wings while the aircraft is parked. That’s bad. Since they also increase drag (especially in landing configuration) in windy/gusty situations they also increase the forces on the brakes and chocks while parked. The risk of the aircraft moving uncontrollably, tipping, flipping, etc is all significantly increased with the flaps down on the ground.
So they retract them when they don’t need them.
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