Boeing 717 "Dial-A-Flap" explained
Video from the channel MT Aviation Photo & Film about Boeing 717, linked on its Above Ten Thousand entry. Duration: 2:50. Language: English. Video type: Documentary.
The video explains the Boeing 717's variable takeoff flap system, known as "Dial-A-Flap." Using a selector wheel, the pilot can set any angle between 0 and 20 degrees, in addition to the fixed flap and slat lever positions.
The 717-200 was born as McDonnell Douglas's MD-95, the last variant of the family that began with the DC-9, and it shares this system with the DC-9, the MD-80 and the MD-90.
The lever, connected to a cable drum, acts on the hydraulic valve that moves the flaps. Choosing the angle according to weight, airport and weather improves takeoff and climb performance, and allows operation from short runways, in heat or at altitude.