The DC-9 wings were designed to be fast on cruise and perform well on short runways. The final wing design was the optimal combination of wing-sweep angle, 24 degree sweep back at the center chord, and wing thickness to yield the lowest operating cost for a given cruise speed (M.80), payload-range ability and field length requirements. Designed to provide a stable, sturdy and reliable airplane structure, the all metal wing was produced to withstand the stress of frequent takeoffs and landings which jets operating short haul endure.
The wings on the DC-9-30 are fitted with full span leading edge slats and double slotted trailing edge flaps which extend from the back of the wing over two thirds of the span.This gives the aircraft excellent short field performance as well as satisfactory stall characteristics. The aircraft recovered successfully from about 2,000 stalls during the flight testing.
The dark gray stripes shaped like a triangle on top of the wings are there to help detect clear ice on the wings. If the stripes appear to have a refracted appearance, the wing upper surfaces may be contaminated with clear ice and both wings must be physically inspected.
Click the pictures below for full resolution versions.