Some general flap comments.
Flap settings:
- Flap settings vary based upon the AC being flown.
- Flap settings also very depending on the type of Take-Off or Landing you are doing.
- Flap settings are usually expressed in degrees.
- Retracted --> Fully up. For example, zero degrees flaps.
- Extended --> Partially or fully extended. For example 10 degrees or 40 degrees flaps.
- Full Down --> The maximum degree setting. Sometimes pilots will refer to this as maximum flap setting.
Some planes have mechanical flaps. There is a lever like a parking brake that the pilot uses to set the flaps. This mechanical system is very effective for doing some very interesting effects. Due to the nature of mechanical flaps they are limited to small aircraft.
Most airplanes have actuated flaps. The pilot selects a setting and the actuator moves the flaps to the desired setting. This will usually take a few seconds after the pilot changes the setting. This lag exists for both extending or retracting flaps.
Flaps change the effective camber and angle of attack of the wing. When extending or retracting flaps the attitude of the aircraft will vary. For example, when adding flaps (increasing the degrees) the nose of the aircraft will generally drop.
On many aircraft low flap settings are used for Take-Off. For example 10 degrees of flaps. Full flaps are not used for normal Take-Off.
Flaps add drag to the wing. At low settings the additional drag is overcome by lift so there usually is a positive lift effect. At high flap settings the opposite is true. Depending on the aircraft flaps can be used as an air-brake.
There are different types of flaps based upon their construction. Two common types are slotted and fowler flaps. I've attached a picture of a slotted flap.
For those who are not pilots, the next time you fly an airline plane, try to get a seat just behind the wing and you can see how the control surfaces work. It's really fascinating on the large jets like 747s.
On a side note, there is only one simulator that I have tried that did accelerated stalls correctly and that was A-10 Attack.